Induction of notochordal differentiation of bone marrow mesenchymal-derived stem cells via the stimulation of notochordal cell-rich nucleus pulposus tissue

The degeneration of intervertebral disc (IVD) tissue, initiated following the disappearance of notochordal cells (NCs), is characterized by the decreased number of nucleus pulposus (NP) cells (NPCs) and extracellular matrix. Transplanting proper cells into the IVD may sustain cell numbers, resulting in the synthesis of new matrix; this represents a minimally invasive regenerative therapy. However, the lack of cells with a correct phenotype severely hampers the development of regenerative therapy. The present study aimed to investigate whether porcine NC-rich NP tissue stimulates bone marrow-derived mesenchymal stem cell (BM-MSC) differentiation toward NC-like cells, which possess promising regenerative ability, for the treatment of disc degeneration diseases. BM-MSCs were successfully isolated from porcine femurs and tibiae, which expressed CD90 and CD105 markers and did not express CD45. Differentiation induction experiments revealed that the isolated cells had osteogenic and adipogenic differentiation potential. When co-cultured with NC-rich NP tissue, the BM-MSCs successfully differentiated into NC-like cells. Cell morphological analysis revealed that the cells exhibited an altered morphology, from a shuttle-like to a circular one, and the expression of NC marker genes, including brachyury, keratin-8, and keratin-18, was enhanced, and the cells exhibited the ability to generate aggrecan and collagen II. Taken together, the findings of the present study demonstrated that the primarily isolated and cultured BM-MSCs may be stimulated to differentiate into NC-like cells by porcine NC-rich NP explants, potentially providing an ideal cell source for regenerative therapies for disc degeneration diseases.