Workshop 5: Wound Healing

(March 9,2009 - March 13,2009 )

Organizers


Philip Maini
Centre for Mathematical Biology, Mathematical Institute
Chandan Sen
Depts of Surgery & Molecular & Cellular Biochemistry, The Ohio State University

Abnormal healing of wounds in, for example, diabetics, or aged patients, as well as formation of scar tissue, has resulted in the need to understand the fundamental processes involved in wound healing. This workshop aims to bring together experimentalists, clinicians and theoreticians working at the different scales apparent in this problem and to determine approaches for combining these in a multiscale modeling framework. From a clinical standpoint, we would like to be able to predict from an initial time course what is the longer term prognosis for a wound. At one level, this could be done statistically, as perhaps from data already available trends could be discovered. However, this would not provide a mechanistic understanding which would inform a clinician of what therapeutical intervention to make if the model predicts that a wound would not heal properly.

The first three days will focus on particular spatial scales. Day 1 will begin with an overview talk that will introduce participants to the stages involved in wound healing, together with imaging of actual wound healing processes to illustrate the state of the art in experimental measurement and visualization techniques. It will then investigate aspects of signaling networks within cells which determine cell responses to wounding. Day 2 will focus on angiogenesis, the process by which new vasculature evolves. A specific aim here is to understand the origin of the biphasic response of healing to oxygen tension and its implications, for example, in wound infections where oxygen is used up thus impairing the healing process. Day 3 will address problems arising at the level of cell movement and laying down of matrix with important implications for scar tissue formation.

To arrive at a comprehensive model (or suite of models) one needs to integrate processes occurring on many different time and length scales. It is clearly impossible to simply include everything, so a major challenge for modelers is to extract from detailed models the essence of the processes occurring at each scale and interface them appropriately in a multiscale framework. Day 4 will consist of talks on this subject.

Day 5 will present a number of clinical case studies which will lay down future challenges in developing the generic modeling frameworks presented in the first four days to specific problems. Examples here will include healing in diabetic patients, elderly patients.

Accepted Speakers

Marc Basson
Departments of Surgery, Anatomy and Cell Biology, Wayne State University
Helen Byrne
Centre for Mathematical Medicine and Biology, University of Nottingham
Pierre Coulombe
Biochemistry and Molecular Biology, Johns Hopkins University
John Dallon
Department of Mathematics, Brigham Young University
Bob Diegelmann
Biochemistry, Anatomy & Emergency Medicine, Virginia Commonwealth University
Luisa DiPietro
Center for Wound Healing & Tissue Regeneration, University of California, Irvine
Geoffrey Gurtner
Department of Surgery, Stanford University
Rovshan Ismailov
Department of Epidemiology, University of Pittsburgh
Kevin Kesseler
Dept. of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill
John King
School of Mathematical Sciences, University of Nottingham
Sanjay Kumar
Department of Bioengineering, University of California, Berkeley
Periannan Kuppusamy
Internal Medicine & Biomedical Engineering, The Ohio State University
Anie Philip
Director, Plastic Surgery Research, McGill University, Macdonald Campus
Len Sander
Department of Physics, University of Michigan
John Ward
School of Mathematics, Loughborough University
Sarah Waters
Mathematical Institute, University of Oxford
Ronald Xu
Biomedical Engineering, The Ohio State University
Benjamin Yu
Division of Dermatology, University of California, San Diego
Min Zhao
School of Medicine, University of California, Davis
Monday, March 9, 2009
Time Session
09:30 AM
10:30 AM
Bob Diegelmann - Overview of Wound Healing

The normal healing response begins the moment the tissue is injured. As the blood components spill into the site of injury, the platelets come into contact with exposed collagen and other elements of the extracellular matrix. This contact triggers the platelets to release clotting factors as well as essential growth factors and cytokines such as platelet-derived growth factor (PDGF) and transforming growth factor beta (TGF-ß). Following hemostasis, the neutrophils then enter the wound site and begin the critical task of phagocytosis to remove foreign materials, bacteria and damaged tissue. As part of this inflammatory phase, the macrophages appear and continue the process of phagocytosis as well as releasing more PDGF and TGFß. Once the wound site is cleaned out, fibroblasts migrate in to begin the proliferative phase and deposit new extracellular matrix. The new collagen matrix then becomes cross-linked and organized during the final remodeling phase. In order for this efficient and highly controlled repair process to take place, there are numerous cell-signaling events that are required. In pathologic conditions such as non-healing pressure ulcers, this efficient and orderly process is lost and the ulcers are locked into a state of chronic inflammation characterized by abundant neutrophil infiltration with associated reactive oxygen species and destructive enzymes. Healing proceeds only after the inflammation is controlled. On the opposite end of the spectrum, fibrosis is characterized by excessive matrix deposition, contraction and reduced remodeling.


Reference:



  1. Diegelmann, R.F. and Evans, M.C. Wound Healing: an overview of acute, fibrotic and delayed. Frontiers in Bioscience 9, 283-289, January 1, 2004.

  2. Diegelmann, R.F. Excessive neutrophils characterize non-healing pressure ulcers. Wound Repair and Regeneration 11:490-495, 2003.

