Stem Cell Replacement Therapy Research Articles

Advances in Organoid Technology: A Focus on Corneal Limbal Organoids.

Organoid technology provides a versatile platform for simulating organogenesis, investigating disease pathogenesis, and exploring therapeutic interventions. Among various types of organoids that have been developed, corneal limbal organoids, the three-dimensional miniaturized corneas which are derived from either pluripotent stem cells or limbal epithelial stem cells, are particularly promising for clinical translation. This narrative review summarized the state-of-the-art in corneal limbal organoids research including the cultivation methods, clinical relevance and its limitations and challenges. The potential of corneal limbal organoids in mimicking corneal development, disease modelling, drug screening, and regenerative medicine was discussed. Technical improvements in cultivation techniques, imaging modalities, and gene editing tools are anticipated to overcome current limitations and further promote its clinical potential. Despite challenges and difficulties, the development of corneal limbal organoids opens a new era of regenerative medicine and provides a potential source of stem cell replacement therapies for challenging corneal diseases with the establishment of an in vitro corneal limbal organoid bank.

Advancements in autologous stem cell transplantation for Parkinson's Disease.

Parkinson's disease (PD) is a progressive neurodegenerative disease marked by comparatively focal dopaminergic neuron degeneration in the substantia nigra of the midbrain and dopamine loss in the striatum, which causes motor and non-motor symptoms. Currently, pharmacological therapy and deep brain stimulation(DBS) are the primary treatment modalities for PD in clinical practice. While these approaches offer temporary symptom control, they do not address the underlying neurodegenerative process, and complications often arise. Stem cell replacement therapy is anticipated to prevent further progression of the disease due to its regenerative capacity, and considering the cost of immunosuppression and the potential immune dysfunctions, autologous stem cell transplantation holds promise as a significant method against allogeneic one to treat Parkinson's disease. In this review, the safety concerns surrounding tumorigenicity and complications associated with transplantation are discussed, along with methods utilized to evaluate the efficacy of such procedures. Subsequently, we summarize the preclinical and clinical studies involving autologous stem cell transplantation for PD, and finally talk about the benefits of autologous stem cell transplantation against allogeneic transplants.

Retinal Progenitor Cells Exhibit Cadherin-Dependent Chemotaxis across Transplantable Extracellular Matrix of In Vitro Developmental and Adult Models

Retinal degeneration is an escalating public health challenge, as diseases such as age-related macular degeneration, diabetic retinopathy, and retinitis pigmentosa cause irreversible vision loss in millions of adults each year. Regenerative medicine has pioneered the development of stem cell replacement therapies, which treat degeneration by replacing damaged retinal neurons with transplanted stem-like cells (SCs). While the collective migration of SCs plays critical roles during retinal development, our understanding of collective SC behaviors within biomaterials transplanted into adult tissue remains understudied. This project examines the potential therapeutic impacts of collective SC migration during transplantation by correlating the expression of cadherin, cell-cell cohesion molecules that maintain intercellular communication during development, with receptor proteins of chemoattractant molecules prevalent in degenerated adult tissue. Experiments examine these well-conserved biomechanisms by using two different model organisms: Drosophila melanogaster, a seminal model for retinal development, and Mus, an important preclinical model for transplantation. Results indicate that SCs from both animal models significantly upregulate cadherin expression to achieve more directed collective migration towards species-specific chemoattractants and exhibit longer distance motility upon different extracellular matrix substrates.

Immunomodulation: The next target of mesenchymal stem cell-derived exosomes in the context of ischemic stroke.

Ischemic stroke (IS) is the most prevalent form of brain disease, characterized by high morbidity, disability, and mortality. However, there is still a lack of ideal prevention and treatment measures in clinical practice. Notably, the transplantation therapy of mesenchymal stem cells (MSCs) has been a hot research topic in stroke. Nevertheless, there are risks associated with this cell therapy, including tumor formation, coagulation dysfunction, and vascular occlusion. Also, a growing number of studies suggest that the therapeutic effect after transplantation of MSCs is mainly attributed to MSC-derived exosomes (MSC-Exos). And this cell-free mediated therapy appears to circumvent many risks and difficulties when compared to cell therapy, and it may be the most promising new strategy for treating stroke as stem cell replacement therapy. Studies suggest that suppressing inflammation via modulation of the immune response is an additional treatment option for IS. Intriguingly, MSC-Exos mediates the inflammatory immune response following IS by modulating the central nervous system, the peripheral immune system, and immunomodulatory molecules, thereby promoting neurofunctional recovery after stroke. Thus, this paper reviews the role, potential mechanisms, and therapeutic potential of MSC-Exos in post-IS inflammation in order to identify new research targets.

