Sean W Limesand
Chair, Institutional Animal Care-USE Committee
Director, Agriculture Research Complex
Professor, Animal and Comparative Biomedical Sciences
Professor, BIO5 Institute
Professor, Obstetrics and Gynecology
Professor, Physiological Sciences - GIDP
Department Affiliations
(520) 626-8903
Work Summary
Our current research program use an integrative approach at the whole animal, isolated organ, cellular and molecular levels to investigate developmental adaptations in pancreatic β-cells and insulin sensitivity that result from early life risk factors, such as intrauterine growth restriction, and increase risk of glucose intolerance and Diabetes in later life.
Research Interest
Sean W. Limesand, PhD, is an Associate Professor in the School of Animal and Comparative Biomedical Sciences at the University of Arizona in the College of Agriculture and Life Sciences. He is also a member of the UA’s BIO5 Institute and Department of Obstetrics and Gynecology. Dr. Limesand is nationally and internationally recognized for his work studying fetal endocrinology and metabolism in pregnancy and in pregnancies compromised by pathology such as intrauterine growth restriction and diabetes. His research is focused on defining developmental consequences resulting from a compromised intrauterine environment. Specifically, he is focused on fetal adaptations in insulin secretion and action that when altered in utero create lifelong metabolic complications. Dr. Limesand has lead the charge on prenatal origins of –cell dysfunction as the Principal Investigator for a number of federal and foundation grant awards and published more than 40 peer-reviewed articles on topics related to this research. Keywords: Diabetes, Pregnancy, Perinatal Biology

Publications

Cole, L., Anderson, M., Antin, P. B., & Limesand, S. W. (2009). One process for pancreatic beta-cell coalescence into islets involves an epithelial-mesenchymal transition. The Journal of endocrinology, 203(1), 19-31.
BIO5 Collaborators
Parker B Antin, Sean W Limesand

Islet replacement is a promising therapy for treating diabetes mellitus, but the supply of donor tissue for transplantation is limited. To overcome this limitation, endocrine tissue can be expanded, but this requires an understanding of normal developmental processes that regulate islet formation. In this study, we compare pancreas development in sheep and human, and provide evidence that an epithelial-mesenchymal transition (EMT) is involved in beta-cell differentiation and islet formation. Transcription factors know to regulate pancreas formation, pancreatic duodenal homeobox factor 1, neurogenin 3, NKX2-2, and NKX6-1, which were expressed in the appropriate spatial and temporal pattern to coordinate pancreatic bud outgrowth and direct endocrine cell specification in sheep. Immunofluorescence staining of the developing pancreas was used to co-localize insulin and epithelial proteins (cytokeratin, E-cadherin, and beta-catenin) or insulin and a mesenchymal protein (vimentin). In sheep, individual beta-cells become insulin-positive in the progenitor epithelium, then lose epithelial characteristics, and migrate out of the epithelial layer to form islets. As beta-cells exit the epithelial progenitor cell layer, they acquire mesenchymal characteristics, shown by their acquisition of vimentin. In situ hybridization expression analysis of the SNAIL family members of transcriptional repressors (SNAIL1, -2, and -3; listed as SNAI1, -2, -3 in the HUGO Database) showed that each of the SNAIL genes was expressed in the ductal epithelium during development, and SNAIL-1 and -2 were co-expressed with insulin. Our findings provide strong evidence that the movement of beta-cells from the pancreatic ductal epithelium involves an EMT.

Hiscox, A. M., Stone, A. L., Limesand, S., Hoying, J. B., & Williams, S. K. (2008). An islet-stabilizing implant constructed using a preformed vasculature. Tissue Engineering - Part A., 14(3), 433-440.

