Gene and cell therapies for diabetes mellitus: strategies and clinical potential

Cell Loss during Pseudoislet Formation Hampers Profound Improvements in Islet Lentiviral Transduction Efficacy for Transplantation Purposes

Islet transplantation is a promising treatment in type 1 diabetes, but the need for chronic immunosuppression is a major hurdle to broad applicability. Ex vivo introduction of agents by lentiviral vectors—improving β-cell resistance against immune attack—is an attractive path to pursue. The aim of this study was to investigate whether dissociation of islets to single cells prior to viral infection and reaggregation before transplantation would improve viral transduction efficacy without cytotoxicity. This procedure improved transduction efficacy with a LV-pWPT-CMV-EGFP construct from 11.2 ± 4.1% at MOI 50 in whole islets to 80.0 ± 2.8% at MOI 5. Viability (as measured by Hoechst/PI) and functionality (as measured by glucose challenge) remained high. After transplantation, the transfected pseudoislet aggregates remained EGFP positive for more than 90 days and the expression of EGFP colocalized primarily with the insulin-positive β-cells. No increased vulnerability to immune attack was observed in vitro or in vivo. These data demonstrate that dispersion of islets prior to lentiviral transfection and reaggregation prior to transplantation is a highly efficient way to introduce genes of interest into islets for transplantation purposes in vitro and in vivo, but the amount of β-cells needed for normalization of glycemia was more than eightfold higher when using dispersed cell aggregates versus unmanipulated islets. The high price to pay to reach stable and strong transgene expression in islet cells is certainly an important cell loss.

Gene therapy and enhancement for diabetes (and other diseases): the multiplicity of considerations

Gene therapy has reached the forefront of studies and research over the last 30 years because of its potential for curing, treating, and preventing diseases associated with DNA mutations. Type 1 and type 2 diabetes are two examples of very common polygenic and multifactorial diseases. The huge amount of scientific literature on this topic reflects a growing general interest in the possibilities of altering our genetic heritage and thus controlling the onset of diseases associated with mutations and relative risk factors. We have focussed on the new treatment opportunities and possibility of enhancing an individual's health, physical well-being, and even an individual's behaviour through technologies specially designed for therapeutic purposes, which have been presented in literature. This historical perspective shows how this type of research, however, was immediately subjected to an ethical evaluation, especially regarding the decoding of the human genome and the questions raised by the alteration of our genetic heritage through new biotechnologies. Moreover, understanding the limitations of gene therapy protocol experiments and the multifactorial nature of many diseases, which have a genetic base, also contributes to these considerations.

Critical issues for engineering cord blood stem cells to produce insulin

BACKGROUND/OBJECTIVES

The objectives of using cord blood stem cells for treating type 1 diabetes are simple in principle yet complex in biological and molecular mechanisms. These are defined by the complexity of the insulin-producing unit of the pancreas, the islet. Islets are composed of various cell types that arise from diverse lineages and communicate by hormones, growth factors and small-molecule mediators. These processes are regulated by integration of signal transduction pathways. While advances have been made to engineer umbilical cord blood stem cells to produce insulin, these studies only illuminate the potential of such cells to fulfil a necessary, but not sufficient, requirement for transplantation.

RESULTS/CONCLUSIONS

The challenges ahead demand detailed understanding of molecular mechanisms to move from an opportunistic, phenotypic approach to transplantation and amelioration of blood glucose, to an orderly and logical approach to a biologically and medically meaningful solution. The issues include expansion to generate large numbers of cells, self-renewal to regulate the destiny of cord blood stem cells to repopulate the hematopoietic system, and multipotency of stem cells to generate the distinct cell types of an islet.

Directed engineering of umbilical cord blood stem cells to produce C-peptide and insulin

OBJECTIVES

In this study, we investigated the potential of umbilical cord blood stem cell lineages to produce C-peptide and insulin.

MATERIALS AND METHODS

Lineage negative, CD133+ and CD34+ cells were analyzed by flow cytometry to assess expression of cell division antigens. These lineages were expanded in culture and subjected to an established protocol to differentiate mouse embryonic stem cells (ESCs) toward the pancreatic phenotype. Phase contrast and fluorescence immunocytochemistry were used to characterize differentiation markers with particular emphasis on insulin and C-peptide.

RESULTS

All 3 lineages expressed SSEA-4, a marker previously reported to be restricted to the ESC compartment. Phase contrast microscopy showed all three lineages recapitulated the treatment-dependent morphological changes of ESCs as well as the temporally restricted expression of nestin and vimentin during differentiation. After engineering, each isolate contained both C-peptide and insulin, a result also obtained following a much shorter protocol for ESCs.

CONCLUSIONS

Since C-peptide can only be derived from de novo synthesis and processing of pre-proinsulin mRNA and protein, we conclude that these results are the first demonstration that human umbilical cord blood-derived stem cells can be engineered to engage in de novo synthesis of insulin.

Tissue-culture surfaces with mixtures of aminated and fluorinated functional groups. Part 2. Growth and function of transgenic rat insulinoma cells (betaG I/17)

Interactions of transplantable cells with synthetic polymers can influence the function of biohybrid artificial organs. This study explored growth and secretion of human insulin by betaG I/17 cells cultured on surfaces bearing diamine groups (N2), trifluoropropyl groups (F3) and mixtures of the two. Cells cultured on high-F3 and high-N2 surfaces spread well, grew rapidly and produced >1.8 mol lactate per mol glucose consumed, closely resembling cells grown on the permissive control, glass. On one mixed surface, with a molar ratio of 33 N2 groups:67 F3 groups, cells had a lower lactate/glucose ratio, adopted a rounded form, grew slowly and were quick to form emergent aggregates, similar to cultures on the inhibitory control, untreated polystyrene. Cultures on surfaces with higher F3 content secreted the most insulin and, in the case of the highest-F3 surface, showed improved responsiveness to secretagogues. Hormone secretion was roughly 50% greater when cells were grown on F3 surfaces conditioned by earlier cultures of betaG I/17. Incubation of conditioned surfaces with high concentrations of a polyclonal anti-laminin serum prior to re-plating partially abolished this improvement in secretory function. Polymers bearing trifluoropropyl groups appear to be attractive candidates for use in the artificial endocrine pancreas. Surface coatings that include laminin might promote function of transgenic insulinoma cells in vitro and in vivo.