Transplantation of Retinal Progenitor Cells in a NanoFe2O3 Delivery System to Alleviate Retinitis Pigmentosa

Retinal precursor cells (RPCs) have weak migration and infiltration abilities and are susceptible to host immune rejection. An effective delivery system for the transplantation of RPCs to the target needs to be further studied to improve their efficacy in treating retinitis pigmentosa (RP). Thus, we constructed a nanoFe2O3–RPC nano-delivery system to transplant RPCs into the host retina. First, we successfully isolated RPCs from surgical samples and established the stability of the nanoFe2O3 carrier. We demonstrated that nanoFe2O3 enhances the transplantation efficiency of RPCs to target retina tissue and facilitates the replacement by these stem cells of dysfunctional photoreceptor cells while simultaneously retaining the viability and differentiation ability of the RPCs. This delivery system successfully restored ailing pigment epithelial cells to a healthier status and improved the thickness of the pigment epithelial layer in an RP rat model. Thus, the nanoFe2O3–RPC system offers therapeutic benefits to patients with RP and presents a potential option for stem cell replacement therapy in RP.

Transplanted human induced pluripotent stem cells- derived retinal ganglion cells embed within mouse retinas and are electrophysiologically functional

Glaucoma is an optic neuropathy characterized by permanent visual field loss caused by the death of retinal ganglion cells (RGCs) and it is the leading cause of irreversible blindness worldwide. Consequently, there is an unmet need for the development of new strategies for its treatment. We investigated RGC replacement therapy as a treatment for ganglion cell loss. Human-induced pluripotent stem cells (hiPSCs) were differentiated into mature, functional RGCs invitro, labeled with AAV2.7m8-SNCG-eGFP, and transplanted intravitreally in wild-type 4-month-old C57BL/6J mice. Survival of the transplanted hiPSC-RGCs was assessed by color fundus photography and histological studies confirmed the localization of the transplanted hiPSC-RGCs within the retina. Two-photon live imaging of retinal explants and electrophysiological studies confirmed that the morphology and function of the transplanted hiPSC-RGCs were similar to native RGCs. These experiments will provide key strategies to enhance the efficiency of stem cell replacement therapy for neurodegenerative diseases, including glaucoma.

Stem cell therapy for insulin-dependent diabetes: Are we still on the road?

In insulin-dependent diabetes, the islet β cells do not produce enough insulin and the patients must receive exogenous insulin to control blood sugar. However, there are still many deficiencies in exogenous insulin supplementation. Therefore, the replacement of destroyed functional β cells with insulin-secreting cells derived from functional stem cells is a good idea as a new therapeutic idea. This review introduces the development schedule of mouse and human embryonic islets. The differences between mouse and human pancreas embryo development were also listed. Accordingly to the different sources of stem cells, the important research achievements on the differentiation of insulin-secreting β cells of stem cells and the current research status of stem cell therapy for diabetes were reviewed. Stem cell replacement therapy is a promising treatment for diabetes, caused by defective insulin secretion, but there are still many problems to be solved, such as the biosafety and reliability of treatment, the emergence of tumors during treatment, untargeted differentiation and autoimmunity, etc. Therefore, further understanding of stem cell therapy for insulin is needed.

Proteomic Analysis of Retinal Conditioned Medium: The Effect on Early Differentiation of Embryonic Stem Cells into Retina.

