Calvarial and femoral osteoblasts differ in their responsiveness to mechanically-induced strain in vitro.

Objectives: Objective: A biocompatible, osteoconductive and osteoinductive framework on which to grow osteoblasts would of great benefit for tissue-engineering. The support must resist a mechanical load, which is important in bone growth, and is a promoter of osteogenic differentiation in vitro. The origin of the osteoblasts, with regard to their mechanical responsiveness, also needs to be considered. Therefore, the design and validation of a model for the 3D culture of osteoblasts under mechanical strain was undertaken.
Methods: Methods: Human calvarial and femoral osteoblasts were cultured for 21-days in a semi-synthetic hyaluronan-gelatin polyethylene (glycol) diacrylate (PEDGA) cross-linked hydrogel under a cyclic mechanical strain (1 Hz for 5 sec every hr for 6 hrs over 21 days). Cell proliferation, hydroxyapatite deposition and mRNA expression levels of alkaline phosphatase (ALP), bone morphogenetic protein 2 (BMP2), osteocalcin (OCN), collagen type 1 alpha 1 chain (Col1A1) and collagen type 2 alpha 1 chain (Col2A1) for calvarial and femoral osteoblasts were compared.
Results: Results: Cell proliferation and hydroxyapatite deposition increased for each cell line over 21 days. A highly cross-linked hydrogel scaffold was found to promote osteoblast attachment. The mechanical load did not affect ALP mRNA expression in either the calvarial or the femoral osteoblasts (P = 0.132) but it caused a 53.9-fold increase in BMP2 (P = 0.0043) and a 5.15-fold increase in Col1A1 (P = 0.0022) mRNA expression in the femoral osteoblast group. No OCN or Col2A1 mRNA was detected in either group.
Conclusions: Conclusion: Thiol-modified hyaluronan-gelatin-PEGDA cross-linked hydrogel is a suitable scaffold for the study of osteoblasts in vitro. Further experiments over a longer time period are required to assess the differences in the responses of calvarial and femoral osteoblasts to mechanical strain.