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The isolation of human and animal cells about a decade ago initiated "Therapeutic Cell Technology" that leads to advances in field of biomedical research. The individual characteristic features of the cells accomplished extension of useful applications. Many advances have been shown in the interest of "Therapeutic Cell Technology" are as follows:
Study of human diseases using induced pluripotent stem cells technology (Lee and Studer, 2010).
Cell based drug delivery by applying use of Bioactive Cell - Hydrogel microcapsules (Orive et al., 2009).
Use of Embryonic stem cells such as effect of leukemia inhibitory factor on
embryonic stem cell differentiation: implications for supporting neuronal differentiation (He et al., 2006).
4) Use of induced pluripotent stem cells for isolation of functional murine cardiac
mycocytes. (Mauritz et al., 2008).
For the cell encapsulation use of two component protein-engineered physical
hydrogels (Wong et al., 2009).
Drug Delivery systems by using hydrogels (Schmidt et al., 2008).
And, many more using cells as a key in approach to therapeutic cell technology.
Although of the approaches the uses of induced pluripotent stem cells provide a scenario as potential utility and promising therapy for human degenerative diseases. Each organ of the body comprises of different types of tissue groups consisting of multiple cell types. Depending upon the competency of donor cells to transform into all beneficial cell types lost in the objective organ gives results in successful cell replacement (Dong et al., 2003). The innovation of induced pluripotent cells which are only somatic cells modified genetically to possess pluripotent characteristics in 2006 has built up new approach in clinical medicines (Takahashi and Yamanka, 2006). These induced pluripotent cells should have the aim to resolve dead cells. The pluripotent stem cells have the unique property to differentiate in to all of the various cell types of the human body (not extra embryonic cells) (Das and Pal, 2010). These cells are discovery based technology that converts somatic cells into embryonic stem(ES) - like cells with having potential of pluripotency by the exogenous expression of many worthy genes ( Jin et al., 2009). With having a characteristic desired genetic background, induced pluripotent cells can be traced out, together with patient-specific induced pluripotent cells for disease models with not having any doubt with rejection by body immune system (Yu et al., 2009). For merging candidate genes into somatic cells derived from any human body part, there is utilization of specific types of viruses like retroviruses, lentiviruses, adenoviruses and plasmids during induced pluripotent cells formation. and moreover, it is also able to make disease based induced pluripotent cells which are most likely to revolutionize research in comparison to the pathophysiology of most debilitating diseases, as in laboratory these can be make copies ex-vivo (Das and Pal, 2010) .Induced pluripotent cells can be used for safety and efficacious study of drugs or drug candidates having potential for specific diseased condition, thus making less need for animal studies and specifically reducing money and time for innovating new drugs.(Jin et al., 2009). These innovative findings make the path for using these induced pluripotent cells in cell replacement therapy for many degenerative diseases. Recently, there is isolation of functional cardiomyocytes Mauritz et al.(2008), pancreatic islet cells Tateishi et al.(2008), kidney cells Mu et al.(2005), neurons Onorati et al.(2010) and cells of retina from induced pluripotent cells Oskada et al.(2009), thus reconfirming the cell's capacity for differentiation and pluripotency. Additionally, point to discuss how iPS cell generation, maintenance, and differentiation have a high-cost and are technically difficult. It can be used as an unlimited source for cell differentiation or tissue engineering, either of which is a promising therapy for human degenerative diseases (Jin et al., 2009).
