Priming of human bone marrow-derived mesenchymal stromal cells with various down-stream effectors of the Transforming Growth Factor 1 pathway boosts their hematopoiesis-supportive ability.

Mesenchymal stromal cells (MSCs) isolated from various tissues are frequently used to expand hematopoietic stem/ progenitor cells (HSCs/HSPCs) in vitro. They are also co-infused with the HSCs to improve the HSC engraftment. However, the MSCs sourced from non-hematopoietic tissues could be less efficient in their hematopoiesis-supportive ability. Likewise, the hematopoiesis-supportive ability of the MSCs is known to decline after continuous in vitro culture – an unavoidable manipulation to get clinically relevant cell numbers. Hence, it may be necessary to boost the hematopoietic-supportive ability of the long-time cultured MSCs before their clinical applications in hematological disorders. In my earlier work, I showed that priming of MSCs isolated from human bone marrow (BMSC) with Transforming Growth Factor β1 (TGFβ1) boosts their hematopoiesis-supportive ability via activation of AKT-eNOS pathway. Accordingly, I also demonstrated that priming the BMSCs with nitric oxide (NO) donors mimics the effect of TGFβ1. Here I show that brief exposure of human BMSCs to pharmacological modulators of PKC and intracellular calcium – two downstream participants in the TGFβ1-eNOS signaling pathway – also boosts their hematopoiesis-supportive ability. Such an approach comprising priming the BMSCs with pharmacological compounds for a short duration and briefly exposing the HSCs to them can be used in clinical settings to improve the efficacy of stem cell transplantations. This concept would be helpful in other regenerative medicine protocols after identifying suitable pharmacological modulators giving desired effects on the target cells.