Are MSCs angiogenic cells? New insights on human nestin-positive bone marrow-derived multipotent cells

In vitro models of breast cancer bone metastasis: analyzing drug resistance through the lens of the microenvironment

Even though breast cancers usually have a good outcome compared to other tumors, the cancer can progress and create metastases in different parts of the organism, the bone being a predilection locus. These metastases are usually the cause of death, as they are mostly resistant to treatments. This resistance can be caused by intrinsic properties of the tumor, such as its heterogeneity, but it can also be due to the protective role of the microenvironment. By activating signaling pathways protecting cancer cells when exposed to chemotherapy, contributing to their ability to reach dormancy, or even reducing the amount of drug able to reach the metastases, among other mechanisms, the specificities of the bone tissue are being investigated as important players of drug resistance. To this date, most mechanisms of this resistance are yet to be discovered, and many researchers are implementing in vitro models to study the interaction between the tumor cells and their microenvironment. Here, we will review what is known about breast cancer drug resistance in bone metastasis due to the microenvironment and we will use those observations to highlight which features in vitro models should include to properly recapitulate these biological aspects in vitro. We will also detail which elements advanced in vitro models should implement in order to better recapitulate in vivo physiopathology and drug resistance.

Single-Cell and Spatial Transcriptomics Decodes Wharton's Jelly-Derived Mesenchymal Stem Cells Heterogeneity and a Subpopulation with Wound Repair Signatures

The highly heterogeneous characteristics of Wharton's jelly mesenchymal stem cells (WJ-MSCs) may be responsible for the poor clinical outcomes and poor reproducibility of treatments based on WJ-MSCs. Exploration of WJ-MSC heterogeneity with multimodal single-cell technologies will aid in establishing accurate MSC subtyping and developing screening protocols for dominant functional subpopulations. Here, the characteristics of WJ-MSCs are systematically analyzed by single cell and spatial transcriptome sequencing. Single-cell transcriptomics analysis identifies four WJ-MSC subpopulations, namely proliferative_MSCs, niche-supporting_MSCs, metabolism-related_MSCs and biofunctional-type_MSCs. Furthermore, the transcriptome, cellular heterogeneity, and cell-state trajectories of these subpopulations are characterized. Intriguingly, the biofunctional-type MSCs (marked by S100A9, CD29, and CD142) selected in this study exhibit promising wound repair properties in vitro and in vivo. Finally, by integrating omics data, it has been found that the S100A9⁺ CD29⁺ CD142⁺ subpopulation is more enriched in the fetal segment of the umbilical cord, suggesting that this subpopulation deriving from the fetal segment may have potential for developing into an ideal therapeutic agent for wound healing. Overall, the presented study comprehensively maps the heterogeneity of WJ-MSCs and provides an essential resource for future development of WJ-MSC-based drugs.

Mesenchymal Stromal Cell Therapy in Spinal Cord Injury: Mechanisms and Prospects

Spinal cord injury (SCI) often leads to severe motor, sensory, and autonomic dysfunction in patients and imposes a huge economic cost to individuals and society. Due to its complicated pathophysiological mechanism, there is not yet an optimal treatment available for SCI. Mesenchymal stromal cells (MSCs) are promising candidate transplant cells for use in SCI treatment. The multipotency of MSCs, as well as their rich trophic and immunomodulatory abilities through paracrine signaling, are expected to play an important role in neural repair. At the same time, the simplicity of MSCs isolation and culture and the bypassing of ethical barriers to stem cell transplantation make them more attractive. However, the MSCs concept has evolved in a specific research context to encompass different populations of cells with a variety of biological characteristics, and failure to understand this can undermine the quality of research in the field. Here, we review the development of the concept of MSCs in order to clarify misconceptions and discuss the controversy in MSCs neural differentiation. We also summarize a potential role of MSCs in SCI treatment, including their migration and trophic and immunomodulatory effects, and their ability to relieve neuropathic pain, and we also highlight directions for future research.

Single-cell Transcriptomic Analysis Reveals the Cellular Heterogeneity of Mesenchymal Stem Cells

Ex vivo-expanded mesenchymal stem cells (MSCs) have been demonstrated to be a heterogeneous mixture of cells exhibiting varying proliferative, multipotential, and immunomodulatory capacities. However, the exact characteristics of MSCs remain largely unknown. By single-cell RNA sequencing of 61,296 MSCs derived from bone marrow and Wharton’s jelly, we revealed five distinct subpopulations. The developmental trajectory of these five MSC subpopulations was mapped, revealing a differentiation path from stem-like active proliferative cells (APCs) to multipotent progenitor cells, followed by branching into two paths: 1) unipotent preadipocytes or 2) bipotent prechondro-osteoblasts that were subsequently differentiated into unipotent prechondrocytes. The stem-like APCs, expressing the perivascular mesodermal progenitor markers CSPG4/MCAM/NES, uniquely exhibited strong proliferation and stemness signatures. Remarkably, the prechondrocyte subpopulation specifically expressed immunomodulatory genes and was able to suppress activated CD3⁺ T cell proliferation in vitro, supporting the role of this population in immunoregulation. In summary, our analysis mapped the heterogeneous subpopulations of MSCs and identified two subpopulations with potential functions in self-renewal and immunoregulation. Our findings advance the definition of MSCs by identifying the specific functions of their heterogeneous cellular composition, allowing for more specific and effective MSC application through the purification of their functional subpopulations.

