Axon growth-promoting properties of human bone marrow mesenchymal stromal cells

Mesenchymal stromal cells are promising candidate donor cells for promoting functional tissue repair following traumatic spinal cord injury (SCI), however, the mechanism(s) of action remain poorly defined. Here, we describe an in vitro study of the axon growth-promoting properties of highly enriched populations of adult human mesenchymal stromal cells (hMSC). A random, non-oriented pattern of neuritic outgrowth was observed from dissociated adult rat DRG neurons seeded onto confluent A431 cells and PLL/laminin positive control substrata. Confluent hMSC formed arrays of similarly orientated cell bodies and processes which supported the regeneration of significantly more primary neurites but a slightly lower overall neuritic length than was observed over the PLL/laminin control substrate. The hMSC exerted a strong influence on the direction of neuritic outgrowth, with many regenerating processes following the orientation of underlying hMSC. The production of extracellular matrix appeared to be responsible for neuritic directionality, but the release of growth factors was a significant promoter for DRG neuritic outgrowth. This suggests that further investigations into the properties of hMSC may be of particular interest in the development of transplant-mediated strategies intending to promote functional axonal regeneration after SCI.