Lung tissue engineering : in vitro synthesis of lung tissue from neonatal and fetal rat lung cells cultured in a three-dimensional collagen matrix

The focus of this study was to investigate the histology of tissue formed when fetal (16-20 days gestation) and neonatal (2 days old) rat lung cells were grown in a collagen-glycosaminoglycan scaffold. This project employed a collagen-GAG scaffold specifically developed for tissue engineering and investigated the effect of this substratum on the formation of lung histotypic structures in vitro. A cell isolation procedure was developed whereby 19-days gestation type II alveolar cells reaggregated to form alveolar-like structures. The effects of selected scaffold design variables including pore diameter and degradation rate of the substratum on lung tissue regeneration were explored. Lung cell behavior revealed as the cells interact with an analog of the extracellular matrix was also examined. Differences in fetal and neonatal lung cell behavior were identified using histological analysis. Lung cells were obtained from Sprague-Dawley rats after 16-, 19-, and 20-days of gestation and at 2 days after term. These cells were seeded into type I collagen-GAG matrices, sized 8mm in diameter by 2mm in thickness. The medium used, F12K and Ham's nutrient mixture, was supplemented with 10% fetal bovine serum. A seeding density between 1 to 5 million cells per sponge sample was used. Histology studies were performed at termination periods of 2, 14, and 28 days. This paper describes the in vitro formation and long-term maintenance of alveolar-like structures from enzymatically dissociated 19-days gestation fetal rat lung cells cultured on a collagen sponge substrate as a model system for lung tissue engineering.