Disc-Derived Induced Pluripotent Stem Cells and Environmental Cues for Nucleus Pulposus Regeneration

Notochordal cells (NCs), abundantly found in the developing nucleus pulposus (NP), show potential for intervertebral disc regeneration because of their unique instructive and healthy matrix-producing capacity. However, NCs are lost early in life, and attempts at <i>in vitro</i> expansion have failed because they lose their specific phenotype. Therefore, much effort is focused on the generation of cells resembling the properties of healthy matrix-producing NP-like cells from human induced pluripotent stem cells (hiPSCs). They are considered a promising alternative for employing native NCs. Given the ongoing challenges in the field to fine-tune the differentiation protocol and obtain a high yield of mature matrix-producing cells, this study aims to build on the epigenetic memory and instructive capacity of healthy NP tissue. For this, we employed the epigenetic memory of tissue-specific hiPSCs derived from TIE2⁺ NP progenitor cells (NPPCs) and microenvironmental cues of decellularized porcine NC-derived matrix (dNCM), consisting of matrix components and bioactive factors to differentiate hiPSC into mature, healthy matrix-producing cells for NP repair. As a comparison, donor-matched minimally invasive peripheral blood mononuclear cell-derived hiPSCs were used. The results show that employing NPPC-derived hiPSCs instructed by natural cues provided by dNCM resulted in an increased expression of healthy phenotypic and matrisome-related NP markers. Furthermore, within this <i>in vitro</i> environment, differentiation of blood-derived hiPSC lines led to augmented differentiation into the hematopoietic and neural cell lineage. In conclusion, we demonstrate that hiPSCs derived from NPPCs achieve enhanced differentiation outcomes in the presence of dNCM, highlighting the potential impact of the epigenetic memory.