Rodent Xenografts of Human and Porcine Fetal Tissue

Transplantation of pancreatic islet tissue provides an attractive alternative to parenteral administration of insulin as a therapy for insulin-dependent diabetes mellitus (IDDM). However, this approach suffers from two major obstacles: (1) implanting sufficient functional tissue to overcome the diabetic condition and (2) immune rejection of the implanted tissue. Clinical transplantation of adult islets has met with only limited success to date. Isolation of islets from a mature pancreas is difficult, yields are low, purity has been variable, and the therapeutic effects of implants have been short lived (1,2). Fetal pancreas tissue offers a number of advantages for transplantation. For example, the fetal pancreas has a much higher ratio of endocrine to exocrine tissue than does the adult pancreas (3,4), reducing the potential for autodigestion and other problems associated with the presence of high concentrations of digestive enzymes. In addition, fetal endocrine tissue has a greater proliferative capacity than do adult islets (5) and fetal tissue may be less immunogenic than adult islets (6,7).