Characterization and Isolation of Very Small Embryonic-like (VSEL) Stem Cells Obtained from Various Human Hematopoietic Cell Sources

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.

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.

Isolation of Swine Bone Marrow Lin-/CD45-/CD133 + Cells and Cardio-protective Effects of its Exosomes

BACKGROUND

The identification in murine bone marrow (BM) of CD133 + /Lin-/CD45- cells, possessing several features of pluripotent stem cells, encouraged us to investigate if similar population of cells could be also isolated from the swine BM. Heart failure is the terminal stage of many cardiovascular diseases, and its key pathological basis is cardiac fibrosis (CF). Research showed that stem cell derived exosomes may play a critical role in cardiac fibrosis. The effect of exosomes (Exos) on CF has remained unclear.

OBJECTIVE

To establish an isolation and amplification method of CD133 + /Lin-/CD45- cells from newbron swine BM in vitro, explore an highly efficient method to enrich swine bone marrow derived CD133 + /Lin-/CD45- cells and probe into their biological characteristics further. Furher more, to extract exosomes from it and explore its effect on CF.

METHODS

The mononuclear cells isolated from swine bone marrow by red blood cell (RBC) lysing buffer were coated by adding FcR blocking solution and coupled with CD133 antibody immunomagnetic beads, obtaining CD133 + cell group via Magnetic Activated Cell Sorting (MACS). In steps, the CD133 + /Lin-/CD45- cells were collected by fluorescence-activated cell sorting (FACS) labeled with CD133, Lin and CD45 antibodies, which were cultured and amplified in vitro. The biological features of CD133 + /Lin-/CD45- cells were studied in different aspects, including morphological trait observed with inverted microscope, ultrastructural characteristics observed under transmission electron microscope, expression of pluripotent markersidentified by immunofluorescent staining and Alkaline phosphatase staining. The Exos were extracted using a sequential centrifugation approach and its effects on CF were analyzed in Angiotensin II (Ang-II) induced-cardiac fibrosis in vivo. Rats in each group were treated for 4 weeks, and 2D echocardiography was adopted to evaluate the heart function. The degree of cardiac fibrosis was assessed by Hematoxylin-Eosin (HE) and Masson's trichrome staining.

RESULTS

The CD133 + /Lin-/CD45- cells accounted for about 0.2%-0.5% of the total mononuclear cells isolated from swine bone marrow. The combination of MACS and FACS to extract CD133 + /Lin-/CD45- cells could improved efficiency and reduced cell apoptosis. The CD133 + /Lin-/CD45- cells featured typical traits of pluripotent stem cells, the nucleus is large, mainly composed of euchromatin, with less cytoplasm and larger nucleoplasmic ratio, which expressed pluripotent markers (SSEA-1, Oct-4, Nanog and Sox-2) and alkaline phosphatase staining was positive.Animal experiment indicated that the cardiac injury related indexes (BNP、cTnI、CK-MB and TNF-α), the expression of key gene Smad3 and the degree of cardiac fibrosis in Exo treatment group were significantly reduced compared with the control group. 4 weeks after the treatment, cardiac ejection fraction (EF) value in the model group showed a remarkable decrease, indicating the induction of HF model. While Exo elevated the EF values, demonstrating cardio-protective effects.

CONCLUSION

The CD133 + /Lin-/CD45- cells derived from swine bone marrow were successfully isolated and amplified, laying a good foundation for further research on this promising therapeutic cell. The Exos may be a promising potential treatment strategy for CF.

Sources, Characteristics, and Therapeutic Applications of Mesenchymal Cells in Tissue Engineering

Tissue engineering (TE) is a therapeutic option within regenerative medicine that allows to mimic the original cell environment and functional organization of the cell types necessary for the recovery or regeneration of damaged tissue using cell sources, scaffolds, and bioreactors. Among the cell sources, the utilization of mesenchymal cells (MSCs) has gained great interest because these multipotent cells are capable of differentiating into diverse tissues, in addition to their self-renewal capacity to maintain their cell population, thus representing a therapeutic alternative for those diseases that can only be controlled with palliative treatments. This review aimed to summarize the state of the art of the main sources of MSCs as well as particular characteristics of each subtype and applications of MSCs in TE in seven different areas (neural, osseous, epithelial, cartilage, osteochondral, muscle, and cardiac) with a systemic revision of advances made in the last 10 years. It was observed that bone marrow-derived MSCs are the principal type of MSCs used in TE, and the most commonly employed techniques for MSCs characterization are immunodetection techniques. Moreover, the utilization of natural biomaterials is higher (41.96%) than that of synthetic biomaterials (18.75%) for the construction of the scaffolds in which cells are seeded. Further, this review shows alternatives of MSCs derived from other tissues and diverse strategies that can improve this area of regenerative medicine.

