WNT3A and intervertebral disk degenerative disorder: Some data suggest that exo‐miR‐15a promotes the chondrogenic differentiation of nucleus pulposus‐mesenchymal stem cells (NP‐MSCs) by downregulating MMP‐3 via the PI3K/Akt and Wnt3a/β‐catenin axes, thereby deferring the progression of IDD [20].