  3. Chin, GA, Schultz, GS, Chegini, N and Diegelmann, RF: Biochemistry of Wound Healing in Wound Care Practice, 2nd edition; Sheffield, Smith & Fife, eds. Best Publishing Co., 2007

10:30 AM
11:30 AM
Luisa DiPietro - Inflammation in the Healing Wound: Friend or Foe

The appropriate function of inflammatory cells has generally been considered indispensable for successful wound healing. Multiple types of leukocytes migrate into healing wounds, and both the number and functions of these cells represent quantifiable components of the repair process. There is little argument that proper leukocyte activity assists in microbial decontamination of wounds. In addition, there are several logical arguments in support of a role for leukocytes in healing, even within sterile wounds. However, a number of recent studies challenge the established paradigm, and suggest that leukocytes are primarily detrimental to the healing process. Many questions remain, including the relative importance of the many interactions among inflammatory cells and other cell types in the wound, and the utility of modulating the inflammatory response at the site of an injury to improve the quality of healing.

01:30 PM
02:30 PM
John King - Mathematical modelling of tissue growth

Some mathematical models for the growth of biological tissue will be outlined, particular focus being given to the hole-closure problem that describes the behaviour as the tissue grows to fill in the entire domain.

Tuesday, March 10, 2009
Time Session
09:00 AM
10:00 AM
Sanjay Kumar - Cell-Matrix Mechanobiology: Biophysics, Therapeutics, and Biointerfacial Design

The ability of a living cell to control its three-dimensional structure is critical to normal tissue physiology. An individual cell derives this morphological control from its cytoskeleton, the three-dimensional network of biopolymers whose collective dynamics and mechanics define cell shape and enable cells to sense, process, and respond to a variety of physical cues in the environment, including mechanical force and the geometry and stiffness of the extracellular matrix (ECM). I will describe several experimental approaches my colleagues and I have taken to understanding how cytoskeletal polymers contribute to cellular mechanics and biophysical crosstalk with the ECM, which include the use of various micro/nanoscale technologies to probe the biophysical properties of contractile and adhesive structures within living cells. I will also discuss our recent efforts to determine the role of cell-ECM mechanobiology in influencing the growth and invasion of tumors of the nervous system, as well as our attempts to leverage cell-ECM mechanobiology to engineer cell fate and assembly in bottom-up tissue engineering systems.

10:00 AM
11:00 AM
John Ward - A mathematical model of normal and chronic wound development

N/A

01:00 PM
02:00 PM
John Dallon - Fibroblast Populated Collagen Lattices

Bell's introduction of the fibroblast populated collagen lattice (FPCL) has facilitated the study of collagen-cell interactions. As a result of the numerous modifications of the casting of FPCL's, the in vivo applications of these in vitro findings has been confusing. The experimental FPCL contraction findings will be viewed with regard to three proposed mechanisms responsible for lattice contraction. The cellular mechanisms responsible for generating FPCL contraction are: cell contraction, cell tractional forces related to cell locomotion, and initial cell elongation and spreading. I will introduce a mathematical model of FPCL and some preliminary results.

02:00 PM
03:00 PM
Pierre Coulombe - Intermediate Filaments and Wound Repair: Cellular Mechanics and Beyond

N/A

Wednesday, March 11, 2009
Time Session
09:00 AM
10:00 AM
Periannan Kuppusamy - Imaging of Tissue Oxygen Tension

N/A

10:00 AM
11:00 AM
Ronald Xu - Multimodal imaging for wound assessment and healing

Normal wound healing process involves the reparative phases of inflammation, proliferation, and remodeling. Interruption of any phase during the wound healing process may result in chronically unhealed wounds, amputation, or even patient death. Accurate characterization of structural, functional, and molecular changes at each phase of the wound healing process will help to quantitatively guide the therapeutic process and objectively assess the clinical outcome. However, many existing techniques and clinical procedures for wound assessment are qualitative and subjective. Limited tools are available for clinicians to systemically evaluate and document wound healing progression or regression.


We developed a portable multimodal imaging system for quantitative imaging of wound. The imaging system can be used for multiple clinical applications such as wound margin detection, hypoxia imaging, infection detection, perfusion assessment, and therapeutic guidance. We also developed a biodegradable and biocompatible carrier for targeted delivery of multiple contrast enhancement agents and drugs. In this talk, we will show our preliminary results and discuss about potential clinical applications.

01:00 PM
02:00 PM
Len Sander - Discrete and continuum models of wound healing

N/A

02:00 PM
03:00 PM
Min Zhao - Electric fields are a powerful directional signal in wound healing

Endogenous wound electric fields were measured at wounds centuries ago. Recent experiments provide compelling evidence that the wound electric fields may play a far more important role than generally perceived. Electric fields of the strength that can be measured in vivo override many well accepted directional cues (such as contact inhibition release, population pressure and chemical gradients) and guide the migration of epithelial cells in wound healing. Genetic study demonstrates that PI3 kinase/Akt and Pten are essential molecules in the response and are activated asymmetrically by the electric fields. Continuous medium perfusion and genetic decoupling experiments argue that the electric field-directed cell migration is not at least exclusively mediated by chemotaxis. The endogenous DC electric fields thus may represent a fundamental signaling mechanism to give cells and tissues a direction to heal and to regenerate in wound healing.

