Infoscience

Thesis

Fetal bone cells for tissue engineering

In this thesis, the potential use of fetal bone cells for tissue engineering was evaluated. At first, fetal bone cells were characterized in vitro regarding their proliferation rate, the induction of their osteoblastic phenotype, and their antigenicity. They showed rapid proliferation and were able to differentiate into mature osteoblasts as shown by the expression of bone differentiation markers on the protein (alkaline phosphatase, ALP)) as well on the gene level (cbfa-1, ALP, alpha1 chain of type I collagen, and osteocalcin). Furthermore, they were able to mineralize their extracellular matrix in vitro. Antigenicity was investigated with respect to their immune profile on the protein and gene expression level and their interaction with lymphocytes in chemotaxis and immuno modulation assays, showing the immunoprivilege of fetal bone cells. In a second phase, fetal bone cells were seeded on porous scaffolds made of poly(L-lactic acid) (PLA) reinforced with 5 %wt β-tricalcium phosphate (β-TCP) or with 5 %wt hydroxyapatite (HA) to test the behaviour of such a new bone graft substitute in vitro. When seeded on these scaffolds, fetal bone cells were still able to differentiate as shown by the induction of alkaline phosphatase enzyme activity, osteocalcine production and in vitro mineralization. Next, host tissue reaction and bone repair were evaluated in vivo with scaffolds implanted in rats. Host tissue reaction to scaffolds was shown to decrease with time of exposure and osteoconductive properties of PLA/ceramic scaffolds were assessed. Finally, the new bone graft substitute consisting of fetal bone cells and PLA/TCP scaffolds was integrated in trabecular and cortical bone defects in rats to evaluate their potential for tissue repair in vivo. Histological and radiographic analysis showed improved trabecular bone infiltration in a drill defect model in the femoral condyles as well as enhanced porous ossification of the implant in critical size defects in the parietal bone when compared with the scaffold material alone. We conclude that fetal bone cells reveal an interesting potential for therapeutic use in bone tissue engineering.

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