Abstract

This study explores the suitability of using encapsulated genetically modified fibroblasts for orthopedic tissue engineering by examining cell survival and persistence of human transforming growth factor-beta (hTGF-beta) overexpression in xenogeneic and allogeneic implant models. Human wild-type fibroblasts, modified to produce a latent form of hTGF-beta, and murine mutant-type fibroblasts, engineered to release a constitutively active form of hTGF-beta, were encapsulated separately in Ca2+ -alginate microcapsules. Following a percentage viability assessment by MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) test, microcapsules were implanted into either the subcutaneous or intraperitoneal cavities of mice. Explanted encapsulated cells were characterized for percentage viability and subjected to a release study and a viability test 1 week and 3 weeks following implantation, a time frame consistent with the requirement for orthopedic tissue engineering application of this growth factor. On average, percentage viabilities of encapsulated cells were 64%at implantation, 52% at explantation, and 56%after 1 week following either 1- or 3-week explantation. hTGF-beta release declined following in vivo implantation, more so for xenogeneic than allogeneic models, but remained in the clinically attractive range of 2 to 30 ng/(10(6) implanted cells 24 h). This technical platform for hTGF-beta is very encouraging for cartilage regeneration using orthopedic tissue engineering, and further evaluation is warranted.