Thursday, March 12, 2009
Time Session
09:00 AM
10:00 AM
Sarah Waters - Mathematical models for tissue engineering applications

The broad goal of tissue engineers is to grow functional tissues and organs in the laboratory to replace those which have become defective through age, trauma, and disease and which can be used in drug screening applications. To achieve this goal, tissue engineers aim to control accurately the biomechanical and biochemical environment of the growing tissue construct, in order to engineer tissues with the desired composition, biomechanical and biochemical properties (in the sense that they mimic the in vivo tissue). The growth of biological tissue is a complex process, resulting from the interaction of numerous processes on disparate spatio-temporal scales. Advances in the understanding of tissue growth processes promise to improve the viability and suitability of the resulting tissue constructs. In this talk, I highlight some of our recent mathematical modelling work that aims to provide insights into tissue engineering applications.

10:00 AM
11:00 AM
Marc Basson - Intestinal epithelial wound healing: Influence of diameter, depth, duration, and deformation

Gut mucosal injury ranges from the subcellular membrane defects and microscopic erosions engendered by interaction with luminal contents and which normally heal within seconds or minutes to large deep ulcerations that may never heal. The biology of healing depends upon the nature of the injury as well as the mucosal milieu. Mucosal healing is itself known to be regulated by a variety of growth factors and cytokines. However, new evidence will be reviewed that suggests that the healing process may also be influenced by physical forces such as repetitive deformation and increased extracellular pressure in a complex frequency- and amplitude-dependent manner.

10:00 AM
11:00 AM
Kevin Kesseler - A Predictive Mathematical Model of the G2 DNA Damage Checkpoint

We have constructed a mathematical model of the protein-protein interactions and protein modifications that comprise the G2 to M transition and the G2 DNA damage checkpoint. This model was constructed from interactions known to play a role in these processes. This construction allows us to determine if behaviors observed in this system can be accounted for by the known interactions or if additional mechanisms are required, giving us insight into how the G2 to M transition and G2 checkpoint operate. Additionally, this model provides a platform to rapidly simulate experiments to help determine what physical experiments might be significant such as the model prediction that depletion of the protein Wee1 will result in an accumulation of inactive MPF (a complex of Cyclin B and CDK1 which triggers mitosis) in the nucleus during a DNA damage arrest of the cell cycle. In addition, the model provides a means to investigate situations which are difficult or impossible to reproduce experimentally such as the depletion or overexpression of several proteins simultaneously.

01:00 PM
02:00 PM
Geoffrey Gurtner - Understanding the importance of progenitor cell mediated repair following injury

Neovascularization is essential for normal tissue repair. Bone marrow (BM)-derived vascular progenitor cells capable of contributing to new vessel formation have been postulated to play a critical role in ischemic neovascularization and are thought to have therapeutic potential as cell-based vectors to augment neovascularization following injury. However, the specific lineage of these cells remains unclear. Moreover early clinical trials using whole BM-derived cells to enhance neovascularization have yielded disappointing results, possibly due to heterogeneity in this population1, 2 More recently, mesenchymal stem cells (MSCs) from bone marrow or fat have been proposed as promising agents to improve the response to injury and promote tissue regeneration. However, once again the lineage and mechanism of action of these cells remains unknown3-5. It seems likely that a more precise characterization of these cells will be required to develop cell based therapeutics for regenerative medicine.


We have developed a novel technique for high-throughput single cell gene expression analysis (microfluidic large-scale integration) to characterize putative stem cells (ESCs, MSCs). Using a panel of 48 genes contained on a microfluidic chip, we are able to define the transcriptional activity of genes important for pluripotency, differentiation fates and cell cycle regulation in every cell individually in any given population. To analyze the data we employ fuzzy c-means clustering, optimized with Akaike Information Criterion (AIC), to detect discrete sub-populations and generate associated characteristic marker profiles. Using this approach we have developed a standardized metric for comparison of population heterogeneity based on transcriptional variation over relevant gene sets. In a murine model of diabetes, where alterations in progenitor cells have been suggested in human and animal systems, we are able to demonstrate reduced expression of several important stem cell genes within BM-derived MSCs and deletion of entire sub-populations of progenitors. These results suggest that derangements in specific progenitor sub-populations may underlie the impairments in neovascularization characteristic of diabetes.


References:



  1. Rosenzweig A. Cardiac cell therapy--mixed results from mixed cells. N Engl J Med. 2006;355:1274-1277.

  2. Schachinger V, Erbs S, Elsasser A, et al. Intracoronary bone marrow-derived progenitor cells in acute myocardial infarction. N Engl J Med. 2006;355:1210-1221.

  3. Fu X, Li H. Mesenchymal stem cells and skin wound repair and regeneration: possibilities and questions. Cell and Tissue Research. 2009;335:317-321.

  4. Herdrich BJ, Lind RC, Liechty KW. Multipotent adult progenitor cells: their role in wound healing and the treatment of dermal wounds. Cytotherapy. 2008;10:543-550.

  5. Wu Y, Wang J, Scott PG, et al. Bone marrow-derived stem cells in wound healing: a review. Wound Repair Regen. 2007;15 Suppl 1:S18-26.


