Joslin Diabetes Research - Section Details

Because reduced beta-cell mass is fundamental to the pathogenesis of both type 1 and type 2 diabetes, a major goal is to restore this deficiency with β-cell replacement or regeneration. The long-standing collaboration among the lab heads in this section is exceptional, especially with Weir (diabetic and transplant models, and islet function), Bonner-Weir (cell biology of islet structure, growth and development) and Sharma (molecular biology and development). Dr. Lipes, a more recent addition to the section, has collaborated with Weir and Bonner-Weir on the development of surrogate beta cells. Although the section’s emphasis is on preclinical work, it does participate in a clinical program in islet transplantation, which has provided benefit to a small number of patients. There are projects focused on the transcriptional control of pancreas and islet development in fetal life and in embryonic stem cells. As concerns the postnatal period, there is work on the development of new islets from rodent and human pancreatic progenitor cells. Studies on transdifferentiation explore whether hepatocytes can be genetically induced to become beta cells. Genetic engineering is used to enable pituitary cells to secrete insulin in response to glucose. Biomaterials are being used to coat islets to protect them from the immune destruction when transplanted. Beta cells exposed to the hyperglycemia of diabetes have deranged function, leading to decreased insulin secretion; the molecular mechanisms responsible are being evaluated.

Weir Lab:

Projects include clinical and preclinical islet transplantation, microencapsulation of islets, transdifferentiation, beta-cell expansion and beta-cell changes induced by the diabetic state. More specifically:

Assessment of isolated islets prior to transplantation for cell composition, viability and function. Use of flow cytometry to sort cells prior to transplantation.

Encapsulation to protect rodent and porcine islet cells from transplant rejection and autoimmunity with an emphasis on improving packing density and function using islet cell aggregates and perfluorocarbon.

Use of high-throughput screening of chemical libraries to find agents that stimulate beta-cell replication.

Transdifferentiation of mouse hepatocytes with viral transduction of islet transcription factors.

Use of laser-capture microdissection and gene expression to assess human beta cells in type 2 diabetes and after transplantation into rodent recipients.

Bonner-Weir Lab:

The lab is primarily concerned with the study of new beta-cell formation through neogenesis, embryonic stem cells and beta-cell replication. For example:

Lineage tracing in transgenic mice using carbonic anhydrase II to mark ductal cells showing that they function as progenitors for islet and pancreas regeneration.

In vitro lineage tracing of human pancreatic cells to track progenitors of the newly generated beta cells.

Search for surface markers on newly formed beta cells to separate early stages of beta cell differentiation

Determination of factors involved in regeneration in vivo; their use in vitro to enhance islet differentiation.

Sharma Lab:

The primary focus of this group is to study transcription factors and transcriptional control in regulating pancreas development and beta-cell function. Current approaches include knockout and transgenic mice, ex-vivo and cell culture systems, lenti-, retro-, and adenoviral expression systems, RNAi, transfections, and biochemical and molecular characterization of transcription factors. Major foci of study include:

Discovery of MafA by the lab led to examination of the role of the Maf family of transcription factors in pancreas development and beta-cell function.

Identification of transcription factors regulating duct-specific gene expression.

Determination of signals that regulate pancreas regeneration.

Lipes Lab:

The lab uses genetic engineering to develop surrogate beta cells for the treatment of T1D, and studies the mechanisms of their susceptibility to immune attack. Other work focuses on heart as a target for autoimmunity.
Some of the major areas of interest are:

Intermediate lobe pituitary cells transgenically engineered to produce large amounts of insulin can reverse hyperglycemia when transplanted into diabetic NOD mice, and these cells evade autoimmune attack. Adenoviral vectors and transgenic mouse techniques introduce glucose-sensing properties into cells, and their evaluation includes Fura-2 Ca2+ imaging, specialized cell-culture systems and transplantation.

Autoimmune myocarditis, previously thought to be of infectious etiology, was shown to be an organ-specific autoimmune disease associated with HLA-DQ8. Tissue injury from myocardial infarction precipitates pathogenic autoimmune heart disease in NOD mice, with clinical studies of similar findings in a subset of human T1D patients.

Five recent “highpoints”:

Identification and cloning of transcription factor MafA. Proc. Natl. Acad. Sci., 2002.

Demonstration using lineage tracing that pancreatic duct cells serve as multipotent progenitors for pancreas and islet regeneration.

Discovery that myocardial infarction can precipitate pathogenic autoimmunity in NOD mice.

Demonstration that differentiation of insulin expressing cells proceeds through a switch in the expression of Maf factors that follows induction of transcription factor PDX-1. Dev. Biol., 2006.

Finding that simple alginate microcapsules can protect transplanted porcine islet cells from immune destruction. Diabetes, 2003; Am J Trans, 2004.