Camillo Ricordi

Targeting recombinant adeno-associated virus vectors to enhance gene transfer to pancreatic islets and liver

Human pancreatic islet cells and hepatocytes represent the two most likely target cells for genetic therapy of type I diabetes. However, limits to the efficiency of rAAV serotype 2 (rAAV2)-mediated gene transfer have been reported for both of these cell targets. Here we report that nonserotype 2 AAV capsids can mediate more efficient transduction of islet cells, with AAV1 being the most efficient serotype in murine islets, suggesting that receptor abundance could be limiting. In order to test this, we generated rAAV particles that display a ligand (ApoE) that targets the low-density lipoprotein receptor, which is present on both of these cell types. The rAAV/ApoE viruses greatly enhanced the efficiency of transduction of both islet cells ex vivo and murine hepatocytes in vivo when compared to native rAAV2 serotype (220- and four-fold, respectively). The use of receptor-targeted rAAV particles may circumvent the lower abundance of receptors on certain nonpermissive cell types.

Bone Marrow-Derived Stem Cell Transplantation for the Treatment of Insulin-Dependent Diabetes

The bone marrow is an invaluable source of adult pluripotent stem cells, as it gives rise to hematopoietic stem cells, endothelial progenitor cells, and mesenchymal cells, amongst others. The use of bone marrow-derived stem cell (BMC) transplantation (BMT) may be of assistance in achieving tissue repair and regeneration, as well as in modulating immune responses in the context of autoimmunity and transplantation. Ongoing clinical trials are evaluating the effects of BMC to preserve functional beta-cell mass in subjects with type 1 and type 2 diabetes, and to favor engraftment and survival of transplanted islets. Additional trials are evaluating the impact of BMT (i.e., mesenchymal stem cells) on the progression of diabetes complications. This article reviews the progress in the field of BMC for the treatment of subjects with insulin-dependent diabetes, and summarizes clinical data of pilot studies performed over the last two decades at our research center by combining allogeneic islet transplantation with donor-specific BMC. Clinical data is summarized from pilot studies performed at our research center over the last two decades.

Adeno-associated virus transduction of islets with interleukin-4 results in impaired metabolic function in syngeneic marginal islet mass transplantation.

Previous studies suggest that therapeutic expression of interleukin (IL)-4 by islet cells improves their efficacy in transplantation models directed at reversing type 1 diabetes. We investigated the effects of introducing IL-4 into islets with recombinant adeno-associated virus (rAAV) on the reversal of hyperglycemia in a syngeneic marginal islet mass transplantation model. C57BL/6 islets were mock-transduced or transduced with rAAV expressing murine IL-4 (rAAV-IL-4) or rAAV expressing green fluorescent protein (rAAV-GFP) before transplantation of a marginal mass into diabetic mice. Normoglycemia was achieved in only 1/7 mice receiving rAAV-IL-4 transduced islets in comparison to 6/6 mock-transduced and 4/6 rAAV-GFP transduced animals. The failure of IL-4 expressing islets was not associated with cellular toxicity of rAAV or impairment of glucose-stimulated insulin release in vitro. Islet expression of IL-4 led to impaired metabolic function in mice receiving a marginal mass of syngeneic islets.

Chapter 15:Regenerative Strategies for the Endocrine Pancreas: From Islets to Stem Cells and Tissue Reprogramming

The seemingly sudden advent of regenerative medicine as a recognized research and clinical field has allowed us to envisage a number of potential treatments for diseases thus far considered incurable. Nowadays, it is not uncommon to discuss prospective stem cell therapies for the recovery of motor function following spinal cord injury, the replacement of dopaminergic neurons in Parkinsons disease or even the generation of patient-matched gametes in some cases of infertility, just to mention a few examples. While the promise of this emerging field is substantive enough to justify the pursuit of regeneration strategies for these and other conditions, the truth is that, to date, there is none for most of them. Whether or not we will come up with any such therapies in the future is not known. Diabetes is one clear exception. For more than two decades, islet transplantation has shown its clinical efficacy, with many patients either completely off-insulin or with a much improved metabolic control years after the procedure. Based on this palpable proof of principle, we can safely assume that, if stem cells could be induced to differentiate into insulin-secreting beta cells, the benefits of islet transplantation could be made available to millions of patients. Here we review the clinical perspectives of the regeneration of the endocrine function of the pancreas, an ongoing effort that is building upon, and going beyond, the success of islet transplantation.