Stem Cell Therapy: Repurposing Cell-Based Regenerative Medicine Beyond Cell Replacement

An update on stem cell therapy for stroke patients: Where are we now?

With a foundation built upon initial work from the 1980s demonstrating graft viability in cerebral ischemia, stem cell transplantation has shown immense promise in promoting survival, enhancing neuroprotection and inducing neuroregeneration, while mitigating both histological and behavioral deficits that frequently accompany ischemic stroke. These findings have led to a number of clinical trials that have thoroughly supported a strong safety profile for stem cell therapy in patients but have generated variable efficacy. As preclinical evidence continues to expand through the investigation of new cell lines and optimization of stem cell delivery, it remains critical for translational models to adhere to the protocols established through basic scientific research. With the recent shift in approach towards utilization of stem cells as a conjunctive therapy alongside standard thrombolytic treatments, key issues including timing, route of administration, and stem cell type must each be appropriately translated from the laboratory in order to resolve the question of stem cell efficacy for cerebral ischemia that ultimately will enhance therapeutics for stroke patients towards improving quality of life.

Regeneration of the Retina Using Pluripotent Stem Cells: A Comprehensive Review

Retinitis pigmentosa and age-related macular degeneration are the most frequent causes of irreversible visual impairment in the world. Existing therapeutic methods could be more effective, underscoring the necessity of new treatments. Reconstructing the retinal photoreceptors through the transplantation of human pluripotent stem cells, representing an attractive approach for restoring vision, has gained momentum. This paper gives an exhaustive account of what has been known in this field, the discoveries made, and the recent progress. This review paper outlines the retina's organisation, cell types, the pathophysiology of retinal injury/degeneration, and the reasoning behind using pluripotent stem cells in retinal regeneration. This article investigates differentiation strategies, molecular components that dictate cell type specification, and the recreation of retinal development in vitro, genetically engineering and manipulating epigenetic marks using various techniques for driving specific cell fates and improving therapy efficacy. Subretinal injection methods, cell encapsulation techniques, scaffold-based approaches, cell sheet transplantation, and their impact on integrating implanted cells into a functional retina are thoroughly reviewed. Using bioengineering approaches, biomaterials and growth factors form a favourable micro-ambience for grafted cells. Issues around safety and efficacy (tumorigenicity, immunological rejection, and long-term integration/functionality) are explored. Moreover, the paper emphasises the significance of rigorous characterisation, immunomodulatory strategies, and clinical and pre-clinical studies to ensure the safety and effectiveness of retinal regeneration therapy. Future perspectives and challenges are presented, looking at fine-tuning differentiation strategies, improving functional integration and regulatory aspects, and using co-therapy and supportive treatments.

Senotherapeutics for mesenchymal stem cell senescence and rejuvenation

Mesenchymal stem cells (MSCs) are susceptible to replicative senescence and senescence-associated functional decline, which hampers their use in regenerative medicine. Senotherapeutics are drugs that target cellular senescence through senolytic and senomorphic functions to induce apoptosis and suppress chronic inflammation caused by the senescence-associated secreted phenotype (SASP), respectively. Therefore, senotherapeutics could delay aging-associated degeneration. They could also be used to eliminate senescent MSCs during in vitro expansion or bioprocessing for transplantation. In this review, we discuss the role of senotherapeutics in MSC senescence, rejuvenation, and transplantation, with examples of some tested compounds in vitro. The prospects, challenges, and the way forward in clinical applications of senotherapeutics in cell-based therapeutics are also discussed.

HOW STEM CELLS ARE SHAPING OUR DRUG DISCOVERY TECHNIQUES?

Stem cell biology is a fast-developing field of research that has made significant contributions to a wide range of scientific specialties, from developmental biology to regenerative medicine. One of the most promising implications of stem cell biology in recent years has been drug development. Stem cells are rapidly being employed in novel ways to enhance the drug development processes with applications ranging from academia to biotech start-ups to big pharmaceutical businesses.