Isolation Methods for Human CD34 Subsets Using Fluorescent and Magnetic Activated Cell Sorting: an In Vivo Comparative Study

INTRODUCTION

Acute myocardial infarction (AMI) and resulting cardiac damage and heart failure are leading causes of morbidity and mortality worldwide. Multiple studies have examined the utility of CD34⁺ cells for the treatment of acute and ischemic heart disease. However, the optimal strategy to enrich CD34 cells from clinical sources is not known. We examined the efficacy of fluorescence activated cell sorting (FACS) and magnetic beads cell sorting (MACS) methods for CD34 cell isolation from mobilized human mononuclear peripheral blood cells (mhPBMNCs).

METHODS

mhPBCs were processed following acquisition using FACS or MACS according to clinically established protocols. Cell viability, CD34 cell purity and characterization of surface marker expression were assessed using a flow cytometer. For in vivo characterization of cardiac repair, we conducted LAD ligation surgery on 8-10 weeks female NOD/SCID mice followed by intramyocardial transplantation of unselected mhPBMNCs, FACS or MACS enriched CD34⁺ cells.

RESULTS

Both MACS and FACS isolation methods achieved high purity rates, viability, and enrichment of CD34⁺ cells. In vivo studies following myocardial infarction demonstrated retention of CD34⁺ in the peri-infarct region for up to 30 days after transplantation. Retained CD34⁺ cells were associated with enhanced angiogenesis and reduced inflammation compared to unselected mhPBMNCs or PBS treatment arms. Cardiac scar and fibrosis as assessed by immunohistochemistry were reduced in FACS and MACS CD34⁺ treatment groups. Finally, reduced scar and augmented angiogenesis resulted in improved cardiac functional recovery, both on the global and regional function and remodeling assessments by echocardiography.

CONCLUSION

Cell based therapy using enriched CD34⁺ cells sorted by FACS or MACS result in better cardiac recovery after ischemic injury compared to unselected mhPBMNCs. Both enrichment techniques offer excellent recovery and purity and can be equally used for clinical applications.

Pou5f3.3 is involved in establishment and maintenance of hematopoietic cells during Xenopus development

Three POU family class V gene homologues are expressed in the development of Xenopus. In contrast to the expression of Pou5f3.1 and Pou5f3.2 in organogenesis, Pou5f3.3 is expressed during oogenesis in ovary. We investigated the expression and function of Pou5f3.3 in organogenesis of Xenopus laevis. RT-PCR and immunohistochemical analysis indicated that Pou5f3.3 was expressed in a small number of adult liver cells and blood cells. Immunocytochemical investigation proved that Bmi1, a marker for hematopoietic progenitor cells, was co-expressed in Pou5f3.3-expressing small spherical cells in the peripheral blood. In anemic induction by intraperitoneal injection of phenyl hydrazine, the number of Pou5f3.3-expressing cells significantly increased within 3 days after phenyl hydrazine injection. In CRISPR/Cas mutagenesis of Pou5f3.3, Bmi1-positive hematopoietic progenitor cell count decreased in the hematopoietic dorsal-lateral plate (DLP) region, resulting in a considerable reduction in peripheral blood cells. CRISPR/Cas-induced hematopoietic deficiency was completely rescued by Pou5f3.3 supplementation, but not by Pou5f3.1 or Pou5f3.2. Transplantation experiments using the H2B-GFP transgenic line demonstrated that DLP-derived Pou5f3.3-positive and Bmi1-positive cells were translocated into the liver and bone through the bloodstream. These results suggest that Pou5f3.3 plays an essential role in the establishment and maintenance of hematopoietic progenitor cells during Xenopus development.

SARS-CoV-2 Entry Receptor ACE2 Is Expressed on Very Small CD45- Precursors of Hematopoietic and Endothelial Cells and in Response to Virus Spike Protein Activates the Nlrp3 Inflammasome

Angiotensin-converting enzyme 2 (ACE2) plays an important role as a member of the renin–angiotensin–aldosterone system (RAAS) in regulating the conversion of angiotensin II (Ang II) into angiotensin (1–7) (Ang [1–7]). But at the same time, while expressed on the surface of human cells, ACE2 is the entry receptor for SARS-CoV-2. Expression of this receptor has been described in several types of cells, including hematopoietic stem cells (HSCs) and endothelial progenitor cells (EPCs), which raises a concern that the virus may infect and damage the stem cell compartment. We demonstrate for the first time that ACE2 and the entry-facilitating transmembrane protease TMPRSS2 are expressed on very small CD133⁺CD34⁺Lin⁻CD45⁻ cells in human umbilical cord blood (UCB), which can be specified into functional HSCs and EPCs. The existence of these cells known as very small embryonic-like stem cells (VSELs) has been confirmed by several laboratories, and some of them may correspond to putative postnatal hemangioblasts. Moreover, we demonstrate for the first time that, in human VSELs and HSCs, the interaction of the ACE2 receptor with the SARS-CoV-2 spike protein activates the Nlrp3 inflammasome, which if hyperactivated may lead to cell death by pyroptosis. Based on this finding, there is a possibility that human VSELs residing in adult tissues could be damaged by SARS-CoV-2, with remote effects on tissue/organ regeneration. We also report that ACE2 is expressed on the surface of murine bone marrow-derived VSELs and HSCs, although it is known that murine cells are not infected by SARS-CoV-2. Finally, human and murine VSELs express several RAAS genes, which sheds new light on the role of these genes in the specification of early-development stem cells.

