Mesenchymal Stem and Progenitor Cells in Regeneration: Tissue Specificity and Regenerative Potential. Stem Cells Int. 2017;2017:5173732. [PMID: 28286525 PMCID: PMC5327785 DOI: 10.1155/2017/5173732]

Immunomodulatory and cardio-protective effects of differentially originated multipotent mesenchymal stroma cells during polymicrobial sepsis in mice

PURPOSE

Sepsis is a life-threatening condition with cardiac complications being an independent predictor of poor outcome. Although their mechanisms have been widely investigated, therapeutic options remain limited. One promising therapeutic tool are mesenchymal stromal cells (MSCs). The aim of this study is to investigate the immunomodulatory effects of human MSCs from two different sources (bone marrow/BMMSC and adipose tissue/ASC) and to evaluate their cardioprotective potential.

METHODS

60 adult male C57BL/6 mice were divided into sham, sepsis (cecal ligation puncture (CLP)) and two i.v. treatment groups CLP + human BMMSC and CLP + human ASC with 5 animals in each group. The observation periods were 8, 24 and 72 h. Left ventricular tissue was analyzed histologically, by qPCR (C3ar, C5ar1, Il-1b, Il-6, Il-10, Tlr2, Tlr4, Tnfa, and Nlrp3) and western blot. Cardiac damage markers troponin I and heart fatty acid binding protein (HFABP) were detected in serum by ELISA.

RESULTS

Troponin I and HFABP were significantly increased in CLP group after 8 h compared to sham. In cardiac tissue the expression of C3ar, C5ar1, Il-1b, Il-6, Il-10, Tlr2, Tlr4, Tnfa and Nlrp3 inflammasome was upregulated up to 24h after CLP compared to sham. After BMMSC treatment, C3ar as well as C5ar, Tlr2 and Il-10 mRNA expression in left ventricle was downregulated compared to CLP, whereas ASC treatment was associated with the downregulation of Il-6 and Nlrp3.

CONCLUSIONS

CLP-induced polymicrobial sepsis in mice was associated with cardiac damage and increased inflammation in left ventricular tissue. Therapeutic systemic application of human BMMSC and ASC ameliorated damage and inflammation in the heart.

Mesenchymal stem cell secretome for regenerative medicine: Where do we stand?

BACKGROUND

Mesenchymal stem cell (MSC)-based therapies have yielded beneficial effects in a broad range of preclinical models and clinical trials for human diseases. In the context of MSC transplantation, it is widely recognized that the main mechanism for the regenerative potential of MSCs is not their differentiation, with in vivo data revealing transient and low engraftment rates. Instead, MSCs therapeutic effects are mainly attributed to its secretome, i.e., paracrine factors secreted by these cells, further offering a more attractive and innovative approach due to the effectiveness and safety of a cell-free product.

AIM OF REVIEW

In this review, we will discuss the potential benefits of MSC-derived secretome in regenerative medicine with particular focus on respiratory, hepatic, and neurological diseases. Both free and vesicular factors of MSC secretome will be detailed. We will also address novel potential strategies capable of improving their healing potential, namely by delivering important regenerative molecules according to specific diseases and tissue needs, as well as non-clinical and clinical studies that allow us to dissect their mechanisms of action.

KEY SCIENTIFIC CONCEPTS OF REVIEW

MSC-derived secretome includes both soluble and non-soluble factors, organized in extracellular vesicles (EVs). Importantly, besides depending on the cell origin, the characteristics and therapeutic potential of MSC secretome is deeply influenced by external stimuli, highlighting the possibility of optimizing their characteristics through preconditioning approaches. Nevertheless, the clarity around their mechanisms of action remains ambiguous, whereas the need for standardized procedures for the successful translation of those products to the clinics urges.

Intermittent Fasting During Ramadan Increases the Absolute Number of Circulating Progenitor Stem Cells in Healthy Subjects

Fasting regimens have shown profound impact on pro-longevity and tissue regeneration in diverse species. Physiological events can induce a regenerative response in adult stem cells. However, little is known about signaling and activation of adult stem cells which are modulated by fasting. This study analyzed the presence of hematopoietic stem/progenitor cells (HSPCs) and their circulation in the peripheral blood (PB) of healthy male adults practicing Ramadan fasting. Ten healthy male volunteers were enrolled in this prospective observational study. PB samples were collected twice daily on days 0, 10, 20, and 30 of Ramadan fasting (RF). Populations of stem cells and serum soluble factors were analyzed by flow cytometry. As a response to RF, we report an increase in the average absolute count of circulating of HSPCs, defined as LIN-CD45- and LIN-CD45+ cell subsets expressing the stem markers, CD34 and CD133. Changes in the number of HSPCs subsets reflected changes in the peripheral concentration of chemoattractant soluble factors during fasting. A chemotaxis assay showed a migratory property of HSPCs towards plasma, collected at D30 of fasting that contained a higher concentration of SCF and G-CSF. The relationship between RF and an increase in the number of circulating HSPCs in part, describes a regenerative response to the physiological changes during fasting and may open opportunities to define the role of dietary intervention in the stem cell therapy.

Enforced hematopoietic cell E-selectin/L-selectin ligand expression enhances bone marrow stromal cells homing and amelioration of cerebral ischemia-reperfusion injury via induction of prostaglandin E2

Ischemic stroke (IS) is a significant and potentially life-threatening disease with limited treatment options, often resulting in severe disability. Bone marrow stromal cells (BMSCs) transplantation has exhibited promising neuroprotection following cerebral ischemia-reperfusion injury (CIRI). However, the effectiveness is hindered by their low homing rate when administered through the vein. In this study, we aimed to enhance the homing ability of BMSCs through lentivirus transfection to express fucosyltransferase 7. This glycosylation engineered CD44 on BMSCs to express hematopoietic cell E-selectin/L-selectin ligand (HCELL), which is the most potent E-selectin ligand. Following enforced HCELL expression, the transplantation of BMSCs was then evaluated in a middle cerebral artery occlusion model. Results showed that HCELL+BMSCs significantly ameliorated neurological deficits and reduced the volume of cerebral infarction. Furthermore, the transplantation led to a decrease in apoptosis by upregulating BCL-2 and downregulating BAX, also reduced the mRNA levels of inflammatory factors, such as interleukin-1β (IL-1β), IL-2, IL-6, and tumor necrosis factor-alpha (TNF-α) in the ischemic brain tissue. Notably, enforced HCELL expression facilitated the migration of BMSCs toward cerebral ischemic lesions and their subsequent transendothelial migration through the upregulation of PTGS-2, increased production of PGE2 and activation of VLA-4. In summary, our study demonstrates that transplantation of HCELL+BMSCs effectively alleviates CIRI, and that enforced HCELL expression enhances the homing of BMSCs to cerebral ischemic lesions and their transendothelial migration via PTGS-2/PGE2/VLA-4. These findings indicate that enforced expression of HCELL on BMSCs could serve as a promising therapeutic strategy for the treatment of ischemic stroke.

Advanced therapy to cure diabetes: mission impossible is now possible?

Cell and Gene therapy are referred to as advanced therapies that represent overlapping fields of regenerative medicine. They have similar therapeutic goals such as to modify cellular identity, improve cell function, or fight a disease. These two therapeutic avenues, however, possess major differences. While cell therapy involves introduction of new cells, gene therapy entails introduction or modification of genes. Furthermore, the aim of cell therapy is often to replace, or repair damaged tissue, whereas gene therapy is used typically as a preventive approach. Diabetes mellitus severely affects the quality of life of afflicted individuals and has various side effects including cardiovascular, ophthalmic disorders, and neuropathy while putting enormous economic pressure on both the healthcare system and the patient. In recent years, great effort has been made to develop cutting-edge therapeutic interventions for diabetes treatment, among which cell and gene therapies stand out. This review aims to highlight various cell- and gene-based therapeutic approaches leading to the generation of new insulin-producing cells as a topmost "panacea" for treating diabetes, while deliberately avoiding a detailed molecular description of these approaches. By doing so, we aim to target readers who are new to the field and wish to get a broad helicopter overview of the historical and current trends of cell- and gene-based approaches in β-cell regeneration.

Molecular and Cellular Mechanisms of the Therapeutic Effect of Mesenchymal Stem Cells and Extracellular Vesicles in Corneal Regeneration

The cornea is a vital component of the visual system, and its integrity is crucial for optimal vision. Damage to the cornea resulting from trauma, infection, or disease can lead to blindness. Corneal regeneration using mesenchymal stem cells (MSCs) and MSC-derived extracellular vesicles (MSC-EVs) offers a promising alternative to corneal transplantation. MSCs are multipotent stromal cells that can differentiate into various cell types, including corneal cells. They can also secrete a variety of anti-inflammatory cytokines and several growth factors, promoting wound healing and tissue reconstruction. This review summarizes the current understanding of the molecular and cellular mechanisms by which MSCs and MSC-EVs contribute to corneal regeneration. It discusses the potential of MSCs and MSC-EV for treating various corneal diseases, including corneal epithelial defects, dry eye disease, and keratoconus. The review also highlights finalized human clinical trials investigating the safety and efficacy of MSC-based therapy in corneal regeneration. The therapeutic potential of MSCs and MSC-EVs for corneal regeneration is promising; however, further research is needed to optimize their clinical application.

