ACL Group | PCL Group | MCL Group
Shoulder Group | Hand and Upper Extremity Group
Research Objectives:Our research is primarily in the area of cellular and tissue mechanobiology. We are specially interested in studying cellular biological responses and extracellular matrix remodeling under repetitive mechanical loading, and improving the biological, biochemical and biomechanical properties of the healing tendon and ligament with functional tissue engineering. In addition, we are also interested in probing and controlling individual cellular phenotype expression with MEMS technology.
- "Altered mechanical stretching of the human aortic endothelial cells results in dysfunctional cellular responses." PI: James H-C. Wang, Ph.D., 2/1/02 - 1/31/04, The Competitive Medical Research Fund (CMRF), UPMC.
- "Bioengineering study of tendinitis." PI: James H-C. Wang, Ph.D., 9/1/01-8/31/04, Whitaker Foundation.
- "Tendinitis is due to repetitive exposure of PGE2 to tendon fibroblasts." PI: James H-C. Wang, Ph.D. 7/1/01-6/30/02, Albert B. Ferguson, JR., MD Orthopaedic Fund.
- "Inflammatory reaction and apoptosis of tendon fibroblasts." PI: James H-C. Wang, Ph.D. 7/1/01 - 6/30/04, Arthritis Foundation.
- "In vitro model study of the molecular mechanism of tendinitis". PI: James H-C. Wang, Ph.D. 3/01/01-2/28/04, NIH.
A multidisciplinary study of the pathophysiology of tendinitis:
The overall goal of this study is to elucidate the pathophysiological mechanisms for tendinitis using a novel in vitro model and an animal model. Our working hypothesis is that tendon fibroblasts are responsible for the development of tendinitis by producing PGE2, which is upregulated by increased expression levels of PLA2, COX-1 and COX-2, and that high levels of PGE2 cause dysfunction of the tendon fibroblasts, thus resulting in pathophysiological changes in tendons. The specific aims of this project are: 1) to investigate the role of PLA2 and COX expression in the production of PGE2 by human tendon fibroblasts under repetitive mechanical stretching using a novel in vitro model; 2) to investigate the effect of stretching-induced PGE2 on proliferation and collagen synthesis of the human tendon fibroblasts using a novel in vitro model; and 3) to determine the effect of repeated exposure of the patellar tendon to PGE2 on its biological, biochemical, and biomechanical properties in a rabbit model. To accomplish these aims, we will use a multidisciplinary approach based on mechano-biology, molecular biology and biomechanics. When completed, this study will provide insights into the pathophysiological mechanisms for tendinitis at the cellular and molecular levels. It will also provide clinically valuable data about the effect of repetitive inflammation due to PGE2 on the tendon structure and function, which will help develop strategies to prevent and treat tendinitis effectively.
Microarray (Gene-Chip) analysis of differential gene expression in human tendon fibroblasts subjected to cyclic mechanical stretching:
Currently, our understanding of the molecular mechanisms for repetitive motion disorders such as tendinitis is inadequate. This is due to the fact that there is the lack of information regarding how mechanical forces regulate multiple inflammatory genes in the tendon fibroblasts. The rapid development of molecular and bioengineering technologies has made it possible to examine expression of a large number of genes simultaneously. One such powerful tool is microarray technology. This approach has the potential to discover new marker genes in the tendon fibroblasts in response to repetitive mechanical loading. Our working hypothesis in this study is that high levels of PGE2 produced by the stretched human tendon fibroblasts mediate the expression of inflammatory genes (IL-1a, IL-1b, IL-2, IL-6, and TNFa) in an autocrine fashion. To test the hypothesis, we will use the microarray to examine expression profiles of these inflammatory genes under cyclic stretching conditions. This investigation has the potential to expedite our understanding of the role of the PGE2 in tendon pathophysiology due to repetitive mechanical loading. It also allows the development of new hypotheses concerning genetic networks regulated by mechanical loads on the tendon.
Regulation of tendon fibroblast contraction to enhance biological, biochemical and biomechanical properties of the healing tendon:
Tendon injuries often result in the formation of scar tissue, which is characterized by over-produced, disorganized collagen matrix. Cell contraction is thought to contribute to scar tissue formation. Transforming growth factor-b1 (TGF-b1) is linked with increasing fibroblast contraction and scar formation, whereas TGF-b3 is thought to reduce scarring in skin tissue. The overall objective of this study is then to determine the role of TGF-b1 and TGF-b3 in tendon scar tissue formation. Our working hypothesis is that TGF-b1 and TGF-b3 differentially regulate tendon fibroblast contraction and thereby differentially regulate DNA and extracellular matrix production of the cells. To test the hypothesis, a fibroblast-populated collagen gel (FPCG) model will be used to examine cellular contraction with the treatment of TGF-b1 and TGF-b3. In addition, DNA and collagen syntheses will be determined. The in vitro study will be further extended to in vivo study, in which cellular contraction in the wound tendon in a rabbit will be controlled, so that biological, biochemical and biomechanical properties of the healing tendon may be improved.
Application of cellular force monitor to studying extracellular matrix remodeling by mechanical forces:
It is well established that connective tissues adapt to changes in their mechanical environment. A typical example is the "trajectorial hypothesis" of Wolff, which suggests that trabeculae align in response to the principle compressive and tensile stresses. However, the cellular and molecular mechanisms responsible for the mechanical-force regulated extracellular matrix remodeling is not well understood. We have developed a cellular force monitor (CFM) to study the effect of altered mechanical forces on the biosynthetic response of tendon fibroblasts embedded within a collagen type-I matrix and the matrix remodeling. Using the CFM to apply precisely controlled "micro-forces" to the matrix, the expression levels of procollagen type-I, -III and -V, elastin, fibronectin, as well as expression of collagenase levels, will be measured. The results of this study will provide new insights into the molecular mechanisms for regulation of extracellular matrix by mechanical forces.
The effects of cell organization on biochemical compositions of extracellular matrix:
Cells are responsible for establishing and remodeling of extracellular matrix. However, how cell organization influences structure and biochemical compositions of extracellular matrix is not well understood. We have developed an in vitro model with which MC3T3 cells are grown in microgrooved surfaces instead of commonly used smooth culture surfaces. Using this model, we have shown that cells are aligned in the microgrooves, and the aligned cells produce aligned collagen matrix. In this study, we will test the hypothesis that cell organization/alignment affects biochemical compositions of the extracellular matrix. Collagen type-I, -III, and -V gene and protein expression levels will be measured with PCR and Western blot. When completed, the study will shed light on the mechanism for formation of the disorganized collagen matrix seen in healing tendons or ligaments. It will also provide a base-line data to study the possible synergistic effects of cell organization and applied mechanical forces on the cells.
A novel model system for the study of cellular biological responses under controlled mechanical stretching (A). The system consists of a stretching apparatus and silicone dishes (arrow) containing microgrooved culture surfaces, as shown by the scanning electron microphotograph (B).
A cell force monitor system (CFM) in the incubator. The system is custom made to study cellular and molecular mechanisms of soft tissue wound healing.