Combination of Stem Cells and Rehabilitation Therapies for Ischemic Stroke

Stem cell transplantation with rehabilitation therapy presents an effective stroke treatment. Here, we discuss current breakthroughs in stem cell research along with rehabilitation strategies that may have a synergistic outcome when combined together after stroke. Indeed, stem cell transplantation offers a promising new approach and may add to current rehabilitation therapies. By reviewing the pathophysiology of stroke and the mechanisms by which stem cells and rehabilitation attenuate this inflammatory process, we hypothesize that a combined therapy will provide better functional outcomes for patients. Using current preclinical data, we explore the prominent types of stem cells, the existing theories for stem cell repair, rehabilitation treatments inside the brain, rehabilitation modalities outside the brain, and evidence pertaining to the benefits of combined therapy. In this review article, we assess the advantages and disadvantages of using stem cell transplantation with rehabilitation to mitigate the devastating effects of stroke.

Quercetin promotes osteogenic differentiation and antioxidant responses of mouse bone mesenchymal stem cells through activation of the AMPK/SIRT1 signaling pathway

Decrepitude and apoptosis of bone mesenchymal stem cells (BMSCs) induced by reactive oxygen species (ROS) lead to inhibited osteogenic differentiation, causing decreased bone density and osteoporosis. Quercetin, a bioactive component of Solanum muricatum extracts, promotes the osteogenic differentiation of BMSCs and ameliorates the symptoms of osteoporosis in vivo. However, the detailed mechanism underlying this process remains unclear. The study aims to reveal the regulatory mechanism of quercetin in BMSCs. Mouse BMSCs (mBMSCs) were isolated from the bone marrow and characterized by flow cytometry. QRT-PCR and western blot assays were performed to evaluate the expression levels of related genes and proteins. Alkaline phosphatase (ALP) staining and Oil Red O staining of lipids were used to estimate the osteogenesis and adipogenesis levels of mBMSCs, respectively. Quercetin treatment (2 and 5 μM) induced significant upregulation of antioxidant enzymes, SOD1 and SOD2, in mBMSCs. Quercetin promoted osteogenic differentiation and inhibited adipogenic differentiation of mBMSCs. Quercetin treatment enhanced the phosphorylation of AMPK protein and upregulated the expression of SIRT1, thus activating the AMPK/SIRT1 signaling pathway in mBMSCs. Quercetin promoted osteogenic differentiation and antioxidant responses of mBMSCs by activating the AMPK/SIRT1 signaling pathway.

Biphasic roles of pentraxin 3 in cerebrovascular function after white matter stroke

Recent clinical studies suggest that pentraxin 3 (PTX3), which is known as an acute-phase protein that is produced rapidly at local sites of inflammation, may be a new biomarker of disease risk for central nervous system disorders, including stroke. However, the effects of PTX3 on cerebrovascular function in the neurovascular unit (NVU) after stroke are mostly unknown, and the basic research regarding the roles of PTX3 in NVU function is still limited. In this reverse translational study, we prepared mouse models of white matter stroke by vasoconstrictor (ET-1 or L-Nio) injection into the corpus callosum region to examine the roles of PTX3 in the pathology of cerebral white matter stroke. PTX3 expression was upregulated in GFAP-positive astrocytes around the affected region in white matter for at least 21 days after vasoconstrictor injection. When PTX3 expression was reduced by PTX3 siRNA, blood-brain barrier (BBB) damage at day 3 after white matter stroke was exacerbated. In contrast, when PTX3 siRNA was administered at day 7 after white matter stroke, compensatory angiogenesis at day 21 was promoted. In vitro cell culture experiments confirmed the inhibitory effect of PTX3 in angiogenesis, that is, recombinant PTX3 suppressed the tube formation of cultured endothelial cells in a Matrigel-based in vitro angiogenesis assay. Taken together, our findings may support a novel concept that astrocyte-derived PTX3 plays biphasic roles in cerebrovascular function after white matter stroke; additionally, it may also provide a proof-of-concept that PTX3 could be a therapeutic target for white matter-related diseases, including stroke.