Paving the way to a neural fate - RNA signatures in naive and trans-differentiating mesenchymal stem cells

Mesenchymal Stem Cells (MSCs) derived from the embryonic mesoderm persist as a viable source of multipotent cells in adults and have a crucial role in tissue repair. One of the most promising aspects of MSCs is their ability to trans-differentiate into cell types outside of the mesodermal lineage, such as neurons. This characteristic positions MSCs as potential therapeutic tools for neurological disorders. However, the definition of a clear MSC signature is an ongoing topic of debate. Likewise, there is still a significant knowledge gap about functional alterations of MSCs during their transition to a neural fate. In this study, our focus is on the dynamic expression of RNA in MSCs as they undergo trans-differentiation compared to undifferentiated MSCs. To track and correlate changes in cellular signaling, we conducted high-throughput RNA expression profiling during the early time-course of human MSC neurogenic trans-differentiation. The expression of synapse maturation markers, including NLGN2 and NPTX1, increased during the first 24 h. The expression of neuron differentiation markers, such as GAP43 strongly increased during 48 h of trans-differentiation. Neural stem cell marker NES and neuron differentiation marker, including TUBB3 and ENO1, were highly expressed in mesenchymal stem cells and remained so during trans-differentiation. Pathways analyses revealed early changes in MSCs signaling that can be linked to the acquisition of neuronal features. Furthermore, we identified microRNAs (miRNAs) as potential drivers of the cellular trans-differentiation process. We also determined potential risk factors related to the neural trans-differentiation process. These factors include the persistence of stemness features and the expression of factors involved in neurofunctional abnormalities and tumorigenic processes. In conclusion, our findings contribute valuable insights into the intricate landscape of MSCs during neural trans-differentiation. These insights can pave the way for the development of safer treatments of neurological disorders.

The complexity of extracellular vesicles: Bridging the gap between cellular communication and neuropathology

Brain-derived extracellular vesicles (EVs) serve a prominent role in maintaining homeostasis and contributing to pathology in health and disease. This review establishes a crucial link between physiological processes leading to EV biogenesis and their impacts on disease. EVs are involved in the clearance and transport of proteins and nucleic acids, responding to changes in cellular processes associated with neurodegeneration, including autophagic disruption, organellar dysfunction, aging, and other cell stresses. In neurodegenerative disorders (e.g., Alzheimer's disease, Parkinson's disease, etc.), EVs contribute to the spread of pathological proteins like amyloid β, tau, ɑ-synuclein, prions, and TDP-43, exacerbating neurodegeneration and accelerating disease progression. Despite evidence for both neuropathological and neuroprotective effects of EVs, the mechanistic switch between their physiological and pathological functions remains elusive, warranting further research into their involvement in neurodegenerative disease. Moreover, owing to their innate ability to traverse the blood-brain barrier and their ubiquitous nature, EVs emerge as promising candidates for novel diagnostic and therapeutic strategies. The review uniquely positions itself at the intersection of EV cell biology, neurophysiology, and neuropathology, offering insights into the diverse biological roles of EVs in health and disease.

Mechanical stimulation-induced purinome priming fosters osteogenic differentiation and osteointegration of mesenchymal stem cells from the bone marrow of post-menopausal women

BACKGROUND

Mechanical stimulation (MS) significantly increases the release of adenine and uracil nucleotides from bone marrow-derived mesenchymal stem cells (BM-MSCs) undergoing osteogenic differentiation. Released nucleotides acting via ionotropic P2X7 and metabotropic P2Y6 purinoceptors sensitive to ATP and UDP, respectively, control the osteogenic commitment of BM-MSCs and, thus, bone growth and remodelling. Yet, this mechanism is impaired in post-menopausal (Pm)-derived BM-MSCs, mostly because NTPDase3 overexpression decreases the extracellular accumulation of nucleotides below the levels required to activate plasma membrane-bound P2 purinoceptors. This prompted us to investigate whether in vitro MS of BM-MSCs from Pm women could rehabilitate their osteogenic commitment and whether xenotransplantation of MS purinome-primed Pm cells promote repair of critical bone defects in an in vivo animal model.

METHODS

BM-MSCs were harvested from the neck of femora of Pm women (70 ± 3 years old) undergoing total hip replacement. The cells grew, for 35 days, in an osteogenic-inducing medium either submitted (SS) or not (CTR) to MS (90 r.p.m. for 30 min) twice a week. Increases in alkaline phosphatase activity and in the amount of osteogenic transcription factors, osterix and osteopontin, denoted osteogenic cells differentiation, while bone nodules formation was ascertain by the alizarin red-staining assay. The luciferin-luciferase bioluminescence assay was used to quantify extracellular ATP. The kinetics of the extracellular ATP (100 µM) and UDP (100 µM) catabolism was assessed by HPLC. The density of P2Y6 and P2X7 purinoceptors in the cells was assessed by immunofluorescence confocal microscopy. MS-stimulated BM-MSCs from Pm women were xenotransplanted into critical bone defects drilled in the great trochanter of femora of one-year female Wistar rats; bone repair was assessed by histological analysis 10 days after xenotransplantation.

RESULTS

MS-stimulated Pm BM-MSCs in culture (i) release 1.6-fold higher ATP amounts, (ii) overexpress P2X7 and P2Y6 purinoceptors, (iii) exhibit higher alkaline phosphatase activity and overexpress the osteogenic transcription factors, osterix and osteopontin, and (iv) form larger bone nodules, than CTR cells. Selective blockage of P2X7 and P2Y6 purinoceptors with A438079 (3 µM) and MRS 2578 (0.1 µM), respectively, prevented the osteogenic commitment of cultured Pm BM-MSCs. Xenotransplanted MS purinome-primed Pm BM-MSCs accelerated the repair of critical bone defects in the in vivo rat model.

CONCLUSIONS

Data suggest that in vitro MS restores the purinergic cell-to-cell communication fostering the osteogenic differentiation and osteointegration of BM-MSCs from Pm women, a strategy that may be used in bone regeneration and repair tactics.

Comparative Evaluation of the Differentiation and Proliferation Potential of Dental Pulp Stem Cells on Hydroxyapatite/Beta-Tricalcium Bone Graft and Bovine Bone Graft: An In Vitro Study

BACKGROUND

Stem cells of mesenchymal origin have good proliferative capacity when compared to other stem cell types. Dental pulp stem cells (DPSCs) are a variety of mesenchymal cells obtained from the pulpal tissue of teeth and are abundantly available and easy to obtain. DPSCs facilitate and improve the formation of new bone using different bone graft scaffolds. This present study aims to evaluate and compare the osteogenic potential of DPSCs on alloplastic and xenogeneic bone grafts.

MATERIALS AND METHODS

Hydroxyapatite and beta-tricalcium bone graft and bovine bone graft were used in a triplicate manner in the laboratory. DPSCs were obtained from the pulpal tissue of extracted third molars in the laboratory. The cytotoxicity, osteogenic potential, and difference in the rate of proliferation of mesenchymal cells on the biomaterials were assessed.

RESULTS

Darker purple staining was seen in the case of hydroxyapatite/beta-tricalcium bone graft on MTT colorimetric assay stating that there was an increase in cell viability in hydroxyapatite/beta-tricalcium bone graft as compared to the bovine bone graft. Hydroxyapatite/beta-tricalcium bone graft showed more osteogenic potential as compared to the bovine bone graft as a higher degree of red staining was seen in Alizarin staining.

CONCLUSION

Higher cell viability and higher osteogenic proliferation and differentiation were seen on the hydroxyapatite/beta-tricalcium bone graft compared to the bovine bone scaffold.

Mesenchymal Stem Cells and Their Role in Neurodegenerative Diseases

Mesenchymal stem cells (MSCs) have garnered significant interest in the field of regenerative medicine for their ability to potentially treat various diseases, especially neurodegenerative disorders [...].

