Histological evaluation of poly(L-lactide/epsiloncaprolactone) membrane implanted subcutaneously in rats.

Background: Poly(L-lactide/epsilon-caprolactone) [P(L-LA/epsilon-CL)] 50/50 membranes is an absorbable membarane which has been developed recently for possible use in tissue engineering. Aims: To look at histological tissue reactions to the membrane and its beha viour upon its in vivo implantation in rats. Material and methods: P(L-LA/e-CL) 50/50 membranes, 0.4 mm thick, were impl anted subcutaneously in the dorsal neck of 20 Wistar rats. The rats were fo llowed-up for 1, 3, 6, 12 and 28 months. After sacrifice, subcutaneous tiss ues with implants were taken as specimens, inspected for any gross abnormal ity and histological examination was carried out. Results: No significant macroscopic changes were noticed except for two imp lants that were grossly rounded. Histologically, the membranes had undergon e cracking, fragmentation and progressive degradation. Cracks appeared init ially at the periphery of the implant. Large cracks progressed mainly in lo ngitudinal planes. Cracks occurred in the middle of implants and led to mem brane bending in some cases. "Neomembrane" formation, comprised of fibrous tissue and the implant, was seen. The foreign-body reaction to the membrane involved macrophages and foreign-body giant cells. In one case an acute ty pe of polymorphonuclear cell reaction was observed and in a second case a p redominantly lymphocytic reaction was seen at three months. They were thoug ht to be the results of infection. No other adverse effects were seen. Conclusions: P(L-LA/e-CL) 50/50 membrane was found to be biocompatible when implanted subcutaneously in rats. It was degraded to a great extent but no t completely in 28 months.