Short heat shock has a long-term effect on mesenchymal stem cells’ transcriptome

Background Mesenchymal stem cells (MSCs) are multipotent stromal, non-hematopoietic cells with self-renewal and differentiation properties and are therefore a preferred source for cellular therapies. However, a better understanding of culture techniques is required to harness their full potential. Here we aim to compare the effects of short and long heat shock (HS) on the transcriptomic landscape of MSCs.

Methods MSCs were extracted from the umbilical cord of a bovine fetus, cultured, and validated as MSCs. Early passage cells were exposed to 40.5°C for six hours or three days. RNA sequencing and bioinformatics analysis were performed to systematically examine the transcriptional changes following each treatment and to identify specific biological features and processes.

Results The data indicates that while long heat stress influences many cell processes, such as immune response, cell cycle, and differentiation, the short HS mostly upregulates the cellular stress response. Once normothermia is resumed the long-term effects of the short HS can be revealed: although most genes revert to their original expression levels, a subgroup of epigenetically marked genes termed bivalent genes, maintains high expression levels. These genes are known to support cell lineage specification and are carefully regulated by a group of chromatin modifiers. One family of those chromatin modifiers, called MLL genes, is highly over-represented in the cluster of genes that are transiently upregulated following six hours of HS. Therefore, our data provide a mechanistic explanation for the long-term phenotype of short HS on development-related genes and could be used to predict the long-term effect of HS on cell identity.

Conclusions Understanding the influence of culture conditions on morphology, phenotype, proliferative capacity, and fate decision of MSCs is needed to optimize culture conditions suitable for clinical or commercial use. Here, we suggest that simple and short stress can alter the cell’s proliferation and differentiation capacities and therefore, following future optimizations, be used to shift the cells toward a more desirable functionality.