Impaired receptivity of thin endometrium: therapeutic potential of mesenchymal stem cells

The endometrium is a resilient and highly dynamic tissue, undergoing cyclic renewal in preparation for embryo implantation. Cyclic endometrial regeneration depends on the intact function of several cell types, including parenchymal, endothelial, and immune cells, as well as adult stem cells that can arise from endometrial or extrauterine sources. The ability of the endometrium to undergo rapid, repeated regeneration without scarring is unique to this tissue. However, if this tissue renewal process is disrupted or dysfunctional, women may present clinically with infertility due to endometrial scarring or persistent atrophic/thin endometrium. Such disorders are rate-limiting in the treatment of female infertility and in the success of in vitro fertilization because of a dearth of treatment options specifically targeting the endometrium. A growing number of studies have explored the potential of adult stem cells, including mesenchymal stem cells (MSCs), to treat women with disorders of endometrial regeneration. MSCs are multipotent adult stem cells with capacity to differentiate into cells such as adipocytes, chondrocytes, and osteoblasts. In addition to their differentiation capacity, MSCs migrate toward injured sites where they secrete bioactive factors (e.g. cytokines, chemokines, growth factors, proteins and extracellular vesicles) to aid in tissue repair. These factors modulate biological processes critical for tissue regeneration, such as angiogenesis, cell migration and immunomodulation. The MSC secretome has therefore attracted significant attention for its therapeutic potential. In the uterus, studies utilizing rodent models and limited human trials have shown a potential benefit of MSCs and the MSC secretome in treatment of endometrial infertility. This review will explore the potential of MSCs to treat women with impaired endometrial receptivity due to a thin endometrium or endometrial scarring. We will provide context supporting leveraging MSCs for this purpose by including a review of mechanisms by which the MSC secretome promotes regeneration and repair of nonreproductive tissues.

CREB1 Facilitates GABAergic Neural Differentiation of Human Mesenchymal Stem Cells through BRN2 for Pain Alleviation and Locomotion Recovery after Spinal Cord Injury

The transplantation of GABAergic neuron cells has been reported to alleviate nerve pain and improve motor function after spinal cord injury (SCI). However, human mesenchymal stem cell (hMSC) differentiation into GABAergic neuron cells in a sufficient quantity remains to be accomplished. From a database screening, cAMP-responsive element-binding protein 1 (CREB1) was chosen as a potential modulator due to its critical role in the protein-protein interaction of genes related to GABAergic neural differentiation. Here, CREB1 was overexpressed in transfected hMSCs, where CREB1 could induce differentiation into GABAergic neuron cells with an upregulation of Map2 and GAD1 by 2- and 3.4-fold, respectively. Additionally, GABAergic neural differentiation was enhanced, while Notch signaling was inhibited, and BRN2 transcriptional activation played an important role in neuronal maturation. Moreover, transfected hMSCs injected into immunocompromised mice caused by CsA exhibited the neuronal markers Tuj1 and Map2 via the intraspinal route, suggesting an improvement in survival and neural differentiation. Significantly, improvement in both BMS scores (6.2 ± 1.30 vs. 4 ± 0) and thermal hyperalgesia latency (7.74 ± 2.36 s vs. 4.52 ± 0.39 s) was seen compared with the SCI naïve treatment at 4 weeks post-transplantation. Our study demonstrates that CREB1 is crucial in generating induced GABAergic neuron cells (iGNs) originating from hMSCs. Transplanting iGNs to injured spinal cord provides a promising strategy for alleviating neuropathic pain and locomotion recovery after SCI.

Surface-tethered ROS-responsive micelle backpacks for boosting mesenchymal stem cell vitality and modulating inflammation in ischemic stroke treatment

Mesenchymal stem cells (MSCs) exhibited remarkable therapeutic potential in ischemic stroke due to their exceptional immunomodulatory ability and paracrine effect; they have also been regarded as excellent neuroprotectant delivery vehicles with inflammatory tropism. However, the presence of high levels of reactive oxygen species (ROS) and an oxidative stress environment at the lesion site inhibits cell survival and further therapeutic effects. Using bioorthogonal click chemistry, ROS-responsive luteolin-loaded micelles were tethered to the surface of MSCs. As MSCs migrated to the ischemic brain, the micelles would achieve ROS-responsive release of luteolin to protect MSCs from excessive oxidative damage while inhibiting neuroinflammation and scavenging ROS to ameliorate ischemic stroke. This study provided an effective and prospective therapeutic strategy for ischemic stroke and a framework for a stem cell-based therapeutic system to treat inflammatory cerebral diseases.

Bone-on-a-Chip: Biomimetic Models Based on Microfluidic Technologies for Biomedical Applications

With the increasing importance of preclinical evaluation of newly developed drugs or treatments, in vitro organ or disease models are necessary. Although various organ-specific on-chip (organ-on-a-chip, or OOC) systems have been developed as emerging in vitro models, bone-on-a-chip (BOC) systems that recapitulate the bone microenvironment have been less developed or reviewed compared with other OOCs. The bone is one of the most dynamic organs and undergoes continuous remodeling throughout its lifetime. The aging population is growing worldwide, and healthcare costs are rising rapidly. Since in vitro BOC models that recapitulate native bone niches and pathological features can be important for studying the underlying mechanism of orthopedic diseases and predicting drug responses in preclinical trials instead of in animals, the development of biomimetic BOCs with high efficiency and fidelity will be accelerated further. Here, we review recently engineered BOCs developed using various microfluidic technologies and investigate their use to model the bone microenvironment. We have also explored various biomimetic strategies based on biological, geometrical, and biomechanical cues for biomedical applications of BOCs. Finally, we addressed the limitations and challenging issues of current BOCs that should be overcome to obtain more acceptable BOCs in the biomedical and pharmaceutical industries.

Current developments and therapeutic potentials of exosomes from induced pluripotent stem cells-derived mesenchymal stem cells

Mesenchymal stem cells (MSCs) are multipotent cells derived from adult human tissues that have the ability to proliferate in vitro and maintain their multipotency, making them attractive cell sources for regenerative medicine. However, MSCs reportedly show limited proliferative capacity with inconsistent therapeutic outcomes due to their heterogeneous nature. On the other hand, induced pluripotent stem cells (iPSC) have emerged as an alternative source for the production of various specialized cell types via their ability to differentiate from all three primary germ layers, leading to applications in regenerative medicine, disease modeling, and drug therapy. Notably, iPSCs can differentiate into MSCs in monolayer, commonly referred to as induced mesenchymal stem cells (iMSCs). These cells show superior therapeutic qualities compared with adult MSCs as the applications of the latter are restricted by passage number and autoimmune rejection when applied in tissue regeneration trials. Furthermore, increasing evidence shows that the therapeutic properties of stem cells are a consequence of the paracrine effects mediated by their secretome such as from exosomes, a type of extracellular vesicle secreted by most cell types. Several studies that investigated the potential of exosomes in regenerative medicine and therapy have revealed promising results. Therefore, this review focuses on the recent findings of exosomes secreted from iMSCs as a potential noncell-based therapy.

Promotion of cutaneous diabetic wound healing by subcutaneous administration of Wharton's jelly mesenchymal stem cells derived from umbilical cord

Wound healing is a major problem in diabetic patients, and current treatments have been confronted with limited success. The present study examined the benefit of Wharton's jelly mesenchymal stem cells (WJ-MSCs) derived from the human umbilical cord (UC) in wound healing in diabetic rats. Thirty days after inducing diabetes, a circular excision was created in the skin of rats, and the treatments were performed for 21 days. Two groups were studied, which included the Control group and WJ-MSCs group. The studied groups were sampled on the 7th, 14th, and 21st days after wounding. Histological ultrasound imaging of dermis and epidermis in the wound area for thickness and density measurement and skin elasticity were evaluated. Our results on post-wounding days 7, 14, and 21 showed that the wound closure, thickness, and density of new epidermis and dermis, as well as skin elasticity in the healed wound, were significantly higher in the WJ-MSCs group compared to the Control group. Subcutaneous administration of WJ-MSCs in diabetic wounds can effectively accelerate healing. Based on this, these cells can be used along with other treatment methods in the healing of different types of chronic wounds.

Research and Therapeutic Approaches in Stem Cell Genome Editing by CRISPR Toolkit

The most widely used genome editing toolkit is CRISPR (clustered regularly interspaced short palindromic repeats). It provides the possibility of replacing and modifying DNA and RNA nucleotides. Furthermore, with advancements in biological technology, inhibition and activation of the transcription of specific gene(s) has become possible. Bioinformatics tools that target the evolution of CRISPR-associated protein 9 (Cas9) turn this protein into a vehicle that is specific for a DNA or RNA region with single guide RNA (sgRNA). This toolkit could be used by researchers to investigate the function of stem cell gene(s). Here, in this review article, we cover recent developments and applications of this technique in stem cells for research and clinical purposes and discuss different CRISPR/Cas technologies for knock-out, knock-in, activation, or inhibition of gene expression. Additionally, a comparison of several deliveries and off-target detecting strategies is discussed.