Diversity of Vascular Niches in Bones and Joints During Homeostasis, Ageing, and Diseases

The bones and joints in the skeletal system are composed of diverse cell types, including vascular niches, bone cells, connective tissue cells and mineral deposits and regulate whole-body homeostasis. The capacity of maintaining strength and generation of blood lineages lies within the skeletal system. Bone harbours blood and immune cells and their progenitors, and vascular cells provide several immune cell type niches. Blood vessels in bone are phenotypically and functionally diverse, with distinct capillary subtypes exhibiting striking changes with age. The bone vasculature has a special impact on osteogenesis and haematopoiesis, and dysregulation of the vasculature is associated with diverse blood and bone diseases. Ageing is associated with perturbed haematopoiesis, loss of osteogenesis, increased adipogenesis and diminished immune response and immune cell production. Endothelial and perivascular cells impact immune cell production and play a crucial role during inflammation. Here, we discuss normal and maladapted vascular niches in bone during development, homeostasis, ageing and bone diseases such as rheumatoid arthritis and osteoarthritis. Further, we discuss the role of vascular niches during bone malignancy.

Mesangiogenic Progenitor Cells Are Tissue Specific and Cannot Be Isolated From Adipose Tissue or Umbilical Cord Blood

Mesangiogenic progenitor cells (MPCs) have been isolated from human bone marrow (BM) mononuclear cells. They attracted particular attention for the ability to differentiate into exponentially growing mesenchymal stromal cells while retaining endothelial differentiative potential. MPC power to couple mesengenesis and angiogenesis highlights their tissue regenerative potential and clinical value, with particular reference to musculoskeletal tissues regeneration. BM and adipose tissue represent the most promising adult multipotent cell sources for bone and cartilage repair, although discussion is still open on their respective profitability. Culture determinants, as well as tissues of origin, appeared to strongly affect the regenerative potential of cell preparations, making reliable methods for cell isolation and growth a prerequisite to obtain cell-based medicinal products. Our group had established a definite consistent protocol for MPC culture, and here, we present data showing MPCs to be tissue specific.

Single-Cell Atlas Reveals Fatty Acid Metabolites Regulate the Functional Heterogeneity of Mesenchymal Stem Cells

Bone marrow mesenchymal stem cells (MSCs) are widely used clinically due to their versatile roles in multipotency, immunomodulation, and hematopoietic stem cell (HSC) niche function. However, cellular heterogeneity limits MSCs in the consistency and efficacy of their clinical applications. Metabolism regulates stem cell function and fate decision; however, how metabolites regulate the functional heterogeneity of MSCs remains elusive. Here, using single-cell RNA sequencing, we discovered that fatty acid pathways are involved in the regulation of lineage commitment and functional heterogeneity of MSCs. Functional assays showed that a fatty acid metabolite, butyrate, suppressed the self-renewal, adipogenesis, and osteogenesis differentiation potential of MSCs with increased apoptosis. Conversely, butyrate supplement significantly promoted HSC niche factor expression in MSCs, which suggests that butyrate supplement may provide a therapeutic approach to enhance their HSC niche function. Overall, our work demonstrates that metabolites are essential to regulate the functional heterogeneity of MSCs.

The Role of Angiogenesis-Inducing microRNAs in Vascular Tissue Engineering

Angiogenesis is an important process in tissue repair and regeneration as blood vessels are integral to supply nutrients to a functioning tissue. In this review, the application of microRNAs (miRNAs) or anti-miRNAs that can induce angiogenesis to aid in blood vessel formation for vascular tissue engineering in ischemic diseases such as peripheral arterial disease and stroke, cardiac diseases, and skin and bone tissue engineering is discussed. Endothelial cells (ECs) form the endothelium of the blood vessel and are recognized as the primary cell type that drives angiogenesis and studied in the applications that were reviewed. Besides ECs, mesenchymal stem cells can also play a pivotal role in these applications, specifically, by secreting growth factors or cytokines for paracrine signaling and/or as constituent cells in the new blood vessel formed. In addition to delivering miRNAs or cells transfected/transduced with miRNAs for angiogenesis and vascular tissue engineering, the utilization of extracellular vesicles (EVs), such as exosomes, microvesicles, and EVs collectively, has been more recently explored. Proangiogenic miRNAs and anti-miRNAs contribute to angiogenesis by targeting the 3'-untranslated region of targets to upregulate proangiogenic factors such as vascular endothelial growth factor (VEGF), basic fibroblast growth factor, and hypoxia-inducible factor-1 and increase the transduction of VEGF signaling through the PI3K/AKT and Ras/Raf/MEK/ERK signaling pathways such as phosphatase and tensin homolog or regulating the signaling of other pathways important for angiogenesis such as the Notch signaling pathway and the pathway to produce nitric oxide. In conclusion, angiogenesis-inducing miRNAs and anti-miRNAs are promising tools for vascular tissue engineering for several applications; however, future work should emphasize optimizing the delivery and usage of these therapies as miRNAs can also be associated with the negative implications of cancer.

Combinational therapy with antibiotics and antibiotic-loaded adipose-derived stem cells reduce abscess formation in implant-related infection in rats

Implant-related infection is difficult to treat without extended antibiotic courses. However, the long-term use of antibiotics has led to the development of multidrug- and methicillin-resistant Staphylococcusaureus. Thus, alternatives to conventional antibiotic therapy are needed. Recently, mesenchymal stem cells have been shown to have antimicrobial properties. This study aimed to evaluate the antimicrobial activity and therapeutic effect of local treatment with antibiotic-loaded adipose-derived stem cells (ADSCs) plus an antibiotic in a rat implant-associated infection model. Liquid chromatography/tandem mass spectrometry revealed that ADSCs cultured in the presence of ciprofloxacin for 24 h showed time-dependent antibiotic loading. Next, we studied the therapeutic effects of ADSCs and ciprofloxacin alone or in combination in an implant-related infection rat model. The therapeutic effects of ADSCs plus antibiotics, antibiotics, and ADSCs were compared with no treatment as a control. Rats treated with ADSCs plus ciprofloxacin had the lowest modified osteomyelitis scores, abscess formation, and bacterial burden on the implant among all groups (P < 0.05). Thus, local treatment with ADSCs plus an antibiotic has an antimicrobial effect in implant-related infection and decrease abscess formation. Thus, our findings indicate that local administration of ADSCs with antibiotics represents a novel treatment strategy for implant-associated osteomyelitis.

