NeuroD-betacellulin gene therapy induces islet neogenesis in the liver and reverses diabetes in mice

Abstract

To explore induced islet neogenesis in the liver as a strategy for the treatment of diabetes, we used helper-dependent adenovirus (HDAD) to deliver the pancreatic duodenal homeobox-1 gene (Ipf1; also known as Pdx-1) to streptozotocin (STZ)-treated diabetic mice. HDAD is relatively nontoxic as it is devoid of genes encoding viral protein. Mice treated with HDAD-Ipf1 developed fulminant hepatitis, however, because of the exocrine-differentiating activity of Ipf1. The diabetes of STZ mice was partially reversed by HDAD-mediated transfer of NeuroD (Neurod), a factor downstream of Ipf1, and completely reversed by a combination of Neurod and betacellulin (Btc), without producing hepatitis. Treated mice were healthy and normoglycemic for the duration of the experiment (>120 d). We detected in the liver insulin and other islet-specific transcripts, including proinsulin-processing enzymes, beta-cell-specific glucokinase and sulfonylurea receptor. Immunocytochemistry detected the presence of insulin, glucagon, pancreatic polypeptide and somatostatin-producing cells organized into islet clusters; immuno-electron microscopy showed typical insulin-containing granules. Our data suggest that Neurod-Btc gene therapy is a promising regimen to induce islet neogenesis for the treatment of insulin-dependent diabetes.

A feat of metabolic proportions: Pdx1 orchestrates islet development and function in the maintenance of glucose homeostasis

“…Given the broad role of Pdx1 in the differentiation of cell types with the pancreas and in the maintenance of β cell function and mass (see summary in Table I), preclinical studies have recently focused on the therapeutic potential for Pdx1 and related factors to reverse Type 1 diabetes. For example, viral-mediated expression of Pdx1 in liver cells appears to stimulate a host of pancreas-related genes (including insulin), leading to reversal of chemically-induced diabetes in mice [158][159][160][161]. From a delivery perspective, transduction of Pdx1 using viruses may not be requisite.…”

Gutless adenovirus: last-generation adenovirus for gene therapy

“…68 Gutless vectors have been shown to express non-immunogenic transgenes during the whole life of the mouse, while expression driven by first-generation adenovirus lasted at most for 3 months. [80][81][82] Therapeutic genes carried by gutless vectors have been administered to the liver of mouse models for different diseases, such as hemophilia A and B, 83,84 obesity, 66 familial hypercholesterolemia, 81,85-87 ornithine transcarbamylase deficiency, 88 diabetes 89 and chronic viral hepatitis. 90,91 Therapeutic levels of most proteins have been documented for a long-term duration.…”

Liver stem cell-derived β-cell surrogates for treatment of type 1 diabetes

“…However, neither of these genes has successfully converted hepatocytes into purely endocrine pancreas [17,18]. Severe hepatitis observed in mice treated with Pdx-1 [19] was attributed to the production of pancreatic exocrine enzymes released by Pdx-1-induced pancreatic/hepatic hybrid cells [19]. Other studies demonstrate that transient expression of Pdx1-VP16, a constitutively active form of Pdx1, designed to activate target genes without the need for protein partners [20], in the liver resulted in more effective conversion of liver to pancreatic tissue than Pdx1 [21][22][23].…”

“…Controversy arose as to whether expression of Pdx1 alone is sufficient to convert the liver cells into pancreatic beta-cells [17,19]. Transient adenovirus-mediated expression of Pdx1 alone in mouse liver activates pancreatic endocrine and exocrine genes [17,18], the latter reportedly resulting in severe hepatitis [19].…”