Biodistribution of Intratracheal, Intranasal, and Intravenous Injections of Human Mesenchymal Stromal Cell-Derived Extracellular Vesicles in a Mouse Model for Drug Delivery Studies

Mesenchymal stromal cell-derived extracellular vesicles (MSC-EVs) are extensively studied as therapeutic tools. Evaluation of their biodistribution is fundamental to understanding MSC-EVs' impact on target organs. In our work, MSC-EVs were initially labeled with DiR, a fluorescent lipophilic dye, and administered to BALB/c mice (2.00 × 10¹⁰ EV/mice) through the following routes: intravenous (IV), intratracheal (IT) and intranasal (IN). DiR-labeled MSC-EVs were monitored immediately after injection, and after 3 and 24 hours (h). Whole-body analysis, 3 h after IV injection, showed an accumulation of MSC-EVs in the mice abdominal region, compared to IT and IN, where EVs mainly localized at the levels of the chest and brain region, respectively. After 24 h, EV-injected mice retained a stronger positivity in the same regions identified after 3 h from injection. The analyses of isolated organs confirmed the accumulation of EVs in the spleen and liver after IV administration. Twenty-four hours after the IT injection of MSC-EVs, a stronger positivity was detected selectively in the isolated lungs, while for IN, the signal was confined to the brain. In conclusion, these results show that local administration of EVs can increase their concentration in selective organs, limiting their systemic biodistribution and possibly the extra-organ effects. Biodistribution studies can help in the selection of the most appropriate way of administration of MSC-EVs for the treatment of different diseases.

In vitro comparison of the osteogenic capability of human pulp stem cells on alloplastic, allogeneic, and xenogeneic bone scaffolds

BACKGROUND

A rigorous search for alternatives to autogenous bone grafts to avoid invasiveness at the donor site in the treatment of maxillomandibular bone defects. Researchers have used alloplastic, allogeneic, and xenogeneic bone graft substitutes in clinical studies with varying degrees of success, although their in vitro effects on stem cells remain unclear. Dental pulp stem cells (DPSCs) can potentially enhance the bone regeneration of bone graft substitutes. The present in vitro study investigates the osteogenic capability of DPSCs on alloplastic (biphasic calcium phosphate [BCP]), allogeneic (freeze-dried bone allografts [FDBAs]), and xenogeneic (deproteinized bovine bone mineral [DBBM]) bone grafts.

METHODS

Human DPSCs were seeded on 0.5 mg/ml, 1 mg/ml, and 2 mg/ml of BCP, FDBA, and DBBM to evaluate the optimal cell growth and cytotoxicity. Scaffolds and cell morphologies were analyzed by scanning electron microscopy (SEM). Calcein AM and cytoskeleton staining were performed to determine cell attachment and proliferation. Alkaline phosphatase (ALP) and osteogenesis-related genes expressions was used to investigate initial osteogenic differentiation.

RESULTS

Cytotoxicity assays showed that most viable DPSCs were present at a scaffold concentration of 0.5 mg/ml. The DPSCs on the DBBM scaffold demonstrated a significantly higher proliferation rate of 214.25 ± 16.17 (p < 0.001) cells, enhancing ALP activity level and upregulating of osteogenesis-related genes compared with other two scaffolds.

CONCLUSION

DBBP scaffold led to extremely high cell viability, but also promoted proliferation, attachment, and enhanced the osteogenic differentiation capacity of DPSCs, which hold great potential for bone regeneration treatment; however, further studies are necessary.

Skin-Derived ABCB5+ Mesenchymal Stem Cells for High-Medical-Need Inflammatory Diseases: From Discovery to Entering Clinical Routine

The ATP-binding cassette superfamily member ABCB5 identifies a subset of skin-resident mesenchymal stem cells (MSCs) that exhibit potent immunomodulatory and wound healing-promoting capacities along with superior homing ability. The ABCB5+ MSCs can be easily accessed from discarded skin samples, expanded, and delivered as a highly homogenous medicinal product with standardized potency. A range of preclinical studies has suggested therapeutic efficacy of ABCB5+ MSCs in a variety of currently uncurable skin and non-skin inflammatory diseases, which has been substantiated thus far by distinct clinical trials in chronic skin wounds or recessive dystrophic epidermolysis bullosa. Therefore, skin-derived ABCB5+ MSCs have the potential to provide a breakthrough at the forefront of MSC-based therapies striving to fulfill current unmet medical needs. The most recent milestones in this regard are the approval of a phase III pivotal trial of ABCB5+ MSCs for treatment of recessive dystrophic and junctional epidermolysis bullosa by the US Food and Drug Administration, and national market access of ABCB5+ MSCs (AMESANAR®) for therapy-refractory chronic venous ulcers under the national hospital exemption pathway in Germany.

Gangliosides and Their Role in Multilineage Differentiation of Mesenchymal Stem Cells

Gangliosides (GGs) are a glycolipid class present on Mesenchymal Stem Cells (MSCs) surfaces with a critical appearance role in stem cell differentiation, even though their mechanistic role in signaling and differentiation remains largely unknown. This review aims to carry out a critical analysis of the predictive role of gangliosides as specific markers of the cellular state of undifferentiated and differentiated MSCs, towards the osteogenic, chondrogenic, neurogenic, and adipogenic lineage. For this reason, we analyzed the role of GGs during multilineage differentiation processes of several types of MSCs such as Umbilical Cord-derived MSCs (UC-MSCs), Bone Marrow-derived MSCs (BM-MSCs), Dental Pulp derived MSCs (DPSCs), and Adipose derived MSCs (ADSCs). Moreover, we examined the possible role of GGs as specific cell surface markers to identify or isolate specific stem cell isotypes and their potential use as additional markers for quality control of cell-based therapies.

Extracellular Vesicles of Mesenchymal Stem Cells Are More Effectively Accessed through Polyethylene Glycol-Based Precipitation than by Ultracentrifugation

Extracellular vesicles (EVs) have been identified as cell-cell communication agents, and EVs derived from mesenchymal stem cells (MSCs) exhibit therapeutic effects similar to those of the cells of origin. Precipitation methods have been used extensively for EV harvests, such as UC- (ultracentrifugation-) or PEG- (polyethylene glycol-) based methods, and the difference in EVs derived from MSCs by UC and PEG is not fully understood. We harvested EVs from amniotic fluid MSCs (AF-MSCs) by UC- or PEG-based precipitation methods and conducted a comparison study of those EVs derived by the two methods: output, RNA, and protein expression of EVs and EV biological reaction in a THP-1-cell model of LPS induction, which was considered an infection model. There was no difference in morphology, size, or specific marker-positive ratio of PEG-EVs and UC-EVs, but PEG obtained more EV particles, protein, and RNA than the UC method. In our THP-1 model of LPS induction, MSC-EVs did not lead to a change in protein expression but inhibited the LPS-induced increase in cytokine secretion. UC-EVs were more effective for TNF-α inhibition, and PEG-EVs were more effective for IL10 inhibition. Thus, our findings provide evidence that PEG-based precipitation is a more efficient mesenchymal stem cell-extracellular vesicle-derived method than UC.

Effect of Crohn's disease mesenteric mesenchymal stem cells and their extracellular vesicles on T-cell immunosuppressive capacity

Crohn's disease (CD) is a chronic inflammatory disease of the gastrointestinal intestinal tract and has characteristic hypertrophic adipose changes observed in the mesentery. To better understand the role of the mesentery in the pathophysiology of Crohn's disease (CD), we evaluated the immunomodulatory potential of mesenchymal stem cells (MSCs) and their secreted extracellular vesicles (EVs) derived from Crohn's patients. MSCs and EVs were isolated from the mesentery and subcutaneous tissues of CD patients and healthy individuals subcutaneous tissues, and were analysed for differentiation, cytokine expression, self‐renewal and proliferation. The varying capacity of these tissue‐derived MSCs and EVs to attenuate T‐cell activation was measured in in vitro and an in vivo murine model. RNA sequencing of inflamed Crohn's disease mesentery tissue revealed an enrichment of T‐cell activation compared to non‐inflamed subcutaneous tissue. MSCs and MSC‐derived EVs isolated from Crohn's mesentery lose their ability to attenuate DSS‐induced colitis compared to subcutaneous tissue‐derived cell or EV therapy. We found that treatment with subcutaneous isolated MSCs and their EV product compared to Crohn's mesentery MSCs or EVs, the inhibition of T‐cell proliferation and IFN‐γ, IL‐17a production increased, suggesting a non‐inflamed microenvironment allows for T‐cell inhibition by MSCs/EVs. Our results demonstrate that Crohn's patient‐derived diseased mesentery tissue MSCs lose their immunosuppressive capacity in the treatment of colitis by distinct regulation of pathogenic T‐cell responses and/or T‐cell infiltration into the colon.

Bone Marrow-Derived Mesenchymal Stromal Cell Therapy in Severe COVID-19: Preliminary Results of a Phase I/II Clinical Trial

Background

Treatment of acute respiratory distress syndrome (ARDS) associated with COronaVIrus Disease-2019 (COVID-19) currently relies on dexamethasone and supportive mechanical ventilation, and remains associated with high mortality. Given their ability to limit inflammation, induce immune cells into a regulatory phenotype and stimulate tissue repair, mesenchymal stromal cells (MSCs) represent a promising therapy for severe and critical COVID-19 disease, which is associated with an uncontrolled immune-mediated inflammatory response.

