A bioengineered artificial interstitium supports long-term islet xenograft survival in nonhuman primates without immunosuppression.

Cell-based therapies hold promise for many chronic conditions; however, the continued need for immunosuppression along with challenges in replacing cells to improve durability or retrieving cells for safety are major obstacles. We subcutaneously implanted a device engineered to exploit the innate transcapillary hydrostatic and colloid osmotic pressure generating ultrafiltrate to mimic interstitium. Long-term stable accumulation of ultrafiltrate was achieved in both rodents and nonhuman primates (NHPs) that was chemically similar to serum and achieved capillary blood oxygen concentration. The majority of adult pig islet grafts transplanted in non-immunosuppressed NHPs resulted in xenograft survival >100 days. Stable cytokine levels, normal neutrophil to lymphocyte ratio, and a lack of immune cell infiltration demonstrated successful immunoprotection and averted typical systemic changes related to xenograft transplant, especially inflammation. This approach eliminates the need for immunosuppression and permits percutaneous access for loading, reloading, biopsy, and recovery to de-risk the use of "unlimited" xenogeneic cell sources to realize widespread clinical translation of cell-based therapies.