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

Background: Poly(L-lactide/epsilon-caprolactone) [P(L-LA/epsilon-CL)] 50/50 membranes is an absorbable membrane which has been developed recently for possible use in tissue engineering.

Aims: To look at histological tissue reactions to the membrane and its behaviour upon its in vivo implantation in rats.

Material and methods: P(L-LA/e-CL) 50/50 membranes, 0.4 mm thick, were implanted subcutaneously in the dorsal neck of 20 Wistar rats. The rats were followed-up for 1, 3, 6, 12 and 28 months. After sacrifice, subcutaneous tissues with implants were taken as specimens, inspected for any gross abnormality and histological examination was carried out.

Results: No significant macroscopic changes were noticed except for two implants that were grossly rounded. Histologically, the membranes had undergone cracking, fragmentation and progressive degradation. Cracks appeared initially at the periphery of the implant. Large cracks progressed mainly in longitudinal planes. Cracks occurred in the middle of implants and led to membrane 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 type of polymorphonuclear cell reaction was observed and in a second case a predominantly lymphocytic reaction was seen at three months. They were thought 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 not completely in 28 months.