C. D. Marshall1, M. S. Hu2, R. C. Ransom1, L. A. Barnes1, A. A. Moore1,3, T. D. Leavitt1, H. P. Lorenz1, M. T. Longaker1 1Stanford University School Of Medicine,Department Of Surgery,Stanford, CA, USA 2University Of Hawai’i John A. Burns School Of Medicine,Department Of Surgery,Honolulu, HI, USA 3Brigham And Women’s Hospital,Department Of Surgery,Boston, MA, USA
Introduction:
Abdominal adhesions resulting from surgery are the most common cause of small bowel obstruction. Their presence complicates subsequent operations and contributes to infertility. Adhesion formation depends on fibroblast collagen production. The precise cell populations and molecular signals that induce adhesion formation are not known. As a result, no effective pharmaceutical anti-adhesion therapies exist. An improved understanding of the cellular and molecular basis of adhesions would allow for the development of improved treatments.
Methods:
Laparotomy was performed on wild type mice and the cecum and abdominal sidewall were abraded using sandpaper. The resulting adhesion tissue was examined with immunohistochemistry and was digested with collagenase, allowing adhesion fibroblasts to be subjected to immunocytochemical analysis. In an abdominal wall transplant model, the abdominal muscular wall of a pan-RFP mouse was sutured onto the inner surface of the abdominal wall of a pan-GFP mouse before adhesions were created. Fluorescent imaging of adhesion tissue forming within the red-green interface was used to determine the origin of adhesion cells. Finally, adhesions were created in transgenic inducible multi-color Rainbow mice, allowing for the assessment of adhesion cell clonality.
Results:
Adhesion fibroblasts expressed known fibroblast markers: vimentin, fibronectin, FSP, PDGFRα , and collagen. Additionally, many fibroblasts expressed the myofibroblast and smooth muscle marker α SMA, the mechanical transduction mediator FAK, and CD26, a surface marker implicated in fibrosis. After two weeks, smooth muscle cells migrated out of the intestinal wall into the adhesion space. Abdominal wall transplantation revealed that >80% of cells in the adhesion tissue were green and hence derived from the bowel surface, rather than red and derived from the abdominal wall (Figure 1). Assessment of cell proliferation in the adhesion using rainbow mice showed that individual intestine surface cells multiply after injury and expand clonally into the adhesion space.
Conclusion:
Adhesion fibroblasts express several cell markers associated with fibrosis that may provide molecular targets for future anti-adhesion therapies. Smooth muscle cells of the intestinal wall migrate into the adhesion and may contribute to inflammation and the formation of permanent adhesions. There is likely significant overlap between cells traditionally defined as fibroblasts and smooth muscle cells in the adhesion. Cells of the intestinal surface are substantially more active in adhesion formation than cells of the abdominal wall surface. Individual progenitor cells of the intestinal surface produce progeny that proliferate clonally and populate the adhesion.
