Stem cells to replace or regenerate the diabetic pancreas: Huge potential & existing hurdles.

Various stem cell sources are being explored to treat diabetes since the proof-of-concept for cell therapy was laid down by transplanting cadaveric islets as a part of Edmonton protocol in 2000. Human embryonic stem (hES) cells derived pancreatic progenitors have got US-FDA approval to be used in clinical trials to treat type 1 diabetes mellitus (T1DM). However, these progenitors more closely resemble their foetal counterparts and thus whether they will provide long-term regeneration of adult human pancreas remains to be demonstrated. In addition to lifestyle changes and administration of insulin sensitizers, regeneration of islets from endogenous pancreatic stem cells may benefit T2DM patients. The true identity of pancreatic stem cells, whether these exist or not, whether regeneration involves reduplication of existing islets or ductal epithelial cells transdifferentiate, remains a highly controversial area. We have recently demonstrated that a novel population of very small embryonic-like stem cells (VSELs) is involved during regeneration of adult mouse pancreas after partial-pancreatectomy. VSELs (pluripotent stem cells in adult organs) should be appreciated as an alternative for regenerative medicine as these are autologous (thus immune rejection issues do not exist) with no associated risk of teratoma formation. T2DM is a result of VSELs dysfunction with age and uncontrolled proliferation of VSELs possibly results in pancreatic cancer. Extensive brainstorming and financial support are required to exploit the potential of endogenous VSELs to regenerate the pancreas in a patient with diabetes.

An ideal oocyte activation protocol and embryo culture conditions for somatic cell nuclear transfer using sheep oocytes.

Pluripotent stem cells are possibly the best candidates for regenerative medicine, and somatic cell nuclear transfer (SCNT) is one of the viable options to make patient-specific embryonic stem cells. Till date efficacy of SCNT embryos is very low and requires further improvement like ideal oocyte activation and in vitro culture system. The aim of the present study was to evaluate ideal oocyte activation using different stimulation protocols and to study the effect of cumulus co-culture conditions on embryo development. Results demonstrate that between electric stimulation and chemical stimulation using calcium ionomycin and ionophore, best oocyte activation was obtained using calcium ionomycin (5 μM for 5 min) which resulted in 83% cleavage followed by 7% of early blastocyst which further increased to 15% when a cumulus bed was also introduced during embryo culture. Sequential modified Charles Rosenkrans 2 (mCR2) medium was used for embryo culture in which glucose levels were increased from 1 mM to 5 mM from Day 3 onwards. SCNT using cumulus cells as donor somatic cell, calcium ionomycin to activate the reconstructed oocyte and embryo culture on a cumulus bed in sequential mCR2 medium, resulted in the development of 6% embryos to early blastocyst stage. Such technological advances will make SCNT a viable option to make patient-specific pluripotent stem cell lines in near future.

Stem Cells Cloning and Therapeutic Potential.

Stem cells have huge potential to transform current manner in which medicine is practiced. Rather than treating diseased cells with medicines and antibiotics, stem cells can just replace the diseased cells with healthy cells. But it will take time before this research gets translated to the clinic. At present, various types of stem cells like human embryonic stem (hES) cells, induced pluripotent stem (iPS) cells, fetal stem cells, adult tissue-specific stem cells (HSCs, MSCs, etc.), very small embryonic-like stem cells (VSELs) and related technologies like therapeutic cloning are subject to extensive research. Clinicians appear to be in a hurry to apply the stem cells to their patients and there is a huge industry banking stem cells for future autologus use. However, the scientifc community is still not sure which is the best stem cell candidate for regenerative medicine. The chapter provides an update on various fronts and also discusses whether there exists a need to bank stem cells for future use. The author is puzzled by realizing as to what needs to be repaired/ regenerated-the stem cells or their microenvironment ‘niche’!

Pluripotent stem cells for cardiac regeneration: Overview of recent advances & emerging trends.

Cell based regenerative therapy has emerged as one of the most promising options of treatment for patients suffering from heart failure. Various adult stem cells types have undergone extensive clinical trials with limited success which is believed to be more of a cytokine effect rather than cell therapy. Pluripotent human embryonic stem cells (hESCs) have emerged as an attractive candidate stem cell source for obtaining cardiomyocytes (CMs) because of their tremendous capacity for expansion and unquestioned potential to differentiate into CMs. Studies carried out in animal models indicate that ES-derived CMs can partially remuscularize infarcted hearts and improve contractile function; however, the effect was not sustained over long follow up periods due to their limited capacity of cell division in vivo. Thus, the concept of transplanting multipotent cardiovascular progenitors derived from ES cells has emerged since the progenitors retain robust proliferative ability and multipotent nature enabling repopulation of other myocardial elements also in addition to CMs. Transplantation of CMs (progenitors) seeded in biodegradable scaffold and gel based engineered constructs has met with modest success due to issues like cell penetration, nutrient and oxygen availability and inflammation triggered during scaffold degradation inversely affecting the seeded cells. Recently cell sheet based tissue engineering involving culturing cells on ‘intelligent’ polymers has been evolved. Generation of a 3-D pulsatile myocardial tissue has been achieved. However, these advances have to be looked at with cautious optimism as many challenges need to be overcome before using these in clinical practice.

Clinical experience with the use of Fluorescence in Situ Hybridization on uncultured cells for prenatal diagnosis.

The aim of the study was to prospectively evaluate the usefulness and limitations of Fluorescence In Situ Hybridization (FISH) on uncultured cells for prenatal diagnosis of numeric aneuploidies of chromosomes 13, 18, 21, X and Y. Hundred prospectively selected pregnant women that were at high risk of giving birth to an abnormal child were offered prenatal diagnosis by FISH after appropriate counseling. Fetal tissue was obtained by chorionic villus sampling (n=26), amniocentesis (n=62) and or fetal blood sampling (n=12) and processed for FISH using commercial probes. Six cases were excluded initially owing to maternal blood contamination or inadequate sample. FISH results were available in 98% of cases, in 2% of cases there was FISH failure. Of the remaining 92 cases, chromosome aneuploidy was detected in eleven cases. FISH was found extremely valuable in cases presenting with fetal abnormalities detected on ultrasonography and also for rapid screening of aneuploidies in cases of abnormal triple marker test. But as the diagnosis is limited to only a small number of chromosomes, appropriate evaluation of the cases with counseling regarding the limitations of FISH is mandatory before offering this test for prenatal diagnosis.