Joseph Fusco

Epidermal Growth Factor Receptor Signaling Regulates β Cell Proliferation in Adult Mice

A thorough understanding of the signaling pathways involved in the regulation of β cell proliferation is an important initial step in restoring β cell mass in the diabetic patient. Here, we show that epidermal growth factor receptor 1 (EGFR) was significantly up-regulated in the islets of C57BL/6 mice after 50% partial pancreatectomy (PPx), a model for workload-induced β cell proliferation. Specific deletion of EGFR in the β cells of adult mice impaired β cell proliferation at baseline and after 50% PPx, suggesting that the EGFR signaling pathway plays an essential role in adult β cell proliferation. Further analyses showed that β cell-specific depletion of EGFR resulted in impaired expression of cyclin D1 and impaired suppression of p27 after PPx, both of which enhance β cell proliferation. These data highlight the importance of EGFR signaling and its downstream signaling cascade in postnatal β cell growth.

Forkhead Box Protein 1 (FoxO1) Inhibits Accelerated β Cell Aging in Pancreas-specific SMAD7 Mutant Mice

The mechanisms underlying the effects of exocrine dysfunction on the development of diabetes remain largely unknown. Here we show that pancreatic depletion of SMAD7 resulted in age-dependent increases in β cell dysfunction with accelerated glucose intolerance, followed by overt diabetes. The accelerated β cell dysfunction and loss of proliferation capacity, two features of β cell aging, appeared to be non-cell-autonomous, secondary to the adjacent exocrine failure as a “bystander effect.” Increased Forkhead box protein 1 (FoxO1) acetylation and nuclear retention was followed by progressive FoxO1 loss in β cells that marked the onset of diabetes. Moreover, forced FoxO1 expression in β cells prevented β cell dysfunction and loss in this model. Thus, we present a model of accelerated β cell aging that may be useful for studying the mechanisms underlying β cell failure in diabetes. Moreover, we provide evidence highlighting a critical role of FoxO1 in maintaining β cell identity in the context of SMAD7 failure.

Autophagy protects pancreatic beta cell mass and function in the setting of a high-fat and high-glucose diet

Autophagy is a major regulator of pancreatic beta cell homeostasis. Altered autophagic activity has been implicated in the beta cells of patients with type 2 diabetes, and in the beta cells of obese diabetic rodents. Here, we show that autophagy was induced in beta cells by either a high-fat diet or a combined high-fat and high-glucose diet, but not by high-glucose alone. However, a high-glucose intake alone did increase beta cell mass and insulin secretion moderately. Depletion of Atg7, a necessary component of the autophagy pathway, in beta cells by pancreatic intra-ductal AAV8-shAtg7 infusion in C57BL/6 mice, resulted in decreased beta cell mass, impaired glucose tolerance, defective insulin secretion, and increased apoptosis when a combined high-fat and high-glucose diet was given, seemingly due to suppression of autophagy. Taken together, our findings suggest that the autophagy pathway may act as a protective mechanism in pancreatic beta cells during a high-calorie diet.

PNA lectin for purifying mouse acinar cells from the inflamed pancreas

Better methods for purifying human or mouse acinar cells without the need for genetic modification are needed. Such techniques would be advantageous for the specific study of certain mechanisms, such as acinar-to-beta-cell reprogramming and pancreatitis. Ulex Europaeus Agglutinin I (UEA-I) lectin has been used to label and isolate acinar cells from the pancreas. However, the purity of the UEA-I-positive cell fraction has not been fully evaluated. Here, we screened 20 widely used lectins for their binding specificity for major pancreatic cell types, and found that UEA-I and Peanut agglutinin (PNA) have a specific affinity for acinar cells in the mouse pancreas, with minimal affinity for other major pancreatic cell types including endocrine cells, duct cells and endothelial cells. Moreover, PNA-purified acinar cells were less contaminated with mesenchymal and inflammatory cells, compared to UEA-I purified acinar cells. Thus, UEA-I and PNA appear to be excellent lectins for pancreatic acinar cell purification. PNA may be a better choice in situations where mesenchymal cells or inflammatory cells are significantly increased in the pancreas, such as type 1 diabetes, pancreatitis and pancreatic cancer.

SMAD3/Stat3 Signaling Mediates β-Cell Epithelial-Mesenchymal Transition in Chronic Pancreatitis–Related Diabetes

Many patients with chronic pancreatitis develop diabetes (chronic pancreatitis–related diabetes [CPRD]) through an undetermined mechanism. Here we used long-term partial pancreatic duct ligation (PDL) as a model to study CPRD. We found that long-term PDL induced significant β-cell dedifferentiation, followed by a time-dependent decrease in functional β-cell mass—all specifically in the ligated tail portion of the pancreas (PDL-tail). High levels of transforming growth factor β1 (TGFβ1) were detected in the PDL-tail and were mainly produced by M2 macrophages at the early stage and by activated myofibroblasts at the later stage. Loss of β-cell mass was then found to result from TGFβ1-triggered epithelial-mesenchymal transition (EMT) by β-cells, rather than resulting directly from β-cell apoptosis. Mechanistically, TGFβ1-treated β-cells activated expression of the EMT regulator gene Snail in a SMAD3/Stat3-dependent manner. Moreover, forced expression of forkhead box protein O1 (FoxO1), an antagonist for activated Stat3, specifically in β-cells ameliorated β-cell EMT and β-cell loss and prevented the onset of diabetes in mice undergoing PDL. Together, our data suggest that chronic pancreatitis may trigger TGFβ1-mediated β-cell EMT to lead to CPRD, which could substantially be prevented by sustained expression of FoxO1 in β-cells.