PMID: 18333795;Abstract:

Islet transplantation for the purpose of treating insulin-sensitive diabetes is currently limited by several factors, including islet survival posttransplantation. In the current study, a tissue-engineered prevascularized pancreatic encapsulating device (PPED) was developed. Isolated islets were placed in collagen gels, and they exhibited fourfold more insulin release than islets not in collagen. The insulin released by β-cells in islets encapsulated in collagen exhibited unobstructed diffusion within the collagen gels. Subsequent studies evaluated the ability to create a sandwich comprised of two layers of prevascularized collagen gels around a central collagen gel containing islets. In vitro characterization of the islets showed that islets are functional and responded to glucose stimulation. The PPEDs were implanted subcutaneously into severe combined immunodeficient mice. Islet survival was assessed after 7, 14, and 28 days. Immunohistochemical analysis was performed on the implants to detect insulin and the presence of intraislet endothelial cells. At all time points, insulin was localized in association with intact and partially dissociated islets. Moreover, cells that exhibited insulin staining were colocalized with intraislet endothelial cells. These data indicate that the PPED enhances islet survival by supporting islet viability and maintaining intraislet endothelial cell structures. © Copyright 2008, Mary Ann Liebert, Inc.

Green, A. S., Rozance, P. J., & Limesand, S. W. (2010). Consequences of a compromised intrauterine environment on islet function (Journal of Endocrinology (2010) 205 (211-224)). Journal of Endocrinology, 206(3), 335-.
Limesand, S. W., & Hay Jr., W. W. (2003). Adaptation of ovine fetal pancreatic insulin secretion to chronic hypoglycaemia and euglycaemic correction. Journal of Physiology, 547(1), 95-105.

PMID: 12562941;PMCID: PMC2342612;Abstract:

Fetal pancreatic adaptations to relative hypoglycaemia, a characteristic of intra-uterine growth restriction, may limit pancreatic β-cell capacity to produce and/or secrete insulin. The objective of this study was to measure β-cell responsiveness in hypoglycaemic (H) fetal sheep and ascertain whether a 5 day euglycaemic recovery period would restore insulin secretion capacity. Glucose-stimulated insulin secretion (GSIS) was measured in euglycaemic (E) control fetuses, fetuses made hypoglycaemic for 14 days, and in a subset of 14-day hypoglycaemic fetuses returned to euglycaemia for 5 days (R fetuses). Hypoglycaemia significantly decreased plasma insulin concentrations in H (0.13 ± 0.01 ng ml-1) and R fetuses (0.11 ± 0.01 ng ml-1); insulin concentrations returned to euglycaemic control values (0.30 ± 0.01 ng ml-1) in R fetuses (0.29 ± 0.04 ng ml-1) during their euglycaemic recovery period. Mean steady-state plasma insulin concentration during the GSIS study was reduced in H fetuses (0.40 ± 0.07 vs. 0.92 ± 0.10 ng ml-1 in E), but increased (P -1) to concentrations not different from those in the E group. Nonlinear modelling of GSIS showed that response time was greater (P -1 in H vs. 1.82 ± 0.17 ng ml-1 in E, P -1 in R, P

Anthony, R. V., Limesand, S. W., & Jeckel, K. M. (2001). Transcriptional regulation in the placenta during normal and compromised fetal growth. Biochemical Society Transactions, 29(2), 42-48.

PMID: 11356124;Abstract:

The placenta synthesizes a number of cytokines and growth factors that are involved in the establishment, maintenance or regulation of pregnancy. Included are interferons, placental lactogens, other members of the growth hormone/prolactin gene family, leptin, and an array of angiogenic growth factors. While their roles in pregnancy differ, in their absence pregnancy is either lost or compromised. Therefore an understanding of the cell-specific transcriptional regulation of these genes is imperative if we are ever to alter their expression to benefit pregnancy progression. Our understanding of transcriptional regulation in the placenta is still in its infancy, and there appears to be considerable divergence in the transcriptional regulation of these genes between species, as well as between the various cytokine genes being examined. For example, while there are some commonalities in the regulation of human, rodent and ruminant placental lactogens, there are differences that require the study of placental lactogen gene regulation across species. However, one common theme that is emerging with the angiogenic growth factors, such as vascular endothelial growth factor and the angiopoietins, is the transcriptional control of these genes by oxygen tension within the placenta. Examination of transcriptional regulation in normal and compromised pregnancies will provide additional insight in this area.