Introduction
There are no other cells in the human body that can generate more different cells than stem cells. Research scientists have developed an interest in stem cells’ composition and applicability in the medical field (Wang et al., 2017). Cell division of the stem cells can generally occur in the body or laboratories to create more different cells. The newly formed stem cells either become specialized for other functions or become new stem cells. Stem cells are of three different types (1) embryonic stem cells (ESCs), (2) adult stem cells, (3) induced pluripotent stem cells (iPSCs). The ECSs are generated from the blastocyst-stage embryos’ interior cell mass, iPSCs emanate from the somatic cells through genetic reprogramming, and adult stem cells are derived from fully developed tissues. Stem cells can renew and differentiate themselves on their own into many cell lines.
The ability of stem cells to undergo differentiation into different forms makes them admissible in treating many chronic diseases. The iPSCs and ESCs are pluripotent cells that undergo differentiation to form cells meant for different adult heredities such as the endoderms, ectoderms, and mesoderms (Wang et al., 2017). The adult stem cells are in two forms, namely, unipotent and multipotent stem cells. The multipotent stem cells also undergo differentiation to form different cell types under a single lineage. For instance, mesenchymal stem cells can undergo differentiation to form fat cells, osteoblasts, and chondrocytes. Unipotent stem cells undergo differentiation into only one cell type, such as the epidermal or satellite stem cells. However, it is worth noting that stem cell research application faces criticism from fatalities resulting from the protracted time of suppressed immunity after transplants; the ability to self-renew and differentiate into different lineages makes stem cell admissible in tissue engineering and treatment of diseases related to the central nervous system (CNS), heart, and brain in human beings.
Pros of Stem Cells Research
Following advancements in medical field research, MSCs have become frequently used in tissue engineering and regenerative treatment. MSCs were first discovered in the bone marrow. Still, science has proven that they are usually situated around the sinusoidal endothelium, whereby they are closely associated with neighborhood hematopoietic stem cells (Fitzsimmons et al., 2018). Besides the bone marrow, MSCs are also localized in various adult tissues such as the tendons, cartilages, lungs, skin, hearts, brain, kidneys, adipose tissues, and pancreas. The MSCs are obtained from many tissues such as the umbilical cords, bone marrow, and adipose tissue. The MSCs can also be cultured before their medical application. The MSC suspensions are introduced through injections or intravenously depending on the desired therapeutical purpose. When aiming to engineer specific tissues, the MSCs are first facilitated to differentiate towards a particular desired cell type. Then after that, they are implanted surgically, usually together with the scaffold materials. MCSs are used in the treatment of autoimmune ailments or stimulation of local tissue maintenance.
The relentless effort from stem cell researchers has yearned to introduce medical practices that are less aggressive and more efficient in treating diseases. The pluripotent stem cells have been reported to be suitable in therapeutical methods since they easily distinguish into different cell types (Rikhtegar et al., 2019). Researchers have given the identification of fully developed CSCs and their capability to repair the body tissues emphasis. Research scientists have shown that iPSCs are broadly applicable in constructing disease models and the formulation of treatment transplants. Additionally, iPSC derivatives have also been significantly proposed for the experimental treatments of neurological diseases. It is worth noting that stem cell research scientists have brought about substantial knowledge about how tissue regeneration can help repair damaged parts of the human body. Treatments on heart and brain diseases have been made possible by applying stem cell research findings (Song et al., 2018). The inception of stem cell application in the medical field has proposed various medical practices that are more effective in treating chronic diseases.
Tissue Regeneration
Stem cells are self-renewing and undergo differentiation into several lineages. The stem cells have been proven to maintain, generate and replace the incurably differentiated cells in their particular tissues resulting from tissue injuries (Fitzsimmons et al., 2018; Song et al., 2018). Tissue engineering encompasses three fundamental parts, namely
- the source or cells must have the suitable genetic composition and phenotype to successfully retain the particular functioning of the tissue
- the scaffolds housing the cells serve as the substitutes for the injured tissues
- bioreactive components or signals that trigger cells into functioning. The sources of the stem cells used in tissue engineering comprise adult stem cells or embryonic stem cells.
