Background and objective: Osteoblastic differentiation from mesenchymal stem cells (MSCs) is regulated by many hormonal and autocrine/paracrine factors. Recently, immunocytochemistry revealed that CD44, a transmembrane glycoprotein, is more expressed in osteoblasts than in MSCs during osteoblast differentiation (Kim et al., 2008). We examined whether CD44 might be involved in osteoblast differentiation.
Methods: CD44 transcript, CD44 protein and calcium deposit levels were measured by RT PCR, real time PCR, Western blot and Alizarin Red S staining during osteogenic differentiation of mouse multipotent stem cells (D1 cell line) in various time points.
Results: Our data have shown that CD44 expressed in both MSCs and osteoblasts. CD44 transcriptional levels changed during osteoblastic differentiation, but that alkaline phosphatase (ALP) transcript levels gradually increased. In addition, the ectopic expression of CD44 protein in MSCs did not affect osteoblastogenesis. Calcium deposit was not different between D1 cells and CD44-over expressed D1 cells. When CD44 protein was blocked with CD44 antibody, ALP mRNA, osteocalcin protein and calcium deposit levels in inhibited cells were similar to in uninhibited D1 cells.
Conclusions: Our data suggest that CD44 does not directly effect on the osteoblastic differentiation of MSCs, but that it can be used as a marker protein for detecting osteoblasts produced by the osteogenic differentiation of MSCs.