Various attempts have been made to straightly change somatic cells into pluripotent cells. It should be noticed that there is constrained use of ES cells due to ethical laws and concerns, this causes no possibility of generating patient specific ES cell lines (Jin et al., 2009).In order to over come this handicap, patient-specific induced pluripotent stem cell lines have been subjected from patients suffering from Parkinson's disease Park et al.(2008), Fanconi anemia Raya et al. (2009) and sickle cell anemia Ye et al.(2009) and this eradicate with the risk of immune-rejection with cell replacement therapies. Induced pluripotent cells, the first pioneered approach by Shinya Yamanaka's group enables successfully reprogramming of somatic cells to pluripotent state through over expression of pluripotency in relation with transcription factors. After one year the same group Takahashi et al. ( 2007) and another group Yu et al. (2007) successfully generated human induced pluripotent cells although direct programming of defined transcription factors that are highly expressed in pluripotent cells. Induced pluripotent stem cells comprise unique characteristic features of differentiating into all types of cells of human body known as somatic cells. Much progress has been achieved with relation to higher scale competence, assimilating free strategy in the innovation of induced pluripotent cells (Jin et al., 2009). In view of human induced pluripotent stem cells, the first report Takahashi et al. (2007) along with his colleagues showed a relatively low output of colonies based on ES. But in compare to above report now, many groups submitted highly efficient induced pluripotent stem cells with the addition of supplement factors like valproic acid (histone deacetylase inhibitor) and the SV40 large T antigen (Huangfu et al., 2008; Mali et al., 2008).Much progress has been made by Yamanaka's group projected in discovering a non-viral method demonstrating the virus vectors altered by plasmids (Okita et al., 2008). Recently, non-integrating episomal vectors Yu et al. (2009) are being used to generate induced pluripotent stem cells directly. In addition, the induced pluripotent cells' production have been shown to increase by using micro RNA- a class of short single - stranded RNA molecules (Judson et al., 2009). Various methods are taken Lowry et al. (2008) to use dermal fibroblasts easily obtained from an individual human to generate induced pluripotent cells by ectopic expression of set defined transcription factors known as KLF4, OCT4, SOX2 and C-MYC. This Lowery work results in generation of cell lines which are morphologically indistinguishable from human embryonic stem cells generated from inner cell mass of human pre-implantation embryo, so this conclude with human iPS cells share a nearly identical-gene expression profile with two established HESC lines. From this clearly provide evidence that human iPS cells can be induced to differentiate along lineages representatives of three embryonic germ layers indicating the pluripotency of cells (Lowery et al., 2008) These induced pluripotent cells have the potential to differentiate into any cell types, making them a potential source from which to produce cells as a therapeutic platform for the treatment of wide range of diseases (Carr et al., 2009). So, Induced Pluripotent Stem cells have been produced from patients suffering from Parkinson's disease, thalassemia, amyotrophic lateral sclerosis, type1diabetes mellitus, Fanconi anemia, adenosine deaminase deficiency-related severe combined immunodeficiency, Shwachman-Bodian-Diamond syndrome, Gaucher disease type III, Duchenne and Becker muscular dystrophy, Huntington disease, juvenile-onset, Down's syndrome/trisomy 21, and Lesch-Nyhan syndrome(Dimos et al. 2008; Park et al.2008; Raya et al.2009; Ye et al.2009) and these cells also provide a capability, based on disease models (Jin et al., 2009). Most of human inherited diseases are miscellaneous when link with genetics and clinical basis. Different genes comprising of most mutations that give rise to distinct diseases and each mutation provides the distinct phenotype and with each reported mutation, it is not possible to create animal models, but it is possible to create such induced pluripotent stem cells as disease models, so taking into an account, establishing appropriate therapies are not possible for most retinal degenerative diseases like AMD and RP (Jin et al., 2009). In order to over come from above , if patient's own induced pluripotent cells capable of generating useful retinal neurons can be a good idea for eradicating different mechanisms of disease. This would an ease to find information based on intrinsic factors such as apoptosis in patients and point to be noticed that these cells also provide a capability based resource for drug screening and biological resource(Jin et al., 2009). It has been mention that ES cells have been used for study pharmacology (Ho and Li, 2006). So, this says that induced pluripotent cells can also be subjected as biological tool for toxicity screening in addition to drug discovery. So as in case of regular research, there is unavailability of retinal cells from patients, these cells can help during clinical trials to examine both toxicity and effectiveness of a new drug (Jin et al., 2009). As per good aspects of induced pluripotent stem cells there are some difficulties facing up this technology. Firstly, a guideline for defining the pluripotency of iPS cells has been given by Daley et al. 2009; however, further studies should be their to establish a gold standard for line selection and to make out a high-throughput process to control quality. Secondly, current differentiation procedures are not good to use enough to guarantee efficiency
and safety for example, photoreceptor cells differentiated from iPS cells are not high-performance in cell number. Although Rey's group efficiently generated retinal progenitor cells and photoreceptor precursors, the final photoreceptor cells seemed very rare. Addionally, iPS cells generation, maintenance and differentiation have a high-cost and are technically difficult, and hence, developing methods of ips operation based on chemicals and differentiation may reduce the costs and increase safety (Jin et al., 2009). But taking into all above discussion, growing advancements in this field, certainly looking forward to many advancements in both the basic science and therapeutics for various degenerative diseases.
After discussing various aspects, it concludes that these induced pluripotent cells open up new ventures for biological science and regenerative medicine for the treatment of various diseases and can also be subjected as biological tool for toxicity screening in addition to drug discovery, however this new technology still facing many difficulties. Additionally, the clinical utility of iPS cells will depend on the efficiency, safety, and cost-effectiveness, more studies are required to determine the full potential of iPS technology. Currently, iPS cell generation, maintenance, and differentiation have a high-cost and are technically difficult; hence, developing chemically defined methods of iPS operation and differentiation may reduce the costs and increase safety (Jin et al., 2009).