In situ Tissue Engineering for Lung Regeneration Using a Collagen Sponge Scaffold

Abstract

Background: Although a large number of studies have been done on lung regeneration, most of them have observed only repair process after drug induced injury. We have been trying to regenerate new lung tissue in the defect made beforehand, using implantation of collagen sponge as a scaffold by means of in situ tissue engineering. Materials and methods: Used collagen was atelo-collagen extracted from porcine skin. Porous sponge was made from collagen by freeze-drying and it waa heated in vacuo for 3–12 h to induce cross-linking between the collagen molecules. Collagen sponges with a volume of 1.0cm3 were implanted in the lung parenchyma of twenty adult Japanese white rabbits. The rabbits were put sacrificed at intervals from 3 days to 8 weeks. The specimens were then subjected to pathological routine process and immunobistochemstry. Results: Serial specimens of several intervals after implantation revealed morphologic changes of regenerating process. Implanted collagen sponge was absorbed in a week. Cell infiltration occurred in the scaffold, then implanted collagen fibers absorbed. Self-secreted collagen was replaced in the space where collagen sponge was implanted. Ductal structure appeared in the border between scaffold and surrounding lung tissue. This ductal structure changed into interstitial pneumonia-like finding as far from scaffold, and then into normal alveolar tissue. Such process went forward the central portion of scaffold and went along. In 8 weeks after implantation, scaffold was replaced by newly regenerated lung tissue. The ductal structure consisted of cells which were immuno-positive with FCNA and TTF-1. Conclusion: Our study suggests that appropriate scaffold such as collagen sponge regenerate new tissue in lung. Serial morphologic observation revealed that newly emerged ductal structures in the scaffold changed into regenerated lung tissue. This is the first report of in situ tissue engineered lung.