This proposal focuses on understanding how the major physiological changes occurring during the first postnatal month regulate the sharp changes in expression of key phenotypic ? cell genes and drive functional maturation of ? cells. Surprisingly little is known about the later stages of ? cell maturation. This has assumed practical importance because in vitro human ES-derived cells insulin-producing cells lack the glucose-responsive insulin secretion that is characteristic of a functional ? cell. Neonatal rodent islets also lack this glucose responsiveness and so serve as a model for the induction of the maturation process. Across the first postnatal month as the glucose-stimulated insulin secretion gradually develops, we found multiple patterns of islet gene expression, most with striking inflection points between P7 and 9 days and again about P15. While we have shown that adenoviral-mediated expression of MafA induced glucose- stimulated insulin secretion (GSIS) almost to adult levels, the developmental enhancement of MafA and other necessary genes must be regulated by physiological stimuli. The dynamic neonatal environment that is very different from that of the adult provides the landscape of these changes: at P1 blood glucose levels are low, as are levels of thyroid hormones (T3 and T4), of corticosterone (the main glucocorticoid of the rat) and of prolactin, and the diet is only milk. Serum T4 levels start changing around P7 and peak at P13 while leptin surges also about P8;there are surges of corticosterone and prolactin around P15 The timing of these hormonal surges suggests that they are the physiological regulators needed for neonatal ? cells to become functional. To address this question we have three specific aims.
Specific aim 1. To determine the mechanisms for thyroid hormone enhancement of ? cell maturation. We show preliminary data that T3 induces glucose responsive insulin secretion and that is mediated by the transcription factor MafA. We propose experiments to dissect the mechanism of T3's regulation of MafA and other genes induced for functional maturation.
Specific aim 2. To determine the importance of the candidate factors T3, leptin, corticosterone and prolactin on ? cell maturation. The environment of the neonate is very different than that of the adult and dynamic. We hypothesize that various physiological factors regulate the maturation of the ? cell and are particularly attracted to three hormonal candidates, in addition to thyroid hormone, that may play key roles: plasma leptin concentrations surge at about the P7 inflection point, while corticosterone and prolactin concentrations are gradually increasing until a surge at about P15, the second key inflection point.
Specific aim 3. To determine if the physiological factors that are effective in maturing the neonatal rat B cell will similarly direct in vitro functional maturation of the immature human pancreatic progenitors. In this translational aim our goal is to transfer to fetal human pancreatic cells the knowledge of the physiological signals for in vivo maturation gained in the first two aims.
Diabetes results from an inadequate mass of functional insulin-secreting ? cells, so the replacement or expansion of the pancreatic ? cells is seen as attractive potential therapies. This application is focused on the important question of how ? cells mature to secrete insulin in response to increasing glucose. Understanding the molecular mechanisms that govern maturation of functional ? cells should provide a basis for the development of new in vitro techniques to provide ? cells that can be used for the treatment of diabetes.
|Cavelti-Weder, Claudia; Li, Weida; Zumsteg, Adrian et al. (2016) Hyperglycaemia attenuates in vivo reprogramming of pancreatic exocrine cells to beta cells in mice. Diabetologia 59:522-32|
|Bonner-Weir, Susan; Aguayo-Mazzucato, Cristina (2016) Physiology: Pancreatic Î²-cell heterogeneity revisited. Nature 535:365-6|
|Vegas, Arturo J; Veiseh, Omid; Doloff, Joshua C et al. (2016) Combinatorial hydrogel library enables identification of materials that mitigate the foreign body response in primates. Nat Biotechnol 34:345-52|
|Bonner-Weir, Susan; Aguayo-Mazzucato, Cristina; Weir, Gordon C (2016) Dynamic development of the pancreas from birth to adulthood. Ups J Med Sci 121:155-8|
|Bonner-Weir, Susan; Sullivan, Brooke A; Weir, Gordon C (2015) Human Islet Morphology Revisited: Human and Rodent Islets Are Not So Different After All. J Histochem Cytochem 63:604-12|
|Yamada, Takatsugu; Cavelti-Weder, Claudia; Caballero, Francisco et al. (2015) Reprogramming Mouse Cells With a Pancreatic Duct Phenotype to Insulin-Producing Î²-Like Cells. Endocrinology 156:2029-38|
|Aguayo-Mazzucato, Cristina; DiIenno, Amanda; Hollister-Lock, Jennifer et al. (2015) MAFA and T3 Drive Maturation of Both Fetal Human Islets and Insulin-Producing Cells Differentiated From hESC. J Clin Endocrinol Metab 100:3651-9|
|Sullivan, Brooke A; Hollister-Lock, Jennifer; Bonner-Weir, Susan et al. (2015) Reduced Ki67 Staining in the Postmortem State Calls Into Question Past Conclusions About the Lack of Turnover of Adult Human Î²-Cells. Diabetes 64:1698-702|
|Caballero, Francisco; Siniakowicz, Karolina; Hollister-Lock, Jennifer et al. (2014) Birth and death of human *-cells in pancreases from cadaver donors, autopsies, surgical specimens, and islets transplanted into mice. Cell Transplant 23:139-51|
|Cavelti-Weder, Claudia; Shtessel, Maria; Reuss, Joshua E et al. (2013) Pancreatic duct ligation after almost complete Î²-cell loss: exocrine regeneration but no evidence of Î²-cell regeneration. Endocrinology 154:4493-502|
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