Use of intraoperative nuclear imaging leads to decreased anesthesia time and real-time confirmation of lesion removal

BACKGROUND Lymphatic mapping to guide sentinel lymph node biopsy (SLNB) typically requires lymphoscintigraphy prior to surgery. In young pediatric patients, this process often requires intubation in the nuclear medicine suite followed by transport to the operating room (OR). METHODS We reviewed 14 pediatric cases in which a portable nuclear imaging camera was utilized to perform the entirety of the SLNB in the OR. RESULTS AND CONCLUSION This method, utilizing intraoperative nuclear imaging, helped to confirm removal of the sentinel lymph node in real time, decreased anesthesia time, and avoided transport of a sedated or intubated child. LEVEL OF EVIDENCE III.

Anatomy, Physiology, and Embryology of the Pancreas

Abstract The pancreas has fascinated developmental biologists, anatomists, and physiologists alike for many years. The embryologic development solely from the endoderm to produce an organ with two entirely distinct functions has led some to refer to the pancreas as truly “two organs in one.” Despite the contrasting function and morphology, these differing cell types are adjacent, allowing for the pancreas to accomplish both an exocrine and endocrine function. The endocrine pancreas, which comprises only 2% of the adult pancreatic mass, is organized into islets of Langerhans consisting of five cell subtypes—α, β, δ, ɛ, and PP cells—secreting glucagon, insulin, somatostatin, ghrelin, and pancreatic polypeptide hormones, respectively. The exocrine tissue on the other hand, which forms nearly 98% of the adult pancreatic mass, is composed of acinar and ductal epithelial cells. An understanding of the complex signaling pathways that lead to the development of pancreatic tissue could allow for the elucidation of treatment targets for a number of ailments afflicting the pancreas, including diabetes, pancreatitis, and pancreatic cancer. Here we review the basic anatomic and embryologic development of the pancreas.

GLP-1/Exendin-4 induces β-cell proliferation via the epidermal growth factor receptor

Exendin-4 is a long acting glucagon-like peptide 1 (GLP-1) analogue that is an agonist for the GLP-1 receptor, a G-protein coupled receptor (GPCR). Exendin-4 is used to clinically improve glucose tolerance in diabetic patients due to its ability to enhance insulin secretion. In rodents, and possibly in humans, exendin-4 can stimulate β-cell proliferation. The exact mechanism of action to induce β-cell proliferation is not well understood. Here, using a β-cell specific epidermal growth factor receptor (EGFR) null mouse, we show that exendin-4 induced an increase in proliferation and β-cell mass through EGFR. Thus, our study sheds light on the role of EGFR signaling in the effects of exendin-4 on the control of blood glucose metabolism and β-cell mass.

A large single-institution review of tracheoesophageal fistulae with evaluation of the use of transanastomotic feeding tubes

INTRODUCTION Transanastomatic feeding tube (TAT) use in the repair of tracheoesophageal fistulas (TEF) with or without esophageal atresia (EA) and EA with or without TEF allows for earlier enteral feedings, however, may predispose to esophageal stricture. METHODS We review our institutional experience with esophageal atresia repair over a 15-year period from 2000 to 2015 and report on our observed complication rate with emphasis on the surgical approach and use of TATs. RESULTS We identified 110 TEF repairs. Ninety-six were Type C, 7 were Type A, 4 were Type D, and 3 were Type E (H-Type). TATs were used in 74% of patients. The stricture rate with the TAT approached 56% versus 17% without a TAT (p<0.0005). There was no difference in leak rate (p=0.27). Ninety-four TEF repairs were performed via open thoracotomy, and 16 were initially approached thoracoscopically. Six out of 16 that were started thoracoscopically were completed with the minimally invasive approach. Whether the case was started thoracoscopically, completed thoracoscopically, or performed open made no difference in the rate of stricture or anastomotic leak, but we did observe an increase in musculoskeletal complications in the open thoracotomy group (28% vs. 0). CONCLUSION Our data suggests that the use of TATs does not protect against anastomotic leak, but may increase stricture rate. Further, the thoracoscopic group showed no difference in the leak or stricture rate and demonstrated less musculoskeletal complications. Confirmation of these findings will require a prospective study. LEVEL OF EVIDENCE III.

A synopsis of factors regulating beta cell development and beta cell mass

The insulin-secreting beta cells in the endocrine pancreas regulate blood glucose levels, and loss of functional beta cells leads to insulin deficiency, hyperglycemia (high blood glucose) and diabetes mellitus. Current treatment strategies for type-1 (autoimmune) diabetes are islet transplantation, which has significant risks and limitations, or normalization of blood glucose with insulin injections, which is clearly not ideal. The type-1 patients can lack insulin counter-regulatory mechanism; therefore, hypoglycemia is a potential risk. Hence, a cell-based therapy offers a better alternative for the treatment of diabetes. Past research was focused on attempting to generate replacement beta cells from stem cells; however, recently there has been an increasing interest in identifying mechanisms that will lead to the conversion of pre-existing differentiated endocrine cells into beta cells. The goal of this review is to provide an overview of several of the key factors that regulate new beta cell formation (neogenesis) and beta cell proliferation.