The promotion of osteoblastic differentiation of rat bone marrow stromal cells by a polyvalent plant mosaic virus

To investigate the role that the micro/nano-environment plays on the differentiation pathway of bone marrow stromal cells (BMSCs) into osteoblasts, we employed a 2D substrate coated with turnip yellow mosaic virus (TYMV) particles. TYMV is a non-enveloped icosahedral plant virus which has an average diameter 28 nm and the protein cage structure consists of 180 identical subunits. The temporal effect of TYMV coated substrate on the adhesion and differentiation capacity of the BMSCs was monitored for selected time periods of 7, 14 and 21 days. We examined the gene expression profile of BMSCs cultured in primary media (undifferentiated cells) and cells induced to osteoblast lineage by real time PCR analysis. To further corroborate our findings, we investigated the expression of osteogenic markers using immunohistochemistry and cytochemical staining. As expected, the genes involved in the process of osteogenic differentiation were activated more during the growth of cells under osteogenic media. In addition, we found that the BMSCs induced to undergo osteogenic differentiation on TYMV coated substrates formed fully mineralized nodules comprising of osteoblast-like cells around day 14. Comparing the gene expression pattern of BMSCs induced to osteogenic differentiation under standard culture conditions with the cells induced on TYMV substrates, we found significant differences in the temporal expression and level of expression of several key genes. Our findings indicate that TYMV, as a biogenic nanoparticle, can be employed as a model to modulate the nano-environment of the substrates in order to gain an insight into the role that the micro/nano-environment has in regulating adhesion, growth and differentiation of BMSCs towards osteogenic lineage, which will be vital for designing compatible biomaterials for tissue engineering purposes.