Very Small Embryonic-Like Stem Cells (VSELs)

Hyperthermia for Targeting Cancer and Cancer Stem Cells: Insights from Novel Cellular and Clinical Approaches

The Cellular Heat Shock Response and in particular heat shock protein activation are vital stress reactions observed in both healthy and cancer cells. Hyperthermia (HT) has been proposed for several years as an advancing non-invasive cancer therapy. It selectively targets cancer cells through mechanisms influenced by temperature and temperature variations. This article delves into the impact of HT on cancer cells, especially cancer stem cells (CSCs), essential contributors to cancer recurrence and metastasis. HT has shown promise in eliminating CSCs, sensitizing them to conventional treatments and modulating the tumor microenvironment. The exploration extends to mesenchymal stem cells (MSCs), which exhibit both pro-tumorigenic and anti-tumorigenic effects. HT's potential in recruiting therapeutic MSCs for targeted delivery of antitumoral agents is also discussed. Furthermore, the article introduces Brain Thermodynamics-guided Hyperthermia (BTGH) technology, a breakthrough in temperature control and modulation of heat transfer under different conditions. This non-invasive method leverages the brain-eyelid thermal tunnel (BTT) to monitor and regulate internal brain temperature. BTGH technology, with its precision and noninvasive continuous monitoring capabilities, is under clinical investigation for applications in neurological disorders and cancer. The innovative three-phase approach involves whole-body HT, targeted brain HT, and organ-specific HT. In conclusion, the exploration of localized or whole-body HT offers promising avenues for cancer, psychiatric and neurological diseases. The ongoing clinical investigations and potential applications underscore the significance of understanding and harnessing heat's responses to enhance human health.

A Review of the Evidence for Tryptophan and the Kynurenine Pathway as a Regulator of Stem Cell Niches in Health and Disease

Stem cells are ubiquitously found in various tissues and organs in the body, and underpin the body's ability to repair itself following injury or disease initiation, though repair can sometimes be compromised. Understanding how stem cells are produced, and functional signaling systems between different niches is critical to understanding the potential use of stem cells in regenerative medicine. In this context, this review considers kynurenine pathway (KP) metabolism in multipotent adult progenitor cells, embryonic, haematopoietic, neural, cancer, cardiac and induced pluripotent stem cells, endothelial progenitor cells, and mesenchymal stromal cells. The KP is the major enzymatic pathway for sequentially catabolising the essential amino acid tryptophan (TRP), resulting in key metabolites including kynurenine, kynurenic acid, and quinolinic acid (QUIN). QUIN metabolism transitions into the adjoining de novo pathway for nicotinamide adenine dinucleotide (NAD) production, a critical cofactor in many fundamental cellular biochemical pathways. How stem cells uptake and utilise TRP varies between different species and stem cell types, because of their expression of transporters and responses to inflammatory cytokines. Several KP metabolites are physiologically active, with either beneficial or detrimental outcomes, and evidence of this is presented relating to several stem cell types, which is important as they may exert a significant impact on surrounding differentiated cells, particularly if they metabolise or secrete metabolites differently. Interferon-gamma (IFN-γ) in mesenchymal stromal cells, for instance, highly upregulates rate-limiting enzyme indoleamine-2,3-dioxygenase (IDO-1), initiating TRP depletion and production of metabolites including kynurenine/kynurenic acid, known agonists of the Aryl hydrocarbon receptor (AhR) transcription factor. AhR transcriptionally regulates an immunosuppressive phenotype, making them attractive for regenerative therapy. We also draw attention to important gaps in knowledge for future studies, which will underpin future application for stem cell-based cellular therapies or optimising drugs which can modulate the KP in innate stem cell populations, for disease treatment.

Multipotent/pluripotent stem cell populations in stromal tissues and peripheral blood: exploring diversity, potential, and therapeutic applications

The concept of "stemness" incorporates the molecular mechanisms that regulate the unlimited self-regenerative potential typical of undifferentiated primitive cells. These cells possess the unique ability to navigate the cell cycle, transitioning in and out of the quiescent G0 phase, and hold the capacity to generate diverse cell phenotypes. Stem cells, as undifferentiated precursors endow with extraordinary regenerative capabilities, exhibit a heterogeneous and tissue-specific distribution throughout the human body. The identification and characterization of distinct stem cell populations across various tissues have revolutionized our understanding of tissue homeostasis and regeneration. From the hematopoietic to the nervous and musculoskeletal systems, the presence of tissue-specific stem cells underlines the complex adaptability of multicellular organisms. Recent investigations have revealed a diverse cohort of non-hematopoietic stem cells (non-HSC), primarily within bone marrow and other stromal tissue, alongside established hematopoietic stem cells (HSC). Among these non-HSC, a rare subset exhibits pluripotent characteristics. In vitro and in vivo studies have demonstrated the remarkable differentiation potential of these putative stem cells, known by various names including multipotent adult progenitor cells (MAPC), marrow-isolated adult multilineage inducible cells (MIAMI), small blood stem cells (SBSC), very small embryonic-like stem cells (VSELs), and multilineage differentiating stress enduring cells (MUSE). The diverse nomenclatures assigned to these primitive stem cell populations may arise from different origins or varied experimental methodologies. This review aims to present a comprehensive comparison of various subpopulations of multipotent/pluripotent stem cells derived from stromal tissues. By analysing isolation techniques and surface marker expression associated with these populations, we aim to delineate the similarities and distinctions among stromal tissue-derived stem cells. Understanding the nuances of these tissue-specific stem cells is critical for unlocking their therapeutic potential and advancing regenerative medicine. The future of stem cells research should prioritize the standardization of methodologies and collaborative investigations in shared laboratory environments. This approach could mitigate variability in research outcomes and foster scientific partnerships to fully exploit the therapeutic potential of pluripotent stem cells.

Initiation of Cancer: The Journey From Mutations in Somatic Cells to Epigenetic Changes in Tissue-resident VSELs

Multiple theories exist to explain cancer initiation, although a consensus on this is crucial for developing effective therapies. 'Somatic mutation theory' suggests that mutations in somatic cells during DNA repair initiates cancer but this concept has several attached paradoxes. Research efforts to identify quiescent cancer stem cells (CSCs) that survive therapy and result in metastasis and recurrence have remained futile. In solid cancers, CSCs are suggested to appear during epithelial-mesenchymal transition by the dedifferentiation and reprogramming of epithelial cells. Pluripotent and quiescent very small embryonic-like stem cells (VSELs) exist in multiple tissues but remain elusive owing to their small size and scarce nature. VSELs are developmentally connected to primordial germ cells, undergo rare, asymmetrical cell divisions and are responsible for the regular turnover of cells to maintain tissue homeostasis throughout life. VSELs are directly vulnerable to extrinsic endocrine insults because they express gonadal and gonadotropin hormone receptors. VSELs undergo epigenetic changes due to endocrine insults and transform into CSCs. CSCs exhibit genomic instability and develop mutations due to errors during DNA replication while undergoing excessive proliferation and clonal expansion to form spheroids. Thus tissue-resident VSELs offer a connection between extrinsic insults and variations in cancer incidence reported in various body tissues. To conclude, cancer is indeed a stem cell disease with mutations occurring as a consequence. In addition to immunotherapy, targeting mutations, and Lgr5 + organoids for developing new therapeutics, targeting CSCs (epigenetically altered VSELs) by improving their niche and epigenetic status could serve as a promising strategy to treat cancer.

The Endometrial Stem/Progenitor Cells and Their Niches

Endometrial stem/progenitor cells are a type of stem cells with the ability to self-renew and differentiate into multiple cell types. They exist in the endometrium and form niches with their neighbor cells and extracellular matrix. The interaction between endometrial stem/progenitor cells and niches plays an important role in maintaining, repairing, and regenerating the endometrial structure and function. This review will discuss the characteristics and functions of endometrial stem/progenitor cells and their niches, the mechanisms of their interaction, and their roles in endometrial regeneration and diseases. Finally, the prospects for their applications will also be explored.

Murine and Human-Purified very Small Embryonic-like Stem Cells (VSELs) Express Purinergic Receptors and Migrate to Extracellular ATP Gradient

Purinergic signaling is an ancient primordial signaling system regulating tissue development and specification of various types of stem cells. Thus, functional purinergic receptors are present in several types of cells in the body, including multiple populations of stem cells. However, one stem cell type that has not been evaluated for expression of purinergic receptors is very small embryonic stem cells (VSELs) isolated from postnatal tissues. Herein, we report that human umbilical cord blood (UCB) and murine bone marrow (BM) purified VSELs express mRNA for P1 and P2 purinergic receptors and CD39 and CD73 ectonucleotidases converting extracellular ATP (eATP) into its signaling metabolite extracellular adenosine (eAdo), that antagonizes eATP effects. More importantly, we demonstrate that human and murine VSELs respond by chemotaxis to eATP, and eAdo inhibits this migration. These responses to eATP are mediated by activation of Nlrp3 inflammasome, and exposure of VSELs to its specific inhibitor MCC950 abolished the chemotactic response to ATP. We conclude that purinergic signaling plays an essential, underappreciated role in the biology of these cells and their potential role in response to tissue/organ injuries.