Downstream strategies have been embraced recently in tissue engineering and making the whole venture more promising. The downstream process entails implanting the precultured cells into the damaged part of the body and their synthetic scaffold complexes (Fitzsimmons et al., 2018; Song et al., 2018). The sources or cells taken away from the host’s target tissues are then expanded into vitro. They are then preseeded to the scaffold to offer a porous 3D component that provides accommodation to the seeded cells, forming an extracellular matrix. After that, various approaches such as cell printing, sheeting, aggregation, and micro-fabrication are employed in the generation of modular tissues. The abovementioned modular tissues are then accumulated randomly or cell sheets stacked into engineered tissues with a particular micro-architectural characteristic. Later, the tissues are transplanted into the damaged part of the human body. The method enables scientists to change the nanostructure of the components by regulating polymer degradation rates with the extracellular matrix generation and cellular infiltrations, increasing cell binding sequences.
The upstream alternative makes tissue engineering a promising venture through the combination of cells and biomaterial scaffolds. The upstream method encompasses two strategies of manufacturing the engineered tissues (1) culturing and consolidating biomaterial scaffolds and cells is carried out till the cells fill up the supportive structure, thus forming the engineered tissue. (2) The delivery of the integrated biomolecules and acellular scaffolds occurs following an injury. It can optionally incorporate progenitor cells within the defective area and facilitate differentiation and differentiation, making the injured tissue repaired (Fitzsimmons et al., 2018; Song et al., 2018). The upstream approach entails the combination and culturing of biomaterial scaffolds and cells into engineered tissue.
Treatment of Neurological Disorders
Neurological disorders are generally irreversible owing to insufficient production in the central nervous system. The central nervous system is deemed the most intricate and least understood system in a human being (Song et al., 2018). Diseases related to the central nervous system usually result in permanent damage to the nervous tissue structures and functioning. Through the research on stem cells’ rationale and admissibility, stem therapy is applicable in treating neurological complications. Neural stem cells have been proven to be significant in transplantation therapy in treating central nervous complications due to their ability to self-renew and produce different neural cell types. Apart from neural stem cells, other types of stem cells such as ESCs, iPSCs, and MSCs have also been found to be acceptable alternatives in central nervous system implantations.
Parkinson’s disease causes inflexibility and slowed physical movements in patients. Conventionally, Parkinson’s disease was being treated mainly using pharmacological therapies and brain stimulation whereby electrodes were implanted surgically into the host (Song et al., 2018). However, the above methods were not effective in alleviating the symptoms resulting from the disorder. Dopaminergic cells, gotten from different stem cell sources, have been found to survive in the host. They are used in triggering behavioral improvement and motor recovery. The transplanted cells enhance recovery based on two approaches. Firstly, each cell usually transplanted stays alive, expresses tyrosine hydroxylase, releases and uptakes dopamine, thus replacing the lost function neurons. Secondly, the transplanted cells can amount to asymptomatic relief using the protective and neurotrophic aspects. Dopaminergic cells have been found to alleviate Parkinson’s disease symptoms.
Indeed, transplants of neuro stem cells can result in neuroprotection by controlling the host niche using the local astrocytes’ facilitation, taking part in de-differentiation, and promoting the expression of the host-derived growth parameters. Research has shown that the use of the iPSCs has eased the process of obtaining cells from the somatic cells of a patient, thus averting the issues of immune refusal (Song et al., 2018). From the research on stem cells, it has been found that there are no tumor cases reported within the first 10-36 months following iPSCs administration. After successfully implanting the stem cells and their derivatives, there are improvements in the patients who have Parkinson’s disease. The patients usually show a decrease in tremors, inflexibility, and freezing attacks. Research has made it possible to use stem cells in the treatment of Parkinson’s disease.
