Objectives It is widely accepted that growth factors (GFs) powerfully regulate the biological responses of mesenchymal stem cells (MSCs). TGF-β has been attracting attention in the tenogenic regenerative field as it participates in all phases of tendon healing process. Moreover, TGF-β involves in tendon differentiation of MSCs. Since passage number influence function and behavior of the cells as well as gene expression profile, this study was aimed to investigate mRNA expression of TGF-β1 in equine MSCs at different passages. Materials and Methods Equine MSCs were isolated from the fat tissue of gluteal region and expanded. The cells at passages 5 and 8 were seeded and maintained in basic culture medium. 75 % confluency of cels was considered as day 0 and cells were harvested at days 1 and 3. Then, total RNA was extracted and transcribed into cDNA using commercially available kits. Primers for GAPDH (as internal control) and TGF-β1 were designed. Quantitative RT-PCR (qPCR) was performed using a SYBR green master mix and data was analyzed using Student t-test. Results The mRNA expression of TGF-β1 at P5 and P8 of equine MSCs were compared at 1 and 3 days after 75% confluency. Our data revealed that TGF-β1 expression was significantly higher at P5 compared with P8 in day 1, but there was no significant difference at day 3. Conclusions Based on the results, the expression level of TGF-β1 is significantly affected by the cell passage number. So, tenogenic differentiation capability of quine MSCs can be affected by passage number which should be considered in tenogenic differentiation experiments.

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