The effects of primary cilia-mediated mechanical stimulation on nestin-BMSCs during bone-tendon healing.

Introduction: Mechanical stimulation has been proven to promote bone-tendon interface (BTI) healing, but the mechanism remains unclear.

Objective: To investigate the effects of mechanical stimulation on the biological behavior of nestin-bone mesenchymal stem cells (BMSCs) during the BTI healing, and to reveal the mechanisms of mechanical stimulation affecting BTI healing by primary cilia on the nestin-BMSCs.

Methods: Transgenic tracing mice (nestin cre:: IFT88/ROSA26 YFP) with primary cilia on nestin-BMSCs conditioned knocked out were constructed, and the littermates (nestin cre:: ROSA26 YFP) with normal cilia on nestin-BMSCs were the control. After establishing mouse supraspinatus insertion injury models, samples were collected at week-2 (n = 5 per group), 4 and 8 (n = 15 per group, respectively). In vivo, the repair efficiency was evaluated by histology, imaging, biomechanics, and the migration of nestin-BMSCs, detected by immunofluorescence staining. In vitro, nestin BMSCs were sorted and stimulated by tensile force to study the mechanisms of primary cilium-mediated mechanosensitive basis.

Results: Mechanical stimulation (MS) accelerated the recruitment of nestin-BMSCs and promoted osteogenic and chondrogenic capacity. Histological, imaging and biomechanical results showed that the BTI healing quality of the IFT88, MS group was better than that of the other groups. After the conditionally knockout IFT88 in nestin-BMSCs, the repair ability of the BTI was obviously deteriorated, even though mechanical stimulation did not increase significantly (IFT88, MS group). In vitro results showed the tensile loading enhanced the proliferation, migration and osteogenic or chondrogenic gene expression of nestin-BMSCs with normal cilia. On the other hand, osteogenesis and chondrogenic expression were significantly decreased after inhibiting actin- Hippo/YAP pathway components.

Conclusion: The primary cilia mediated mechanical stimulation regulated osteogenic and chondrogenic differentiation potential of nestin-BMSCs through the actin- Hippo/YAP pathway, and then promoted the BTI healing process.