Proinflammatory cytokines inhibit osteogenic differentiation from stem cells: implications for bone repair during inflammation

Objective: The effects of inflammation on bone development from mesenchymal stem cells (MSC) are unclear due to the difficulty in isolating MSC. The aim of this study was to develop a MSC isolation method and to determine the in vitro effects of interleukin-1 beta (IL-1 beta) and tumor necrosis factor alpha (TNF alpha) on their osteogenic differentiation. Methods: Murine MSC were isolated from the limbs of C57/BI6 mice through collagenase digestion of bone and enriched as the Stem cell antigen (Sca-1)(+) CD31(-) CD45(-) population, using lineage immunodepletion, followed by fluorescence-activated cell sorting (FACS). They were differentiated along the osteoblast linage in the presence or absence of IL-1 beta and TNF alpha. Mineralization was measured as was the expression of a number of osteogenic genes by quantitative polymerase chain reaction (PCR). Results: We show that osteogenic differentiation from the MSC population is suppressed by IL-1 beta and TNF alpha. In addition to suppression of bone mineralization, both cytokines inhibited the differentiation-associated increases in alkaline phosphatase (ALP) activity and the gene expression for ALP, alpha 1(I) procollagen, runt-related transcription factor 2 (Runx2) and osterix. However, only TNF alpha inhibited osteonectin and osteopontin mRNA expression and only IL-1 beta reduced cell proliferation. Conclusions: The convenient isolation technique enables the easy generation of sufficient MSC to permit the molecular analysis of their differentiation. We were thus able to show that the proinflammatory cytokines, IL-1 beta and TNF alpha, can compromise bone development from this primary MSC population, although with some significant differences. The potential involvement of specific inflammatory mediators needs to be taken into account if optimal bone repair and presumably that of other tissues are to be achieved with MSC. (C) 2008 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.