Ciclopirox olamine promotes the angiogenic response of endothelial cells and mesenchymal stem cells

BACKGROUND

Prolyl hydroxylase inhibitors (PHIs) are promising compounds to promote angiogenesis by stabilizing hypoxia-inducible factor-1α (HIF-1α), a master regulator of angiogenesis. Increased HIF-1α presence induces expression of proangiogenic genes such as vascular endothelial growth factor (VEGF).

OBJECTIVE

We investigated the pharmacological induction of hypoxia via the PHI ciclopirox olamine (CPX) as angiogenesis strategy on human dermal microvascular endothelial cell (hd-mvEC) spheroids directly and indirectly via activating human mesenchymal stem cells (hMSCs).

METHODS

HMSCs were isolated from bone marrow and hd-mvECs from foreskin biopsies. MSC-conditioned medium after CPX stimulation (MSC-CM CPX) was analyzed by VEGF ELISA and Proteome Profiler™ Human Angiogenesis Array. Direct stimulation with CPX and indirect stimulation via MSC-CM CPX were compared in sprouting assays of hd-mvEC spheroids.

RESULTS

Direct stimulation with CPX significantly increased sprouting of hd-mvEC spheroids. MSC-CM CPX also induced sprouting from hd-mvEC spheroids, which was mediated by angiogenic VEGF and other proangiogenic factors that had been produced by stimulated hMSCs.

CONCLUSIONS

The stimulation with CPX increased the proangiogenic response of hd-mvECs and hMSCs. The direct stimulation of hd-mvECs with CPX has the potential to replace external VEGF supplementation. Thus, CPX can induce angiogenesis in ECs even in the absence of auxiliary cells demonstrating a promising proangiogenic approach.

Placental mesenchymal stromal cells as an alternative tool for therapeutic angiogenesis

Dysregulation of angiogenesis is a phenomenon observed in several disorders such as diabetic foot, critical limb ischemia and myocardial infarction. Mesenchymal stromal cells (MSCs) possess angiogenic potential and have recently emerged as a powerful tool for cell therapy to promote angiogenesis. Although bone marrow-derived MSCs are the primary cell of choice, obtaining them has become a challenge. The placenta has become a popular alternative as it is a highly vascular organ, easily available and ethically more favorable with a rich supply of MSCs. Comparatively, placenta-derived MSCs (PMSCs) are clinically promising due to their proliferative, migratory, clonogenic and immunomodulatory properties. PMSCs release a plethora of cytokines and chemokines key to angiogenic signaling and facilitate the possibility of delivering PMSC-derived exosomes as a targeted therapy to promote angiogenesis. However, there still remains the challenge of heterogeneity in the isolated populations, questions on the maternal or fetal origin of these cells and the diversity in previously reported isolation and culture conditions. Nonetheless, the growing rate of clinical trials using PMSCs clearly indicates a shift in favor of PMSCs. The overall aim of the review is to highlight the importance of this rather poorly understood cell type and emphasize the need for further investigations into their angiogenic potential as an alternative source for therapeutic angiogenesis.

Mesangiogenic progenitor cells are forced toward the angiogenic fate, in multiple myeloma

Multiple myeloma (MM) progresses mainly in the bone marrow where the involvement of a specific microenvironment plays a critical role in maintaining plasma cell growth, spread, and survival. In active disease, the switch from a pre-vascular/non-active phase to a vascular phase is coupled with the impairment of bone turnover. Previously, we have isolated Mesangiogenic Progenitor Cells (MPCs), a bone marrow population that showed mesengenic and angiogenic potential, both in vitro and in vivo. MPC differentiation into musculoskeletal tissue and their ability of sprouting angiogenesis are mutually exclusive, suggesting a role in the imbalancing of the microenvironment in multiple myeloma.

MPCs from 32 bone marrow samples of multiple myeloma and 23 non-hematological patients were compared in terms of frequency, phenotype, mesengenic/angiogenic potential, and gene expression profile. Defective osteogenesis was recorded for MM-derived MPCs that showed longer angiogenic sprouting distances respect to non-hematological MPCs, retaining this capability after mesengenic induction. This altered MPCs differentiation potential was not detected in asymptomatic myelomatous disease.

These in vitro experiments are suggestive of a forced angiogenic fate in MPCs isolated from MM patients, which also showed increased sprouting activity. Taking together our results suggest a possible role of these cells in the “angiogenic switch” in the MM micro-environment.