Alzheimer’s disease is a progressive neurodegenerative condition in human beings in which research has availed its treatment using stem cells. According to Song et al. (2018), more than 48.6 million people are affected by the disorder globally. Studies have found that stem cells offer treatment through the utilization of iPSCs, NSCs, and ESCs together with their respective derivatives. The stem cells and their products transplanted can move into the nervous system and then integrated into the local neural circuits to augment synaptogenesis and improve synaptic transmissions. The iPSCs are proven by research in modeling Alzheimer’s disease, thus reducing the challenge resulting from the species-specific discrepancies and making it possible to stratify drug responses during the personalized medication period. The models also help to offer novel ground for drug screening and toxicological researches. The iPSC Alzheimer’s disease models are a practical approach to understanding Alzheimer’s disease syndrome’s underlying genetic information.
Cardiovascular Disease Treatment
Mesenchymal stem cells help treat heart diseases by improving cardiac functioning and reducing scar size. According to Rikhtegar et al. (2018), heart diseases damage the heart and result in heart failures by stimulating myocyte death and generating fibrosis and ventricular remodelings. During stem cell therapy, progenitor cells and stem cells are usually segregated from allogeneic or autologous source tissue components. The transplanted stem cells resuscitate the cardiac function and commence the myocardial repair directly or indirectly. The pluripotent stem cells effectively treat heart diseases due to their capacity to differentiate into different cell types, such as cardiomyocytes. The pluripotent stem cells are applicable in the treatment of heart diseases since they trivially determine into cardiomyocytes.
Cardiac diseases are treated by the replacement of the faulty muscles with the stem cells. Cardiac therapy is based on stem cells’ application to overcome the challenges posed by gene therapeutical operations through the adoptive dislocation of healthy cells instead of the isolated genes (Rikhtegar et al., 2018). The stem cells function directly through the replacement of the damaged cells in the damaged cardiac tissue. The cells can also work by secreting molecules that trigger endogenous processes for cardiac regeneration and immune control. The cells meant for the transplants are gotten from fully grown tissues such as skeletal, cardiac, and bone marrow tissues. By directly replacing the cardiac tissues, there is a stimulation of endogenous repairment by triggering endogenous heart precursors and cardiomyocyte proliferation, resulting in immunity modulation. The cardiac therapies involve replacing the faulty cardiac muscles with the stem cells from cardiac, bone, or skeletal muscle tissues.
Brain Disease Treatment
The advancement in research has yielded to the application of stem cell implantation in the human brain. Damages on the human brain from abrupt accelerations, blast waves, or penetration wounds usually result in hampered psychological, physical, and cognition functionality (Song et al., 2018). After a transplant, a biobridge is formed between the injured cortex and the neurogenic SVZ. Though it is formerly constituted of the transplanted stem cells, the newly created host’s cells overgrow it. The implanted cells form biobridge between the damaged brain location and the neurogenic site. Then the implanted cells disappear and relinquish their responsibilities to the host’s neurogenic cells. Transplantation of MSCs recruits the host’s cells and enhances endogenous neurogenesis and repair using the stem cell biobridges.
MSCs derived from the bone marrow are effective and safe in treating patients suffering from traumatic brain injuries. Research has shown that patients suffering from motor disorders show improvement after MSCs implantations (Song et al., 2018). Additionally, in a different experiment, patients with visual impairments due to cortical injuries were subjected to treatment. The sample received an intracerebroventricular grafting of human NSCs progenitor cells. The patients then showed improvement in their visual abilities. Another research, whereby a group of patients was subjected to four MSC transplants derived from umbilical cords through lumbar punctures, showed neurological function improvement. The abovementioned patients showed enhanced lower and upper extremity motor abilities, sensation, social cognition, self-care, and balance.
