Human preadipocytes seeded on freeze-dried collagen scaffolds investigatedin vitro and in vivo

Currently, there is no adequate implant material for the correction of soft tissue defects such as after extensive deep burns, after tumor resection a nd in hereditary and congenital defects (e.g. Romberg's disease, Poland syn drome). The autologous transplantation of mature adipose tissue has poor re sults. In this study human preadipocytes of young adults were isolated and cultured. 10(6) preadipocytes were seeded onto collagen sponges with unifor m 40 mum pure size and regular lamellar structure and implanted into immuno deficient mice. Collagen sponges without preadipocytes were used in the con trols. Macroscopical impression, weight, thickness, histology, immunohistoc hemistry (scaffold structure, cellularity, penetration depth of the seeded cells) and ultrastructure were assessed after 24 h in vitro and after expla ntation at 3 and 8 weeks. Preadipocytes penetrated the scaffolds 24 h after seeding at a depth of 299 +/- 55 mum before implantation. Macroscopically after 3 and 8 weeks in vivo layers of adipose tissue accompanied by new ves sels were found on all preadipocyte/collagen grafts. The control grafts app eared unchanged without vessel ingrowth. There was a significant weight los s of all grafts between 24 h in vitro and 3 weeks in vivo (p < 0.05), where as there was only a slight weight reduction from week 3 to 8. The thickness decreased in the first 3 weeks (p < 0.05) in all grafts. The preadipocyte/ collagen grafts were thinner but had a higher weight than the controls at t his point in time. The histology showed adipose tissue and a rich vasculari sation adherent to the scaffolds under a capsule. The control sponges conta ined only few cells and a capsule but no adipose tissue. Human-vimentin pos itive cells were found in all preadipocyte collagen grafts but not in the c ontrols, penetrating 1188 +/- 498 mum (3 weeks) and 1433 +/- 685 mum (8 wee ks). Ultrastructural analysis showed complete in vivo differentiation of vi able adipocytes in the sponge seeded with preadipocytes. Formation of extra cellular matrix was more pronounced in the preadipocyte/collagen grafts. Th e transplantation of isolated and cultured preadipocytes within a standardi sed collagen matrix resulted in well-vascularised adipose-like tissue. It i s assumed that a pore size greater than 40 mum is required, as preadipocyte s enlarge during differentiation due to incorporation of lipids. (C) 2001 E lsevier Science Ltd. All rights reserved.