Publications by authors named "George Harb"

National Eye Institute recently issued a new Strategic Plan outlining priority research areas for the next 5 years. Starting cell source for deriving stem cell lines is as an area with gaps and opportunities for making progress in regenerative medicine, a key area of emphasis within the NEI Strategic Plan. There is a critical need to understand how starting cell source affects the cell therapy product and what specific manufacturing capabilities and quality control standards are required for autologous vs allogeneic stem cell sources.

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Loss of β-cell mass and function can lead to insufficient insulin levels and ultimately to hyperglycemia and diabetes mellitus. The mainstream treatment approach involves regulation of insulin levels; however, approaches intended to increase β-cell mass are less developed. Promoting β-cell proliferation with low-molecular-weight inhibitors of dual-specificity tyrosine-regulated kinase 1A (DYRK1A) offers the potential to treat diabetes with oral therapies by restoring β-cell mass, insulin content and glycemic control.

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Autoimmune deficiency and destruction in either β-cell mass or function can cause insufficient insulin levels and, as a result, hyperglycemia and diabetes. Thus, promoting β-cell proliferation could be one approach toward diabetes intervention. In this report we describe the discovery of a potent and selective DYRK1A inhibitor GNF2133, which was identified through optimization of a 6-azaindole screening hit.

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In vitro differentiation of human stem cells can produce pancreatic β-cells; the loss of this insulin-secreting cell type underlies type 1 diabetes. Here, as a step towards understanding this differentiation process, we report the transcriptional profiling of more than 100,000 human cells undergoing in vitro β-cell differentiation, and describe the cells that emerged. We resolve populations that correspond to β-cells, α-like poly-hormonal cells, non-endocrine cells that resemble pancreatic exocrine cells and a previously unreported population that resembles enterochromaffin cells.

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Small-molecule inhibitors of dual-specificity tyrosine-regulated kinase 1A (DYRK1A) induce human beta cells to proliferate, generating a labeling index of 1.5%-3%. Here, we demonstrate that combined pharmacologic inhibition of DYRK1A and transforming growth factor beta superfamily (TGFβSF)/SMAD signaling generates remarkable further synergistic increases in human beta cell proliferation (average labeling index, 5%-8%, and as high as 15%-18%), and increases in both mouse and human beta cell numbers.

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Type 2 diabetes mellitus is prevalent especially in Gulf countries and poses serious long-term risks to patients. A multifaceted treatment approach can include nutritional supplements with antioxidant properties such as 5-aminolevulinic acid (5-ALA) with sodium ferrous citrate (SFC). This prospective, randomized, single-blind, placebo-controlled, dose escalating pilot clinical trial assessed the safety of 5-ALA with SFC at doses up to 200 mg 5-ALA/229.

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Insufficient pancreatic β-cell mass or function results in diabetes mellitus. While significant progress has been made in regulating insulin secretion from β-cells in diabetic patients, no pharmacological agents have been described that increase β-cell replication in humans. Here we report aminopyrazine compounds that stimulate robust β-cell proliferation in adult primary islets, most likely as a result of combined inhibition of DYRK1A and GSK3B.

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Objective: To evaluate the cost-effectiveness of recombinant human hyaluronidase-facilitated subcutaneous (rHFSC) fluid administration compared to intravenous (IV) fluid administration in children with mild to moderate dehydration in the emergency department (ED).

Methods: A decision analytic model was created based on the results of a controlled clinical trial that compared the administration of isotonic fluids via rHFSC or IV for rehydration. The costs were determined from the hospital's perspective.

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The identification of factors that promote β cell proliferation could ultimately move type 1 diabetes treatment away from insulin injection therapy and toward a cure. We have performed high-throughput, cell-based screens using rodent β cell lines to identify molecules that induce proliferation of β cells. Herein we report the discovery and characterization of WS6, a novel small molecule that promotes β cell proliferation in rodent and human primary islets.

