Infrapatellar fat pad-derived mesenchymal stromal cells from osteoarthritis patients: In vitro genetic stability and replicative senescence.

Different sources of mesenchymal stromal cells can be considered for regenerative medicine applications. Here we analyzed human adipose-derived stromal cells from infrapatellar fat pad (IFPSC) of osteoarthritis patients, representing a very interesting candidate for cartilage regeneration. No data are available concerning IFPSC stability after in vitro expansion. Indeed, replicative potential and multipotency progressively decrease during culture passages while DNA damage and cell senescence increase, thus possibly affecting clinical applications. To investigate whether in vitro expansion influences the genetic stability and replicative senescence of IFPSC, we performed long-term cultures and comparatively analyzed cells at different culture passages. Stromal vascular fraction was harvested from infrapatellar fat pad of 11 osteoarthritis patients undergoing knee replacement surgery. Cell recovery, growth kinetics, surface marker profile, and differentiation ability in inductive culture conditions were recorded. Genetic integrity maintenance was estimated by microsatellite instability analysis and mismatch repair gene expression, whereas telomere length and telomerase activity were assessed to evaluate replicative senescence. Anchorage-dependent growth was tested by soft agar culture. IFPSC displayed a phenotype similar to mesenchymal stromal cells from subcutaneous fat and showed differentiation ability. No microsatellite instability was documented even at advanced culture times in accordance to a sustained expression of mismatch repair genes, thus highlighting stability of short repeated sequences in the genome. No significant telomere attrition nor telomerase activity were documented during culture and cells did not lose anchorage-dependent growth ability. The presented data support the suitability and safety of in vitro expanded IFPSC from osteoarthritis patients for applications in regenerative medicine approaches.