Biomedical subjects

Juan Antonio Reig

Publications and source records attributed to Juan Antonio Reig.

3 recordsLinked to original sources

PubMed2005

Insulin-secreting cells derived from stem cells: clinical perspectives, hypes and hopes.

Diabetes is a degenerative disease that results from the selective destruction of pancreatic beta-cells. These cells are responsible for insulin production and secretion in response to increases in circulating concentrations of nutrients, such as glucose, fatty acids and amino acids. This degenerative disease can be treated by the transplantation of differentiated islets obtained from cadaveric donors, according to a new surgical intervention developed as Edmonton protocol. Compared to the classical double transplant kidney-pancreas, this new protocol presents several advantages, concerning to the nature of the implant, immunosuppressive drug regime and the surgical procedure itself. However, the main problem to face in any islet transplantation program is the scarcity of donor pancreases and the low yield of islets isolated (very often around 50%) from each pancreas. Nevertheless, transplanted patients presented no adverse effects and no progression of diabetic complications. In the search of new cell sources for replacement trials, stem cells from embryonic and adult origins represent a key alternative. In order to become a realistic clinical issue transplantation of insulin-producing cells derived from stem cells, it needs to overcome multiple experimental obstacles. The first one is to develop a protocol that may allow obtaining a pure population of functional insulin-secreting cells as close as possible to the pancreatic beta-cell. The second problem should concern to the transplantation itself, considering issues related to immune rejection, tumour formation, site for implant, implant survival, and biosafety mechanisms. Although transplantation of bioengineered cells is still far in time, experience accumulated in islet transplantation protocols and in experiments with appropriate animal models will give more likely the clues to address this question in the future.

Animals↗

PubMed2005

Ectodermal commitment of insulin-producing cells derived from mouse embryonic stem cells.

Embryonic stem cells possess the ability to differentiate in vitro into a variety of cell lineages, including insulin-producing cells. Pancreatic beta-cells derive from foregut endoderm during embryonic development. However, previous reports using transgenic mice strongly indicate that insulin-positive cells may be generated also through the neuroectoderm pathway. To analyze this point, a culture system was performed in which only ectoderm committed cells were present. Based on published work, we achieved this by maintaining transfected clonal R1 mouse embryonic stem cells in monolayer in the absence of LIF. Contrary to differentiation protocols via embryoid body formation, monolayer cultured cells displayed ectodermal fates according to the marker gene expression pattern. Under these particular conditions, neomycin was added in order to select insulin-expressing cells. The cell lineage obtained expressed Pdx1, Pax6, Isl1, AChE, MBP, TH, and GS genes, confirming ectodermal commitment, even though some of these factors are also expressed in endoderm. In addition these cells displayed excitatory properties similar to astrocytes. Co-expression of insulin II and nestin was observed in monolayer culture and in the presence of specific conditioned media. No expression of early endodermal markers was detected along monolayer cultures. Altogether, these observations suggest that cells with ectoderm fates could participate in vitro in the derivation of insulin-producing cells. These results have implications for insulin gene regulation and hormone secretion in order to generate insulin-producing cells for replacement protocols in the treatment of diabetes.

Animals↗

PubMed2003

Mitochondrial dysfunction is involved in apoptosis induced by serum withdrawal and fatty acids in the beta-cell line INS-1.

The potential toxic effects of high extracellular concentrations of fatty acids were tested in beta(INS-1)-cells cultured in the absence of serum, a condition known to alter cell survival in various systems. This may in part mimic the situation in type 1 or 2 diabetes where beta-cells are already insulted by various stressful conditions, such as cytokines and oxidative stress. Serum removal caused, over a 36-h period, oxidative stress and an early impairment of mitochondrial function, as revealed by increased superoxide production and markedly reduced mitochondrial membrane potential, but a lack of cytochrome c and apoptosis-inducing factor release in the cytosol. The fatty acids palmitate and oleate considerably accelerated the apoptosis process in serum-starved cells, as revealed by fluorescence-activated cell sorting analysis, morphological changes, chromatin condensation, DNA laddering, poly(ADP-ribose) polymerase cleavage, cytochrome c and apoptosis-inducing factor release, and increased levels of Bax and cytosolic caspase-2. The fatty acids also increased nitric oxide production, apparently independently of inducible nitric oxide synthase induction. Under the same experimental conditions, elevated glucose alone had only a marginal effect on beta-cell apoptosis. Together the results indicate that elevated concentrations of fatty acids are particularly efficient in accelerating the rate of apoptosis of already stressed beta(INS-1)-cells displaying altered mitochondrial function, and that the mitochondrial arm of the apoptosis process is involved in beta-cell lipotoxicity.

Apoptosis↗