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Background: Alternative treatment of dehydration is needed when intravenous (IV) or oral rehydration therapy fails. Subcutaneous (SC) hydration facilitated by recombinant human hyaluronidase offers an alternative treatment for dehydration. This clinical trial is the first to compare recombinant human hyaluronidase-facilitated SC (rHFSC) rehydration with standard IV rehydration for use in dehydrated children.

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Introduction: Recombinant human hyaluronidase facilitates subcutaneous (SC) fluid delivery, but little is known about how various access sets influence ease of administration, technical challenges (TCs), or adverse events.

Methods: This randomized, open-label, parallel-group trial was performed to assess the impact of catheter size (20- and 24-gauge short peripheral intravenous catheter, 27-gauge SC button), catheter material (Teflon, polyurethane), and securement method (transparent semipermeable membrane dressing [TSM], double chevron with cloth or plastic tape) on hyaluronidase-facilitated SC fluid delivery. Healthy volunteers (N = 100) were randomized to 1 of 9 access groups using a factorial design.

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Objective: Inducing human β-cell growth while enhancing function is a major goal in the treatment of diabetes. Parathyroid hormone-related protein (PTHrP) enhances rodent β-cell growth and function through the parathyroid hormone-1 receptor (PTH1R). Based on this, we hypothesized that PTH1R is expressed in human β-cells and that PTHrP has the potential to enhance human β-cell proliferation and/or function.

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Objective: To compare pharmacokinetics and safety of recombinant human hyaluronidase (rHuPH20)-facilitated subcutaneous (SC) ceftriaxone administration versus SC ceftriaxone preceded by SC saline placebo or intravenous (IV) ceftriaxone administration.

Research Design And Methods: This Phase I, two-part, placebo-controlled, crossover study was conducted in 54 healthy volunteers. In Part 1 (N = 24), subjects received 1 mL rHuPH20 (150 USP units) or placebo (0.

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Objectives: The Increased Flow Utilizing Subcutaneously-Enabled (INFUSE)-Pediatric Rehydration Study was designed to assess efficacy, safety, and clinical utility of recombinant human hyaluronidase (rHuPH20)-facilitated subcutaneous rehydration in children 2 months to 10 years of age.

Methods: Patients with mild/moderate dehydration requiring parenteral treatment in US emergency departments were eligible for this phase IV, multicenter, single-arm study. They received subcutaneous injection of 1 mL rHuPH20 (150 U), followed by subcutaneous infusion of 20 mL/kg isotonic fluid over the first hour.

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Objective: The retinoblastoma protein family (pRb, p130, p107) plays a central role in the regulation of cell cycle progression. Surprisingly, loss of pRb in the beta-cell has no discernible effect on cell cycle control. Therefore, we explored the effects of individual loss of either p130 or p107 in addition to the simultaneous loss of both pRb/p130 on the beta-cell.

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Allogeneic islet transplantation is an option to treat diabetes however there are obstacles that are limiting its clinical use. We have examined whether mesenchymal stem cells (MSC) improve islet graft survival and whether such therapy allows for better graft acceptance with reduced requirement for immunosuppression. In vitro-expanded syngeneic bone marrow-derived MSC were co-transplanted with islets into omental pouch in a rat model of streptozotocin-induced diabetes.

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Several studies have demonstrated that in vitro culture of islets prolonged islet graft survival in immune-competent mice without administration of antirejection drugs. However, we recently showed that in vitro cultured microencapsulated neonatal porcine islets (NPI) were rejected in immune-competent mice not receiving antirejection therapy. The aim of this study was to determine whether culture of microencapsulated NPI in vivo could promote long-term survival of microencapsulated NPI in immune-competent mice without administration of antirejection drugs.

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Objectives: To comprehensively inventory the proteins that control the G1/S cell cycle checkpoint in the human islet and compare them with those in the murine islet, to determine whether these might therapeutically enhance human beta-cell replication, to determine whether human beta-cell replication can be demonstrated in an in vivo model, and to enhance human beta-cell function in vivo.

