During bone maintenance in vivo, estrogen signals through estrogen receptor (ER)-alpha. The objectives of this study were to investigate the temporal expression of ER alpha 36 and ascertain its functional relevance during osteogenesis in human bone marrow derived stromal cells (BMSC). This was assessed in relation to runt-related transcription factor-2 (runx2), a main modulatory protein involved in bone formation. ER alpha 36 and runx2 subcellular localisation was assessed using immunocytochemistry, and their mRNA expression levels by real time PCR throughout the process of osteogenesis. The osteogenically induced BMSCs demonstrated a rise in ERct36 mRNA during proliferation followed by a decline in expression at day 10, which represents a change in dynamics within the culture between the proliferative stage and the differentiative stage. The mRNA expression profile of runx2 mirrored that of ER alpha 36 and showed a degree subcellular co-localisation with ER alpha 36. This study suggests that ER alpha 36 is involved in the process of osteogenesis in BMSCs, which has implications in estrogen deficient environments. (C) 2014 Elsevier Inc. All rights reserved.