 


Support: NIH: RO1 AG-25016, RO1 DK-074095, DoD #W81XWH-08-2-0032-3

02:00 PM
03:00 PM
Benjamin Yu - How to talk to developmental organizers during wound repair: a strategy to restore size and shape of skin

A long term goal of regenerative medicine is to restore normal size, shape and function of organs following injury or disease. During embryonic development, these same parameters are determined by groups of cells called "organizing centers," whose primary functions are to secrete growth factors and support patterned growth. Organizing centers demonstrate a remarkable level of self-regulation, preventing insufficient or overgrowth of tissue. Surprisingly, many organizing centers are even capable of reforming after experimental ablation. Understanding the robust developmental mechanisms that regulate organizing centers may be critical to achieving the goals of wound repair. The role and regulation of organizing centers in the skin is not completely known. Here we discuss the organizing centers of the skin and show that a key homeostatic mechanism in maintaining organizing centers in the skin is mediated through the RAS/MAPK pathway. Using gain and loss-of-function genetic models, we find that RAS regulates skin surface area, hair follicle size, and other ectodermal organs. RAS/MAPK signals are interpreted through a second organizing center in the hair follicle, which translates increased or decreased RAS signals into reciprocal changes in Sonic Hedgehog expression levels. We discuss these results in the context of a family of human congenital diseases collectively called RAS/MAPK syndromes, which support the model that RAS signal strength plays a role in regulating organizing centers and pattern in human skin. Lastly, we propose that manipulating organizing centers through RAS/MAPK signaling could be used to re-create normal amounts of tissue during wound repair.

04:00 PM
05:00 PM
Anie Philip - Regulation of TGF-beta singaling in skin cells

Of the myriad of growth factors implicated in wound healing, TGF-beta has the broadest spectrum of effects, promoting re-epithelialization, granulation tissue formation and tissue remodeling, as have been demonstrated in animal models. However, clinical results in humans have been modest, possibly due to inappropriate timing of administration or unavailability of the delivered factor. An alternative approach would be to manipulate endogenous TGF-beta action locally using regulatory molecules. Our group has recently identified a novel TGF-beta co-receptor, CD109, which negatively regulates TGF-beta signaling and inhibits extracellular matrix synthesis in skin cells. Our results indicate that the mechanism by which CD109 exerts this effect involves targeting TGF-beta signaling receptors for degradation. To examine CD109 function in vivo, we generated transgenic mice overexpressing CD109 in the epidermis. Using a bleomycin-induced skin fibrosis model, we show that the transgenic mice display diminished TGF-beta signaling, more organized collagen deposition and decreased dermal thickness, as compared to their wild-type littermates. Together these results demonstrate that CD109 is an important regulator of TGF-beta signaling, and may represent a potential molecular target for the treatment of skin disorders such as hypertrophic scarring.

Friday, March 13, 2009
Time Session
09:00 AM
10:00 AM
Philip Maini - The role of angiogenesis in wound healing: continuum and multiscale approaches