Standardisation is the key to the sustained, rapid and healthy development of stem cell-based therapy

BACKGROUND

Stem cell-based therapy (SCT) is an important component of regenerative therapy that brings hope to many patients. After decades of development, SCT has made significant progress in the research of various diseases, and the market size has also expanded significantly. The transition of SCT from small-scale, customized experiments to routine clinical practice requires the assistance of standards. Many countries and international organizations around the world have developed corresponding SCT standards, which have effectively promoted the further development of the SCT industry.

METHODS

We conducted a comprehensive literature review to introduce the clinical application progress of SCT and focus on the development status of SCT standardization.

RESULTS

We first briefly introduced the types and characteristics of stem cells, and summarized the current clinical application and market development of SCT. Subsequently, we focused on the development status of SCT-related standards as of now from three levels: the International Organization for Standardization (ISO), important international organizations, and national organizations. Finally, we provided perspectives and conclusions on the significance and challenges of SCT standardization.

CONCLUSIONS

Standardization plays an important role in the sustained, rapid and healthy development of SCT.

Learning Towards Maturation of Defined Feeder-free Pluripotency Culture Systems: Lessons from Conventional Feeder-based Systems

Pluripotent stem cells (PSCs) are widely recognized as one of the most promising types of stem cells for applications in regenerative medicine, tissue engineering, disease modeling, and drug screening. This is due to their unique ability to differentiate into cells from all three germ layers and their capacity for indefinite self-renewal. Initially, PSCs were cultured using animal feeder cells, but these systems presented several limitations, particularly in terms of Good Manufacturing Practices (GMP) regulations. As a result, feeder-free systems were introduced as a safer alternative. However, the precise mechanisms by which feeder cells support pluripotency are not fully understood. More importantly, it has been observed that some aspects of the need for feeder cells like the optimal density and cell type can vary depending on conditions such as the developmental stage of the PSCs, phases of the culture protocol, the method used in culture for induction of pluripotency, and intrinsic variability of PSCs. Thus, gaining a better understanding of the divergent roles and necessity of feeder cells in various conditions would lead to the development of condition-specific defined feeder-free systems that resolve the failure of current feeder-free systems in some conditions. Therefore, this review aims to explore considerable feeder-related issues that can lead to the development of condition-specific feeder-free systems.

Beyond Vision: An Overview of Regenerative Medicine and Its Current Applications in Ophthalmological Care

Regenerative medicine (RM) has emerged as a promising and revolutionary solution to address a range of unmet needs in healthcare, including ophthalmology. Moreover, RM takes advantage of the body's innate ability to repair and replace pathologically affected tissues. On the other hand, despite its immense promise, RM faces challenges such as ethical concerns, host-related immune responses, and the need for additional scientific validation, among others. The primary aim of this review is to present a high-level overview of current strategies in the domain of RM (cell therapy, exosomes, scaffolds, in vivo reprogramming, organoids, and interspecies chimerism), centering around the field of ophthalmology. A search conducted on clinicaltrials.gov unveiled a total of at least 209 interventional trials related to RM within the ophthalmological field. Among these trials, there were numerous early-phase studies, including phase I, I/II, II, II/III, and III trials. Many of these studies demonstrate potential in addressing previously challenging and degenerative eye conditions, spanning from posterior segment pathologies like Age-related Macular Degeneration and Retinitis Pigmentosa to anterior structure diseases such as Dry Eye Disease and Limbal Stem Cell Deficiency. Notably, these therapeutic approaches offer tailored solutions specific to the underlying causes of each pathology, thus allowing for the hopeful possibility of bringing forth a treatment for ocular diseases that previously seemed incurable and significantly enhancing patients' quality of life. As advancements in research and technology continue to unfold, future objectives should focus on ensuring the safety and prolonged viability of transplanted cells, devising efficient delivery techniques, etc.

Reversing Uteropathies Including Cancer-Like Changes in Mice by Transplanting Mesenchymal Stromal Cells or XAR Treatment

Pluripotent, very small embryonic-like stem cells (VSELs) and tissue-committed 'progenitors' termed endometrial stem cells (EnSCs) are reported in mouse uterus. They express gonadal and gonadotropin hormone receptors and thus are vulnerable to early-life endocrine insults. Neonatal exposure of mouse pups to endocrine disruption cause stem/progenitor cells to undergo epigenetic changes, excessive self-renewal, and blocked differentiation that results in various uteropathies including non-receptive endometrium, hyperplasia, endometriosis, adenomyosis, and cancer-like changes in adult life. Present study investigated reversal of these uteropathies, by normalizing functions of VSELs and EnSCs. Two strategies were evaluated including (i) transplanting mesenchymal stromal cells (provide paracrine support) on D60 or (ii) oral administration of XAR (epigenetic regulator) daily from days 60-100 and effects were studied later in 100 days old mice. Results show normalization of stem/progenitor cells (Oct-4, Oct-4A, Sox-2, Nanog) and Wnt signalling (Wnt-4, β-catenin, Axin-2) specific transcripts. Flow cytometry results showed reduced numbers of 2-6 µm, LIN-CD45-SCA-1 + VSELs. Hyperplasia (Ki67) of epithelial (Pax-8, Foxa-2) and myometrial (α-Sma, Tgf-β) cells was reduced, adenogenesis (differentiation of glands) was restored, endometrial receptivity and differentiation (LIF, c-KIT, SOX-9, NUMB) and stromal cells niche (CD90, VIMENTIN, Pdgfra, Vimentin) were improved, cancer stem cells markers (OCT-4, CD166) were reduced while tumor suppressor genes (PTEN, P53) and epigenetic regulators (Ezh-2, Sirt-1) were increased. To conclude, normalizing VSELs/EnSCs to manage uteropathies provides a novel basis for initiating clinical studies. The study falls under the umbrella of United Nations Sustainable Development Goal 3 to ensure healthy lives and well-being for all of all ages.

Transforming Perspectives in Cardiac Cell Therapy: Hypothesis and Commentary Following Updated Results of a Pilot Study Investigating Very Long-Term Clinical Outcomes in Severe AMI Patients Following Trans-Epicardial Injection of Peripheral Blood CD34+ Cells

Ischemic heart attack is the leading cause of death worldwide. Ten percent of cases will die within an hour. Of the survivors, around 30% will have suffered a severe infarction which will lead to the irreparable destruction of 1 to 2 billion myocardial cells, causing an irreversible secondary heart failure with a poor prognosis in the short. The heart is a totally differentiated organ with a very low capacity for self-regeneration. No current treatment can prevent this fatal outcome, but only slow it down. For these reasons, cell therapy has generated enormous hope, but achieved somewhat disappointing results, depending on the type/source of cells which were used. From the end of 2002, our group conducted a Pilot study using immuno-selected autologous peripheral-blood (PB) CD34+ cells in a small cohort of patients who had experienced a heart attack with poor prognosis. Three of these patients were immediately considered for heart transplant but lacked a readily available donor. CD34+ cells were trans-epicardially delivered at the end of a coronary artery by-pass graft (CABG) operation without reperfusing the ischemic area, which was performed on a compassionate basis. All but one patient showed a marked and sustained improvement in their cardiac function parameters from the baseline values, associated with both cardiac tissue repair and revascularization, as demonstrated by PetScan examination. The patients' outcomes have been recently updated. Six out of seven patients have survived in good enough conditions for at least 12 years after cell therapy, including those three initially recommended for heart transplant and who have avoided it. Presently, five out of seven patients are still alive with an average follow-up of 17 years (range 16-20 years), which is very unusual after CABG for patients with such a poor initially prognosis.

Synergistic Effect of Human Chorionic Gonadotropin and Granulocyte Colony Stimulating Factor in the Mobilization of HSPCs Improves Overall Survival After PBSCT in a Preclinical Murine Model. Are We Far Enough for Therapy?

Strategies to improve hematopoietic stem and progenitor cell (HSPC) mobilization from the bone marrow can have a pivotal role in addressing iatrogenic bone-marrow insufficiency from chemo(radio)therapy and overcoming peripheral blood stem cell transplantation (PBSCT) limitations such as insufficient mobilization. Granulocyte-colony stimulating factor (G-CSF) represents the standard mobilization strategy for HSPC and has done so for more than three decades since its FDA approval. Its association with non-G-CSF agents is often employed for difficult HSPC mobilization. However, obtaining a synergistic effect between the two classes is limited by different timing and mechanisms of action. Based on our previous in vitro results, we tested the mobilization potential of human chorionic gonadotropin (HCG), alone and in combination with G-CSF in vivo in a murine study. Our results show an improved mobilization capability of the combination, which seems to act synergistically in stimulating hematopoiesis. With the current understanding of the dynamics of HSPCs and their origins in more primitive cells related to the germline, new strategies to employ the mobilization of hematopoietic progenitors using chorionic gonadotropins could soon become clinical practice.