Applying hiPSCs and Biomaterials Towards an Understanding and Treatment of Traumatic Brain Injury

Traumatic brain injury (TBI) is the leading cause of disability and mortality in children and young adults and has a profound impact on the socio-economic wellbeing of patients and their families. Initially, brain damage is caused by mechanical stress-induced axonal injury and vascular dysfunction, which can include hemorrhage, blood-brain barrier disruption, and ischemia. Subsequent neuronal degeneration, chronic inflammation, demyelination, oxidative stress, and the spread of excitotoxicity can further aggravate disease pathology. Thus, TBI treatment requires prompt intervention to protect against neuronal and vascular degeneration. Rapid advances in the field of stem cells (SCs) have revolutionized the prospect of repairing brain function following TBI. However, more than that, SCs can contribute substantially to our knowledge of this multifaced pathology. Research, based on human induced pluripotent SCs (hiPSCs) can help decode the molecular pathways of degeneration and recovery of neuronal and glial function, which makes these cells valuable tools for drug screening. Additionally, experimental approaches that include hiPSC-derived engineered tissues (brain organoids and bio-printed constructs) and biomaterials represent a step forward for the field of regenerative medicine since they provide a more suitable microenvironment that enhances cell survival and grafting success. In this review, we highlight the important role of hiPSCs in better understanding the molecular pathways of TBI-related pathology and in developing novel therapeutic approaches, building on where we are at present. We summarize some of the most relevant findings for regenerative therapies using biomaterials and outline key challenges for TBI treatments that remain to be addressed.

Hydrogels Derivatized With Cationic Moieties or Functional Peptides as Efficient Supports for Neural Stem Cells

The increasing incidence of neurodegenerative diseases such as Alzheimer's or Parkinson's disease represents a significant burden for patients and national health systems. The conditions are primarily caused by the death of neurons and other neural cell types. One important aim of current stem cell research is to find a way to replace the lost cells. In this perspective, neural stem cells (NSCs) have been considered as a promising tool in the field of regenerative medicine. The behavior of NSCs is modulated by environmental influences, for example hormones, growth factors, cytokines, and extracellular matrix molecules or biomechanics. These factors can be studied by using well-defined hydrogels, which are polymeric networks of synthetic or natural origin with the ability to swell in water. These gels can be modified with a variety of molecules and optimized with regard to their mechanical properties to mimic the natural extracellular environment. In particular modifications applying distinct units such as functional domains and peptides can modulate the development of NSCs with regard to proliferation, differentiation and migration. One well-known peptide sequence that affects the behavior of NSCs is the integrin recognition sequence RGD that has originally been derived from fibronectin. In the present review we provide an overview concerning the applications of modified hydrogels with an emphasis on synthetic hydrogels based on poly(acrylamides), as modified with either cationic moieties or the peptide sequence RGD. This knowledge might be used in tissue engineering and regenerative medicine for the therapy of spinal cord injuries, neurodegenerative diseases and traumata.

Concise Review: Stem Cell Therapy for Stroke Patients: Are We There Yet?

Four decades of preclinical research demonstrating survival, functional integration, and behavioral effects of transplanted stem cells in experimental stroke models have provided ample scientific basis for initiating limited clinical trials of stem cell therapy in stroke patients. Although safety of the grafted cells has been overwhelmingly documented, efficacy has not been forthcoming. Two recently concluded stroke clinical trials on mesenchymal stem cells (MSCs) highlight the importance of strict adherence to the basic science findings of optimal transplant regimen of cell dose, timing, and route of delivery in enhancing the functional outcomes of cell therapy. Echoing the Stem Cell Therapeutics as an Emerging Paradigm for Stroke and Stroke Treatment Academic Industry Roundtable call for an NIH‐guided collaborative consortium of multiple laboratories in testing the safety and efficacy of stem cells and their derivatives, not just as stand‐alone but preferably in combination with approved thrombolytic or thrombectomy, may further increase the likelihood of successful fruition of translating stem cell therapy for stroke clinical application. The laboratory and clinical experience with MSC therapy for stroke may guide the future translational research on stem cell‐based regenerative medicine in neurological disorders. stem cells translational medicine2019;8:983&988

