SPOCK2 controls the proliferation and function of immature pancreatic ß-cells through MMP2.

Human pluripotent stem cell-derived ß-cells (SC-ß-cells) represent an alternative cell source for transplantation in diabetic patients. While mitogens could in theory be employed to expand ß-cells, adult ß-cells very rarely replicate. Conversely, newly formed ß-cells, including SC-ß-cells, display higher proliferative capacity and distinct transcriptional and functional profiles. Through bidirectional expression modulation and single-cell RNA-seq, we identified SPOCK2, an ECM protein, as inhibitor of immature ß-cell proliferation. Human ß-cells lacking SPOCK2 demonstrated elevated MMP2 expression and activity, leading to ß-integrin-FAK-c-JUN pathway activation. Treatment with MMP2 protein resulted in pronounced short- and long-term SC-ß-cell expansion, significantly, increasing glucose-stimulated insulin secretion in vitro and in vivo. This suggests that SPOCK2 mediates fetal ß-cell proliferation and maturation. Together, we identified molecular mechanism that specifically regulates SC-ß-cell proliferation and function, highlighting a unique signaling milieu of SC-ß-cells with promising potential for robust derivation of fully functional cells for transplantation. Overall design: bulk RNA-sequencing of two independent samples of EndoC-BH1 with SPOCK2 KD, GIPZ control, SPOCK2 OE and WT cells and scRNA-sequencing of stem cells derived WT and SPOCK2 KO ß-cell spheroids.