262-LB: Human Pancreas-Derived Multipotent Stromal Cells Secrete Islet Regenerative Stimuli

Abstract

We recently demonstrated that intra-pancreatic (iPan) delivery of conditioned media (CM) generated by human bone marrow-derived multipotent stromal cells (hBM-MSC) can act as a biotherapeutic to reduce hyperglycemia in STZ-treated mice by stimulating endogenous islet regeneration. We have established analogous stromal cell lines derived from human islet cultures that grow adherent to plastic and possess multipotent mesodermal differentiation in vitro. Furthermore, CM generated by these human pancreas-derived MSC (hPanc-MSC) contained proangiogenic stimuli within extracellular vesicles (EVs) that accelerated blood vessel regeneration after injection into ischemic hindlimbs. Herein, we investigated whether iPan-injection of CM generated by hPanc-MSC could stimulate islet regeneration in STZ-treated mice. We hypothesized that islet regenerative stimuli would be harboured within EVs secreted by hPanc-MSC. iPan-injection of unfractioned CM (6µg) generated by hBM-MSC and hPanc-MSC equally reduced hyperglycemia in STZ-treated mice, compared to mice injected with media control (*p<0.05). To determine whether islet regenerative stimuli was harboured within EVs, ultrafiltration was used to separate CM into EV enriched (EV+) or depleted (EV-) subfractions. Enrichment of EVs was validated by nanoscale flow cytometry and atomic force microscopy, and the EV+ and EV- hPANC-MSC subfractions were compared for protein content by label-free mass spectrometry. Expression of typical EV-associated proteins (CD9, CD81, CD63) were exclusive to the EV+ fraction and putative islet regenerative factors were detected in both the EV- and EV+ subfractions C. Mice iPan-injected with either EV+ or EV- CM sub-fractions showed significantly reduced hyperglycemia compared to unconditioned media controls (*p<0.05). These initial studies provide a foundation to further explore the use the hPanc-MSC secretome or related small-molecule pharmaceuticals to enhance islet-regeneration in situ. Disclosure T. Cooper: None. J. Ma: None. G.I. Bell: None. G. Lajoie: None. D.A. Hess: None.