Stem cell replacement therapy has emerged as one of the most promising treatment options for retinal degenerative diseases, which are the main causes of irreversible vision loss. Three-dimensional (3D) retinal organoid culture is a cutting-edge technology for differentiating embryonic stem cells into retinal cells by forming a laminated retinal structure. However, 3D culture systems have strict requirements with respect to the experimental environment and culture technologies. Our study aimed to investigate the effect of retinal conditioned medium (RCM) at different developmental stages on the early differentiation of embryonic stem cells into retina in a 3D culture system. In this study, we added RCM to the 3D culture system and found that it could promote the differentiation of mouse embryonic stem cells (mESCs) into neuroretina. We further explored the possible mechanisms of RCM that regulate differentiation through proteomic analysis. RCM at different time points disclosed different protein profiles. Proteins which improved energy metabolism of mESCs might help improve the viability of embryonic bodies. We then screened out Snap25, Cntn1, Negr1, Dpysl2, Dpysl3, and Crmp1 as candidate proteins that might play roles in the differentiation and neurogenesis processes of mESCs, hoping to provide a basis for optimizing a retinal differentiation protocol from embryonic stem cells.

Therapeutic Strategies For Tay-Sachs Disease.

Tay-Sachs disease (TSD) is an autosomal recessive disease that features progressive neurodegenerative presentations. It affects one in 100,000 live births. Currently, there is no approved therapy or cure. This review summarizes multiple drug development strategies for TSD, including enzyme replacement therapy, pharmaceutical chaperone therapy, substrate reduction therapy, gene therapy, and hematopoietic stem cell replacement therapy. In vitro and in vivo systems are described to assess the efficacy of the aforementioned therapeutic strategies. Furthermore, we discuss using MALDI mass spectrometry to perform a high throughput screen of compound libraries. This enables discovery of compounds that reduce GM2 and can lead to further development of a TSD therapy.

EGF/bFGF promotes survival, migration and differentiation into neurons of GFP-labeled rhesus monkey neural stem cells xenografted into the rat brain

Stem cell replacement therapy is considered a promising treatment for diseases of the central nervous system. Improving the ratio of surviving transplanted cells and the efficiency of differentiation into functional neuronal cells are the most important issues related to research on neuroregenerative medicine. Epidermal growth factor (EGF) and basic fibroblast growth factor (bFGF) have been reported to promote the proliferation and differentiation of neural stem cells (NSCs) in vitro, but whether they have the same effect in vivo is unclear. In this study, NSCs derived from rhesus monkey embryonic stem cells (ESCs) were resuspended in medium with or without EGF/bFGF and xenotransplanted into the rat striatum. No behavioral abnormalities or teratoma formation were observed in the recipient engrafted rats. GFP-labeled cells exhibited a higher survival rate and longer migration in the EGF/bFGF group than control group at 2 months after transplantation. Moreover, the percentages of Tuj1+ neurons and Map2+ neurons in the EGF/bFGF group were significantly higher than those in the control group, while the percentages of astrocytes and oligodendrocytes were significantly lower in the EGF/bGFG group than control group. These findings indicated that EGF/bFGF can promote protrusion of nerve fibers and the survival and neuronal differentiation of transplanted NSCs in the recipient brain, suggesting that EGF/bFGF has a potential application for stem cell therapy.

The Roles of Different Multigene Combinations of Pdx1, Ngn3, Sox9, Pax4, and Nkx2.2 in the Reprogramming of Canine ADSCs Into IPCs

Adipose-derived mesenchymal stem cells (ADSCs) are ideal sources for the treatment of diabetes, and the differentiation of ADSCs into insulin-producing cells (IPCs) through transfection of exogenous regulatory genes in vitro has been studied in depth. The differentiation of ADSCs is strictly regulated by a variety of transcription factors such as Pdx1, Ngn3, Pax4, Nkx2.2, and Sox9. However, whether these genes can coordinately regulate the differentiation of ADSCs into IPCs is still unknown. In this study, five multigene coexpressing adenovirus vectors (pAdTrack-Pdx1-Ngn3-AdEasy, pAdTrack-Pdx1-Ngn3-Sox9-AdEasy, pAdTrack-Pdx1-Ngn3-Pax4-Sox9-AdEasy, pAdTrack-Pdx1-Ngn3-Nkx2.2-Sox9-AdEasy, and pAdTrack-Pdx1-Ngn3-Nkx2.2-Pax4-AdEasy) were constructed, and then the stocks of the packaged adenoviruses were used to infect the canine ADSCs (cADSCs). Based on results of morphological observation, dithizone staining, sugar-stimulated insulin secretion test, cellular insulin immunofluorescence assays, and the detection of pancreatic β-cell development–related genes in the induced cells, the best induction combination (pAdTrack-Pdx1-Ngn3-Nkx2.2-Pax4-AdEasy) was identified after comparative screening. This study provides a theoretical reference and an experimental basis for further research on stem cell replacement therapy for diabetes.

