Effects of infrared laser irradiation on aging of mesenchymal stem cells in culture

Mesenchymal stem cells (MSCs) represent a significant interest for cell therapy applications and, being primary cells, undergo gradual aging in culture. We studied the effects of low-intensity infrared laser irradiation during aging of MSCs in culture. Both young and aged MSCs respond to low irradiation doses (0.17 J / cm²) by growth activation and to middle doses (2.1 J / cm²) by growth retardation. Aged cells demonstrate a relatively higher growth response to low doses, but they are significantly more susceptible to deleterious effects of middle doses compared to young cells. Studies of MSC aging during long-term culture under hypoxia conditions demonstrate that low-dose irradiation of MSCs every 2 days in culture substantially increases the number of population doublings, compared to the control group. In addition, irradiated cells persisted in culture for two passages (4 days) longer than their control counterparts. However, irradiated cells did not proliferate more rapidly if irradiation was omitted. We conclude that growth responses of young and aged murine MSCs to infrared laser irradiation differ significantly and that regular irradiation affects MSC aging in culture but does not result in a bonafide retardation of aging process.