The Transplantation of hBM-MSCs Increases Bone Neo-Formation and Preserves Hearing Function in the Treatment of Temporal Bone Defects - on the Experience of Two Month Follow Up

Temporal bone reconstruction is a persisting problem following middle ear cholesteatoma surgery. Seeking to advance the clinical transfer of stem cell therapy we attempted the reconstruction of temporal bone using a composite bioartificial graft based on a hydroxyapatite bone scaffold combined with human bone marrow-derived mesenchymal stromal cells (hBM-MSCs). The aim of this study was to evaluate the effect of the combined biomaterial on the healing of postoperative temporal bone defects and the preservation of physiological hearing functions in a guinea pig model. The treatment's effect could be observed at 1 and 2 months after implantation of the biomaterial, as opposed to the control group. The clinical evaluation of our results included animal survival, clinical signs of an inflammatory response, and exploration of the tympanic bulla. Osteogenesis, angiogenesis, and inflammation were evaluated by histopathological analyses, whereas hBM-MSCs survival was evaluated by immunofluorescence assays. Hearing capacity was evaluated by objective audiometric methods, i.e. auditory brainstem responses and otoacoustic emission. Our study shows that hBM-MSCs, in combination with hydroxyapatite scaffolds, improves the repair of bone defects providing a safe and effective alternative in their treatment following middle ear surgery due to cholesteatoma.

The Pluripotent Microvascular Pericytes Are the Adult Stem Cells Even in the Testis

The pericytes of the testis are part of the omnipresent population of pericytes in the vertebrate body and are the only true pluripotent adult stem cells able to produce structures typical for the tree primitive germ layers: ectoderm, mesoderm, and endoderm. They originate very early in the embryogenesis from the pluripotent epiblast. The pericytes become disseminated through the whole vertebrate organism by the growing and differentiating blood vessels where they remain in specialized periendothelial vascular niches as resting pluripotent adult stem cells for tissue generation, maintenance, repair, and regeneration. The pericytes are also the ancestors of the perivascular multipotent stromal cells (MSCs). The variable appearance of the pericytes and their progeny reflects the plasticity under the influence of their own epigenetic and the local environmental factors of the host organ. In the testis the pericytes are the ancestors of the neuroendocrine Leydig cells. After activation the pericytes start to proliferate, migrate, and build transit-amplifying cells that transdifferentiate into multipotent stromal cells. These represent progenitors for a number of different cell types in an organ. Finally, it becomes evident that the pericytes are a brilliant achievement of the biological nature aiming to supply every organ with an omnipresent population of pluripotent adult stem cells. Their fascinating features are prerequisites for future therapy concepts supporting cell systems of organs.

Endowing iPSC-Derived MSCs with Angiogenic and Keratinogenic Differentiation Potential: A Promising Cell Source for Skin Tissue Engineering

Induced pluripotent stem cells (iPSC) hold tremendous potential for personalized cell-based therapy for skin regeneration. Aiming to establish human iPSCs as a potential cell source for skin tissue engineering, we expect to obtain an epidermal-like cell line with angiogenic and keratinogenic differentiation potential via inducing iPSC-derived mesenchymal stem cells (iPSC-MSCs) with basic fibroblast growth factor (bFGF) and/or keratinocyte growth factor (KGF). The results show that iPSC-MSCs were successfully induced with a positive FGFR/KGFR expression on the cell surface. BFGF/KGF induction could significantly increase the expression of vascularization marker CD31 and keratinization marker CK10, respectively, while when combined together, although CD31 and CK10 were still positively expressed, their expressions were lower than that of the single induction group, suggesting that the effects of the two growth factors interfered with each other. This cell line with angiogenic and keratinogenic differentiation potential provides a promising new source of cells for the construction of well vascularized and keratinized tissue engineered skin, furthermore establishing an effective strategy for iPSC-based therapy in skin tissue engineering.

Pooled human serum: A new culture supplement for bioreactor-based cell therapies. Preliminary results

BACKGROUND

Bone Marrow MSCs are an appealing source for several cell-based therapies. Many bioreactors, as the Quantum Cell Expansion System, have been developed to generate a large number of MSCs under Good Manufacturing Practice conditions by using Human Platelet Lysate (HPL). Previously we isolated in the human bone marrow a novel cell population, named Mesodermal Progenitor Cells (MPCs), which we identified as precursors of MSCs. MPCs could represent an important cell source for regenerative medicine applications. As HPL gives rise to a homogeneus MSC population, limiting the harvesting of other cell types, in this study we investigated the efficacy of pooled human AB serum (ABS) to provide clinically relevant numbers of both MSCs and MPCs for regenerative medicine applications by using the Quantum System.

METHODS

Bone marrow aspirates were obtained from healthy adult individuals undergoing routine total hip replacement surgery and used to generate primary cultures in the bioreactor. HPL and ABS were tested as supplements to culture medium. Morphological observations, cytofluorimetric analysis, lactate and glucose level assessment were performed.

RESULTS

ABS gave rise to both heterogeneous MSC and MPC population. About 95% of cells cultured in HPL showed a fibroblast-like morphology and typical mesenchymal surface markers, but MPCs were scarcely represented.

DISCUSSION

The use of ABS appeared to sustain a large scale MSC production, as well as the recovery of a subset of MPCs, and resulted a suitable alternative to HPL in the cell generation based on the Quantum System.

The Effects of Administrated Sildenafil Citrate on Uterine Luminal Epithelium Height Associated with Ovarian Angiogenesis: An Experimental Animal Study

Background

Ovarian angiogenesis (OA) remains in lifetime and normal ovarian function depends to this continual remodeling of a complex vascular system. Endometrial thickness (ET) is one of the strongest predictors of successful implantation and pregnancy. Appropriate OA effects on ET by facilitating of ovarian hormone delivery.

Materials and Methods

Thirty adult female mice and twenty adult male mice were purchased. The female mice were divided into three groups: (1) control group without any intervention (n = 10), (2) gonadotropin group: receiving human menopausal gonadotropin (HMG) and human chorionic gonadotropin (n = 10), and (3) gonadotropin and sildenafil citrate (SC) group: receiving HMG and SC administration (n = 10). After mating, animals were deeply anesthetized, and the ovary and uterus was rapidly removed for histology and immunohistochemistry process.

