Effect of inoculation density of bone marrow mesenchymal stem cells cultured on calcium phosphate cement scaffold on osteogenic differentiation.

Abstract

Calcium phosphate cements (CPCs) are biocompatible materials that have been evaluated as scaffolds in bone tissue engineering. At present, the stem cell density of inoculation on CPC scaffold varies. The aim of this study is to analyze the effect of seeding densities on cell growth and osteogenic differentiation of bone marrow mesenchymal stem cells (BMMSCs) on a calcium phosphate cements (CPCs) scaffold. BMMSCs derived from minipigs were seeded onto a CPC scaffold at three densities [1million/mL (1M), 5 million/mL (5M) and 25million/mL 25M)], and cultured for osteogenic induction for 1, 4 and 8 days. Well adhered and extended BMMSCs on the CPC scaffold showed significantly different proliferation rates within each seeding density group at different time points (P <0.05). The number of live cells per unit area in 1M, 5M and 25M increased by 3.5, 3.9 and 2.5 folds respectively. The expression of ALP peaked at 4 days post inoculation with the fold-change being 2.6 and 2.8 times higher in 5M and 25M respectively as compared to 1M. The expression levels of OC, Coll-1 and Runx-2 peaked at 8 days post inoculation. An optimal seeding density may be more conducive for cell proliferation, differentiation, and extracellular matrix synthesis on scaffolds. We suggest the optimal seeding density should be 5million/mL.