N/A

Name Email Affiliation
Agarwal, Gunjan agarwal.60@osu.edu Biomedical Engineering, The Ohio State University
Agarwal, Sudha agarwal.61@osu.edu Oral Biology, The Ohio State University
Aguda, Baltazar bdaguda@gmail.com MBI - Long Term Visitor, The Ohio State University
Arciero, Julia jarciero@pitt.edu Mathematics, University of Pittsburgh
Banerjee, Jaideep banerjee.42@osu.edu Surgery, The Ohio State University
Bartlett, Jeffrey jeffrey.bartlett@nationwidechildrens.org Pediatrics, Gene Therapy Center, Nationwide Children's Hospital and OSU
Basson, Marc mdbasson@gmail.com Departments of Surgery, Anatomy and Cell Biology, Wayne State University
Bentley, Katie katie.bentley@cancer.org.uk pathology, Beth Israel Hospital, Harvard Medical School
Bergdall, Valerie bergdall.1@osu.edu ULAR/VPM, The Ohio State University
Best, Janet jbest@mbi.osu.edu
Biswas, Sabyasachi biswas.16@osu.edu Department of Surgery, The Ohio State University
Boushaba, Khalid boushaba@iastate.edu MBI - Long Term Visitor, The Ohio State University
Byrne, Helen helen.byrne@nottingham.ac.uk Centre for Mathematical Medicine and Biology, University of Nottingham
Coskun, Huseyin hcusckun@mbi.osu.edu MBI - Postdoc, The Ohio State University
Coulombe, Pierre coulombe@jhmi.edu Biochemistry and Molecular Biology, Johns Hopkins University
Dallon, John dallon@math.byu.edu Department of Mathematics, Brigham Young University
Day, Judy jday@mbi.osu.edu MBI - Postdoc, The Ohio State University
Diegelmann , Bob rdiegelm@vcu.edu Biochemistry, Anatomy & Emergency Medicine, Virginia Commonwealth University
DiPietro, Luisa ldipiet@uic.edu Center for Wound Healing & Tissue Regeneration, University of California, Irvine
Druhan, Lawrence lawrence.druhan@osumc.edu Davis Heart and Lung Research Institute, The Ohio State University
Eubank, Tim tim.eubank@osumc.edu Internal Medicine/Pulmonary Medicine, The Ohio State University
Fall, Chris fall@uic.edu MBI - Long Term Visitor, The Ohio State University
Faraimunashe, Chirove chirove_faraimunashe@yahoo.com MBI - Long Term Visitor, The Ohio State University
Federico, Paula pfederico@mbi.osu.edu MBI - Postdoc, The Ohio State University
Friedman, Avner afriedman@mbi.osu.edu MBI - Long Term Visitor, The Ohio State University
Gooch, Keith gooch.20@osu.edu Biomedical Engineering, The Ohio State University
Gordillo, Gayle gayle.gordillo@osumc.edu Plastic Surgery, The Ohio State University
Green, Edward egreen@mbi.osu.edu MBI - Postdoc, The Ohio State University
Grzybowski, Deborah grzybowski.3@osu.edu Department of Ophthalmology, The Ohio State University
Gurtner, Geoffrey ggurtner@stanford.edu Department of Surgery, Stanford University
Hamilton, Ian hamilton.598@osu.edu MBI - Long Term Visitor, The Ohio State University
Hansford, Derek hansford.4@osu.edu Biomedical Engineering, The Ohio State University
Hovmoller, Rasmus rhovmoller@mbi.osu.edu MBI - Postdoc, The Ohio State University
Hunt, Thomas thomas.hunt@ucsfmedctr.org Department of Surgery, University of California Medical Center
Ismailov, Rovshan rovshani@yahoo.com Department of Epidemiology, University of Pittsburgh
Januszyk, Michael januszyk@uchicago.edu Department of Surgery, Stanford University
Kao, Chiu-Yen kao.71@osu.edu MBI - Long Term Visitor, The Ohio State University
Kawasaki, Haruhisa haruhisa.kawasaki@osumc.edu Department of Pathology, The Ohio State University
Kesseler, Kevin kevin@kesseler.net Dept. of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill
Kim, Yangjin ykim@mbi.osu.edu MBI - Postdoc, The Ohio State University
King, John john.king@nottingham.ac.uk; School of Mathematical Sciences, University of Nottingham
Kollar, Richard kollar@umich.edu Department of Mathematics, University of Michigan
Kumar , Sanjay skumar@berkeley.edu Department of Bioengineering, University of California, Berkeley
Kuppusamy, Periannan periannan.kuppusamy@osumc.edu Internal Medicine & Biomedical Engineering, The Ohio State University
Leblebicioglu, Binnaz leblebicioglu.1@osu.edu Periodontology, The Ohio State University
Liu, Paul pliu@rwmc.org Chairman of Surgery, Roger Williams Medical Center
Lou, Yuan lou@math.ohio-state.edu MBI - Long Term Visitor, The Ohio State University
Lungu, Edward lunguem@mopipi.ub.bw MBI - Long Term Visitor, The Ohio State University
Maini, Philip maini@maths.ox.ac.uk Centre for Mathematical Biology, Mathematical Institute
Mani, Raj rm1@soton.ac.uk R&D Lead Division 5, Southampton University Hospitals Trust
McDaniel, Jodi mcdaniel.561@osu.edu College of Nursing, The Ohio State University
McDougall, Steven steve.mcdougall@pet.hw.ac.uk Institute of Petroleum Engineering, Heriot-Watt University
Moldovan, Leni leni.moldovan@osumc.edu Davis Heart and Lung Research Institute, The Ohio State University
Moldovan, Nicanor moldovan.6@osu.edu Internal Medicine/Cardiology, The Ohio State University
Oster, Andrew aoester@mbi.osu.edu MBI - Postdoc, The Ohio State University
Parent, Allison parent.14@osu.edu Department of Pathology, The Ohio State University
Philip, Anie anie.philip@mcgill.ca Director, Plastic Surgery Research, McGill University, Macdonald Campus
Powell, Heather powell.299@osu.edu Biomedical Engineering, The Ohio State University
Rempe, Michael mrempe@mbi.osu.edu MBI - Postdoc, The Ohio State University
Reynolds, Angela angelareynolds@gmail.com Mathematics, Virginia Commonwealth University
Roy, Sashwati sashwati.roy@osumc.edu Department of Surgery, The Ohio State University
Sander, Len len.sander@gmail.com Department of Physics, University of Michigan
Schley, Jeremiah j.schley@gmail.com Biomedical Engineering, The Ohio State University
Schmidt, Deena dschmidt@mbi.osu.edu
Schricker, Scott schricker.1@osu.edu College of Dentistry, The Ohio State University
Schugart, Richard richard.schugart@wku.edu Department of Mathematics, Western Kentucky University
Segal, Rebecca rasegal@vcu.edu Mathematics, Virginia Commonwealth University
Sen, Chandan Chandan.Sen@osumc.edu Depts of Surgery & Molecular & Cellular Biochemistry, The Ohio State University
Sheehan, Peter psheehan@verizon.net Endocrinologist, Mount Sinai School of Medicine, CUNY
Sheridan, John sheridan.1@osu.edu Oral Biology, The Ohio State University
Siegal-Gaskins, Dan dsiegal-gaskins@mbi.osu.edu
Stevenson, Mark mstevenson@bme.ohio-state.edu Biomedical Engineering, The Ohio State University
Stone, Carmen carmen.cantemir@osumc.edu Cancer Genetics, The Ohio State University
Su, Jianzhong su@uta.edu Department of Mathematics, University of Texas
Sun, Shuying ssun@mbi.osu.edu MBI - Postdoc, The Ohio State University
Sutradhar, Alok alok.sutradhar@osumc.edu Surgery (Plastic Surgery), The Ohio State University
Szomolay, Barbara b.szomolay@imperial.ac.uk MBI - Postdoc, The Ohio State University
Tamama, Kenichi (Ken) kenichi.tamama@osumc.edu Department of Pathology, The Ohio State University
Ward, John john.ward@lboro.ac.uk School of Mathematics, Loughborough University
Waters , Sarah waters@maths.ox.ac.uk Mathematical Institute, University of Oxford
Wilgus, Traci traci.wilgus@osumc.edu Department of Pathology, The Ohio State University
Wulff, Brian wulff.12@osu.edu Department of Pathology, The Ohio State University
Xiong, Wei xiong@ima.umn.edu IMA, Institute for Math and Its Applications
Xu, Ronald xu.202@osu.edu Biomedical Engineering, The Ohio State University
Xue, Chuan cxue@mbi.osu.edu MBI - Postdoc, The Ohio State University
Yang, Le yangl4@vcu.edu Integrated Life Sciences, Virginia Commonwealth University
Yu, Benjamin byu@ucsd.edu Division of Dermatology, University of California, San Diego
Zhao, Min minzhao@ucdavis.edu School of Medicine, University of California, Davis
Zheng, Fengyuan zheng.504@osu.edu Restorative Dentistry, The Ohio State University
Zweier, Jay jay.zweier@osumc.edu Davis Heart and Lung Research Institute, The Ohio State University
Intestinal epithelial wound healing: Influence of diameter, depth, duration, and deformation

