Formation of new tissue from an arteriovenous loop in the absence of addedextracellular matrix

A major requirement for the microsurgical repair of contour defects of the skin, for example, following removal of a skin cancer on the face, is a mas s of vascularised subcutaneous tissue. Such tissue can be generated irt viv o using basic tissue engineering principles. In previous studies in our lab oratory, we have used a model comprising an arteriovenous (AV) shunt loop s andwiched in artificial dermis, placed in a cylindrical plastic growth cham ber, and inserted subcutaneously to grow new connective tissue progressivel y up to 4 weeks. To learn more about the basic growth characteristics with this model, the same AV shunt loop within a chamber without added extracell ular matrix was inserted subcutaneously into the groins of rats for 2, 4, o r 12 weeks (n = 5 per group). There was a progressive increase in the mass and volume of tissue such that the chamber was two-thirds full after 12 wee ks. Histological examination showed that at 2 weeks there was evidence of f ibroblast and vascular outgrowth from the AV shunt, with the formation of g ranulation tissue, surrounded by a mass of coagulated exudate. At 4 weeks t he connective tissue deposition was more extensive, with a mass of more mat ure granulation tissue containing considerable collagen. By 12 weeks there was an extensive, well vascularized mass of mature fibrous tissue. The bloo d vessels and residual adventitia of the AV shunt were the likely source of growth factors and of the cells which populated the chamber with new matur ing connective tissue. A patent AV shunt in an isolated chamber appears to be the minimal requirement for the generation of new vascularized tissue th at is potentially suitable for microsurgical transplantation.