Graphical Abstract

Safety and efficacy of autologous non-hematopoietic enriched stem cell nebulization in COVID-19 patients: a randomized clinical trial, Abu Dhabi 2020

BACKGROUND

The novel SARS-CoV-2 has caused the coronavirus disease 2019 (COVID-19) pandemic. Currently, with insufficient worldwide vaccination rates, identifying treatment solutions to reduce the impact of the virus is urgently needed.

METHOD

An adaptive, multicentric, open-label, and randomized controlled phase I/II clinical trial entitled the "SENTAD-COVID Study" was conducted by the Abu Dhabi Stem Cells Center under exceptional conditional approval by the Emirates Institutional Review Board (IRB) for COVID-19 Research Committee from April 4th to July 31st, 2020, using an autologous peripheral blood non-hematopoietic enriched stem cell cocktail (PB-NHESC-C) administered by compressor (jet) nebulization as a complement to standard care therapy. The primary endpoints include safety and efficacy assessments, adverse events, the mortality rate within 28 days, and the time to clinical improvement as measured by a 2-point reduction on a seven-category ordinal scale or discharge from the hospital whichever occurred first.

RESULTS

The study included a total of 139 randomized COVID-19 patients, with 69 in the experimental group and 70 in the control group (standard care). Overall survival was 94.20% for the cocktail-treated group vs. 90.27% for the control group. Adverse events were reported in 50 (72.46%) patients receiving PB-NHESC-C and 51 (72.85%) in the control group (p = 0.9590), with signs and symptoms commonly found in COVID-19. After the first 9 days of the intervention, 67.3% of cocktail-treated patients recovered and were released from hospitals compared to 53.1% (RR = 0.84; 95% CI, 0.56-1.28) in the control group. Improvement, i.e., at least a 2-point reduction in the severity scale, was more frequently observed in cocktail-treated patients (42.0%) than in controls (17.0%) (RR = 0.69; 95% CI, 0.56-0.88).

CONCLUSIONS

Cocktail treatment improved clinical outcomes without increasing adverse events. Thus, the nebulization of PB-NHESC-C was safe and effective for treatment in most of these patients.

TRIAL REGISTRATION

ClinicalTrials.gov. NCT04473170. It was retrospectively registered on July 16th, 2020.

Role of Stem-Cell Transplantation in Leukemia Treatment

Stem cells (SCs) play a major role in advanced fields of regenerative medicine and other research areas. They are involved in the regeneration of damaged tissue or cells, due to their self-renewal characteristics. Tissue or cells can be damaged through a variety of diseases, including hematologic and nonhematologic malignancies. In regard to this, stem-cell transplantation is a cellular therapeutic approach to restore those impaired cells, tissue, or organs. SCs have a therapeutic potential in the application of stem-cell transplantation. Research has been focused mainly on the application of hematopoietic SCs for transplantation. Cord blood cells and human leukocyte antigen-haploidentical donors are considered optional sources of hematopoietic stem-cell transplantation. On the other hand, pluripotent embryonic SCs and induced pluripotent SCs hold promise for advancement of stem-cell transplantation. In addition, nonhematopoietic mesenchymal SCs play their own significant role as a functional bone-marrow niche and in the management of graft-vs-host disease effects during the posttransplantation process. In this review, the role of different types of SCs is presented with regard to their application in SC transplantation. In addition to this, the therapeutic value of autologous and allogeneic hematopoietic stem-cell transplantation is assessed with respect to different types of leukemia. Highly advanced and progressive scientific research has focused on the application of stem-cell transplantation on specific leukemia types. We evaluated and compared the therapeutic potential of SC transplantation with various forms of leukemia. This review aimed to focus on the application of SCs in the treatment of leukemia.

The Blood Circulating Rare Cell Population. What is it and What is it Good For?

Blood contains a diverse cell population of low concentration hematopoietic as well as non-hematopoietic cells. The majority of such rare cells may be bone marrow-derived progenitor and stem cells. This paucity of circulating rare cells, in particular in the peripheral circulation, has led many to believe that bone marrow as well as other organ-related cell egress into the circulation is a response to pathological conditions. Little is known about this, though an increasing body of literature can be found suggesting commonness of certain rare cell types in the peripheral blood under physiological conditions. Thus, the isolation and detection of circulating rare cells appears to be merely a technological problem. Knowledge about rare cell types that may circulate the blood stream will help to advance the field of cell-based liquid biopsy by supporting inter-platform comparability, making use of biological correct cutoffs and “mining” new biomarkers and combinations thereof in clinical diagnosis and therapy. Therefore, this review intends to lay ground for a comprehensive analysis of the peripheral blood rare cell population given the necessity to target a broader range of cell types for improved biomarker performance in cell-based liquid biopsy.