Abstract
Natural bone healing following fractures is initiated by osteoblasts (OBs) and mesenchymal stem cells (MSCs), a cell combination with possible potential in tissue engineering techniques for bony defects. The aim of the study was to investigate MSC/OB-crosstalk, in order to determine optimal cell culture conditions for osteogenic differentiation. Human OBs and MSCs interactions were investigated in an in vitro trans-well co-culture study over a time period of 28 days. Calcification was determined by optical density (OD) at 450 nm and Alizarin red staining. Messenger RNA expression was assessed by quantitative PCR. Osteogenic medium containing 1% fetal bovine serum resulted in superior levels of calcification in MSCs in co-culture with OBs compared to 2% or 5% fetal bovine serum (p<0.05). Comparing MSCs and OBs alone with the MSC/OB co-culture, calcification, as measured by OD 450 nm, increased over time in all groups. The highest values were recorded in the co-culture (p<0.05). Osteogenic differentiation potential showed significant interindividual differences. In order to predict differentiation potential, OD 450 nm measurements and mRNA expression of alkaline phosphatase were correlated with the population doubling rate during the expansion period. For OBs and MSCs, statistically significant associations of proliferation and differentiation potential were found (p<0.001). The addition of transforming growth factor beta resulted in up-regulation of collagen type I and Sp7 mRNA, and down-regulation of alkaline phosphatase mRNA. The results suggest the idea of soluble paracrine factors being secreted by OBs to induce osteogenic differentiation of MSCs.
Highlights
Isolated bone or osteochondral defects in joints are seen following osteochondritis dissecans or traumatic injuries and are associated with a significant risk for development of consecutive osteoarthritis or non-unions
Optical density measured for the cultures with 1% fetal bovine serum (FBS) reached the highest absorbance in donor 2 followed by donor 1 (0.23 – 0.06, p = 0.248) and donor 3 (0.11 – 0.15, p = 0.0495)
The most important finding of this study was the induction of calcification in mesenchymal stem cells (MSCs) by a co-culture with OBs, which was highly dependent on serum concentration
Summary
Isolated bone or osteochondral defects in joints are seen following osteochondritis dissecans or traumatic injuries and are associated with a significant risk for development of consecutive osteoarthritis or non-unions. This is supported by their immune-suppressive regulatory properties,[3] a characteristic that might be useful in cases with activation of inflammatory responses following acute impacts or fracture repair Another theoretical advantage is the described higher tolerance of hypoxia compared with fully differentiated osteoblasts, allowing more time for the formation of a vascular network to supply the bone component.[4] Knowledge about MSC differentiation a Martina Glueck et al 2015; Published by Mary Ann Liebert, Inc. Another theoretical advantage is the described higher tolerance of hypoxia compared with fully differentiated osteoblasts, allowing more time for the formation of a vascular network to supply the bone component.[4] Knowledge about MSC differentiation a Martina Glueck et al 2015; Published by Mary Ann Liebert, Inc
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