Body fluid-derived stem cells - an untapped stem cell source in genitourinary regeneration

Somatic stem cells have been obtained from solid organs and tissues, including the bone marrow, placenta, corneal stroma, periosteum, adipose tissue, dental pulp and skeletal muscle. These solid tissue-derived stem cells are often used for tissue repair, disease modelling and new drug development. In the past two decades, stem cells have also been identified in various body fluids, including urine, peripheral blood, umbilical cord blood, amniotic fluid, synovial fluid, breastmilk and menstrual blood. These body fluid-derived stem cells (BFSCs) have stemness properties comparable to those of other adult stem cells and, similarly to tissue-derived stem cells, show cell surface markers, multi-differentiation potential and immunomodulatory effects. However, BFSCs are more easily accessible through non-invasive or minimally invasive approaches than solid tissue-derived stem cells and can be isolated without enzymatic tissue digestion. Additionally, BFSCs have shown good versatility in repairing genitourinary abnormalities in preclinical models through direct differentiation or paracrine mechanisms such as pro-angiogenic, anti-apoptotic, antifibrotic, anti-oxidant and anti-inflammatory effects. However, optimization of protocols is needed to improve the efficacy and safety of BFSC therapy before therapeutic translation.

Stem cells in central nervous system diseases: Promising therapeutic strategies

Central nervous system (CNS) diseases are a leading cause of death and disability. Due to CNS neurons have no self-renewal and regenerative ability as they mature, their loss after injury or disease is irreversible and often leads to functional impairments. Unfortunately, therapeutic options for CNS diseases are still limited, and effective treatments for these notorious diseases are warranted to be explored. At present, stem cell therapy has emerged as a potential therapeutic strategy for improving the prognosis of CNS diseases. Accumulating preclinical and clinical evidences have demonstrated that multiple molecular mechanisms, such as cell replacement, immunoregulation and neurotrophic effect, underlie the use of stem cell therapy for CNS diseases. However, several issues have yet to be addressed to support its clinical application. Thus, this review article aims to summarize the role and underlying mechanisms of stem cell therapy in treating CNS diseases. And it is worthy of further evaluation for the potential therapeutic applications of stem cell treatment in CNS disease.

Immune Privileges as a Result of Mutual Regulation of Immune and Stem Systems

Immune privileges of cancer stem cells is a well-known and widely studied problem, as presence of such cells in tumors is associated with refractoriness, recurrence, and metastasis. Accumulating evidence also suggests presence of immune privileges in non-pathological stem cells in addition to their other defense mechanisms against damaging factors. This similarity between pathological and normal stem cells raises the question of why stem cells have such a potentially dangerous property. Regulation of vital processes of autoimmunity control and regeneration realized through interactions between immune cells, stem cells, and their microenvironment are reviewed in this work as causes of formation of the stem cell immune privilege. Deep mutual integration between regulations of stem and immune cells is noted. Considering diversity and complexity of mutual regulation of stem cells, their microenvironment, and immune system, I suggest the term "stem system".

The "Mystery Cell Population" Residing in Murine Bone Marrow - A Missing Link Between Very Small Embryonic Like Stem Cells and Hematopoietic Stem Cells?

Bone marrow (BM) contains not only hematopoietic stem cells (HSCs) but also some very rare, early development, small quiescent stem cells that, upon activation, may differentiate across germlines. These small cells, named very small embryonic like stem cells (VSELs), can undergo specification into several types of cells including HSCs. Interestingly, murine BM is also home to a "mystery" population of small CD45+ stem cells with many of the phenotypic characteristics attributed to resting HSCs. Since the size of the "mystery" population cells are between that of VSELs and HSCs, and because CD45- VSELs can be specified into CD45+ HSCs, we hypothesized that the quiescent CD45+ "mystery" population could be a missing developmental link between VSELs and HSCs. To support this hypothesis, we showed that VSELs first became enriched for HSCs after acquiring expression of the CD45 antigen already expressed on "mystery" stem cells. Moreover, VSELs freshly isolated from BM similar to the "mystery" population cells, are quiescent and do not reveal hematopoietic potential in in vitro and in vivo assays. However, we noticed that CD45+ "mystery" population cells, similar to CD45- VSELs, became specified into HSCs after co-culture over OP9 stroma. We also found that mRNA for Oct-4, a pluripotency marker that is highly expressed in VSELs, is also detectable in the "mystery" population cells, albeit at a much lower level. Finally, we determined that the "mystery" population cells specified over OP9 stroma support were able to engraft and establish hematopoietic chimerism in lethally irradiated recipients. Based on these results, we propose that the murine BM "mystery" population could be an intermediate population between BM-residing VSELs and HSCs already specified for lympho-hematopoietic lineages.

Current Progress in Stem Cell Therapy for Male Infertility

Infertility has become one of the most common issues worldwide, which has negatively affected society and infertile couples. Meanwhile, male infertility is responsible for about 50% of infertility. Accordingly, a great number of researchers have focused on its treatment during the last few years; however, current therapies such as assisted reproductive technology (ART) are not effective enough in treating male infertility. Because of their self-renewal and differentiation capabilities and unlimited sources, stem cells have recently raised great hope in the treatment of reproductive system disorders. Stem cells are undifferentiated cells that can induce different numbers of specific cells, such as male and female gametes, demonstrating their potential application in the treatment of infertility. The present review aimed at identifying the causes and potential factors that influence male fertility. Besides, we highlighted the recent studies that investigated the efficiency of stem cells such as spermatogonial stem cells (SSCs), embryonic stem cells (ESCs), very small embryonic-like stem cells (VSELs), induced pluripotent stem cells (iPSCs), and mesenchymal stem cells (MSCs) in the treatment of various types of male infertility.

Preventing/Reversing Adverse Effects of Endocrine Disruption on Mouse Testes by Normalizing Tissue Resident VSELs

Reproductive health of men is declining in today's world due to increased developmental exposure to endocrine-disrupting chemicals (EDCs). We earlier reported that neonatal exposure to endocrine disruption resulted in reduced numbers of seminiferous tubules in Stage VIII, decreased sperm count, and infertility along with testicular tumors in 65% of diethylstilbestrol (DES) treated mice. Epigenetic changes due to EDCs, pushed the VSELs out of a quiescent state to enter cell cycle and undergo excessive self-renewal while transition of c-KIT- stem cells into c-KIT + germ cells was blocked due to altered MMR axis (Np95, Pcna, Dnmts), global hypomethylation (reduced expression of 5-methylcytosine) and loss of imprinting at Igf2-H19 and Dlk1-Meg3 loci. The present study was undertaken to firstly show similar defects in FACS sorted VSELs from DES treated testis and to further explore the reversal of these testicular pathologies by (i) oral administration of XAR (a nano-formulation of resveratrol) or (ii) inter-tubular transplantation of mesenchymal stromal cells (MSCs). Similar defects as reported earlier in the testes were evident, based on RNAseq data, on FACS sorted VSELs from DES treated mice. Both strategies were found effective, improved spermatogenesis, increased number of tubules in Stage VIII, normalized numbers of VSELs and c-KIT + cells, improved epigenetic status of VSELs to restore quiescent state, and reduced cancer incidence from 65% after DES to 13.33% and 20% after XAR treatment or MSCs transplantation respectively. Results provide a basis for initiating clinical studies and the study falls under the umbrella of United Nations Sustainable Development Goal 3 to ensure healthy lives and well-being for all of all ages.

Molecular analysis and comparison of CD34+ and CD133+ very small embryonic-like stem cells purified from umbilical cord blood

Very small embryonic like stem cells (VSELs) are a dormant population of stem cells that, as proposed, are deposited during embryogenesis in various tissues, including bone marrow (BM). These cells are released under steady state conditions from their tissue locations and circulate at a low level in peripheral blood (PB). Their number increases in response to stressors as well as tissue/organ damage. This increase is evident during neonatal delivery, as delivery stress prompts enrichment of umbilical cord blood (UCB) with VSELs. These cells could be purified from BM, PB, and UCB by multiparameter sorting as a population of very small CXCR4+ Lin- CD45- cells that express the CD34 or CD133 antigen. In this report, we evaluated a number of CD34+ Lin- CD45- and CD133+ Lin- CD45- UCB-derived VSELs. We also performed initial molecular characterization of both cell populations for expression of selected pluripotency markers and compared these cells at the proteomic level. We noticed that CD133+ Lin- CD45- population is more rare and express, at a higher level, mRNA for pluripotency markers Oct-4 and Nanog as well as the stromal-derived factor-1 (SDF-1) CXCR4 receptor that regulates trafficking of these cells, however both cells population did not significantly differ in the expression of proteins assigned to main biological processes.

Intensive neurorehabilitation and allogeneic stem cells transplantation in canine degenerative myelopathy

Introduction

Degenerative myelopathy (DM) is a neurodegenerative spinal cord disease with upper motor neurons, with progressive and chronic clinical signs, similar to amyotrophic lateral sclerosis (ALS). DM has a complex etiology mainly associated with SOD1 gene mutation and its toxic role, with no specific treatment. Daily intensive rehabilitation showed survival time near 8 months but most animals are euthanized 6-12 months after clinical signs onset.

Methods

This prospective controlled blinded cohort clinical study aims to evaluate the neural regeneration response ability of DM dogs subjected to an intensive neurorehabilitation protocol with mesenchymal stem cells (MSCs) transplantation. In total, 13 non-ambulatory (OFS 6 or 8) dogs with homozygous genotype DM/DM and diagnosed by exclusion were included. All were allocated to the intensive neurorehabilitation with MSCs protocol (INSCP) group (n = 8) or to the ambulatory rehabilitation protocol (ARP) group (n = 5), which differ in regard to training intensity, modalities frequency, and MSCs transplantation. The INSCP group was hospitalized for 1 month (T0 to T1), followed by MSCs transplantation (T1) and a second month (T2), whereas the ARP group was under ambulatory treatment for the same 2 months.