Research Design And Methods: Thirty-four G1/S regulatory proteins were examined in human islets. Effects of adenoviruses expressing cdk-6, cdk-4, and cyclin D1 on proliferation in human beta-cells were studied in both in vitro and in vivo models.

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Objective: Rodent insulinoma cell lines may serve as a model for designing continuously replicating human beta-cell lines and provide clues as to the central cell cycle regulatory molecules in the beta-cell.

Research Design And Methods: We performed a comprehensive G1/S proteome analysis on the four most widely studied rodent insulinoma cell lines and defined their flow cytometric profiles and growth characteristics.

Results: 1) Despite their common T-antigen-derived origins, MIN6 and BTC3 cells display markedly different G1/S expression profiles; 2) despite their common radiation origins, RINm5F and INS1 cells display striking differences in cell cycle protein profiles; 3) phosphorylation of pRb is absent in INS1 and RINm5F cells; 4) cyclin D2 is absent in RINm5F and BTC3 cells and therefore apparently dispensable for their proliferation; 5) every cell cycle inhibitor is upregulated, presumably in a futile attempt to halt proliferation; 6) among the G1/S proteome members, seven are pro-proliferation molecules: cyclin-dependent kinase-1, -2, -4, and -6 and cyclins A, E, and D3; and 7) overexpression of the combination of these seven converts arrested proliferation rates in primary rat beta-cells to those in insulinoma cells.

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Leptin injections evoke weight loss by causing a reduction in food consumption and an increase in energy expenditure. Also, the administration of leptin lowers blood glucose levels in some rodent models of diabetes and in humans with lipodystrophy. We explored the therapeutic potential of delivering leptin to obese, diabetic ob/ob mice and to mice fed on a high-fat diet (HFD), by transplanting gut-derived cells engineered to produce leptin, under the regulation of an inducing agent, mifepristone.

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Closure of pancreatic beta-cell ATP-sensitive potassium (K(ATP)) channels links glucose metabolism to electrical activity and insulin secretion. It is now known that saturated, but not polyunsaturated, long-chain acyl-coenyzme A esters (acyl-CoAs) can potently activate K(ATP) channels when superfused directly across excised membrane patches, suggesting a plausible mechanism to account for reduced beta-cell excitability and insulin secretion observed in obesity and type 2 diabetes. However, reduced beta-cell excitability due to elevation of endogenous saturated acyl-CoAs has not been confirmed in intact pancreatic beta-cells.

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Unlabelled: Chronic hepatitis B and its life-threatening sequelae are highly prevalent in China. There is a need for effective new therapies to suppress hepatitis B virus (HBV) replication and ameliorate liver disease. In this study, we compared the efficacy of telbivudine, a nucleoside analogue, with lamivudine in Chinese patients.

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Background: Neonatal porcine islets (NPI) are a potentially useful source of beta cells for transplantation to treat type 1 diabetes mellitus. However, cytokine exposure following xenotransplantation is likely to prevent successful NPI xenograft survival. In this study, we examined the effects of human proinflammatory cytokines (IL-1 beta, IFN gamma, TNFalpha) on NPI function and cell death.

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Background: The efficacy of nucleoside and nucleotide analogues for hepatitis B has been linked to the magnitude and durability of hepatitis B virus (HBV) suppression.

Objective: To compare the antiviral efficacy of telbivudine and adefovir dipivoxil, and the effects of switching from adefovir to telbivudine, in hepatitis B e antigen (HBeAg)-positive patients with chronic hepatitis B.

Design: Randomized, controlled, open-label trial.

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Prolonged exposure to high glucose can influence the function, growth, and survival of pancreatic beta-cells. In this study, we examine the effects of prolonged in vitro exposure to high glucose on neonatal porcine beta-cells, a potentially useful source of insulin-producing cells for clinical islet transplantation. Neonatal porcine islets were prepared by culturing collagenase-digested pancreases for 1 week in 5.

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