Gut mucosal injury ranges from the subcellular membrane defects and microscopic erosions engendered by interaction with luminal contents and which normally heal within seconds or minutes to large deep ulcerations that may never heal. The biology of healing depends upon the nature of the injury as well as the mucosal milieu. Mucosal healing is itself known to be regulated by a variety of growth factors and cytokines. However, new evidence will be reviewed that suggests that the healing process may also be influenced by physical forces such as repetitive deformation and increased extracellular pressure in a complex frequency- and amplitude-dependent manner.

Intermediate Filaments and Wound Repair: Cellular Mechanics and Beyond

N/A

Fibroblast Populated Collagen Lattices

Bell's introduction of the fibroblast populated collagen lattice (FPCL) has facilitated the study of collagen-cell interactions. As a result of the numerous modifications of the casting of FPCL's, the in vivo applications of these in vitro findings has been confusing. The experimental FPCL contraction findings will be viewed with regard to three proposed mechanisms responsible for lattice contraction. The cellular mechanisms responsible for generating FPCL contraction are: cell contraction, cell tractional forces related to cell locomotion, and initial cell elongation and spreading. I will introduce a mathematical model of FPCL and some preliminary results.

Overview of Wound Healing

The normal healing response begins the moment the tissue is injured. As the blood components spill into the site of injury, the platelets come into contact with exposed collagen and other elements of the extracellular matrix. This contact triggers the platelets to release clotting factors as well as essential growth factors and cytokines such as platelet-derived growth factor (PDGF) and transforming growth factor beta (TGF-ß). Following hemostasis, the neutrophils then enter the wound site and begin the critical task of phagocytosis to remove foreign materials, bacteria and damaged tissue. As part of this inflammatory phase, the macrophages appear and continue the process of phagocytosis as well as releasing more PDGF and TGFß. Once the wound site is cleaned out, fibroblasts migrate in to begin the proliferative phase and deposit new extracellular matrix. The new collagen matrix then becomes cross-linked and organized during the final remodeling phase. In order for this efficient and highly controlled repair process to take place, there are numerous cell-signaling events that are required. In pathologic conditions such as non-healing pressure ulcers, this efficient and orderly process is lost and the ulcers are locked into a state of chronic inflammation characterized by abundant neutrophil infiltration with associated reactive oxygen species and destructive enzymes. Healing proceeds only after the inflammation is controlled. On the opposite end of the spectrum, fibrosis is characterized by excessive matrix deposition, contraction and reduced remodeling.


Reference:



  1. Diegelmann, R.F. and Evans, M.C. Wound Healing: an overview of acute, fibrotic and delayed. Frontiers in Bioscience 9, 283-289, January 1, 2004.

  2. Diegelmann, R.F. Excessive neutrophils characterize non-healing pressure ulcers. Wound Repair and Regeneration 11:490-495, 2003.

  3. Chin, GA, Schultz, GS, Chegini, N and Diegelmann, RF: Biochemistry of Wound Healing in Wound Care Practice, 2nd edition; Sheffield, Smith & Fife, eds. Best Publishing Co., 2007

Inflammation in the Healing Wound: Friend or Foe

The appropriate function of inflammatory cells has generally been considered indispensable for successful wound healing. Multiple types of leukocytes migrate into healing wounds, and both the number and functions of these cells represent quantifiable components of the repair process. There is little argument that proper leukocyte activity assists in microbial decontamination of wounds. In addition, there are several logical arguments in support of a role for leukocytes in healing, even within sterile wounds. However, a number of recent studies challenge the established paradigm, and suggest that leukocytes are primarily detrimental to the healing process. Many questions remain, including the relative importance of the many interactions among inflammatory cells and other cell types in the wound, and the utility of modulating the inflammatory response at the site of an injury to improve the quality of healing.