Results

Survival mean time of total population was 375 days, with 438 days for the INSCP group and 274 for the ARP group, with a marked difference on the Kaplan-Meier survival analysis. When comparing the literature's results, there was also a clear difference in the one-sample t-test (p = 0.013) with an increase in time of approximately 70%. OFS classifications between groups at each time point were significantly different (p = 0.008) by the one-way ANOVA and the independent sample t-test.

Discussion

This INSCP showed to be safe, feasible, and a possibility for a long progression of DM dogs with quality of life and functional improvement. This study should be continued.

Endometrial and placental stem cells in successful and pathological pregnancies

The endometrium is a dynamic tissue that undergoes extensive remodeling during the menstrual cycle and further gets modified during pregnancy. Different kinds of stem cells are reported in the endometrium. These include epithelial stem cells, endometrial mesenchymal stem cells, side population stem cells, and very small embryonic-like stem cells. Stem cells are also reported in the placenta which includes trophoblast stem cells, side population trophoblast stem cells, and placental mesenchymal stem cells. The endometrial and placental stem cells play a pivotal role in endometrial remodeling and placental vasculogenesis during pregnancy. The dysregulation of stem cell function is reported in various pregnancy complications like preeclampsia, fetal growth restriction, and preterm birth. However, the mechanisms by which it does so are yet elusive. Herein, we review the current knowledge of the different type of stem cells involved in pregnancy initiation and also highlight how their improper functionality leads to pathological pregnancy.

Multipotent fetal stem cells in reproductive biology research

Due to the limited accessibility of the in vivo situation, the scarcity of the human tissue, legal constraints, and ethical considerations, the underlying molecular mechanisms of disorders, such as preeclampsia, the pathological consequences of fetomaternal microchimerism, or infertility, are still not fully understood. And although substantial progress has already been made, the therapeutic strategies for reproductive system diseases are still facing limitations. In the recent years, it became more and more evident that stem cells are powerful tools for basic research in human reproduction and stem cell-based approaches moved into the center of endeavors to establish new clinical concepts. Multipotent fetal stem cells derived from the amniotic fluid, amniotic membrane, chorion leave, Wharton´s jelly, or placenta came to the fore because they are easy to acquire, are not associated with ethical concerns or covered by strict legal restrictions, and can be banked for autologous utilization later in life. Compared to adult stem cells, they exhibit a significantly higher differentiation potential and are much easier to propagate in vitro. Compared to pluripotent stem cells, they harbor less mutations, are not tumorigenic, and exhibit low immunogenicity. Studies on multipotent fetal stem cells can be invaluable to gain knowledge on the development of dysfunctional fetal cell types, to characterize the fetal stem cells migrating into the body of a pregnant woman in the context of fetomaternal microchimerism, and to obtain a more comprehensive picture of germ cell development in the course of in vitro differentiation experiments. The in vivo transplantation of fetal stem cells or their paracrine factors can mediate therapeutic effects in preeclampsia and can restore reproductive organ functions. Together with the use of fetal stem cell-derived gametes, such strategies could once help individuals, who do not develop functional gametes, to conceive genetically related children. Although there is still a long way to go, these developments regarding the usage of multipotent fetal stem cells in the clinic should continuously be accompanied by a wide and detailed ethical discussion.

Deciphering the Cardiovascular Potential of Human CD34+ Stem Cells

Ex vivo monitored human CD34⁺ stem cells (SCs) injected into myocardium scar tissue have shown real benefits for the recovery of patients with myocardial infarctions. They have been used previously in clinical trials with hopeful results and are expected to be promising for cardiac regenerative medicine following severe acute myocardial infarctions. However, some debates on their potential efficacy in cardiac regenerative therapies remain to be clarified. To elucidate the levels of CD34⁺ SC implication and contribution in cardiac regeneration, better identification of the main regulators, pathways, and genes involved in their potential cardiovascular differentiation and paracrine secretion needs to be determined. We first developed a protocol thought to commit human CD34⁺ SCs purified from cord blood toward an early cardiovascular lineage. Then, by using a microarray-based approach, we followed their gene expression during differentiation. We compared the transcriptome of undifferentiated CD34⁺ cells to those induced at two stages of differentiation (i.e., day three and day fourteen), with human cardiomyocyte progenitor cells (CMPCs), as well as cardiomyocytes as controls. Interestingly, in the treated cells, we observed an increase in the expressions of the main regulators usually present in cardiovascular cells. We identified cell surface markers of the cardiac mesoderm, such as kinase insert domain receptor (KDR) and the cardiogenic surface receptor Frizzled 4 (FZD4), induced in the differentiated cells in comparison to undifferentiated CD34⁺ cells. The Wnt and TGF-β pathways appeared to be involved in this activation. This study underlined the real capacity of effectively stimulated CD34⁺ SCs to express cardiac markers and, once induced, allowed the identification of markers that are known to be involved in vascular and early cardiogenesis, demonstrating their potential priming towards cardiovascular cells. These findings could complement their paracrine positive effects known in cell therapy for heart disease and may help improve the efficacy and safety of using ex vivo expanded CD34⁺ SCs.

In Vitro Simulated Neuronal Environmental Conditions Qualify Umbilical Cord Derived Highly Potent Stem Cells for Neuronal Differentiation

The healing of neuronal injuries is still an unachieved goal. Medicine-based therapies can only extend the survival of patients, but not finally lead to a healing process. Currently, a variety of stem cell-based tissue engineering developments are the subject of many research projects to bridge this gap. As yet, neuronal differentiation of induced pluripotent stem cells (iPS), embryonic cell lines, or neuronal stem cells could be accomplished and produce functional neuronally differentiated cells. However, clinical application of cells from these sources is hampered by ethical considerations. To overcome these hurdles numerous studies investigated the potential of adult mesenchymal stem cells (MSCs) as a potential stem cell source. Adult MSCs have been approved as cellular therapeutical products due to their regenerative potential and immunomodulatory properties. Only a few of these studies could demonstrate the capacity to differentiate MSCs into active firing neuron like cells. With this study we investigated the potential of Wharton's Jelly (WJ) derived stem cells and focused on the intrinsic pluripotent stem cell pool and their potential to differentiate into active neurons. With a comprehensive neuronal differentiation protocol comprised of mechanical and biochemical inductive cues, we investigated the capacity of spontaneously forming stem cell spheroids (SCS) from cultured WJ stromal cells in regard to their neuronal differentiation potential and compared them to undifferentiated spheroids or adherent MSCs. Spontaneously formed SCSs show pluripotent and neuroectodermal lineage markers, meeting the pre-condition for neuronal differentiation and contain a higher amount of cells which can be differentiated into cells whose functional phenotypes in calcium and voltage responsive electrical activity are similar to neurons. In conclusion we show that up-concentration of stem cells from WJ with pluripotent characteristics is a tool to generate neuronal cell replacement.

Population Dynamics, Plasma Cytokines and Platelet Centrifugation: Technical and Sociodemographic Aspects of 'Ovarian Rejuvenation'

While advanced reproductive technologies have attained remarkable increases in sophistication, success, and availability since the 1980s, clinicians always meet a therapeutic impasse when the ovarian reserve reaches exhaustion. Irrespective of fertility aspirations, the decline in and eventual collapse of ovarian estrogen output means that menopause arrives with tremendous physiologic changes and reduced overall productivity. Because more women are gaining in longevity or delaying the age at pregnancy, the number of affected patients has never been larger. As concerns regarding standard hormone replacement therapy and the limitations of IVF are confronted, a workable path to enable primordial germ cell recruitment and de novo oocyte development would be welcome. Proof-of-concept case reports and clinical studies on autologous activated platelet-rich plasma (PRP) or its condensed cytokine derivatives suggest a way to facilitate these goals. However, ovarian PRP faces vexing challenges that place 'ovarian rejuvenation' under caution as it enters this therapeutic space. Here, we review key features of experimental human ovarian stem cell isolation/handling and reaffirm the need to harmonize laboratory protocols. Recognizing the regenerative science borrowed from other disciplines, specimen centrifugation, platelet processing, and condensed plasma cytokine enrichment are highlighted here. As the refinement of this rejuvenation approach would promise to reprogram adult ovarian physiology, the disruption of established treatment paradigms for infertility, menopause, and perhaps overall women's health seems likely. Emerging roles in reproductive biology and clinical practice are thus placed in a broader social and demographic context.