Induced Pluripotent Stem Cells (iPSCs) and Gene Therapy: A New Era for the Treatment of Neurological Diseases.

To date, gene therapy has employed viral vectors to deliver therapeutic genes. However, recent progress in molecular and cell biology has revolutionized the field of stem cells and gene therapy. A few years ago, clinical trials started using stem cell replacement therapy, and the induced pluripotent stem cells (iPSCs) technology combined with CRISPR-Cas9 gene editing has launched a new era in gene therapy for the treatment of neurological disorders. Here, we summarize the latest findings in this research field and discuss their clinical applications, emphasizing the relevance of recent studies in the development of innovative stem cell and gene editing therapeutic approaches. Even though tumorigenicity and immunogenicity are existing hurdles, we report how recent progress has tackled them, making engineered stem cell transplantation therapy a realistic option.

Retinoic acid and taurine enhance differentiation of the human bone marrow stem cells into cone photoreceptor cells and retinal ganglion cells

Degeneration and apoptotic death of the photoreceptor cell-layer of retina are a major cause of irreversible blindness in the development era. The stem cell replacement therapy is one of the strategies for the retinal repairing. In addition, exogenous signals critically contribute to the direction of lineage decisions that causes the fate-restricted photoreceptor progenitors from stem cell progeny in culture. It has been found that epidermal growth factor (EGF), taurine, and retinoic acid (RA) initially act in the instructive as well as lineage-restricted way in the progenitor lineage for producing neuroretinal cells or photoreceptor like cells from stem cell. The study aims to investigate the effect of RA and taurine in differentiation of the human bone marrow stem cell into cone photoreceptors cells and retinal ganglion cells. Mesenchymal stem cell was derived from human bone marrow of the term delivery. Therefore, the cultured cells have been treated with Dulbecco's modified Eagle's medium (DMEM)/high glucose (H+ ). After the four-cell passage, basal medium was replaced with DMEM/F12 complemented with 50 μmol/L taurine, RA (1 µM) and EGF (1 µg/ml). Subsequently cellular change morphology was detected following 7 and 14 days. Then, gene expression of neuroretinal and photoreceptor cell biomarkers (CRX, OTX2, PKC-α, recoverin, and Rho) were examined by quantitative polymerase chain reaction (Q-PCR). Also, cells were cultured, fixed, and then immunocytochemical analyzed. Primary antibodies included CRX and Rho. Cellular morphology demonstrated spindle elongated morphology. Taurine alone and combination of RA upregulate neuroretinal and photoreceptor cell biomarkers in messenger RNA and protein levels but along with EGF have not significant effect. Our data showed that taurine combination with RA can differentiate bone marrow mesenchymal stem cells into neuroretinal or photoreceptor like cells in vitro that can offer an attractive treatment ground for transplantation in the cell-replacement therapy for some forms of the retinal degeneration.

Distribution and Afferent Effects of Transplanted mESCs on Cochlea in Acute and Chronic Neural Hearing Loss Models.

