The aim of this research was to determine the impact of heat stress on cell differentiation in an equine mesenchymal stem cell model (EMSC) through the application of heat stress to primary EMSCs as they progressed through the cell specialization process. A proteomic analysis was performed using mass spectrometry to compare relative protein abundances among the proteomes of three cell types: progenitor EMSCs and differentiated osteoblasts and adipocytes, maintained at 37 °C and 42 °C during the process of cell differentiation. A cell-type and temperature-specific response to heat stress was observed, and many of the specific differentially expressed proteins were involved in cell-signaling pathways such as Notch and Wnt signaling, which are known to regulate cellular development. Furthermore, cytoskeletal proteins profilin, DSTN, SPECC1, and DAAM2 showed increased protein levels in osteoblasts differentiated at 42 °C as compared with 37 °C, and these cells, while they appeared to accumulate calcium, did not organize into a whorl agglomerate as is typically seen at physiological temperatures. This altered proteome composition observed suggests that heat stress could have long-term impacts on cellular development. We propose that this in vitro stem cell culture model of cell differentiation is useful for investigating molecular mechanisms that impact cell development in response to stressors.

Adipose-derived stem cells (ADSCs) are used in tissue regeneration therapies. The objective of this study is to identify stable reference genes (RGs) for use in gene expression studies in a characterized equine adipose-derived mesenchymal stem cell (EADMSC) differentiation model. ADSCs were differentiated into adipocytes (ADs) or osteoblasts (OBs), and the proteomes from these cells were analyzed by liquid chromatography tandem mass spectrometry. Proteins that were stably expressed in all three cells types were identified, and the mRNA expression stabilities for their corresponding genes were validated by RT-qPCR. PPP6R1, CCDC97, and then either ACTB or EPHA2 demonstrated the most stable mRNA levels. Normalizing target gene Cq data with at least three of these RGs simultaneously, as per MIQE guidelines (PPP6R1 and CCDC97 with either ACTB or EPHA2), resulted in congruent conclusions. FABP5 expression was increased in ADs (5.99 and 8.00 fold, p = 0.00002 and p = 0.0003) and in OBs (5.18 and 5.91 fold, p = 0.0011 and p = 0.0023) relative to ADSCs. RUNX2 expression was slightly higher in ADs relative to ADSCs (1.97 and 2.65 fold, p = 0.04 and p = 0.01), but not in OBs (0.9 and 1.03 fold, p = 0.58 and p = 0.91).