A Simplified and Effective Approach for the Isolation of Small Pluripotent Stem Cells Derived from Human Peripheral Blood

Pluripotent stem cells are key players in regenerative medicine. Embryonic pluripotent stem cells, despite their significant advantages, are associated with limitations such as their inadequate availability and the ethical dilemmas in their isolation and clinical use. The discovery of very small embryonic-like (VSEL) stem cells addressed the aforementioned limitations, but their isolation technique remains a challenge due to their small cell size and their efficiency in isolation. Here, we report a simplified and effective approach for the isolation of small pluripotent stem cells derived from human peripheral blood. Our approach results in a high yield of small blood stem cell (SBSC) population, which expresses pluripotent embryonic markers (e.g., Nanog, SSEA-3) and the Yamanaka factors. Further, a fraction of SBSCs also co-express hematopoietic markers (e.g., CD45 and CD90) and/or mesenchymal markers (e.g., CD29, CD105 and PTH1R), suggesting a mixed stem cell population. Finally, quantitative proteomic profiling reveals that SBSCs contain various stem cell markers (CD9, ITGA6, MAPK1, MTHFD1, STAT3, HSPB1, HSPA4), and Transcription reg complex factors (e.g., STAT5B, PDLIM1, ANXA2, ATF6, CAMK1). In conclusion, we present a novel, simplified and effective isolating process that yields an abundant population of small-sized cells with characteristics of pluripotency from human peripheral blood.

Epigenetic markers in the embryonal germ cell development and spermatogenesis

Spermatogenesis is the process of generation of male reproductive cells from spermatogonial stem cells in the seminiferous epithelium of the testis. During spermatogenesis, key spermatogenic events such as stem cell self-renewal and commitment to meiosis, meiotic recombination, meiotic sex chromosome inactivation, followed by cellular and chromatin remodeling of elongating spermatids occur, leading to sperm cell production. All the mentioned events are at least partially controlled by the epigenetic modifications of DNA and histones. Additionally, during embryonal development in primordial germ cells, global epigenetic reprogramming of DNA occurs. In this review, we summarized the most important epigenetic modifications in the particular stages of germ cell development, in DNA and histone proteins, starting from primordial germ cells, during embryonal development, and ending with histone-to-protamine transition during spermiogenesis.

Very small embryonic-like stem cells have the potential to win the three-front war on tissue damage, cancer, and aging

The concept of dedifferentiation and reprogramming of mature somatic cells holds much promise for the three-front "war" against tissue damage, cancer, and aging. It was hoped that reprogramming human somatic cells into the induced pluripotent state, along with the use of embryonic stem cells, would transform regenerative medicine. However, despite global efforts, clinical applications remain a distant dream, due to associated factors such as genomic instability, tumorigenicity, immunogenicity, and heterogeneity. Meanwhile, the expression of embryonic (pluripotent) markers in multiple cancers has baffled the scientific community, and it has been suggested that somatic cells dedifferentiate and "reprogram" into the pluripotent state in vivo to initiate cancer. It has also been suggested that aging can be reversed by partial reprogramming in vivo. However, better methods are needed; using vectors or Yamanaka factors in vivo, for example, is dangerous, and many potential anti-aging therapies carry the same risks as those using induced pluripotent cells, as described above. The present perspective examines the potential of endogenous, pluripotent very small embryonic-like stem cells (VSELs). These cells are naturally present in multiple tissues; they routinely replace diseased tissue and ensure regeneration to maintain life-long homeostasis, and they have the ability to differentiate into adult counterparts. Recent evidence suggests that cancers initiate due to the selective expansion of epigenetically altered VSELs and their blocked differentiation. Furthermore, VSEL numbers have been directly linked to lifespan in studies of long- and short-lived transgenic mice, and VSEL dysfunction has been found in the ovaries of aged mice. To conclude, a greater interest in VSELs, with their potential to address all three fronts of this war, could be the "light at the end of the tunnel."

Proteomic Analysis of Murine Bone Marrow Very Small Embryonic-like Stem Cells at Steady-State Conditions and after In Vivo Stimulation by Nicotinamide and Follicle-Stimulating Factor Reflects their Germ-Lineage Origin and Multi Germ Layer Differentiation Potential

Very small embryonic-like stem cells (VSELs) are a dormant population of development early stem cells deposited in adult tissues that as demonstrated contribute to tissue/organ repair and regeneration. We postulated developmental relationship of these cells to migrating primordial germ cells (PGCs) and explained the quiescent state of these cells by the erasure of differently methylated regions (DMRs) at some of the paternally imprinted genes involved in embryogenesis. Recently, we reported that VSELs began to proliferate and expand in vivo in murine bone marrow (BM) after exposure to nicotinamide (NAM) and selected pituitary and gonadal sex hormones. In the current report, we performed proteomic analysis of VSELs purified from murine bone marrow (BM) after repeated injections of NAM + Follicle-Stimulating Hormone (FSH) that in our previous studies turned out to be an effective combination to expand these cells. By employing the Gene Ontology (GO) resources, we have performed a combination of standard GO annotations (GO-CAM) to produce a network between BM steady-state conditions VSELs (SSC-VSELS) and FSH + NAM expanded VSELs (FSH + NAM VSELs). We have identified several GO biological processes regulating development, organogenesis, gene expression, signal transduction, Wnt signaling, insulin signaling, cytoskeleton organization, cell adhesion, inhibiting apoptosis, responses to extra- and intracellular stimuli, protein transport and stabilization, protein phosphorylation and ubiquitination, DNA repair, immune response, and regulation of circadian rhythm. We report that VSELs express a unique panel of proteins that only partially overlapped with the proteome of BM - derived hematopoietic stem cells (HSCs) and hematopoietic mononuclear cells (MNCs) and respond to FSH + NAM stimulation by expressing proteins involved in the development of all three germ layers. Thus, our current data supports further germ-lineage origin and multi germ layer differentiation potential of these cells.

De novo testicular tissue generation from non-testicular cell lines, biologic and synthetic scaffolds: Current findings and future translational applications

In recent decades, reproductive science has revolutionized the options for biological parenthood for the 20-50% of infertility cases affected by male factors. However, current solutions exclude those who are infertile due to absent testicular tissue. This includes anorchic 46, XY individuals due to trauma or congenital factors and transgender men with a 46, XX genotype. There is a clinical need for methods to restore testicular function independent of pre-existing testicular tissue. This mini-review analyzes studies that have applied non-testicular cell lines to generate germline and non-germline testicular parenchymal components. While only 46, XY cell lines have been evaluated in this context to date, the potential for future application of cell lines from 46, XX individuals is also included. Additionally, the role of varied culture methods, media supplementation, and biologic and synthetic scaffolds to further support testicular parenchyma generation are critiqued. De novo testicular tissue generation in this manner will require a focus on both cellular and environmental aspects of tissue engineering. Put together, these studies highlight the future potential for expanded clinical, reproductive, and endocrine management options for individuals who are currently excluded from aspects of biologic reproduction most consistent with their gender identity and reproductive preferences.

Extremely Active Nano-formulation of Resveratrol (XAR™) attenuates and reverses chemotherapy-induced damage in mice ovaries and testes

BACKGROUND

Fertility preservation and restoration in cancer patients/survivors is the need of present times when increased numbers of patients get cured of cancer but face infertility as a serious side effect. Resveratrol has beneficial effects on chemoablated ovaries and testes in mice but has failed to enter the clinics because of extremely poor bioavailability. The present study was undertaken to evaluate the protective and curative effects of Extremely active Resveratrol (XAR™)- a nano-formulation of resveratrol with significantly improved bioavailability- on mouse ovary and testis after chemotherapy. Effects of XAR™ and FSH were compared on stimulation of follicle growth in adult mice ovaries. XAR™ (25 mg/kg) was administered for two days prior to chemotherapy to study the protective effects on the mouse gonads. XAR™ was also administered for 14 days post chemoablation to study the regenerative effects. Besides effect on numbers of primordial and growing follicles and spermatogenesis, the effect of XAR™ was also evaluated on the transcripts specific for ovarian/testicular stem/progenitor/germ cells, their proliferation, differentiation, meiosis, and the antioxidant indices.

RESULTS

Similar to FSH, XAR™ increased the numbers of primordial follicles (PF) as well as growing follicles. It protected the gonads from the adverse effects of chemotherapy and showed the ability to regenerate non-functional, chemoablated gonads. Besides stimulating follicle growth in adult ovaries similar to FSH, XAR™ also protected the testes from the adverse effects of chemotherapy and improved spermatogenesis. This was accompanied by improved anti-oxidant indices.

CONCLUSIONS

The results of the present study potentiate the use of XAR™ in pilot clinical studies to protect gonadal function during oncotherapy and also regenerate non-functional gonads in cancer survivors by improving antioxidant indices and stem cell-based tissue regeneration.

Stem Cells and Organs-on-chips: New Promising Technologies for Human Infertility Treatment

Having biological children remains an unattainable dream for most couples with reproductive failure or gonadal dysgenesis. The combination of stem cells with gene editing technology and organ-on-a-chip models provides a unique opportunity for infertile patients with impaired gametogenesis caused by congenital disorders in sex development or cancer survivors. But how will these technologies overcome human infertility? This review discusses the regenerative mechanisms, applications, and advantages of different types of stem cells for restoring gametogenesis in infertile patients, as well as major challenges that must be overcome before clinical application. The importance and limitations of in vitro generation of gametes from patient-specific human-induced pluripotent stem cells (hiPSCs) will be discussed in the context of human reproduction. The potential role of organ-on-a-chip models that can direct differentiation of hiPSC-derived primordial germ cell-like cells to gametes and other reproductive organoids is also explored. These rapidly evolving technologies provide prospects for improving fertility to individuals and couples who experience reproductive failure.