Extracellular micro/nanovesicles rescue kidney from ischemia-reperfusion injury

Acute renal failure (ARF) is a clinical challenge that is highly resistant to treatment, and its high rate of mortality is alarming. Ischemia-reperfusion injury (IRI) is the most common cause of ARF. Especially IRI is implicated in kidney transplantation and can determine graft survival. Although the exact pathophysiology of renal IRI is unknown, the role of inflammatory responses has been elucidated. Because mesenchymal stromal cells (MSCs) have strong immunomodulatory properties, they are under extensive investigation as a therapeutic modality for renal IRI. Extracellular vesicles (EVs) play an integral role in cell-to-cell communication. Because the regenerative potential of the MSCs can be recapitulated by their EVs, the therapeutic appeal of MSC-derived EVs has dramatically increased in the past decade. Higher safety profile and ease of preservation without losing function are other advantages of EVs compared with their producing cells. In the current review, the preliminary results and potential of MSC-derived EVs to alleviate kidney IRI are summarized. We might be heading toward a cell-free approach to treat renal IRI.

Mitochondrial targeting as a novel therapy for stroke

Stroke is a main cause of mortality and morbidity worldwide. Despite the increasing development of innovative treatments for stroke, most are unsuccessful in clinical trials. In recent years, an encouraging strategy for stroke therapy has been identified in stem cells transplantation. In particular, grafting cells and their secretion products are leading with functional recovery in stroke patients by promoting the growth and function of the neurovascular unit – a communication framework between neurons, their supply microvessels along with glial cells – underlying stroke pathology and recovery. Mitochondrial dysfunction has been recently recognized as a hallmark in ischemia/reperfusion neural damage. Emerging evidence of mitochondria transfer from stem cells to ischemic-injured cells points to transfer of healthy mitochondria as a viable novel therapeutic strategy for ischemic diseases. Hence, a more in-depth understanding of the cellular and molecular mechanisms involved in mitochondrial impairment may lead to new tools for stroke treatment. In this review, we focus on the current evidence of mitochondrial dysfunction in stroke, investigating favorable approaches of healthy mitochondria transfer in ischemic neurons, and exploring the potential of mitochondria-based cellular therapy for clinical applications. This paper is a review article. Referred literature in this paper has been listed in the references section. The data sets supporting the conclusions of this article are available online by searching various databases, including PubMed.

White-matter repair: Interaction between oligodendrocytes and the neurovascular unit

There are currently no adequate treatments for white-matter injury, which often follows central nervous system maladies and their accompanying neurodegenerative processes. Indeed, the white matter is compromised by the deterioration of the blood–brain barrier and the demyelination of neuronal axons. Key repairs to the white matter are mediated by oligodendrocyte lineage cells after damaging events. Oligodendrocytes are supported by other cells in the neurovascular unit and these cells collaborate in processes such as angiogenesis, neurogenesis, and oligodendrogenesis. Understanding the various interactions between these cells and oligodendrocytes will be imperative for developing reparative therapies for impaired white matter. This minireview will discuss how oligodendrocytes and oligodendrocyte lineage cells mend damage to the white matter and restore brain function ensuing neural injury.

Understanding the Role of Dysfunctional and Healthy Mitochondria in Stroke Pathology and Its Treatment

Stroke remains a major cause of death and disability in the United States and around the world. Solid safety and efficacy profiles of novel stroke therapeutics have been generated in the laboratory, but most failed in clinical trials. Investigations into the pathology and treatment of the disease remain a key research endeavor in advancing scientific understanding and clinical applications. In particular, cell-based regenerative medicine, specifically stem cell transplantation, may hold promise as a stroke therapy, because grafted cells and their components may recapitulate the growth and function of the neurovascular unit, which arguably represents the alpha and omega of stroke brain pathology and recovery. Recent evidence has implicated mitochondria, organelles with a central role in energy metabolism and stress response, in stroke progression. Recognizing that stem cells offer a source of healthy mitochondria—one that is potentially transferrable into ischemic cells—may provide a new therapeutic tool. To this end, deciphering cellular and molecular processes underlying dysfunctional mitochondria may reveal innovative strategies for stroke therapy. Here, we review recent studies capturing the intimate participation of mitochondrial impairment in stroke pathology, and showcase promising methods of healthy mitochondria transfer into ischemic cells to critically evaluate the potential of mitochondria-based stem cell therapy for stroke patients.