Methods

In this phase I-II trial, we aimed to evaluate the safety and efficacy of 3 intravenous infusions of bone marrow (BM)-derived MSCs at 3-day intervals in patients with severe COVID-19. All patients also received dexamethasone and standard supportive therapy. Between June 2020 and September 2021, 8 intensive care unit patients requiring supplemental oxygen (high-flow nasal oxygen in 7 patients, invasive mechanical ventilation in 1 patient) were treated with BM-MSCs. We retrospectively compared the outcomes of these MSC-treated patients with those of 24 matched control patients. Groups were compared by paired statistical tests.

Results

MSC infusions were well tolerated, and no adverse effect related to MSC infusions were reported (one patient had an ischemic stroke related to aortic endocarditis). Overall, 3 patients required invasive mechanical ventilation, including one who required extracorporeal membrane oxygenation, but all patients ultimately had a favorable outcome. Survival was significantly higher in the MSC group, both at 28 and 60 days (100% vs 79.2%, p = 0.025 and 100% vs 70.8%, p = 0.0082, respectively), while no significant difference was observed in the need for mechanical ventilation nor in the number of invasive ventilation-free days, high flow nasal oxygenation-free days, oxygen support-free days and ICU-free days. MSC-treated patients also had a significantly lower day-7 D-dimer value compared to control patients (median 821.0 µg/L [IQR 362.0-1305.0] vs 3553 µg/L [IQR 1155.0-6433.5], p = 0.0085).

Conclusions

BM-MSC therapy is safe and shows very promising efficacy in severe COVID-19, with a higher survival in our MSC cohort compared to matched control patients. These observations need to be confirmed in a randomized controlled trial designed to demonstrate the efficacy of BM-MSCs in COVID-19 ARDS.

Clinical Trial Registration

(www.ClinicalTrials.gov), identifier NCT04445454

Two New Potential Therapeutic Approaches in Radiation Cystitis Derived from Mesenchymal Stem Cells: Extracellular Vesicles and Conditioned Medium

Background: Radiation cystitis (RC) results from chronic inflammation, fibrosis, and vascular damage. The urinary symptoms it causes have a serious impact on patients’ quality of life. Despite the improvement in irradiation techniques, the incidence of radiation cystitis remains stable over time, and the therapeutic possibilities remain limited. Mesenchymal stem/stromal cells (MSC) appear to offer2 a promising therapeutic approach by promoting tissue repair through their paracrine action via extracellular vesicles (MSC-EVs) or conditioned medium from human mesenchymal stromal cells (MSC-CM). We assess the therapeutic potential of MSC-EVs or MSC-CM in an in vitro model of RC. Methods:in vitro RC was induced by irradiation of human bladder fibroblasts (HUBF) with the small-animal radiation research platform (SARRP). HUBF were induced towards an RC phenotype after 3 × 3.5 Gy irradiation in the presence of either MSC-EVs or MSC-CM, to assess their effect on fibrosis, angiogenesis, and inflammatory markers. Results: Our data revealed in vitro a higher therapeutic potential of MSC-EVs and MSC-CM in prevention of RC. This was confirmed by down-regulation of α-SMA and CTGF transcription, and the induction of the secretion of anti-fibrotic cytokines, such as IFNγ, IL10 and IL27 and the decrease in the secretion of pro-fibrotic cytokines, IGFBP2, IL1β, IL6, IL18, PDGF, TNFα, and HGF, by irradiated HUBFs, conditioned with MSC-EVs or MSC-CM. The secretome of MSC (MSC-CM) or its subsecretome (MSC-EVs) are proangiogenic, with the ability to induce vessels from HUVEC cells, ensuring the management of bladder vascular lesions induced by irradiation. Conclusion: MSC-EVs and MSC-CM appear to have promising therapeutic potential in the prevention of RC in vitro, by targeting the three main stages of RC: fibrosis, inflammation and vascular damage.

Mesenchymal Stem Cells Derived from Umbilical Cord Blood having Excellent Stemness Properties with Therapeutic Benefits - a New Era in Cancer Treatment

Mesenchymal stem cells (MSCs) are the most promising candidates for cellular therapies, and most therapeutic applications have focused on MSCs produced from adult bone marrow, despite mounting evidence that MSCs are present in a wide range of conditions. Umbilical cord blood (UCB) is a valuable source of hematopoietic stem cells, but its therapeutic potential extends beyond the hematopoietic component, which also suggests solid organ regenerative potential. With potential ranging from embryonic-like to lineage-committed progenitor cells, many different stems and progenitor cell populations have been postulated. MSC is currently inferred by numerous clinical applications for human UCB. aAs stem cell therapy kicks off some new research and these cells show such a boon to stem cell therapy, it is nevertheless characteristic that the prospect of UCB conservation is gaining momentum. Taken together, the experience described here shows that MSCs derived from UCB are seen as attractive therapeutic candidates for various human disorders including cancer. It is argued that a therapeutic stem cell transplant, using stem cells from UCB, provides a reliable repository of early precursor cells that can be useful in a large number of different conditions, considering issues of safety, availability, transplant methodology, rejection, and side effects. In particular, we focus on the concept of isolation and expansion, comparing the phenotype with MSC derived from the UCB, describing the ability to differentiate, and lastly, the therapeutic potential concerning stromal support, stemness characteristic, immune modulation, and cancer stem cell therapy. Thus it is an overview of the therapeutic application of UCB derived MSCs, with a special emphasis on cancer. Besides, the current evidence on the double-edged sword of MSCs in cancer treatment and the latest advances in UCB-derived MSC in cancer research will be discussed.

Competitive Hybridization of a Microarray Identifies CMKLR1 as an Up-Regulated Gene in Human Bone Marrow-Derived Mesenchymal Stem Cells Compared to Human Embryonic Fibroblasts

Mesenchymal stem cells (MSCs) have been widely applied to the regeneration of damaged tissue and the modulation of immune response. The purity of MSC preparation and the delivery of MSCs to a target region are critical factors for success in therapeutic application. In order to define the molecular identity of an MSC, the gene expression pattern of a human bone marrow-derived mesenchymal stem cell (hBMSC) was compared with that of a human embryonic fibroblast (hEF) by competitive hybridization of a microarray. A total of 270 and 173 genes were two-fold up- and down-regulated with FDR < 0.05 in the hBMSC compared to the hEF, respectively. The overexpressed genes in the hBMSC over the hEF, including transcription factors, were enriched for biological processes such as axial pattern formation, face morphogenesis and skeletal system development, which could be expected from the differentiation potential of MSCs. CD70 and CD339 were identified as additional CD markers that were up-regulated in the hBMSC over the hEF. The differential expression of CD70 and CD339 might be exploited to distinguish hEF and hBMSC. CMKLR1, a chemokine receptor, was up-regulated in the hBMSC compared to the hEF. RARRES2, a CMKLR1 ligand, stimulated specific migration of the hBMSC, but not of the hEF. RARRES2 manifested as ~two-fold less effective than SDF-1α in the directional migration of the hBMSC. The expression of CMKLR1 was decreased upon the osteoblastic differentiation of the hBMSC. However, the RARRES2-loaded 10% HA-silk scaffold did not recruit endogenous cells to the scaffold in vivo. The RARRES2−CMKLR1 axis could be employed in recruiting systemically delivered or endogenous MSCs to a specific target lesion.

Lineage Differentiation Potential of Different Sources of Mesenchymal Stem Cells for Osteoarthritis Knee

Tissue engineering and regenerative medicine (TERM) have paved a way for treating musculoskeletal diseases in a minimally invasive manner. The regenerative medicine cocktail involves the usage of mesenchymal stem/stromal cells (MSCs), either uncultured or culture-expanded cells along with growth factors, cytokines, exosomes, and secretomes to provide a better regenerative milieu in degenerative diseases. The successful regeneration of cartilage depends on the selection of the appropriate source of MSCs, the quality, quantity, and frequency of MSCs to be injected, and the selection of the patient at an appropriate stage of the disease. However, confirmation on the most favorable source of MSCs remains uncertain to clinicians. The lack of knowledge in the current cellular treatment is uncertain in terms of how beneficial MSCs are in the long-term or short-term (resolution of pain) and improved quality of life. Whether MSCs treatments have any superiority, exists due to sources of MSCs utilized in their potential to objectively regenerate the cartilage at the target area. Many questions on source and condition remain unanswered. Hence, in this review, we discuss the lineage differentiation potentials of various sources of MSCs used in the management of knee osteoarthritis and emphasize the role of tissue engineering in cartilage regeneration.

Circular RNAs in stem cells: from basic research to clinical implications

Circular RNAs (circRNAs) are a special class of endogenous RNAs with a wide variety of pathophysiological functions via diverse mechanisms, including transcription, microRNA (miRNA) sponge, protein sponge/decoy, and translation. Stem cells are pluripotent cells with unique properties of self-renewal and differentiation. Dysregulated circRNAs identified in various stem cell types can affect stem cell self-renewal and differentiation potential by manipulating stemness. However, the emerging roles of circRNAs in stem cells remain largely unknown. This review summarizes the major functions and mechanisms of action of circRNAs in stem cell biology and disease progression. We also highlight circRNA-mediated common pathways in diverse stem cell types and discuss their diagnostic significance with respect to stem cell-based therapy.

