ALL STEM CELLS

Human embryonic stem cells (ESCs) were first isolated at the University of Wisconsin-Madison in 1998 by James Thomson (Thomson et al., 1998). These cells were established as immortal pluripotent cell lines that are still in existence today. The ESCs were derived from blastocysts donated by couples undergoing treatment for infertility using methodology developed 17 years earlier to obtain mouse ESCs. Briefly, the trophectoderm is first removed from the blastocyst by immunosurgery and the inner cell mass is plated onto a feeder layer of mouse embryonic fibroblasts (Trounson et al., 2001; 2002). However, cells can also be derived from early human embryos at the morula stage (Strelchenko et al. 2004) after the removal of the zona pellucida using an acidified solution, or by enzymatic digestion by pronase (Verlinsky et al., 2005). Nowadays, ESCs can be isolated from many different sources (Fig. 1).
ESCs are pluripotent, which means that they can differentiate into any of the functional cells derived from the three germ layers, including beta cells or insulin-producing cells (IPCs). The differentiation of ESCs into IPCs is prerequisite for their use as a diabetes mellitus treatment, and may occur either in vivo (after transplantation) or in vitro (before transplantation). In vivo differentiation is based on micro environmental conditions at the graft site, whereas in vitro differentiation requires various external factors that induce the phenotypic changes required to produce IPCs. This means that diabetes mellitus can be treated either by direct transplantation of ESCs, or by indirect transplantation of IPCs that have been differentiated from ESCs. However, Naujok et al. (2009) showed that ESCs could modify gene expression and exhibit a phenotype similar to that of islet cells when transplanted into the pancreas only if they are first differentiated in vitro, and that in vitro differentiation is a prerequisite for successful in vivo differentiation (Naujok et al., 2009). Moreover, using ESCs for pancreatic regeneration carries with it the risk of tumour formation after transplantation.
Therefore, the in vitro differentiation of ESCs into IPCs is necessary before they can be used to treat diabetes mellitus. Studies looking at the in vitro differentiation of ESCs into IPCs were first performed in 2001 using mouse cells (Lumelsky et al., 2001). However, the results could not be repeated in subsequent studies (Rajagopal et al., 2003; Hansson et al., 2004; Sipione et al., 2004). Researchers then developed a strategy for selecting ESCs expressing genes related to pancreatic cells (e.g. nestin), and successfully generated IPCs from these ESCs (Soria et al., 2000; Leon-Quinto et al., 2004). Other workers succeeded in creating IPCs from ESCs using gene transfer (Blyszczuk et al., 2003; Schroeder et al., 2006), or phosphoinositol-3 kinase inhibitors (Hori et al., 2002). The differentiation of ESCs into IPCs usually involves differentiation into embryoid bodies. This relatively long process comprises two phases: the embryoid body stage (4–5 days) and the differentiation stage (30–40 days). In 2005, Shi et al. decreased the time taken for this differentiation process to 15 days (Shi et al., 2005).

1. It is unethical to use them.
The process to obtain them destroys a human embryo. The destruction of human life cannot be justified, even if the aim is to save other human life. It is wrong to use an evil means to achieve a good end. We should not kill to save life.
2. It is unnecessary to use them.
Adult stem cells are proving to be a viable alternative. For example umbilical-cord blood and placenta blood are both rich in stem cells. Scientists have found stem cells in adults in virtually every major organ, including the brain. And as we have seen, they have already been successfully used in treatment, while ESCs still offer only theoretical potential for good. With rapid progress being made in the area of ASCs and iPSc, many of the supposed shortcomings listed above are proving to be no longer the case, or will soon be rectified.
3. The use of ASCs seems to solve the problem of immune rejection.
4. Many of the cell lines are in the hands of private companies.
There is big money to be made in the multibillion-dollar biotech industry, and there is always the real concern of companies making profit the first and final consideration. As a commentator put it, “Big Biotech has the same profit-driven agenda as other industries that are viewed sceptically by the media such as Big Tobacco and Big Oil”.