I think he may have been referring to priming/preconditioning...

I think he may have been referring to priming/preconditioning MSCs to increase their therapeutic efficacy/potency. For instance you may prime MSCs with cytokines or growth factors, pharmacological or chemical agents, hypoxia etc with the aim of improving certain attributes such as engraftment and survival in damaged tissues, imunosuppressive and migration properties, regenerative properties etc.

For the layman, let's use a sporting analogy. You may expose an endurance athlete to hypoxic conditions (training at altitude) to improve their efficiency of their oxygen usage (and thereby increase their exercise endurance capability). For a power athlete (albeit usually illegal in competition) you can increase their muscle size, strength, power and recoverability via steroid administration.

Likewise you can also expose MSCs to certain conditions/factors/agents to potentially elicit a greater therapeutic effect (i.e. improved efficacy).

If you want a more in depth understanding of this topic see the link:
https://stemcellres.biomedcentral.com/articles/10.1186/s13287-019-1224-y