Research on stem cells has also provided a basis for glioblastoma therapy. According to Song et al. (2018), glioblastoma refers to the prevalent primary brain tumor type. The condition is highly malignant and deadly to the patients. The glioblastoma condition is generally aggressive and entails attacks and infiltrations. Surgical operations have been proven not to eradicate glioblastoma foci effectively. This condition’s intricacy is evident whereby patients die within less than a year in case of a reoccurrence of the tumor near the resected region. The tumors make chemical therapeutic remedies difficult because of their intricate locations within the brain.
However, stem cell research has made it possible to treat the dreadful glioblastoma conditions. Song et al. (2018) report that various anti-glioblastoma substances are usually incorporated into the NSCs as loads and help kill the tumor cells. Cytokines oncolytic viruses and the enzymes help in the eradicating of the tumor cells too. The cytokines belonging to the interleukin lineage, comprising the IL-23, IL-7, and IL-4, have been found to exhibit antitumor abilities that enhance immune responses. Additionally, the stem cells can transport enzymes that transfer the inactive pro-drugs into poisonous and active substances, helping fight against glioblastoma. Cytosine deaminase, a pro-drug activating enzyme, transmits 5-fluorocytosine into the poisonous 5-fluorouracil. The newly formed 5-fluorouracil kills the glioblastoma cells. Studies on stem cells have resulted in the invention of anti-glioblastoma substances.
The use of oncolytic viruses and herpes simplex viruses has been proven to fight against the human body’s glioblastoma cells. According to Song et al. (2018), the oncolytic virus approach entails the viruses that are cable of infecting, replicating within, and later on lysing the glioblastoma cells. NSCs containing replicating oncolytic adenovirus migrate around the tumor margins then attack the glioblastoma cells. Also, cells containing myxoma viruses and herpes simplex virus are proven to possess the ability to repress tumor growths. Oncolytic, myxoma and herpes simplex viruses are have portrayed efficacy in the fight against brain tumors.
Cons of Stem Cells Research
Though stem cell application in the medical field has been on the rise, there have been pertinent concerns from critics. According to Lukomska et al. (2019), the application of MSCs in treating different diseases has resulted in criticism. The treatment of various diseases using MSCs has been proven to be quite efficient. However, there are other potential risks during the transplant based on long-lasting observations. The authors opine that though there are no reports on the negative impacts of stem cell application in the medical field, there are many concerns worth noting. For instance, it was documented that a patient was reported to have a big tumor-like mass in the spinal cord after eight years of olfactory mucosal grafting. In as much as research on stem cells has yielded to the application of stem cells in the treatment of diseases, it is worth noting that many underlying risks are unreported.
Stem cells have been very admissible in treating heart diseases, whereby MSCs are a promising therapeutic cell. More than 17.3 million lives were lost to cardiac-related diseases in 2008 (Lukomska et al., 2019). Though adult stem cells have been unanimously proposed for myocardial repair by medical researchers, there is a potential risk of patients suffering from other infections. For instance, MSC grafting can increase relapse, pneumonia, fungal, bacterial, and viral infections. Graftings are also reported to fail in some cases. Though the MSC grafts help prevent and treat graft versus host diseases in patients who are not sensitive to steroids, infections are eminent. The acute and chronic graft versus host diseases in patients after an MSC transplant has been proven to be more than those who do not have the MSC. The infection-related deaths are high even after the graft versus host diseases have been determined. The instances are highly associated with the long immunosuppressive impacts of the MSCs. Stem cell implants are significantly associated with high mortality in patients than individuals who do not have the MCS implants.