Single-Cell RNA-Seq Identifies Dynamic Cardiac Transition Program from Adipose Derived Cells Induced by Leukemia Inhibitory Factor

Adipose-derived cells (ADCs) from white adipose tissue (WAT) are promising stem cell candidates because of their large regenerative reserves and the potential for cardiac regeneration. However, given the heterogeneity of ADC and its unsolved mechanisms of cardiac acquisition, ADC-cardiac transition efficiency remains low. In this study, we explored the heterogeneity of ADCs and the cellular kinetics of 39,432 single-cell transcriptomes along the leukemia inhibitory factor (LIF) induced ADC-cardiac transition. We identified distinct ADC subpopulations that reacted differentially to LIF when entering the cardiomyogenic program, further demonstrating that ADC-myogenesis is time-dependent and initiates from transient changes in nuclear factor erythroid 2-related factor 2 (Nrf2) signaling. At later stages, pseudotime analysis of ADCs navigated a trajectory with two branches corresponding to activated myofibroblast or cardiomyocyte-like cells. Our findings offer a high-resolution dissection of ADC heterogeneity and cell fate during ADC-cardiac transition, thus providing new insights into potential cardiac stem cells.

Stem Cells in the Tumor Immune Microenvironment -Part of the Cure or Part of the Disease? Ontogeny and Dichotomy of Stem and Immune Cells has Led to better Understanding

Stem cells are at the basis of tissue homeostasis, hematopoiesis and various regenerative processes. Epigenetic changes in their somatically imprinted genes, prolonged exposure to mutagens/carcinogens or alteration of their niche can lead to the development of an enabling environment for tumor growth and progression. The involvement of stem cells in both health and disease becomes even more compelling with ontogeny as embryonic and extraembryonic stem cells which persist into adulthood in well established and specific niche may have distinct implications in tumorigenesis. Immune surveillance plays an important role in this interplay since the response of immune cells toward the oncogenic process can range from reactivity to placidity and even complicity, being orchestrated by intercellular molecular dialogues with the other key players of the tumor microenvironment. With the current understanding that every developing and adult tissue contains inherent stem and progenitor cells, in this manuscript we review the most relevant interactions carried out between the stem cells, tumor cells and immune cells in a bottom-up incursion through the tumor microenvironment beginning from the perivascular niche and going through the tumoral parenchyma and the related stroma. With the exploitation of various factors that influence the behavior of immune effectors toward stem cells and other resting cells in their niche, new therapeutic strategies to tackle the polarization of immune effectors toward a more immunogenic phenotype may arise.

Characterization of Endothelial Progenitor Cell: Past, Present, and Future

Endothelial progenitor cells (EPCs) are currently being studied as candidate cell sources for revascularization strategies. Despite these promising results, widespread clinical acceptance of EPCs for clinical therapies remains hampered by several challenges. The challenges and issues surrounding the use of EPCs and the current paradigm being developed to improve the harvest efficiency and functionality of EPCs for application in regenerative medicine are discussed. It has been observed that controversies have emerged regarding the isolation techniques and classification and origin of EPCs. This manuscript attempts to highlight the concept of EPCs in a sequential manner, from the initial discovery to the present (origin, sources of EPCs, isolation, and identification techniques). Human and murine EPC marker diversity is also discussed. Additionally, this manuscript is aimed at summarizing our current and future prospects regarding the crosstalk of EPCs with the biology of hematopoietic cells and culture techniques in the context of regeneration-associated cells (RACs).

Testicular cancer in mice: interplay between stem cells and endocrine insults

BACKGROUND

Incidence of type II germ cell tumors (T2GCT) has increased in young men possibly due to fetal/perinatal exposure to estrogenic compounds. Three-fold increased incidence of T2GCT was reported in men exposed in utero to diethylstilbestrol (DES). T2GCT is a development-related disease arising due to blocked differentiation of gonocytes into spermatogonia in fetal testes which survive as germ cell neoplasia in situ (GCNIS) and initiate T2GCT. In our earlier study, T2GCT-like features were observed in 9 out of 10 adult, 100-day-old mice testes upon neonatal exposure to DES (2 μg/pup/day on days 1-5). Neonatal DES exposure affected testicular very small embryonic-like stem cells (VSELs) and spermatogonial stem cells and resulted in infertility, reduced sperm counts and tumor-like changes leading to our postulate that testicular dysgenesis syndrome possibly has a stem cell basis. The present study was undertaken to further characterize testicular tumor in mice testes.

METHODS

DES-exposed mice pups (n = 70) were studied on D100 and after 12 months to understand how T2GCT progresses. Besides histological studies, a carefully selected panel of markers were studied by immuno-fluorescence and qRT-PCR.

RESULTS

DES resulted in either atrophied or highly vascularized, big-sized testes and extra-testicular growth was also observed. GCNIS-like cells with big, vacuolated cytoplasm and increased expression of OCT-4, SSEA-1, SCA-1 and CD166 (cancer stem cells marker) along with reduced c-KIT, MVH and PTEN were evident. Global hypomethylation was found associated with altered expression of Dnmts, Igf2-H19 and Dlk-Meg3 imprinted genes along with reduced expression of Ezh2, cell cycle regulator p57KIP2 and Meg3; however, Pten remained unaltered. Increased expression of PCNA and Ki67 was observed in concert with complete lack of SOX-9 suggesting Sertoli cells independent proliferation.

CONCLUSIONS

Mouse model for T2GCT is described which will have immense potential to understand cancer initiation, cancer stem cells and also to develop effective therapies in future. T2GCT initiates from tissue-resident, pluripotent VSELs due to their altered epigenome. Neonatal exposure to DES blocks differentiation (spermatogenesis) and VSELs get transformed into CD166 positive cancer stem cells that undergo excessive self-renewal and initiate cancer in adult life challenging existing concept of fetal origin of T2GCT.

Industrialized GMP Production of CD34+ Cells (ProtheraCytes®) at Clinical Scale for Treatment of Ischemic Cardiac Diseases Is Feasible and Safe

Regenerative medicine now needs to pass a crucial turning point, from academic research to the market. Several sources/types of cells have been experimented with, more or less successfully. CD34⁺ cells have demonstrated multipotent or even pluripotent capacities, making them good candidates for regenerative medicine, particularly for treating heart diseases. Strongly encouraged by the results we achieved in a pilot study using CD34⁺ stem cells in patients with poor-prognosis acute myocardial infarcts (AMIs), we soon began the development of an industrialized platform making use of a closed automated device (StemXpand^®) and a disposable kit (StemPack^®) for the large-scale expansion of CD34⁺ cells with reproducible good manufacturing practice (GMP). This scalable platform can produce expanded CD34⁺ cells (ProtheraCytes^®) of sufficient quality that, interestingly, express early markers of the cardiac and endothelial pathways and early cardiac-mesoderm markers. They also contain CD34⁺ pluripotent cells characterized as very small embryonic-like stem cells (VSELs), capable of differentiating under appropriate stimuli into different tissue lineages, including endothelial and cardiomyocytic ones.

GFP Tagged VSELs Help Delineate Novel Stem Cells Biology in Multiple Adult Tissues

Various types of stem cells are being researched upon to exploit their potential for regenerative medicine including pluripotent human embryonic stem (hES) cells derived from spare human embryos, induced pluripotent stem (iPS) cells by reprogramming somatic cells to a pluripotent state and multipotent mesenchymal stem/stromal cells (MSCs) obtained in vitro from multiple tissues. More than 50 independent groups have reported another novel population of pluripotent stem cells in adult tissues termed very small embryonic-like stem cells (VSELs). VSELs are developmentally linked to primordial germ cells, which rather than giving rise to the germ cells and later ceasing to exist, survive throughout life in multiple organs along with tissue-specific adult stem cells better described as lineage-restricted, tissue-committed progenitors with limited plasticity. VSELs survive total body irradiation in bone marrow, oncotherapy in the gonads, bilateral ovariectomy in the uterus and partial pancreatectomy in the pancreas of mice and participate in the regeneration of multiple organs under normal physiological conditions. VSELs and tissue-specific progenitor cells work together in a subtle manner, maintain life-long tissue homeostasis and their dysfunction leads to various pathologies including cancer. However, due to their quiescent state, VSELs have invariably eluded lineage-tracing studies reported so far. Present article reviews novel insights into VSELs biology and how VSELs enriched from GFP (green fluorescent protein) mice have enabled to delineate their role in various biological processes in vivo. VSELs biology needs to be understood in-depth as this alone will help evolve the field of regenerative medicine and win the war against cancer.

