The use of mesenchymal stem cells (MSCs) for cartilage and bone tissue engineering needs to be supported by scaffolds that may release stimuli for modulate cell activity.

The objective of this study was to asses if MSC undergo differentiation when cultured upon a membrane of nanofibers of poly-L-lactic acid loaded with hydroxyapatite nanoparticles (PLLA/HAp).

The PLLA/HAp nanocomposite was prepared by electrospinning. Membranes microstructure was evaluated by SEM. MSCs were seeded on PLLA/HAp membranes by standard static seeding and cultured either in basal medium or Chondrogenic Differentiation Medium. Cell attachment and engraftment was assessed 3 days after seeding and MSC differentiation was evaluated by immunostaining for CD29, SOX-9 and Aggrecan under a confocal microscope after 14 days.

PLLA/HAp membrane obtained was composed by fibers (average diameter of 7μm) with nano-dispersed hydroxyapatite aggregates (average diameter of 0.3μm). 3 days after seeding, MSCs were well adhered on the PLLA/HAp fibers with a spindled shape. After 14 days of culture all MSCs were positive for SOX-9 in both basal and chondrogenic media groups. Aggrecan was present around the cells. MSCs were either CD29 positive or negative.

We demonstrated that PLLA/HAp nanocomposites are able to induce differentiation of MSCs in chondrocyte-like cells. Since HAp has osteoinductive properties, the chondrogenic phenotype acquired by the MSCs may be either stable or an intermediate stage toward enchondral ossification. The presence of CD29 and SOX-9 double positive cells indicate intermediate differentiation phases.

This nanocomposite could be a susceptible scaffold for bone or cartilage tissue engineering using undifferentiated MSCs.