Results

Four days after ovarian induction, all three layers of the uterus with specified thickness can be clearly seen. The heights of endometrial epithelial cells in gonadotropin group were not significantly different than those in control group. In gonadotropin and SC group, heights of the cells were significantly (P < 0.05) shorter than control and gonadotropin groups. ETs in all groups were not significantly deferent from each other (P > 0.05 each). Our results of immunohistochemistry survey for ovarian CD31 demonstrated that administrated SC increased OA but not significantly (P > 0.05 each).

Conclusion

It may finally conclude that administration of SC does not cause notable alterations in OA and ET; although for realistic decision about the SC effects on aforementioned parameters, more molecular investigations and longer drug consumption period are necessary.

Nigral dopaminergic neuron replenishment in adult mice through VE-cadherin-expressing neural progenitor cells

The function of dopaminergic neurons in the substantia nigra is of central importance to the coordination of movement by the brain's basal ganglia circuitry. This is evidenced by the loss of these neurons, resulting in the cardinal motor deficits associated with Parkinson's disease. In order to fully understand the physiology of these key neurons and develop potential therapies for their loss, it is essential to determine if and how dopaminergic neurons are replenished in the adult brain. Recent work has presented evidence for adult neurogenesis of these neurons by Nestin⁺/Sox2^– neural progenitor cells. We sought to further validate this finding and explore a potential atypical origin for these progenitor cells. Since neural progenitor cells have a proximal association with the vasculature of the brain and subsets of endothelial cells are Nestin⁺, we hypothesized that dopaminergic neural progenitors might share a common cell lineage. Therefore, we employed a VE-cadherin promoter-driven CRE^ERT2:TH^lox/TH^lox transgenic mouse line to ablate the tyrosine hydroxylase gene from endothelial cells in adult animals. After 26 weeks, but not 13 weeks, following the genetic blockade of tyrosine hydroxylase expression in VE-cadherin⁺ cells, we observed a significant reduction in tyrosine hydroxylase⁺ neurons in the substantia nigra. The results from this genetic lineage tracing study suggest that dopaminergic neurons are replenished in adult mice by a VE-cadherin⁺ progenitor cell population potentially arising from an endothelial lineage.

Considerations on the harvesting site and donor derivation for mesenchymal stem cells-based strategies for diabetes

Mesenchymal Stem Cells (MSCs) possess important characteristics that could be exploited in therapeutic strategies for Type 1 Diabetes (T1D) and for certain complications of Type 2 Diabetes (T2D). MSCs can inhibit autoimmune, alloimmune and inflammatory processes. Moreover, they can promote the function of endogenous and transplanted pancreatic islets. Furthermore, they can stimulate angiogenesis. MSC functions are largely mediated by their secretome, which includes growth factors, exosomes, and other extracellular vesicles. MSCs have shown a good safety profile in clinical trials. MSC-derived exosomes are emerging as an alternative to the transplantation of live MSCs. MSCs harvested from different anatomical locations (e.g. bone marrow, umbilical cord, placenta, adipose tissue, and pancreas) have shown differences in gene expression profiles and function. Data from clinical trials suggest that umbilical cord-derived MSCs could be superior to bone marrow-derived MSCs for the treatment of T1D. Autologous MSCs from diabetic patients may present abnormal functions. BM-MSCs from T1D patients exhibit gene expression differences that may impact in vivo function. BM-MSCs from T2D patients seem to be significantly impaired due to the T2D diabetic milieu. In this review, we highlight how the harvesting site and donor derivation can affect the efficacy of MSC-based treatments for T1D and T2D.

Stem cell manipulation, gene therapy and the risk of cancer stem cell emergence

Stem cells (SCs) have been extensively studied in the context of regenerative medicine. Human hematopoietic stem cell (HSC)-based therapies have been applied to treat leukemic patients for decades. Handling of mesenchymal stem cells (MSCs) has also raised hopes and concerns in the field of tissue engineering. Lately, discovery of cell reprogramming by Yamanaka's team has profoundly modified research strategies and approaches in this domain. As we gain further insight into cell fate mechanisms and identification of key actors and parameters, this also raises issues as to the manipulation of SCs. These include the engraftment of manipulated cells and the potential predisposition of those cells to develop cancer. As a unique and pioneer model, the use of HSCs to provide new perspectives in the field of regenerative and curative medicine will be reviewed. We will also discuss the potential use of various SCs from embryonic to adult stem cells (ASCs), including induced pluripotent stem cells (iPSCs) as well as MSCs. Furthermore, to sensitize clinicians and researchers to unresolved issues in these new therapeutic approaches, we will highlight the risks associated with the manipulation of human SCs from embryonic or adult origins for each strategy presented.

Human adult mesangiogenic progenitor cells reveal an early angiogenic potential, which is lost after mesengenic differentiation

Background

Mesangiogenic progenitor cells (MPCs) have shown the ability to differentiate in-vitro toward mesenchymal stromal cells (MSCs) as well as angiogenic potential. MPCs have so far been described in detail as progenitors of the mesodermal lineage and appear to be of great significance in tissue regeneration and in hemopoietic niche regulation. On the contrary, information regarding the MPC angiogenic process is still incomplete and requires further clarification. In particular, genuine MPC angiogenic potential should be confirmed in-vivo.

Methods

In the present article, markers and functions associated with angiogenic cells have been dissected. MPCs freshly isolated from human bone marrow have been induced to differentiate into exponentially growing MSCs (P2-MSCs). Cells have been characterized and angiogenesis-related gene expression was evaluated before and after mesengenic differentiation. Moreover, angiogenic potential has been tested by in-vitro and in-vivo functional assays.