Molecular Insights into Endometrial Cancer in Mice

Pluripotent, very small embryonic-like stem cells (VSELs) and the 'progenitors' endometrial stem cells (EnSCs) along with associated molecular changes in endometrial cancer, that developed seven months after neonatal exposure to estradiol in one of the sixty mice, were studied in the present study. Endocrine disruption affected both endometrium and myometrium, there was accumulation of endometrial fluid and significant hyperplasia. Disrupted endometrial-myometrial junction resulted in mobilization of myometrial cells into endometrium and epithelial and stromal cells into myometrium suggestive of adenomyosis. Markers specific for VSELs/ EnSCs (OCT-4, NANOG, SSEA-1, SCA-1, c-KIT) showed increased expression in uterine sections and marked upregulation of corresponding transcripts (Oct-4A, Oct-4, Sox-2, Nanog, Sca-1, c-Kit) was noted in RNA extracted from both uterine tissue and stem cells enriched from endometrial fluid. Hormonal receptors (ER-α, ER-β, PR, FSHR) were upregulated in both tumor sections and in endometrial fluid. ER-β and FSHR (Fshr3) expression was prominent suggesting a major role in endometrial cancer. Cancer cells showed global hypomethylation (reduced expression of 5-methyl cytosine), reduced expression of tumor suppressor gene (PTEN) and increased expression of cancer stem cells marker (CD166) which suggested dysregulation and aberrant oncogenic events. Increased expression of PCNA, Ki67, SOX-9 suggested excessive proliferation and hyperplasia which are predominant signs of endometrial cancer. Results suggest that VSELs increase in numbers and possibly transform into cancer stem cells (co-express CD166 and OCT-4) in endometrial cancer. Expression of OCT-4, CD133, ALDHA1 and CD166 in side-population cells from human endometrial cancer samples suggests a possible role of VSELs in human endometrial cancer as well.

Additional evidence to support OCT-4 positive VSELs and EnSCs as the elusive tissue-resident stem/progenitor cells in adult mice uterus

Objective

True identity and specific set of markers to enrich endometrial stem cells still remains elusive. Present study was undertaken to further substantiate that very small embryonic-like stem cells (VSELs) are the true and elusive stem cells in adult mice endometrium.

Methods

This was achieved by undertaking three sets of experiments. Firstly, SSEA-1+ and Oct-4 + positive VSELs, sorted from GFP mice, were transplanted into the uterine horns of wild-type Swiss mice and GFP uptake was studied within the same estrus cycle. Secondly, uterine lumen was scratched surgically and OCT-4 expressing stem/progenitor cells were studied at the site of injury after 24–72 h. Thirdly, OCT-4  expression was studied in the endometrium and myometrium of adult mice after neonatal exposure to estradiol (20 µg/pup/day on days 5–7 after birth).

Results

GFP + ve VSELs expressing SSEA-1 and Oct-4 engrafted and differentiated into the epithelial cells lining the lumen as well as the glands during the estrus stage when maximum remodeling occurs. Mechanical scratching activated tissue-resident, nuclear OCT-4 positive VSELs and slightly bigger ‘progenitors’ endometrial stem cells (EnSCs, cytoplasmic OCT-4) which underwent clonal expansion and further differentiated into luminal and glandular epithelial cells. Neonatal exposure to endocrine disruption resulted in increased numbers of OCT-4 positive VSELs/EnSCs in adult endometrium.

Discussion

Results support the presence of functionally active VSELs in adult endometrium. VSELs self-renew and give rise to EnSCs that further differentiate into epithelial cells under normal physiological conditions. Also, VSELs are vulnerable to endocrine insults. To conclude VSELs are true and elusive uterine stem cells that maintain life-long uterine homeostasis and their dysregulation may result in various pathologies.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02703-8.

Hypes and Hopes of Stem Cell Therapies in Dentistry: a Review

One of the most exciting advances in life science research is the development of 3D cell culture systems to obtain complex structures called organoids and spheroids. These 3D cultures closely mimic in vivo conditions, where cells can grow and interact with their surroundings. This allows us to better study the spatio-temporal dynamics of organogenesis and organ function. Furthermore, physiologically relevant organoids cultures can be used for basic research, medical research, and drug discovery. Although most of the research thus far focuses on the development of heart, liver, kidney, and brain organoids, to name a few, most recently, these structures were obtained using dental stem cells to study in vitro tooth regeneration. This review aims to present the most up-to-date research showing how dental stem cells can be grown on specific biomaterials to induce their differentiation in 3D. The possibility of combining engineering and biology principles to replicate and/or increase tissue function has been an emerging and exciting field in medicine. The use of this methodology in dentistry has already yielded many interesting results paving the way for the improvement of dental care and successful therapies.

Mice Uterine Stem Cells are Affected by Neonatal Endocrine Disruption & Initiate Uteropathies in Adult Life Independent of Circulatory Ovarian Hormones

It is generally believed that ovarian hormones regulate uterine functions and their altered levels result in various uteropathies like non-receptive uterus, endometrial hyperplasia, adenomyosis, endometriosis, leiomyomas and cancer. Uterus harbors two populations of stem cells including pluripotent, very small embryonic-like stem cells (VSELs) and tissue-specific progenitors (endometrial stem cells, EnSCs). Unlike endometrial mesenchymal stem/ stromal cells, VSELs/EnSCs express ERα, ERβ and PR which makes them directly vulnerable to perinatal endocrine insults. Present study was undertaken to evaluate whether uteropathies occur due to altered hormones and/or intrinsic changes in stem/progenitor cells. Mice pups, exposed to estradiol (20 µg/pup/day) on postnatal days 3-7 or vehicle, were subjected to bilateral ovariectomy on day 30 and later exposed sequentially to estradiol and progesterone resulting in receptive uterus in control mice. Despite similar hormonal exposure, endocrine disruption resulted in non-receptive uterus with noticeable endometrial and myometrial hyperplasia and up-regulation of stem cell markers (Oct-4A, Oct-4, Sox2, Nanog). Glands were poorly formed and 'defective' epithelial progenitors were found disseminated into myometrium and blood vessels revealing how adenomyosis and endometriosis possibly initiate. Progesterone resistance and estradiol dominance due to downregulation of Erα & Pr and upregulation of Erβ transcripts was observed in both intact uterus and stem cells enriched from uterus. Transcripts specific for DNA mismatch repair axis (Pcna, NP95 and Dnmt1), repair enzymes (Brca-1, Rad51 and Mlh1) were dysregulated whereas Ki67 was ten-folds increased suggestive of genomic instability. Study reveals role of stem cells in initiating uteropathies during adult life independent of circulatory ovarian hormones. Endocrine disruption affects tissue resident stem/progenitor cells (VSELs/EnSCs) in both endometrium and myometrium, result in epithelial cells hyperplasia, non-receptive endometrium, adenomyosis and defective stem cells and epithelial progenitors were detected in the perimetrium from where they can mobilize to ectopic sites to initiate endometriosis. Study shows stem cell basis for various uteropathies. VSEL: Very small embryonic like stem cell; EnSC: Endometrial stem cell; E + P: Estradiol + Progesterone; E: Endometrium; P: Perimetrium; M: Myometrium; ACD: Asymmetrical cell division; SCD: Symmetrical cell division; CE: Clonal expansion; G: Gland; S: Stromal cell; US: Undifferentiated stromal cell; LE: Luminal epithelium; GE: Glandular epithelium; EP: Epithelial progenitors; SMC: Spindle-shaped myometrial cell; OMC: Oval-shaped myometrial cell.

Endogenous, tissue-resident stem/progenitor cells in gonads and bone marrow express FSHR and respond to FSH via FSHR-3

Follicle stimulating hormone (FSH) is secreted by the anterior pituitary and acts on the germ cells indirectly through Granulosa cells in ovaries and Sertoli cells in the testes. Extragonadal action of FSH has been reported but is still debated. Adult tissues harbor two populations of stem cells including a reserve population of primitive, small-sized, pluripotent very small embryonic-like stem cells (VSELs) and slightly bigger, tissue-specific progenitors which include ovarian stem cells (OSCs) in ovaries, spermatogonial stem cells (SSCs) in testes, endometrial stem cells (EnSCs) in uterus and hematopoietic stem cells (HSCs) in the bone marrow. Data has accumulated in animal models showing FSHR expression on both VSELs and progenitors in ovaries, testes, uterus and bone marrow and eventually gets lost as the cells differentiate further. FSH exerts a direct action on the stem/progenitor cells via alternatively spliced FSHR-3 rather than the canonical FSHR-1. FSH stimulates VSELs to undergo asymmetrical cell divisions to self-renew and give rise to the progenitors that in turn undergo symmetrical cell divisions and clonal expansions followed by differentiation into specific cell types. Excessive self-renewal of VSELs results in cancer and this explains ubiquitous expression of embryonic markers including nuclear OCT-4 along with FSHR in cancerous tissues. Focus of this review is to compile published data to support this concept. FSHR expression in stem/progenitor cells was confirmed by immuno-fluorescence, Western blotting, in situ hybridization and by quantitative RT-PCR. Two different commercially available antibodies (Abcam, Santacruz) were used to confirm specificity of FSHR expression along with omission of primary antibody and pre-incubation of antibody with immunizing peptide as negative controls. Western blotting allowed detection of alternatively spliced FSHR isoforms. Oligoprobes and primers specific for Fshr-1 and Fshr-3 were used to study these alternately-sliced isoforms by in situ hybridization and their differential expression upon FSH treatment by qRT-PCR. To conclude, stem/progenitor cells in adult tissues express FSHR and directly respond to FSH via FSHR-3. These findings change the field of FSH-FSHR biology, call for paradigm shift, explain FSHR expression on cancer cells in multiple organs and provide straightforward explanations for various existing conundrums including extragonadal expression of FSHR.

