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Before the formation of organs, all embryos are composed of a collection of cells with the capacity to originate many different tissues and organs. Stem cells have a plural potentiality and are termed pluripotent. Human embryonic stem cells(hESCs) have a remarkable plasticity(Kiessling & Anderson 9). These cells are derivatives of the inner cell mass of the blastocyst: which is a pre-implantation embryo developed five days after fertilization(Colombo et al 825). In essence, the blastocyst contains all the necessary developmental material for a complete human being. As growth and development progresses, the cells of the inner cell mass differentiate into three germinal layers from which tissue restricted stem cells originate and subsequently tissues and organs.
The reason for the high degree of optimism with regard to the potentiality of embryonic stem cell research are basically hinged on the fact that embryonic stem cells have an indefinite replicative capacity coupled to their capacity to differentiate into different somatic cell types in the human body. In a theoretical sense, human embryonic stem cells(hESCs) can be therapeutically used in the generation of any possible cell type in the body or tissue hence serving as an indefinite source of cells, tissues or organs for the treatment of every possible degenerative disease. Moreover, if the derivation of hESCs is coupled with the novel technologies of nuclear transfer in addition to the mammalian cloning technology, the treatment of patients with genetically identical cloned cell types, tissues or organs may become a reality. The advantage of the possibility of using an identical cell type copy is that the process would completely eliminate the histocompatibility problems which are normally associated with almost all the allogeneic therapies(Chiu & Rao 241).
Just as the potential in therapeutics is creating much interest and optimism, the same is applicable for the capacity of multipotent and transdifferentiation of adult stem cells as well as the directed reprogramming of the same for medical purposes. On the other hand, political and ethical concerns over the potential of hESCs have not been left behind. Key in the political and ethical agenda is the controversy over the derivation and utilization of hESCs, inclusive of those originating from nuclear transfer embryos. There are those who argue as to whether there exists any necessity in exploiting the potential of hESCs owing to the therapeutic advantages of adult stem cells which can easily be derived from the body of an adult human being and used to generate autologous therapies in the absence of the nuclear transfer process(Chiu & Rao 242).
To present a discussion into the disadvantages of hESC research is to briefly analyze the obstacles that have stood in the way of the full exploitation of the theoretical potentiality of hESCs. There are wide ranging ethical concerns, the first being that, for hESC research to be fully exploited, the embryo has to be destroyed. The destruction of the embryo has led to the rise of various religious and ethical arguments with regard to the concept of personhood. While researchers generally agree that the embryo is not a person, those opposing stem cell research point out that life begins at conception. Thus, any medical advancement that pushes for the legalization of embryo destruction, despite the benefits of such a move, only serves to propagate the belief that embryos: as defenseless members of humanity, can be destroyed for the benefit of other human beings.
Citing he inevitability of the destruction of the embryo such as those in infertility treatments, pro-hESC research argue that it is economically sensible to use the embryos for the benefit of the suffering masses, rather than watch them as they deteriorate to inevitable destruction. Another issue is on the commercialization of embryos in which individuals and institutions will resort to mass production of embryos for the sole intention of making a profit. These are just some of the few disadvantages of hESC research. Unless they are amicably addressed through stringent regulatory and legislative framework, embryonic stem cell research may be detrimental to the existence of humanity.
For those who support the preferability of the adult stem cells: which can be isolated from the bone marrow, brain tissue, skin, blood, eyes, liver and muscle, it is prudent that the history of the search for the treatment of degenerative diseases be understood. The prospect of regenerative medicine has been under study for several years. Initially, research was centered on the use of small molecule drugs to achieve the potentials of regenerative medicine. Unfortunately, conventional drug therapies have failed to fully stimulate functional or tissue replacement in the case of degenerative diseases. There are several reasons that prevented the small molecule chemicals from eliciting the desired therapeutic response. What followed next was an attempt to use lineage restricted somatic stem cells to achieve cell and or tissue transplantation therapies as represented by the successes in blood transfusions and the long term replacements in the hematopoietic system. In current medical practice, allogeneic and autologous bone marrow transplants from the cord blood or the bone marrow, with or without accompanying ex vivo expansion have developed to become routine clinical conducts. However, despite these key successes, it is still impossible to indefinitely culture hematopoietic cells in the laboratory(Chiu & Rao 240). This can be explained by the succeeding explanation.
For any endevour to be deemed successful in the generation of transplantable hematopoietic cells, such an endevour must be dependent on the regulation of the growth of the hematopoietic stem cells a well as the early progenitors. This explains why many innovative therapeutics are based on the control of the growth and differentiation of stem cells. In the natural physiological environment, cell growth and differentiation is a tightly regulated process hence the long term maintenance of these stem cells have been far from being satisfactory(Muench et al 32). The isolation of hematopoietic cells in the laboratory is extremely expensive and idiosyncratic. Researchers have also been able to demonstrate that even though these cells are found in many parts of the body, some cell types are inadequate. This inadequacy implies that while while bone marrow transplantation therapies are successful, they cannot be applied in a classical case where batches are to be manufactured in large scale in agreement with a good manufacturing practice(GMP) licenses(Chiu & Rao 241).
Apart from the successes in the hematopoietic stem cell therapies, other clinical successes with other somatic cell therapies, with the exception of the skin, have been barely successful. Lineage- restricted progenitor cells and multipotent stem cells have been identified and demonstrated to have varying degrees of rigor in the mammalian central nervous system, equal successes in therapy have not been achieved. These limitations in adults stem cell and single molecule therapies have increased the optimism levied on human embryonic stem cell(hESCs) research(Chiu & Rao 241; Colombo et al 825). Adult stem cells have been employed in the treatment of some diseases despite their differentiating limitation. One particular advantage of adult stem cells is that they can be genetically matched to a patient.
Umbilical cord derived stem cells have also been isolated and cultured. These cells are primarily obtained from the umbilical vein. These cells closely resemble cultured mesenchymal stem cells(MSCs) that have been isolated from the bone marrow. Other researchers have also reported that contained in the human cord perivascular(HUCPV) cells are a subpopulation of cells which have the capacity to exhibit a functional phenotype. In addition to these umbilical cord derived stem cells are the umbilical cord blood derived stem cells which have also been isolated, characterized and grown under different culture conditions. Preliminary research attest to their possible uses in regenerative medicine, tissue engineering and cellular therapies. However, these cells are deemed comparatively inferior and more primitive than bone marrow stem cells, hematopoietic stem cells and mesenchymal stem cells. This assertion limits the full exploitation of their capacities(Freshney 161).
The attributes of stem cells:embryonic, adult and umbilical, have been detailed. Recent developments are dotted with successes and uncertainties which are driven by fear of the unknown. There are limitations and challenges such as ethical and political considerations. However, what is certain is that with adequate funding, strict legislative and regulatory framework, the potentiality of stem cell research can be fully unlocked to offer relief to millions suffering from various debilitating and incurable diseases.