Results

MPCs showed a distinctive gene expression profile, acetylated-low density lipoprotein uptake, and transendothelial migration capacity. However, mature endothelial markers and functions of endothelial cells, including the ability to form new capillaries, were absent, thus suggesting MPCs to be very immature endothelial progenitors. MPCs showed marked 3D spheroid sprouting activating the related molecular machinery, a clear in-vitro indication of early angiogenesis. Indeed, MPCs applied to chicken chorioallantoic membrane induced and participated in neovessel formation. All of these features were lost in mesengenic terminally differentiated P2-MSCs, showing definite separation of the two differentiation lineages.

Conclusion

Our results confirm the bona-fide angiogenic potential of MPCs and suggest that the high variability reported for MSC cultures, responsible for the controversies regarding MSC angiogenic potential, could be correlated to variable percentages of co-isolated MPCs in the different culture conditions so far used.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-017-0562-x) contains supplementary material, which is available to authorized users.

Antimicrobial Activity of Mesenchymal Stem Cells: Current Status and New Perspectives of Antimicrobial Peptide-Based Therapies

While mesenchymal stem cells (MSCs)-based therapy appears to be promising, there are concerns regarding possible side effects related to the unwanted suppression of antimicrobial immunity leading to an increased risk of infection. Conversely, recent data show that MSCs exert strong antimicrobial effects through indirect and direct mechanisms, partially mediated by the secretion of antimicrobial peptides and proteins (AMPs). In fact, MSCs have been reported to increase bacterial clearance in preclinical models of sepsis, acute respiratory distress syndrome, and cystic fibrosis-related infections. This article reviews the current evidence regarding the direct antimicrobial effector function of MSCs, focusing mainly on the role of MSCs-derived AMPs. The strategies that might modulate the expression and secretion of these AMPs, leading to enhanced antimicrobial effect, are highlighted. Furthermore, studies evaluating the presence of AMPs in the cargo of extracellular vesicles (EVs) are underlined as perspective opportunities to develop new drug delivery tools. The antimicrobial potential of MSCs-derived EVs can also be heightened through cell conditioning and/or drug loading. Finally, improving the pharmacokinetics and delivery, in addition to deciphering the multi-target drug status of AMPs, should synergistically lead to key advances against infections caused by drug-resistant strains.

Antimicrobial Activity of Mesenchymal Stem Cells: Current Status and New Perspectives of Antimicrobial Peptide-Based Therapies

While mesenchymal stem cells (MSCs)-based therapy appears to be promising, there are concerns regarding possible side effects related to the unwanted suppression of antimicrobial immunity leading to an increased risk of infection. Conversely, recent data show that MSCs exert strong antimicrobial effects through indirect and direct mechanisms, partially mediated by the secretion of antimicrobial peptides and proteins (AMPs). In fact, MSCs have been reported to increase bacterial clearance in preclinical models of sepsis, acute respiratory distress syndrome, and cystic fibrosis-related infections. This article reviews the current evidence regarding the direct antimicrobial effector function of MSCs, focusing mainly on the role of MSCs-derived AMPs. The strategies that might modulate the expression and secretion of these AMPs, leading to enhanced antimicrobial effect, are highlighted. Furthermore, studies evaluating the presence of AMPs in the cargo of extracellular vesicles (EVs) are underlined as perspective opportunities to develop new drug delivery tools. The antimicrobial potential of MSCs-derived EVs can also be heightened through cell conditioning and/or drug loading. Finally, improving the pharmacokinetics and delivery, in addition to deciphering the multi-target drug status of AMPs, should synergistically lead to key advances against infections caused by drug-resistant strains.

Supportive angiogenic and osteogenic differentiation of mesenchymal stromal cells and endothelial cells in monolayer and co-cultures

Sites of implantation with compromised biology may be unable to achieve the required level of angiogenic and osteogenic regeneration. The specific function and contribution of different cell types to the formation of prevascularized, osteogenic networks in co-culture remains unclear. To determine how bone marrow-derived mesenchymal stromal cells (BMSCs) and endothelial cells (ECs) contribute to cellular proangiogenic differentiation, we analysed the differentiation of BMSCs and ECs in standardized monolayer, Transwell and co-cultures. BMSCs were derived from the iliac bone marrow of five patients, characterized and differentiated in standardized monolayers, permeable Transwells and co-cultures with human umbilical vein ECs (HUVECs). The expression levels of CD31, von Willebrand factor, osteonectin (ON) and Runx2 were assessed by quantitative reverse transcriptase polymerase chain reaction. The protein expression of alkaline phosphatase, ON and CD31 was demonstrated via histochemical and immunofluorescence analysis. The results showed that BMSCs and HUVECs were able to retain their lineage-specific osteogenic and angiogenic differentiation in direct and indirect co-cultures. In addition, BMSCs demonstrated a supportive expression of angiogenic function in co-culture, while HUVEC was able to improve the expression of osteogenic marker molecules in BMSCs.