Hearing loss is a sensory deprivation that can affect the quality of life. Currently, only rehabilitation devices such as hearing aids and cochlear implants are used, without a definitive cure. However, in chronic hearing-deprived patients, in whom secondary auditory neural degeneration is expected, a relatively poor rehabilitation prognosis is projected. Stem cell therapy for cochlear neural structures would be an easier and feasible strategy compared with cochlear sensory cells. Considering the highly developed cochlear implantation technology, improving cochlear neural health has significant medical and social effects. Stem cell delivery to Rosenthal's canal in an acutely damaged mouse model has been performed and showed cell survival and the possibility of differentiation. The results of stem cell transplantation in chronic auditory neural hearing loss should be evaluated because neural stem cell replacement therapy for chronic (long-term) sensorineural hearing loss is a major target in clinics. In the present study, we established a mouse model that mimicked chronic auditory neural hearing loss (secondary degeneration of auditory neurons after loss of sensory input). Then, mouse embryonic stem cells (mESCs) were transplanted into the scala tympani and survival and distribution of transplanted cells were compared between the acute and chronic auditory neural hearing loss models induced by ouabain or kanamycin (KM), respectively. The mESC survival was similar to the acute model, and perilymphatic distribution of cell aggregates was more predominant in the chronic model. Lastly, the effects of mESC transplantation on neural signal transduction observed in the cochlear nucleus (CN) were compared and a statistical increase was observed in the chronic model compared with other models. These results indicated that after transplantation, mESCs survived in the cochlea and increased the neural signaling toward the central auditory pathway, even in the chronic (secondary) hearing loss mouse model.

Stem Cell-Based Clinical Trials for Diabetes Mellitus.

Since its introduction more than twenty years ago, intraportal allogeneic cadaveric islet transplantation has been shown to be a promising therapy for patients with Type I Diabetes (T1D). Despite its positive outcome, the impact of islet transplantation has been limited due to a number of confounding issues, including the limited availability of cadaveric islets, the typically lifelong dependence of immunosuppressive drugs, and the lack of coverage of transplant costs by health insurance companies in some countries. Despite improvements in the immunosuppressive regimen, the number of required islets remains high, with two or more donors per patient often needed. Insulin independence is typically achieved upon islet transplantation, but on average just 25% of patients do not require exogenous insulin injections five years after. For these reasons, implementation of islet transplantation has been restricted almost exclusively to patients with brittle T1D who cannot avoid hypoglycemic events despite optimized insulin therapy. To improve C-peptide levels in patients with both T1 and T2 Diabetes, numerous clinical trials have explored the efficacy of mesenchymal stem cells (MSCs), both as supporting cells to protect existing β cells, and as source for newly generated β cells. Transplantation of MSCs is found to be effective for T2D patients, but its efficacy in T1D is controversial, as the ability of MSCs to differentiate into functional β cells in vitro is poor, and transdifferentiation in vivo does not seem to occur. Instead, to address limitations related to supply, human embryonic stem cell (hESC)-derived β cells are being explored as surrogates for cadaveric islets. Transplantation of allogeneic hESC-derived insulin-producing organoids has recently entered Phase I and Phase II clinical trials. Stem cell replacement therapies overcome the barrier of finite availability, but they still face immune rejection. Immune protective strategies, including coupling hESC-derived insulin-producing organoids with macroencapsulation devices and microencapsulation technologies, are being tested to balance the necessity of immune protection with the need for vascularization. Here, we compare the diverse human stem cell approaches and outcomes of recently completed and ongoing clinical trials, and discuss innovative strategies developed to overcome the most significant challenges remaining for transplanting stem cell-derived β cells.

Genetic insights, disease mechanisms, and biological therapeutics for Waardenburg syndrome.

Waardenburg syndrome (WS), also known as auditory-pigmentary syndrome, is the most common cause of syndromic hearing loss (HL), which accounts for approximately 2-5% of all patients with congenital hearing loss. WS is classified into four subtypes depending on the clinical phenotypes. Currently, pathogenic mutations of PAX3, MITF, SOX10, EDN3, EDNRB or SNAI2 are associated with different subtypes of WS. Although supportive techniques like hearing aids, cochlear implants, or other assistive listening devices can alleviate the HL symptom, there is no cure for WS to date. Recently major progress has been achieved in preclinical studies of genetic HL in animal models, including gene delivery and stem cell replacement therapies. This review focuses on the current understandings of pathogenic mechanisms and potential biological therapeutic approaches for HL in WS, providing strategies and directions for implementing WS biological therapies, as well as possible problems to be faced, in the future.