Extracellular vesicles from mesenchymal stem cells of dental pulp and adipose tissue display distinct transcriptomic characteristics suggestive of potential therapeutic targets

Objective: Mesenchymal stem cells (MSCs) are isolated from various human tissues and used for therapy, in which beneficial effects are attributed mainly to mesenchymal stem cell-derived extracellular vesicles (MSC-EVs). Whereas MSCs of diverse tissue types share cardinal stem cell features, it is becoming evident that MSCs of each tissue type possess unique properties as well. For designing efficient stem cellbased therapies, it is crucial to understand the unique properties associated with MSCs and MSC-EVs of each tissue type. Such unique properties can be analyzed through transcriptomic approaches using comprehensive gene expression databases and sophisticated analytical tools. Here, we comparatively studied the transcriptomes in MSC-EVs of dental pulp and adipose tissue. Additionally, the transcriptomes of MSC-EVs were compared with the cellular transcriptomes of MSCs for the same tissue types. Methods: MSCs were cultured from human dental pulp and adipose tissue specimens. Conditioned culture media were collected to prepare MSC-EVs, from which RNAs were isolated and subjected to next-generation sequencing for transcriptomic analysis. Gene expression signatures in MSC-EVs of each tissue type were investigated using gene set analysis. Results: MSC-EVs obtained from dental pulp-derived MSCs showed distinct transcriptomic signatures of neurogenesis and neural retina development while MSC-EVs of adipose tissue-derived MSCs showed signatures of mitochondrial activity and skeletal system development. The transcriptomes of MSC-EVs resembled the cellular transcriptomes of MSCs, and the genes associated with neurogenesis were highly expressed in both MSCs and MSC-EVs of dental pulp. Adipose tissue-derived MSCs and MSC-EVs highly expressed genes associated with angiogenesis, hair growth, and dermal matrices. Conclusion: The clear and distinct signatures of neurogenesis and neural retina development in dental pulp-derived MSC-EVs imply neurodegenerative disorders and retinal diseases as putative therapeutic targets. In contrast, the transcripts in adipose tissue-derived MSC-EVs could be useful in rejuvenating the skin and musculoskeletal system. Further insights into MSC-EVs of divergent tissue types may expand the list of potential therapeutic targets.

[Therapeutic applications of extracellular vesicles]

Extracellular vesicles, secreted spontaneously or in response to stress by all cell types, are proposed as alternative biotherapies to cellular therapies and to synthetic nanomedicines. Their logistical advantages (storage, stability, availability, tolerance), their ability to cross biological barriers, to deliver their contents (proteins, lipids and nucleic acids) in order to modify their target cells, as well as their immunomodulatory and regenerative activities, are of growing interest for a very wide spectrum of diseases. Here we review the challenges to bring these biotherapies to the clinic and discuss some promising applications in cancer and regenerative medicine.

Public Opinion and Expectations of Stem Cell Therapies in Orthopaedics

PURPOSE

To explore public opinion, understanding, and preferences regarding the use of stem cell therapies for the treatment of joint and tendon pathologies using online crowdsourcing.

METHODS

A 30-question survey was completed by 931 members of the public using Amazon Mechanical Turk, a validated crowdsourcing method. Outcomes included perceptions and preferences regarding the use of stem cells therapies for the nonsurgical treatment of orthopaedic conditions. Sociodemographic factors and a validated assessment of health literacy were collected. Inclusion criteria were adult participants 18 years or older, residence within the United States, and a valid Social Security number. Multivariable logistic regression modeling was used to determine population characteristics associated with the belief that stem cells represent the most effective treatment for long-standing joint or tendon disorders.

RESULTS

Most respondents reported that stem cell therapies have convincing evidence to support their use for orthopaedic conditions (84.5%) and are approved and regulated by the Food and Drug Administration (65%). About three-quarters of respondents reported that stem cells can stop the progression of and alleviate pain from arthritis or damaged tendons, and over half (53.5%) reported that stem cells can cure arthritis. Factors with the greatest influence on respondents' decision to receive stem cell therapies are research supporting their safety and effectiveness and doctor recommendation. However, 63.3% of respondents stated that they would consider stem cells if their doctor recommended it, regardless of evidence supporting their effectiveness, and over half would seek another doctor if their orthopaedic surgeon did not offer this treatment option.

CONCLUSIONS

The public's limited understanding regarding the current evidence associated with stem cell therapies for osteoarthritis and tendinous pathologies may contribute to unrealistic expectations and misinformed decisions. This study highlights the importance of patient education and expectation setting, as well as evidence transparency, as stem cell therapies become increasingly accessible.

LEVEL OF EVIDENCE

Level IV, case series.

A systematic review and meta-analysis on the efficacy of stem cell therapy on bone brittleness in mouse models of osteogenesis imperfecta

There is no cure for osteogenesis imperfecta (OI), and current treatments can only partially correct the bone phenotype. Stem cell therapy holds potential to improve bone quality and quantity in OI. Here, we conduct a systematic review and meta-analysis of published studies to investigate the efficacy of stem cell therapy to rescue bone brittleness in mouse models of OI. Identified studies included bone marrow, mesenchymal stem cells, and human fetal stem cells. Effect size of fracture incidence, maximum load, stiffness, cortical thickness, bone volume fraction, and raw engraftment rates were pooled in a random-effects meta-analysis. Cell type, cell number, injection route, mouse age, irradiation, anatomical bone, and follow up time were considered as moderators. It was not possible to investigate further parameters due to the lack of standards of investigation between the studies. Despite the use of oim mice in the majority of the investigations considered and the lack of sham mice as control, this study demonstrates the promising potential of stem cell therapy to reduce fractures in OI. Although their low engraftment, cell therapy in mouse models of OI had a beneficial effect on maximum load, but not on stiffness, cortical thickness and bone volume. These parameters all depend on bone geometry and do not inform on its material properties. Being bone fractures the primary symptom of OI, there is a critical need to measure the fracture toughness of OI bone treated with stem cells to assess the actual efficacy of the treatment to rescue OI bone brittleness.

Potential of Bone-Marrow-Derived Mesenchymal Stem Cells for Maxillofacial and Periodontal Regeneration: A Narrative Review

Bone-marrow-derived mesenchymal stem cells (BM-MSCs) are one of the most widely studied postnatal stem cell populations and are considered to utilize more frequently in cell-based therapy and cancer. These types of stem cells can undergo multilineage differentiation including blood cells, cardiac cells, and osteogenic cells differentiation, thus providing an alternative source of mesenchymal stem cells (MSCs) for tissue engineering and personalized medicine. Despite the ability to reprogram human adult somatic cells to induced pluripotent stem cells (iPSCs) in culture which provided a great opportunity and opened the new door for establishing the in vitro disease modeling and generating an unlimited source for cell base therapy, using MSCs for regeneration purposes still have a great chance to cure diseases. In this review, we discuss the important issues in MSCs biology including the origin and functions of MSCs and their application for craniofacial and periodontal tissue regeneration, discuss the potential and clinical applications of this type of stem cells in differentiation to maxillofacial bone and cartilage in vitro, and address important future hopes and challenges in this field.

Novel strategy of cartilage repairing via application of P. atlantica with stem cells and collagen

Osteoarthritis (OA) is an inflammatory joint condition, still lacking effective treatments. Some factors consider as the main causes of OA, including biochemical, mechanical, and genetic factors. The growth of studies confirmed that modern medicine in combination with folk medicine regarding the arrival of reliable, efficient, and safe therapeutic products against OA. In the present study, the effects of various single and combinatorial treatments of knee articular cartilage, including stem cells, collagen, and P. atlantica hydroalcoholic leaves extract were investigated in a rat-induced OA model. On week 12 after OA confirmation, histopathology and radiography assessments were evaluated and the serum and synovial fluid levels of TAC, TNF-α, PEG2, MPO, MMP3, MMP13, and MDA were also measured. Combination therapy of OA-induced rats with hydroalcoholic extract of P. atlantic leaves, stem cells, and collagen considerably increased the efficacy of treatment as evidenced by increasing the TAC and lowering TNF-α, MPO, MMP3, and MMP13 compared to control group and even groups received single therapy. This is in agreement with a high amount of total phenolic compounds and antioxidant capacities of the hydroalcoholic extract of P. atlantic leaves. It is concluded that multifunctional agents targeting the pathophysiology of OA has exhibited significant therapeutic effects against OA.