Growth Factor Content in Human Sera Affects the Isolation of Mesangiogenic Progenitor Cells (MPCs) from Human Bone Marrow

Mesangiogenic Progenitor Cells (MPCs) are human bone marrow-derived multipotent cells, isolated in vitro under selective culture conditions and shown to retain both mesengenic and angiogenic potential. MPCs also co-isolated with multipotent stromal cells (MSCs) when bone marrow primary cultures were set up for clinical applications, using human serum (HS) in place of fetal bovine serum (FBS). MPC culture purity (over 95%) is strictly dependent on HS supplementation with significant batch-to-batch variability. In the present paper we screened different sources of commercially available pooled human AB type serum (PhABS) for their ability to promote MPC production under selective culture conditions. As the majority of "contaminating" cells in MPC cultures were represented by MSC-like cells, we hypothesized a role by differentiating agents present in the sera. Therefore, we tested a number of growth factors (hGF) and found that higher concentrations of FGF-2, EGF, PDGF-AB, and VEGF-A as well as lower concentration of IGF-1 give sub-optimal MPC recovery. Gene expression analysis of hGF receptors was also carried out both in MSCs and MPCs, suggesting that FGF-2, EGF, and PDGF-AB could act promoting MSC proliferation, while VEGF-A contribute to MSC-like cell contamination, triggering MPC differentiation. Here we demonstrated that managing hGF contents, together with applying specific receptors inhibitors (Erlotinib-HCl and Nintedanib), could significantly mitigate the batch-to-batch variability related to serum supplementation. These data represent a fundamental milestone in view of manufacturing MPC-based medicinal products.

Pulp Vascularization during Tooth Development, Regeneration, and Therapy

The pulp is a highly vascularized tissue situated in an inextensible environment surrounded by rigid dentin walls, with the apical foramina being the only access. The pulp vascular system is not only responsible for nutrient supply and waste removal but also contributes actively to the pulp inflammatory response and subsequent regeneration. This review discusses the underlying mechanisms of pulp vascularization during tooth development, regeneration, and therapeutic procedures, such as tissue engineering and tooth transplantation. Whereas the pulp vascular system is established by vasculogenesis during embryonic development, sprouting angiogenesis is the predominant process during regeneration and therapeutic processes. Hypoxia can be considered a common driving force. Dental pulp cells under hypoxic stress release proangiogenic factors, with vascular endothelial growth factor being one of the most potent. The benefit of exogenous vascular endothelial growth factor application in tissue engineering has been well demonstrated. Interestingly, dental pulp stem cells have an important role in pulp revascularization. Indeed, recent studies show that dental pulp stem cell secretome possesses angiogenic potential that actively contributes to the angiogenic process by guiding endothelial cells and even by differentiating themselves into the endothelial lineage. Although considerable insight has been obtained in the processes underlying pulp vascularization, many questions remain relating to the signaling pathways, timing, and influence of various stress conditions.

Type 2 diabetes alters mesenchymal stem cell secretome composition and angiogenic properties

This study aimed at characterizing the impact of type 2 diabetes mellitus (T2DM) on the bone marrow mesenchymal stem cell (BMMSC) secretome and angiogenic properties. BMMSCs from Zucker diabetic fatty rats (ZDF) (a T2DM model) and Zucker LEAN littermates (control) were cultured. The supernatant conditioned media (CM) from BMMSCs of diabetic and control rats were collected and analysed. Compared to results obtained using CM from LEAN‐BMMSCs, the bioactive content of ZDF‐BMMSC CM (i) differently affects endothelial cell (HUVEC) functions in vitro by inducing increased (3.5‐fold; P < 0.01) formation of tubule‐like structures and migration of these cells (3‐fold; P < 0.001), as well as promotes improved vascular formation in vivo, and (ii) contains different levels of angiogenic factors (e.g. IGF1) and mediators, such as OSTP, CATD, FMOD LTBP1 and LTBP2, which are involved in angiogenesis and/or extracellular matrix composition. Addition of neutralizing antibodies against IGF‐1, LTBP1 or LTBP2 in the CM of BMMSCs from diabetic rats decreased its stimulatory effect on HUVEC migration by approximately 60%, 40% or 40%, respectively. These results demonstrate that BMMSCs from T2DM rats have a unique secretome with distinct angiogenic properties and provide new insights into the role of BMMSCs in aberrant angiogenesis in the diabetic milieu.

Are nestin-positive mesenchymal stromal cells a better source of cells for CNS repair?

In recent years there has been a great deal of research within the stem cell field which has led to the definition and classification of a range of stem cells from a plethora of tissues and organs. Stem cells, by classification, are considered to be pluri- or multipotent and have both self-renewal and multi-differentiation capabilities. Presently there is a great deal of interest in stem cells isolated from both embryonic and adult tissues in the hope they hold the therapeutic key to restoring or treating damaged cells in a number of central nervous system (CNS) disorders. In this review we will discuss the role of mesenchymal stromal cells (MSCs) isolated from human olfactory mucosa, with particular emphasis on their potential role as a candidate for transplant mediated repair in the CNS. Since nestin expression defines the entire population of olfactory mucosal derived MSCs, we will compare these cells to a population of neural crest derived nestin positive population of bone marrow-MSCs.

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Human olfactory mucosa is a new source of mesenchymal stromal cells (MSCs).

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Some bone marrow MSCs are nestin-positive, neural crest derived and regulate hematopoietic stem cell activation.

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Human olfactory mucosa contains a population of nestin-positive MSCs that secrete CXCL12 and may have promote CNS repair.

Human Multipotent Mesenchymal Stromal Cells in the Treatment of Postoperative Temporal Bone Defect: An Animal Model

Canal wall down mastoidectomy is one of the most effective treatments for cholesteatoma. However, it results in anatomical changes in the external and middle ear with a negative impact on the patient's quality of life. To provide complete closure of the mastoid cavity and normalize the anatomy of the middle and external ear, we used human multipotent mesenchymal stromal cells (hMSCs), GMP grade, in a guinea pig model. A method for preparing a biomaterial composed of hMSCs, hydroxyapatite, and tissue glue was developed. Animals from the treated group were implanted with biomaterial composed of hydroxyapatite and hMSCs, while animals in the control group received hydroxyapatite alone. When compared to controls, the group implanted with hMSCs showed a significantly higher ratio of new bone formation ( p = 0.00174), as well as a significantly higher volume percentage of new immature bone ( p = 0.00166). Our results proved a beneficial effect of hMSCs on temporal bone formation and provided a promising tool to improve the quality of life of patients after canal wall down mastoidectomy by hMSC implantation.