Understanding the importance of progenitor cell mediated repair following injury

Neovascularization is essential for normal tissue repair. Bone marrow (BM)-derived vascular progenitor cells capable of contributing to new vessel formation have been postulated to play a critical role in ischemic neovascularization and are thought to have therapeutic potential as cell-based vectors to augment neovascularization following injury. However, the specific lineage of these cells remains unclear. Moreover early clinical trials using whole BM-derived cells to enhance neovascularization have yielded disappointing results, possibly due to heterogeneity in this population1, 2 More recently, mesenchymal stem cells (MSCs) from bone marrow or fat have been proposed as promising agents to improve the response to injury and promote tissue regeneration. However, once again the lineage and mechanism of action of these cells remains unknown3-5. It seems likely that a more precise characterization of these cells will be required to develop cell based therapeutics for regenerative medicine.


We have developed a novel technique for high-throughput single cell gene expression analysis (microfluidic large-scale integration) to characterize putative stem cells (ESCs, MSCs). Using a panel of 48 genes contained on a microfluidic chip, we are able to define the transcriptional activity of genes important for pluripotency, differentiation fates and cell cycle regulation in every cell individually in any given population. To analyze the data we employ fuzzy c-means clustering, optimized with Akaike Information Criterion (AIC), to detect discrete sub-populations and generate associated characteristic marker profiles. Using this approach we have developed a standardized metric for comparison of population heterogeneity based on transcriptional variation over relevant gene sets. In a murine model of diabetes, where alterations in progenitor cells have been suggested in human and animal systems, we are able to demonstrate reduced expression of several important stem cell genes within BM-derived MSCs and deletion of entire sub-populations of progenitors. These results suggest that derangements in specific progenitor sub-populations may underlie the impairments in neovascularization characteristic of diabetes.


References:



  1. Rosenzweig A. Cardiac cell therapy--mixed results from mixed cells. N Engl J Med. 2006;355:1274-1277.

  2. Schachinger V, Erbs S, Elsasser A, et al. Intracoronary bone marrow-derived progenitor cells in acute myocardial infarction. N Engl J Med. 2006;355:1210-1221.

  3. Fu X, Li H. Mesenchymal stem cells and skin wound repair and regeneration: possibilities and questions. Cell and Tissue Research. 2009;335:317-321.

  4. Herdrich BJ, Lind RC, Liechty KW. Multipotent adult progenitor cells: their role in wound healing and the treatment of dermal wounds. Cytotherapy. 2008;10:543-550.

  5. Wu Y, Wang J, Scott PG, et al. Bone marrow-derived stem cells in wound healing: a review. Wound Repair Regen. 2007;15 Suppl 1:S18-26.


 


Support: NIH: RO1 AG-25016, RO1 DK-074095, DoD #W81XWH-08-2-0032-3

A Predictive Mathematical Model of the G2 DNA Damage Checkpoint

We have constructed a mathematical model of the protein-protein interactions and protein modifications that comprise the G2 to M transition and the G2 DNA damage checkpoint. This model was constructed from interactions known to play a role in these processes. This construction allows us to determine if behaviors observed in this system can be accounted for by the known interactions or if additional mechanisms are required, giving us insight into how the G2 to M transition and G2 checkpoint operate. Additionally, this model provides a platform to rapidly simulate experiments to help determine what physical experiments might be significant such as the model prediction that depletion of the protein Wee1 will result in an accumulation of inactive MPF (a complex of Cyclin B and CDK1 which triggers mitosis) in the nucleus during a DNA damage arrest of the cell cycle. In addition, the model provides a means to investigate situations which are difficult or impossible to reproduce experimentally such as the depletion or overexpression of several proteins simultaneously.

Mathematical modelling of tissue growth

Some mathematical models for the growth of biological tissue will be outlined, particular focus being given to the hole-closure problem that describes the behaviour as the tissue grows to fill in the entire domain.

Cell-Matrix Mechanobiology: Biophysics, Therapeutics, and Biointerfacial Design

The ability of a living cell to control its three-dimensional structure is critical to normal tissue physiology. An individual cell derives this morphological control from its cytoskeleton, the three-dimensional network of biopolymers whose collective dynamics and mechanics define cell shape and enable cells to sense, process, and respond to a variety of physical cues in the environment, including mechanical force and the geometry and stiffness of the extracellular matrix (ECM). I will describe several experimental approaches my colleagues and I have taken to understanding how cytoskeletal polymers contribute to cellular mechanics and biophysical crosstalk with the ECM, which include the use of various micro/nanoscale technologies to probe the biophysical properties of contractile and adhesive structures within living cells. I will also discuss our recent efforts to determine the role of cell-ECM mechanobiology in influencing the growth and invasion of tumors of the nervous system, as well as our attempts to leverage cell-ECM mechanobiology to engineer cell fate and assembly in bottom-up tissue engineering systems.