Palmitic Acid Methyl Ester Enhances Adipogenic Differentiation in Rat Adipose Tissue-Derived Mesenchymal Stem Cells through a G Protein-Coupled Receptor-Mediated Pathway

Adipogenic differentiation from stem cells has become a research target due to the increasing interest in obesity. It has been indicated that adipocytes can secrete palmitic acid methyl ester (PAME), which is able to regulate stem cell proliferation. However, the effects of PAME on adipogenic differentiation in stem cell remain unclear. Here, we present that the adipogenic differentiation medium supplemented with PAME induced the differentiation of rat adipose tissue-derived mesenchymal stem cells (rAD-MSCs) into adipocyte. rAD-MSCs were treated with PAME for 12 days and then subjected to various analyses. The results from the present study show that PAME significantly increased the levels of adipogenic differentiation markers, PPARγ and Gpd1, and enhanced adipogenic differentiation in rAD-MSCs. Furthermore, the level of GPR40/120 protein increased during induction of adipocyte differentiation in rAD-MSCs. Cotreatment with PAME and a GPR40/120 antagonist together inhibited the PAME-enhanced adipogenic differentiation. Moreover, PAME significantly increased phosphorylation of extracellular signal-regulated kinases (ERK), but not AKT and mTOR. Cotreatment with PAME and a GPR40/120 antagonist together inhibited the PAME-enhanced ERK phosphorylation and adipogenic differentiation. PAME also increased the intracellular Ca²⁺ levels. Cotreatment with PAME and a Ca²⁺ chelator or a phospholipase C (PLC) inhibitor prevented the PAME-enhanced ERK phosphorylation and adipogenic differentiation. Our data suggest that PAME activated the GPR40/120/PLC-mediated pathway, which in turn increased the intracellular Ca²⁺ levels, thereby activating the ERK, and eventually enhanced adipogenic differentiation in rAD-MSCs. The findings from the present study might help get insight into the physiological roles and molecular mechanism of PAME in regulating stem cell differentiation.

PD-L1 overexpression conveys tolerance of mesenchymal stem cell-derived cardiomyocyte-like cells in an allogeneic mouse model

Although the autologously transplanted cells are immunologically durable, allogeneic cell transplantation is inevitable in a series of cases. Mesenchymal stem cells (MSCs) are one of the suitable candidates for cardiac tissue regeneration that have been shown to acquire immunogenicity concurrent with cardiomyogenic differentiation. The present study aimed to exploit PD-L1, as a key immunomodulatory checkpoint ligand to protect the MSCs-derived cardiomyocyte-like cells (CLCs) against the detrimental alloimmunity. Mouse bone marrow-derived MSCs were stably transduced to overexpress PD-L1. MSCs were in vitro differentiated into CLCs and the expressions of immunologic molecules were compared between MSCs and CLCs. The in vitro and in vivo allogeneic immune responses were also examined. The differentiated CLCs had higher expressions of MHC-I and CD80. Upon in vitro coculture with allogeneic splenocytes, CLCs caused more CD4+ and CD8+ T cell activation, lymphocyte proliferation, and interferon-γ (IFN-γ) release in comparison to MSCs. PD-L1 overexpression on CLCs decreased the activation of CD8+ T cells, proliferation of lymphocytes, and release of IFN-γ. The PD-L1-overexpressing CLCs elicited lower in vivo CD4+ and CD8+ T cell activation and reduced the anti-donor antibody response accompanied by increased durability and reduced T cell infiltration. The present study verified the potential of PD-L1 overexpression as a preparative strategy for the protection of allogeneic MSCs-derived CLCs against the detrimental alloreaction.

CD146 controls the quality of clinical grade mesenchymal stem cells from human dental pulp

Background

Human mesenchymal stem cells from dental pulp (hMSC-DP), including dental pulp stem cells from permanent teeth and exfoliated deciduous teeth, possess unique MSC characteristics such as expression of specific surface molecules and a high proliferation rate. Since hMSC-DP have been applied in numerous clinical studies, it is necessary to establish criteria to evaluate their potency for cell-based therapies.

Methods

We compared stem cell properties of hMSC-DP at passages 5, 10 and 20 under serum (SE) and serum-free (SF) culture conditions. Cell morphology, proliferation capacity, chromosomal stability, surface phenotypic profiles, differentiation and immunoregulation ability were evaluated. In addition, we assessed surface molecule that regulates hMSC-DP proliferation and immunomodulation.

Results

hMSC-DP exhibited a decrease in proliferation rate and differentiation potential, as well as a reduced expression of CD146 when cultured under continuous passage conditions. SF culture conditions failed to alter surface marker expression, chromosome stability or proliferation rate when compared to SE culture. SF-cultured hMSC-DP were able to differentiate into osteogenic, adipogenic and neural cells, and displayed the capacity to regulate immune responses. Notably, the expression level of CD146 showed a positive correlation with proliferation, differentiation, and immunomodulation, suggesting that CD146 can serve as a surface molecule to evaluate the potency of hMSC-DP. Mechanistically, we found that CD146 regulates proliferation and immunomodulation of hMSC-DP through the ERK/p-ERK pathway.

Conclusion

This study indicates that SF-cultured hMSC-DP are appropriate for producing clinical-grade cells. CD146 is a functional surface molecule to assess the potency of hMSC-DP.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02559-4.

Extracellular Vesicles in Acute Kidney Injury and Clinical Applications

Acute kidney injury (AKI)--the sudden loss of kidney function due to tissue damage and subsequent progression to chronic kidney disease--has high morbidity and mortality rates and is a serious worldwide clinical problem. Current AKI diagnosis, which relies on measuring serum creatinine levels and urine output, cannot sensitively and promptly report on the state of damage. To address the shortcomings of these traditional diagnosis tools, several molecular biomarkers have been developed to facilitate the identification and ensuing monitoring of AKI. Nanosized membrane-bound extracellular vesicles (EVs) in body fluids have emerged as excellent sources for discovering such biomarkers. Besides this diagnostic purpose, EVs are also being extensively exploited to deliver therapeutic macromolecules to damaged kidney cells to ameliorate AKI. Consequently, many successful AKI biomarker findings and therapeutic applications based on EVs have been made. Here, we review our understanding of how EVs can help with the early identification and accurate monitoring of AKI and be used therapeutically. We will further discuss where current EV-based AKI diagnosis and therapeutic applications fall short and where future innovations could lead us.

Strategies for managing asherman's syndrome and endometrial atrophy: Since the classical experimental models to the new bioengineering approach

Endometrial function is essential for embryo implantation and pregnancy, but managing endometrial thickness that is too thin to support pregnancy or an endometrium of compromised functionality due to intrauterine adhesions is an ongoing challenge in reproductive medicine. Here, we review current and emerging therapeutic and experimental options for endometrial regeneration with a focus on animal models used to study solutions for Asherman's syndrome and endometrial atrophy, which both involve a damaged endometrium. A review of existing literature was performed that confirmed the lack of consensus on endometrial therapeutic options, though promising new alternatives have emerged in recent years (platelet-rich plasma, exosomes derived from stem cells, bioengineering-based techniques, endometrial organoids, among others). In the future, basic research using established experimental models of endometrial pathologies (combined with new high-tech solutions) and human clinical trials with large population sizes are needed to evaluate these emerging and new endometrial therapies.

Enhanced culturing of adipose derived mesenchymal stem cells on surface modified polystyrene Petri dishes fabricated by plasma enhanced chemical vapor deposition system

Mesenchymal stem cells (MSCs) have received considerable attention as therapeutic cells for regenerative medicine and tissue engineering, because of their ability to replace damaged cells or regenerate surrounding cells. There are many technical difficulties in the mass production of high-quality stem cells because the stem cells must maintain an efficient proliferative cell state during in vitro culture. The results of this study show that plasma surface-modification enhanced significantly the culture of adipose-derived mesenchymal stem cells (ASCs) on the polystyrene (PS) Petri dishes. Ar, O₂ , pyrrole, and 4,7,10-trioxa-1,13-tridecanediamine (TTDDA) were used as the gas and/or precursors for plasma modification. Specifically, surfaces of PS Petri dishes, coated with plasma polymerized pyrrole (ppPy) and plasma polymerized TTDDA (ppTTDDA) were found to contain amine and carboxyl functional groups, respectively. Ar and O₂ plasma-treated PS Petri dishes have similar culture abilities (±1.2 times) to commercially available tissue culture polystyrene (TCPS) dishes, and PS Petri dishes coated with ppPy and ppTTDDA have significantly enhanced culture abilities (2.4 times) at 96 hr compared with TCPS dishes. Western blotting was performed using antibodies against stem cell marker proteins to confirm the stemness properties of stem cells, in the sense that the expressions of the antibody proteins such as CD44, CD73, and CD105 in plasma modified samples were similar to or higher than those in TCPS dishes.