Stem cell implantation is detrimental in patients. The MSCs facilitate tumor growth by modulating the tumor microenvironment (Lukomska et al., 2019). The stem cell implantation increases the risk of patients suffering from protumorigenic effects. This risk is augmented by the fact that MSCs are immunosuppressive. Different stem cell transplant types’ risk remains high until the bone marrow makes the white blood cells independently. However, during allogeneic transplants, the risk is highest since patients take drugs that lower their body’s immunity to prevent graft-versus-host diseases from taking place. Graft versus host diseases arises when the recipient’s immunity starts fighting the donor’s cells as foreign bodies, thus permanently destroying the organ. The stem cell is also associated with tumor stroma’s modulation and changes itself into fatal malignant cells. It is worth noting that the infections related to the MSCs remain a concern in medical-related researches.
The recovery time after a stem cell implant varies and can fatal to a patient. The suppression of the host’s body immunity following an implant can last for a while, rendering the patient susceptible to other diseases (Lukomska et al., 2019). Following stem cell grafting, it can take between six to twelve months or more to normalize the patient’s blood composition and immunity. A patient has a challenge of having low blood cell counts following a stem cell grafting since it takes some time for the stem cells to be transported to the bone marrow to start the process of synthesizing new blood cells. For instance, a patient with a low white blood cell count is highly prone to infections. Low blood cell count causes dizziness, fatigue, and malaise. Low platelet count makes the patient have a high risk of prolonged bleeding. It is not guaranteed that the patient’s immunity will quickly be improved since it varies from one individual to another. Kidney problems might also arise when chemotherapy drugs, meant to suppress immunity, are given to a patient before the transplant. The process of stem cell implantation can result in health complications owing to low immunity.
Conclusion
Stem cell research plays a significant role in tissue generation, treatment of neurological disorders, cardiovascular disease treatment, and brain disease treatment due to stem cells’ ability of self-renewing and differentiation into different lineages. However, stem cell application has faced criticism due to the increased fatalities caused by the suppressed immunity during the transplant period, which leaves the patient prone to other infections. Stem cell research has identified MSCs to be vital in tissue engineering. During the treatment exercises, the MSCs undergo differentiation into the desired cell then implanted into the target organ. However, suppressing the host’s body immunity prevents graft-versus-host diseases with fatal results, such as organ damage. Parkinson’s disease and Alzheimer’s disease, affecting many people globally, are now treatable through stem cell research.
MSCs are also admissible in the treatment of cardiac diseases, whereby they replace worn-out tissues. The transplantation of MSCs during brain disease treatment incorporates the host’s cells to facilitate the endogenous neurogenesis and repair using stem cell biobridges. Stem cell research has made it possible to treat the deadly glioblastoma diseases by incorporating anti-glioblastoma components in NSCs that are then used to kill the tumor cells. Occasionally, MSC transplants have also been reported to cause tumors that are sometimes fatal. Though stem cell has some disadvantages in its application, the many applications of stem cell research in the medical field give more hope that it can be admissible in treating many chronic diseases.
References
Fitzsimmons, R. E., Mazurek, M. S., Soos, A., & Simmons, C. A. (2018). Mesenchymal stromal/stem cells in regenerative medicine and tissue engineering. Stem Cells International, 1-16. Web.
Lukomska, B., Stanaszek, L., Zuba-Surma, E., Legosz, P., Sarzynska, S., & Drela, K. (2019). Challenges and controversies in human mesenchymal stem cell therapy. Stem Cells International. Web.
Rikhtegar, R., Pezeshkian, M., Dolati, S., Safaie, N., Rad, A. A., Mahdipour, M., Nouri, M., Jodat, A. R., & Yousefi, M. (2019). Stem cells as therapy for heart disease: iPSCs, ESCs, CSCs, and skeletal myoblasts. Biomedicine & Pharmacotherapy, 109, 304-313. Web.
Song, C. G., Zhang, Y. Z., Wu, H. N., Cao, X. L., Guo, C. J., Li, Y. Q., Zheng, M. H., & Han, H. (2018). Stem cells: A promising candidate to treat neurological disorders. Neural Regeneration Research, 13(7), 1294. Web.
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