Imaging of Tissue Oxygen Tension

N/A

The role of angiogenesis in wound healing: continuum and multiscale approaches

N/A

Regulation of TGF-beta singaling in skin cells

Of the myriad of growth factors implicated in wound healing, TGF-beta has the broadest spectrum of effects, promoting re-epithelialization, granulation tissue formation and tissue remodeling, as have been demonstrated in animal models. However, clinical results in humans have been modest, possibly due to inappropriate timing of administration or unavailability of the delivered factor. An alternative approach would be to manipulate endogenous TGF-beta action locally using regulatory molecules. Our group has recently identified a novel TGF-beta co-receptor, CD109, which negatively regulates TGF-beta signaling and inhibits extracellular matrix synthesis in skin cells. Our results indicate that the mechanism by which CD109 exerts this effect involves targeting TGF-beta signaling receptors for degradation. To examine CD109 function in vivo, we generated transgenic mice overexpressing CD109 in the epidermis. Using a bleomycin-induced skin fibrosis model, we show that the transgenic mice display diminished TGF-beta signaling, more organized collagen deposition and decreased dermal thickness, as compared to their wild-type littermates. Together these results demonstrate that CD109 is an important regulator of TGF-beta signaling, and may represent a potential molecular target for the treatment of skin disorders such as hypertrophic scarring.

Discrete and continuum models of wound healing

N/A

A mathematical model of normal and chronic wound development

N/A

Mathematical models for tissue engineering applications

The broad goal of tissue engineers is to grow functional tissues and organs in the laboratory to replace those which have become defective through age, trauma, and disease and which can be used in drug screening applications. To achieve this goal, tissue engineers aim to control accurately the biomechanical and biochemical environment of the growing tissue construct, in order to engineer tissues with the desired composition, biomechanical and biochemical properties (in the sense that they mimic the in vivo tissue). The growth of biological tissue is a complex process, resulting from the interaction of numerous processes on disparate spatio-temporal scales. Advances in the understanding of tissue growth processes promise to improve the viability and suitability of the resulting tissue constructs. In this talk, I highlight some of our recent mathematical modelling work that aims to provide insights into tissue engineering applications.

Multimodal imaging for wound assessment and healing

Normal wound healing process involves the reparative phases of inflammation, proliferation, and remodeling. Interruption of any phase during the wound healing process may result in chronically unhealed wounds, amputation, or even patient death. Accurate characterization of structural, functional, and molecular changes at each phase of the wound healing process will help to quantitatively guide the therapeutic process and objectively assess the clinical outcome. However, many existing techniques and clinical procedures for wound assessment are qualitative and subjective. Limited tools are available for clinicians to systemically evaluate and document wound healing progression or regression.


We developed a portable multimodal imaging system for quantitative imaging of wound. The imaging system can be used for multiple clinical applications such as wound margin detection, hypoxia imaging, infection detection, perfusion assessment, and therapeutic guidance. We also developed a biodegradable and biocompatible carrier for targeted delivery of multiple contrast enhancement agents and drugs. In this talk, we will show our preliminary results and discuss about potential clinical applications.

How to talk to developmental organizers during wound repair: a strategy to restore size and shape of skin

A long term goal of regenerative medicine is to restore normal size, shape and function of organs following injury or disease. During embryonic development, these same parameters are determined by groups of cells called "organizing centers," whose primary functions are to secrete growth factors and support patterned growth. Organizing centers demonstrate a remarkable level of self-regulation, preventing insufficient or overgrowth of tissue. Surprisingly, many organizing centers are even capable of reforming after experimental ablation. Understanding the robust developmental mechanisms that regulate organizing centers may be critical to achieving the goals of wound repair. The role and regulation of organizing centers in the skin is not completely known. Here we discuss the organizing centers of the skin and show that a key homeostatic mechanism in maintaining organizing centers in the skin is mediated through the RAS/MAPK pathway. Using gain and loss-of-function genetic models, we find that RAS regulates skin surface area, hair follicle size, and other ectodermal organs. RAS/MAPK signals are interpreted through a second organizing center in the hair follicle, which translates increased or decreased RAS signals into reciprocal changes in Sonic Hedgehog expression levels. We discuss these results in the context of a family of human congenital diseases collectively called RAS/MAPK syndromes, which support the model that RAS signal strength plays a role in regulating organizing centers and pattern in human skin. Lastly, we propose that manipulating organizing centers through RAS/MAPK signaling could be used to re-create normal amounts of tissue during wound repair.

Electric fields are a powerful directional signal in wound healing

Endogenous wound electric fields were measured at wounds centuries ago. Recent experiments provide compelling evidence that the wound electric fields may play a far more important role than generally perceived. Electric fields of the strength that can be measured in vivo override many well accepted directional cues (such as contact inhibition release, population pressure and chemical gradients) and guide the migration of epithelial cells in wound healing. Genetic study demonstrates that PI3 kinase/Akt and Pten are essential molecules in the response and are activated asymmetrically by the electric fields. Continuous medium perfusion and genetic decoupling experiments argue that the electric field-directed cell migration is not at least exclusively mediated by chemotaxis. The endogenous DC electric fields thus may represent a fundamental signaling mechanism to give cells and tissues a direction to heal and to regenerate in wound healing.