Viability assessment of human peripheral blood-derived stem cells after three methods of nebulization

BACKGROUND AND OBJECTIVES

Drug delivery by nebulization has become a crucial strategy for treating different respiratory and lung diseases. Emerging evidence implicates stem cell therapy as a promising tool in treating such conditions, not only by alleviating the related symptoms but by improving the prognosis. However, delivery of human peripheral blood-derived stem cells (hPBSCs) to the respiratory airways remains an innovative approach yet to be realized. This study is an analytic, translational, and in vitro research to assess the viability and morphological changes of identified cell populations in hPBSCs cocktail derived from COVID-19 patients.

METHODS AND RESULTS

Peripheral blood (PB) samples were obtained from patients enrolled in the SENTAD-COVID Study (ClinicalTrials.gov Reference: NCT04473170). hPBSCs cocktails (n=15) were provided by the Cells Processing Laboratory of Abu Dhabi Stem Cells Center, and were nebulized by three different methods of nebulization: compressor (jet), ultrasonic, and mesh. Our results reported that nucleated CD45^dim cell count was significantly lower after the three nebulization methods, but nucleated CD45^- cells show a significant decrease only after mesh nebulization. Mesh-nebulized samples had a significant reduction in viability of both CD45^dim and CD45^- cells.

CONCLUSIONS

This study provides evidence that stem cells derived from PB of COVID-19 patients can be nebulized without substantial loss of cell viability, cell count, and morphological changes using the compressor nebulization. Therefore, we recommend compressor nebulizers as the preferable procedure for hPBSCs delivery to the respiratory airways in further clinical settings.

The Treasury of Wharton's Jelly

Background

Postnatal umbilical cord tissue contains valuable mesenchymal progenitor cells of various differentiation stages. While mesenchymal stem cells are plastic-adherent and tend to differentiate into myofibroblastic phenotypes, some round cells detach, float above the adherent cells, and build up cell aggregates, or form spheroids spontaneously. Very small luminescent cells are always involved as single cells or within collective forms and resemble the common well-known very small embryonic-like cells (VSELs). In this study, we investigated these VSELs-like cells in terms of their pluripotency phenotype and tri-lineage differentiation potential.

Methods

VSELs-like cells were isolated from cell-culture supernatants by a process that combines filtering, up concentration, and centrifugation. To determine their pluripotency character, we measured the expression of Nanog, Sox-2, Oct-4, SSEA-1, CXCR4, SSEA-4 on gene and protein level. In addition, the cultured cells derived from UC tissue were examined regarding their potential to differentiate into three germ layers.

Result

The VSELs-like cells express all of the pluripotency-associated markers we investigated and are able to differentiate into meso- endo- and ectodermal precursor cells.

Conclusions

Umbilical cord tissue hosts highly potent VSELs-like stem cells.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s12015-021-10217-8.

Elevated Circulating Stem Cells Level is Observed One Month After Implantation of Carmat Bioprosthetic Total Artificial Heart

The Aeson® total artificial heart (A-TAH) has been developed as a total heart replacement for patients at risk of death from biventricular failure. We previously described endothelialization of the hybrid membrane inside A-TAH probably at the origin of acquired hemocompatibility. We aimed to quantify vasculogenic stem cells in peripheral blood of patients with long-term A-TAH implantation. Four male adult patients were included in this study. Peripheral blood mononuclear cells were collected before A-TAH implantation (T0) and after implantation at one month (T1), between two and five months (T2), and then between six and twelve months (T3). Supervised analysis of flow cytometry data confirmed the presence of the previously identified Lin^-CD133⁺CD45^- and Lin^-CD34⁺ with different CD45 level intensities. Lin^-CD133⁺CD45^-, Lin^-CD34⁺CD45^- and Lin^-CD34⁺CD45⁺ were not modulated after A-TAH implantation. However, we demonstrated a significant mobilization of Lin^-CD34⁺CD45^dim (p = 0.01) one month after A-TAH implantation regardless of the expression of CD133 or c-Kit. We then visualized data for the resulting clusters on a uniform manifold approximation and projection (UMAP) plot showing all single cells of the live Lin^- and CD34⁺ events selected from down sampled files concatenated at T0 and T1. The three clusters upregulated at T1 are CD45^dim clusters, confirming our results. In conclusion, using a flow cytometry approach, we demonstrated in A-TAH-transplanted patients a significant mobilization of Lin^-CD34⁺CD45^dim in peripheral blood one month after A-TAH implantation. Using a flow cytometry approach, we demonstrated in A-TAH transplanted patients a significant mobilization of Lin^-CD34⁺CD45^dim in peripheral blood one month after A-TAH implantation. This cell population could be at the origin of newly formed endothelial cells on top of hybrid membrane in Carmat bioprosthetic total artificial heart.

Actions and Roles of FSH in Germinative Cells

Follicle stimulating hormone (FSH) is produced by the pituitary gland in a coordinated hypothalamic-pituitary-gonadal (HPG) axis event, plays important roles in reproduction and germ cell development during different phases of reproductive development (fetal, neonatal, puberty, and adult life), and is consequently essential for fertility. FSH is a heterodimeric glycoprotein hormone of two dissociable subunits, α and β. The FSH β-subunit (FSHβ) function starts upon coupling to its specific receptor: follicle-stimulating hormone receptor (FSHR). FSHRs are localized mainly on the surface of target cells on the testis and ovary (granulosa and Sertoli cells) and have recently been found in testicular stem cells and extra-gonadal tissue. Several reproduction disorders are associated with absent or low FSH secretion, with mutation of the FSH β-subunit or the FSH receptor, and/or its signaling pathways. However, the influence of FSH on germ cells is still poorly understood; some studies have suggested that this hormone also plays a determinant role in the self-renewal of germinative cells and acts to increase undifferentiated spermatogonia proliferation. In addition, in vitro, together with other factors, it assists the process of differentiation of primordial germ cells (PGCLCs) into gametes (oocyte-like and SSCLCs). In this review, we describe relevant research on the influence of FSH on spermatogenesis and folliculogenesis, mainly in the germ cell of humans and other species. The possible roles of FSH in germ cell generation in vitro are also presented.

Perspective: Why and How Ubiquitously Distributed, Vascular-Associated, Pluripotent Stem Cells in the Adult Body (vaPS Cells) Are the Next Generation of Medicine

A certain cell type can be isolated from different organs in the adult body that can differentiate into ectoderm, mesoderm, and endoderm, providing significant support for the existence of a certain type of small, vascular-associated, pluripotent stem cell ubiquitously distributed in all organs in the adult body (vaPS cells). These vaPS cells fundamentally differ from embryonic stem cells and induced pluripotent stem cells in that the latter possess the necessary genetic guidance that makes them intrinsically pluripotent. In contrast, vaPS cells do not have this intrinsic genetic guidance, but are able to differentiate into somatic cells of all three lineages under guidance of the microenvironment they are located in, independent from the original tissue or organ where they had resided. These vaPS cells are of high relevance for clinical application because they are contained in unmodified, autologous, adipose-derived regenerative cells (UA-ADRCs). The latter can be obtained from and re-applied to the same patient at the point of care, without the need for further processing, manipulation, and culturing. These findings as well as various clinical examples presented in this paper demonstrate the potential of UA-ADRCs for enabling an entirely new generation of medicine for the benefit of patients and healthcare systems.

Stem Cells in Adult Mice Ovaries Form Germ Cell Nests, Undergo Meiosis, Neo-oogenesis and Follicle Assembly on Regular Basis During Estrus Cycle

Very small embryonic-like (VSELs) and ovarian (OSCs) stem cells are located in adult mammalian ovary surface epithelium (OSE). OSCs can expand long-term and differentiate into oocyte-like structures in vitro and have resulted in birth of fertile pups. Lineage tracing studies have provided evidence to suggest OSCs differentiation into oocytes in vivo. But how these stem cells function under normal physiological conditions has not yet been well worked out. Besides studying STRA-8 and SCP-3 expression in enzymatically isolated OSE cells smears, mice were injected BrdU to track mitosis, meiosis and follicle assembly. H&E stained OSE cells during late diestrus and proestrus showed VSELs undergoing asymmetrical cell divisions to give rise to slightly bigger OSCs which in turn underwent symmetrical cell divisions followed by clonal expansion (rapid expansion with incomplete cytokinesis) during early estrus to form germ cell nests (GCN). OCT-4, SSEA-1, MVH and DAZL positive cells in GCN expressed Erα, Erβ and FSHR, were interconnected by ring canals (TEX-14), showed mitochondrial aggregation (Cytochrome C) and Balbiani Body (TRAL). Apoptosis in 'nurse' cells was marked by PARP and putative oocytes were clearly visualized. BrdU was detected in cells undergoing mitosis/meiosis and also in an oocyte of secondary follicle. FACS sorted, green fluorescent protein (GFP) positive VSELs upon transplantation resulted in GFP positive GCN suggesting crucial role for VSELs in adult ovaries. Results suggest that various events described during oogenesis and follicle assembly in fetal ovaries are recapitulated on regular basis in adult ovary and result in the formation of follicles.