Stem cell legislation and its impact on the geographic preferences of stem cell researchers

Proponents describe stem Cell Replacement Therapy and related technologies to be a significant step forward for medicine. However, due to the inherent ethical problems in human Embryonic Stem Cell Research (hESC), it is strictly regulated around the world. The US has passed at the federal and state level, both supportive and restrictive laws over the years. The changing legislative environment at the state and federal levels has created a situation whereby researchers have to choose whether and where to carry out this research. By exploiting the temporal and spatial heterogeneity and legislative shocks, we assess if the affected scientists have voted with their feet, leaving the state or country imposing restrictive rules and whether hESC research has clustered geographically. We find that most of the hESC research is carried out in supportive states, and significant legislative changes have had a minor but noticeable effect on relocation choices. Most importantly, the research has moved to supportive states. This result suggests that several state-level interventions (supportive), which were opposed to federal laws (restrictive), have counteracted each other.

An alternative approach to produce versatile retinal organoids with accelerated ganglion cell development

Genetically complex ocular neuropathies, such as glaucoma, are a major cause of visual impairment worldwide. There is a growing need to generate suitable human representative in vitro and in vivo models, as there is no effective treatment available once damage has occured. Retinal organoids are increasingly being used for experimental gene therapy, stem cell replacement therapy and small molecule therapy. There are multiple protocols for the development of retinal organoids available, however, one potential drawback of the current methods is that the organoids can take between 6 weeks and 12 months on average to develop and mature, depending on the specific cell type wanted. Here, we describe and characterise a protocol focused on the generation of retinal ganglion cells within an accelerated four week timeframe without any external small molecules or growth factors. Subsequent long term cultures yield fully differentiated organoids displaying all major retinal cell types. RPE, Horizontal, Amacrine and Photoreceptors cells were generated using external factors to maintain lamination.

Non-immunogenic Induced Pluripotent Stem Cells, a Promising Way Forward for Allogenic Transplantations for Neurological Disorders.

Neurological disorder is a general term used for diseases affecting the function of the brain and nervous system. Those include a broad range of diseases from developmental disorders (e.g., Autism) over injury related disorders (e.g., stroke and brain tumors) to age related neurodegeneration (e.g., Alzheimer's disease), affecting up to 1 billion people worldwide. For most of those disorders, no curative treatment exists leaving symptomatic treatment as the primary mean of alleviation. Human induced pluripotent stem cells (hiPSC) in combination with animal models have been instrumental to foster our understanding of underlying disease mechanisms in the brain. Of specific interest are patient derived hiPSC which allow for targeted gene editing in the cases of known mutations. Such personalized treatment would include (1) acquisition of primary cells from the patient, (2) reprogramming of those into hiPSC via non-integrative methods, (3) corrective intervention via CRISPR-Cas9 gene editing of mutations, (4) quality control to ensure successful correction and absence of off-target effects, and (5) subsequent transplantation of hiPSC or pre-differentiated precursor cells for cell replacement therapies. This would be the ideal scenario but it is time consuming and expensive. Therefore, it would be of great benefit if transplanted hiPSC could be modulated to become invisible to the recipient's immune system, avoiding graft rejection and allowing for allogenic transplantations. This review will focus on the current status of gene editing to generate non-immunogenic hiPSC and how these cells can be used to treat neurological disorders by using cell replacement therapy. By providing an overview of current limitations and challenges in stem cell replacement therapies and the treatment of neurological disorders, this review outlines how gene editing and non-immunogenic hiPSC can contribute and pave the road for new therapeutic advances. Finally, the combination of using non-immunogenic hiPSC and in vivo animal modeling will highlight the importance of models with translational value for safety efficacy testing; before embarking on human trials.

Molecular Aspects of the Development and Function of Auditory Neurons.

This review provides an up-to-date source of information on the primary auditory neurons or spiral ganglion neurons in the cochlea. These neurons transmit auditory information in the form of electric signals from sensory hair cells to the first auditory nuclei of the brain stem, the cochlear nuclei. Congenital and acquired neurosensory hearing loss affects millions of people worldwide. An increasing body of evidence suggest that the primary auditory neurons degenerate due to noise exposure and aging more readily than sensory cells, and thus, auditory neurons are a primary target for regenerative therapy. A better understanding of the development and function of these neurons is the ultimate goal for long-term maintenance, regeneration, and stem cell replacement therapy. In this review, we provide an overview of the key molecular factors responsible for the function and neurogenesis of the primary auditory neurons, as well as a brief introduction to stem cell research focused on the replacement and generation of auditory neurons.