The importance of low blood glucose in the development of fetal sheep pancreatic endocrine cells transplanted into athymic mice

In Vivo Differentiation of Therapeutic Insulin-Producing Cells from Bone Marrow Cells via Extracellular Vesicle-Mimetic Nanovesicles

The current diabetes mellitus pandemic constitutes an important global health problem. Reductions in the mass and function of β-cells contribute to most of the pathophysiology underlying diabetes. Thus, physiological control of blood glucose levels can be adequately restored by replacing functioning β-cell mass. Sources of functional islets for transplantation are limited, resulting in great interest in the development of alternate sources, and recent progress regarding cell fate change via utilization of extracellular vesicles, also known as exosomes and microvesicles, is notable. Thus, this study investigated the therapeutic capacity of extracellular vesicle-mimetic nanovesicles (NVs) derived from a murine pancreatic β-cell line. To differentiate insulin-producing cells effectively, a three-dimensional in vivo microenvironment was constructed in which extracellular vesicle-mimetic NVs were applied to subcutaneous Matrigel platforms containing bone marrow (BM) cells in diabetic immunocompromised mice. Long-term control of glucose levels was achieved over 60 days, and differentiation of donor BM cells into insulin-producing cells in the subcutaneous Matrigel platforms, which were composed of islet-like cell clusters with extensive capillary networks, was confirmed along with the expression of key pancreatic β-cell markers. The resectioning of the subcutaneous Matrigel platforms caused a rebound in blood glucose levels and confirmed the source of functioning β-cells. Thus, efficient differentiation of therapeutic insulin-producing cells was attained in vivo through the use of extracellular vesicle-mimetic NVs, which maintained physiological glucose levels.

Outcome of xenografted fetal porcine pancreatic tissue is superior in inbred scid (C.B-17/Icr-scid/scid) compared to outbred nude (CD-1-nu/nu) mice

Nude mice are used as recipients of foreign tissue because of their inability to reject these grafts. Our experience has been that there is variable rejection of fetal porcine insulin-producing tissue transplanted into CD-1 (athymic) outbred nude mice. To examine the suitability of this line of nude mouse as a recipient of the tissue, fetal porcine pancreas was grafted either into these outbred animals or into an inbred mutant strain of mice, the more immunocompromised severe combined immunodeficient (scid) mouse. Eight weeks after transplantation grafts were recovered from recipients and assayed for insulin content. Mean insulin levels were not significantly different between the two groups of mice, but a wider range of values was obtained from grafts recovered from nude (CD-1-nu/nu) mice. Reversal of diabetes in hyperglycemic recipients was achieved in 4 of 8 nude mice and 8 of 8 scid (C.B-17/lcr-scid/scid) mice. The time taken to achieve this was longer in the nudes than the scid mice, 121 +/- 12 vs. 44 +/- 2 days, the grafts increasing in size at a slower rate in the nude mice. Time taken for the weight of the grafts to double in size was 94 +/- 17 vs. 32 +/- 1 days, respectively. Histologically the grafts in the scid mice contained mostly epithelial cell clusters, a majority of which were insulin containing. In the nude mice that achieved normoglycemia, a similar pattern was observed and, as well, there was a localized lymphoid infiltrate. In those nude mice that remained diabetic fibrous tissue predominated together with a lymphoid infiltrate. In summary, fetal porcine pancreatic tissue grows and develops more efficiently when xenografted into scid rather than outbred nude mice.