Discovery and validation of islet regenerative proteins secreted by human multipotent stromal cells

Diabetes affects >500 million people worldwide. Despite insulin therapy, most patients develop devastating complications, emphasizing the need for curative strategies. Human multipotent stromal/stem cells (MSC) secrete factors that promote islet regeneration. We previously showed that intrapancreatic (iPan) delivery of Wnt-activated MSC-conditioned media (Wnt+ CM) stimulates islet regeneration without cell transfer. This study aimed to identify and functionally validate specific MSC-secreted proteins with islet regenerative potential.

Comprehensive mass spectrometry-based, quantitative proteomic analyses comparing Wnt-pathway activated versus untreated MSC secretomes were cross-referenced with a prior dataset distinguishing regenerative from nonregenerative MSC CM. Proteins enriched in both conditions were iPan-injected individually or in combination into streptozotocin-treated NOD/SCID mice. Nonfasting glucose, glucose tolerance, beta cell mass, islet morphology, and islet cell proliferation were assessed at 4- and 32-days post-treatment.

Cross-referenced secretome analyses identified eight proteins implicated in islet regeneration: CALU, CTSB, FAM3C, GAL1, PPIA, PSAP, SOD1, and TGM2. A single iPan-injection of the 8-protein combination significantly lowered hyperglycemia, improved glucose tolerance, and increased beta cell mass, comparable to Wnt+ CM. Regenerative effects such as increased beta cell proliferation appeared as early as day 4. Single-protein testing identified CALU and SOD1 as leading candidates, improving glucose tolerance and reducing nonfasting glucose.

This study defines a set of MSC-secreted proteins that promote islet regeneration in vivo, supporting the development of protein-based biologics to preserve or restore beta cell function during diabetes, with potential applications alongside islet replacement therapies to enhance graft survival and function.