Development of annulus fibrosus tissue construct with hydrogel coils containing pre-conditioned mesenchymal stem cell

Low back pain associated with degenerative disc diseases has been a major health concern that brings suffering to the patients physically and economically. Many existing therapeutic strategies provide short-term relief of symptoms rather than treatment of the underlying cause. Development of an engineered tissue for disc regeneration is still in its infancy due to the limited autologous healthy disc cell source from the patients. It is also challenging to mimic the complexity of micro-architecture in the native disc tissue that determine their unique structural properties. To date, simple tissue models that mimic the annulus fibrosus (AF) micro-environment for understanding the potential of mesenchymal stem cells (MSCs) in AF tissue engineering are still lacking. In this study, the assembly of a coiled hydrogel microfiber has shown its capability to encapsulate MSCs and create an engineered tissue model that mimics the multiple lamellae of native AF. Using this model, we investigated the potential of MSCs that were previously induced by ascorbic acid (AA). Compared to non-induced MSCs, AA-induced MSCs exhibited significant increase in AF-associated biomarkers during later development in the engineered AF tissue model and also encouraged collagen accumulation through the down-regulated catabolic gene MMP1 and upregulated anti-catabolic gene TIMP1. Furthermore, AA-induced MSCs exhibited a Col2/Col1 ratio closer to that of a native AF tissue. These results suggested that AA-induced MSCs could be a potential cell source for AF tissue engineering and this established tissue model may provide a simple tool for successful AF tissue engineering strategies in the future.