Priming human adipose-derived mesenchymal stem cells for corneal surface regeneration

Limbal stem cells (LSC) maintain the transparency of the corneal epithelium. Chemical burns lead the loss of LSC inducing an up-regulation of pro-inflammatory and pro-angiogenic factors, triggering corneal neovascularization and blindness. Adipose tissue-derived mesenchymal stem cells (AT-MSC) have shown promise in animal models to treat LSC deficiency (LSCD), but there are not studies showing their efficacy when primed with different media before transplantation. We cultured AT-MSC with standard medium and media used to culture LSC for clinical application. We demonstrated that different media changed the AT-MSC paracrine secretion showing different paracrine effector functions in an in vivo model of chemical burn and in response to a novel in vitro model of corneal inflammation by alkali induction. Treatment of LSCD with AT-MSC changed the angiogenic and inflammatory cytokine profile of mice corneas. AT-MSC cultured with the medium that improved their cytokine secretion, enhanced the anti-angiogenic and anti-inflammatory profile of the treated corneas. Those corneas also presented better outcome in terms of corneal transparency, neovascularization and histologic reconstruction. Priming human AT-MSC with LSC specific medium can potentiate their ability to improve corneal wound healing, decrease neovascularization and inflammation modulating paracrine effector functions in an in vivo optimized rat model of LSCD.

Regenerative Potential of DPSCs and Revascularization: Direct, Paracrine or Autocrine Effect?

A new source of mesenchymal stem cells has recently been discovered, the so-called dental pulp derived stem cells (DPSCs) which therefore could represent potentially tools for regenerative medicine. DPSC originate from the neural crest and are physiologically involved in dentin homeostasis; moreover, they contribute to bone remodeling and differentiation into several tissues including cartilage, bone, adipose and nervous tissues. DPSCs have also been shown to influence the angiogenesis process, for example through the release of secretory factors or by differentiating into vascular and/or perivascular cells. Angiogenesis, that has a pivotal role in tissue regeneration and repair, is defined as the formation of new vessels from preexisting vessels and is mediated by mutual and reciprocal interactions between endothelial cells and perivascular cells. It is also known that co-cultures of perivascular and endothelial cells (ECs) can form a vascular network in vitro and also in vivo. Since DPSCs seem to have characteristics similar to pericytes, understanding the possible mechanism of interaction between DPSCs and ECs during neo-angiogenesis is dramatically important for the development of advanced clinical application in the field of regeneration.

Mesenchymal Stem and Stromal Cells Harness Macrophage-Derived Amphiregulin to Maintain Tissue Homeostasis

The cross-talk between mesenchymal stem and stromal cells (MSCs) and macrophages is critical for the restoration of tissue homeostasis after injury. Here, we demonstrate a pathway through which MSCs instruct macrophages to resolve inflammation and preserve tissue-specific stem cells, leading to homeostasis in mice with autoimmune uveoretinitis and sterile-injury-induced corneal epithelial stem cell deficiency. Distinct from their conventional role in macrophage reprogramming to anti-inflammatory phenotype by a PGE2-dependent mechanism, MSCs enhance the phagocytic activity of macrophages, which partly depends on the uptake of MSC mitochondria-containing extracellular vesicles. The MSC-primed macrophages increase the secretion of amphiregulin (AREG) in a phagocytosis-dependent manner. AREG is essential for MSC-primed macrophages to suppress immune responses through regulatory T (Treg) cells and to protect corneal epithelial stem cells via apoptosis inhibition and proliferation promotion. Hence, the data reveal that MSCs harness macrophage-derived AREG to maintain tissue homeostasis after injury and provide a therapeutic target in immune-mediated disease and regenerative medicine.

Monophosphoryl Lipid A and Retinoic Acid Combinations Increased Germ Cell Differentiation Markers Expression in Human Umbilical Cord-derived Mesenchymal Stromal Cells in an In vitro Ovine Acellular Testis Scaffold

Infertility is known as one of the most common problems among couples. In this regard, generation of male germ cells from adult stem ones are among the current promising priorities of researchers. Mesenchymal stromal cells (MSCs) were previously induced to differentiate into germ-like progenitors in vitro. Monophosphoryl lipid A (MPLA) is a detoxified derivative of lipopolysaccharides (LPS) that lacks many of the endotoxic properties of LPS. Our present study aimed to investigate the expression of migration genes (CXCR4, VCAM1, VEGF, MMP2, and VLA4), and differentiation markers during human umbilical mesenchymal stromal cells (hUMSCs) culture in the presence of retinoic acid (RA) and MPLA-treated acellular testis. Accordingly, the high expression levels of deleted in azoospermia-like (DAZL), piwi-like RNA-mediated gene silencing 2 (PIWIL2) transcripts as well as protein were consequently observed in treated hUMSCs. It was concluded that combination treatment (i.e., MPLA/RA) had more prominent results than each of the treatments alone, even though MPLA and RA could be regarded as inducer of migration and differentiation, respectively. Ultimately, it was suggested to introduce the use of combination treatment as a more effective strategy to improve therapies in regenerative medicine.

Treatment of murine partial thickness scald injuries with multipotent adult progenitor cells decreases inflammation and promotes angiogenesis leading to improved burn injury repair

Stem cells have been shown to have potential as a new therapy for burns and promote wound healing through decreasing inflammation and increasing angiogenesis. Multipotent adult progenitor cells (MAPC® cells) are a subpopulation of bone marrow-derived stem cells with outstanding self-renewal and differentiation capacity. MAPC cells also secrete a wide range of cytokines which can affect cellular activities. This article aimed to examine the effects of MAPC cells treatment on burn injury repair using a mouse model of partial thickness burn injury. The immunomodulatory effect of MAPC cells was investigated in vitro using a simultaneous T-cell proliferation assay. Partial thickness burns were created on the dorsal surface of mice and MAPC cells were administered via intradermal injection to the wound margins 24 h post-burn injury. The burn tissues were analysed macroscopically to determine wound area and histologically assessed to determine wound width and rate of re-epithelialisation. Immunohistochemistry and ELISA were employed to assess cell proliferation, inflammation and angiogenesis and collagen deposition in the burn area. MAPC cells inhibit the proliferation of stimulated T cells in culture. Burns intradermally injected with MAPC cells showed a significant reduction in the macroscopic wound area, histologic wound width and had an increased rate of re-epithelialisation. Immunohistochemistry and ELISA analysis of burn tissues showed dampened inflammation evidenced by a reduction in neutrophilic infiltration and modulation of inflammatory cytokines. Angiogenesis within the burn area was also improved in MAPC cell treated mice. However, no significant effect of MAPC cell treatment was observed on extracellular matrix production. Treatment of burns with MAPC cells improved burn injury repair with reduced time to healing, decreased inflammation and increased angiogenesis. These findings demonstrate the promising effects of MAPC cells on burn injury repair and suggest MAPC cells as a candidate source for clinical cell therapies.

Human fetal liver MSCs are more effective than adult bone marrow MSCs for their immunosuppressive, immunomodulatory, and Foxp3+ T reg induction capacity

BACKGROUND

Mesenchymal stem cells (MSCs) exhibit active abilities to suppress or modulate deleterious immune responses by various molecular mechanisms. These cells are the subject of major translational efforts as cellular therapies for immune-related diseases and transplantations. Plenty of preclinical studies and clinical trials employing MSCs have shown promising safety and efficacy outcomes and also shed light on the modifications in the frequency and function of regulatory T cells (T regs). Nevertheless, the mechanisms underlying these observations are not well known. Direct cell contact, soluble factor production, and turning antigen-presenting cells into tolerogenic phenotypes, have been proposed to be among possible mechanisms by which MSCs produce an immunomodulatory environment for T reg expansion and activity. We and others demonstrated that adult bone marrow (BM)-MSCs suppress adaptive immune responses directly by inhibiting the proliferation of CD4+ helper and CD8+ cytotoxic T cells but also indirectly through the induction of T regs. In parallel, we demonstrated that fetal liver (FL)-MSCs demonstrates much longer-lasting immunomodulatory properties compared to BM-MSCs, by inhibiting directly the proliferation and activation of CD4+ and CD8+ T cells. Therefore, we investigated if FL-MSCs exert their strong immunosuppressive effect also indirectly through induction of T regs.

METHODS

MSCs were obtained from FL and adult BM and characterized according to their surface antigen expression, their multilineage differentiation, and their proliferation potential. Using different in vitro combinations, we performed co-cultures of FL- or BM-MSCs and murine CD3+CD25-T cells to investigate immunosuppressive effects of MSCs on T cells and to quantify their capacity to induce functional T regs.

RESULTS

We demonstrated that although both types of MSC display similar cell surface phenotypic profile and differentiation capacity, FL-MSCs have significantly higher proliferative capacity and ability to suppress both CD4+ and CD8+ murine T cell proliferation and to modulate them towards less active phenotypes than adult BM-MSCs. Moreover, their substantial suppressive effect was associated with an outstanding increase of functional CD4+CD25+Foxp3+ T regs compared to BM-MSCs.

CONCLUSIONS

These results highlight the immunosuppressive activity of FL-MSCs on T cells and show for the first time that one of the main immunoregulatory mechanisms of FL-MSCs passes through active and functional T reg induction.