Study of the involvement of allogeneic MSCs in bone formation using the model of transgenic mice

Mesenchymal stem cells (MSCs) are thought to be the most attractive type of cells for bone repair. However, much still remains unknown about MSCs and needs to be clarified before this treatment can be widely applied in the clinical practice. The purpose of this study was to establish the involvement of allogeneic MSCs in the bone formation in vivo, using a model of transgenic mice and genetically labeled cells. Polylactide scaffolds with hydroxyapatite obtained by surface selective laser sintering were used. The scaffolds were sterilized and individually seeded with MSCs from the bone marrow of 5-week-old GFP(+) transgenic C57/Bl6 or GFP(-)C57/Bl6 mice. 4-mm-diameter critical-size defects were created on the calvarial bone of mice using a dental bur. Immediately after the generation of the cranial bone defects, the scaffolds with or without seeded cells were implanted into the injury sites. The cranial bones were harvested at either 6 or 12 weeks after the implantation. GFP(+) transgenic mice having scaffolds with unlabeled MSCs were used for the observation of the host cell migration into the scaffold. GFP(-) mice having scaffolds with GFP(+)MSCs were used to assess the functioning of the seeded MSCs. The obtained data demonstrated that allogeneic MSCs were found on the scaffolds 6 and 12 weeks post-implantation. By week 12, a newly formed bone tissue from the seeded cells was observed, without an osteogenic pre-differentiation. The host cells did not appear, and the control scaffolds without seeded cells remained empty. Besides, a possibility of vessel formation from seeded MSCs was shown, without a preliminary cell cultivation under controlled conditions.

Mesangiogenic Progenitor Cells Derived from One Novel CD64(bright)CD31(bright)CD14(neg) Population in Human Adult Bone Marrow

Mesenchymal stromal cells (MSCs) have been the object of extensive research for decades, due to their intrinsic clinical value. Nonetheless, the unambiguous identification of a unique in vivo MSC progenitor is still lacking, and the hypothesis that these multipotent cells could possibly arise from different in vivo precursors has been gaining consensus in the last years. We identified a novel multipotent cell population in human adult bone marrow that we first named Mesodermal Progenitor Cells (MPCs) for the ability to differentiate toward the mesenchymal lineage, while still retaining angiogenic potential. Despite extensive characterization, MPCs positioning within the differentiation pathway and whether they can be ascribed as possible distinctive progenitor of the MSC lineage is still unclear. In this study, we describe the ex vivo isolation of one novel bone marrow subpopulation (Pop#8) with the ability to generate MPCs. Multicolor flow cytometry in combination with either fluorescence-activated cell sorting or magnetic-activated cell sorting were applied to characterize Pop#8 as CD64(bright)CD31(bright)CD14(neg). We defined Pop#8 properties in culture, including the potential of Pop#8-derived MPCs to differentiate into MSCs. Gene expression data were suggestive of Pop#8 in vivo involvement in hematopoietic stem cell niche constitution/maintenance. Pop#8 resulted over three logs more frequent than other putative MSC progenitors, corroborating the idea that most of the controversies regarding culture-expanded MSCs could be the consequence of different culture conditions that select or promote particular subpopulations of precursors.

Harnessing the Angiogenic Potential of Stem Cell-Derived Exosomes for Vascular Regeneration

Mesenchymal stem cells (MSCs) are known to display important regenerative properties through the secretion of proangiogenic factors. Recent evidence pointed at the key role played by exosomes released from MSCs in this paracrine mechanism. Exosomes are key mediators of intercellular communication and contain a cargo that includes a modifiable content of microRNA (miRNA), mRNA, and proteins. Since the biogenesis of the MSCs-derived exosomes is regulated by the cross talk between MSCs and their niche, the content of the exosomes and consequently their biological function are dependent on the cell of origin and the physiologic or pathologic status of their microenvironment. Recent preclinical studies revealed that MSCs-derived exosomes have a critical implication in the angiogenic process since the use of exosomes-depleted conditioned medium impaired the MSCs angiogenesis response. In this review, we discuss the current knowledge related to the angiogenic potential of MSCs-exosomes and methods to enhance their biological activities for improved vascular regeneration. The current gain of insight in exosomes studies highlights the power of combining cell based therapies and their secreted products in therapeutic angiogenesis.

Role of VEGF-A in angiogenesis promoted by umbilical cord-derived mesenchymal stromal/stem cells: in vitro study

BACKGROUND

Mesenchymal stromal/stem cells derived from human umbilical cord (UC-MSCs) uniquely combine properties of embryonic and postnatal MSCs and may be the most acceptable, safe, and effective source for allogeneic cell therapy e.g. for therapeutic angiogenesis. In this report we describe pro-angiogenic properties of UC-MSCs as manifested in vitro.

METHODS

UC-MSCs were isolated from human Wharton's jelly by enzymatic digestion. Presence of soluble forms of VEGF-A in UC-MSC-conditioned media was measured by ELISA. Effects of the conditioned media on human umbilical vein-derived endothelial EA.hy926 cells proliferation were measured by MTT-assay; changes in cell motility and directed migration were assessed by scratch wound healing and transwell chamber migration assays. Angiogenesis was modeled in vitro as tube formation on basement membrane matrix. Progressive differentiation of MSCs to endothelioid progeny was assessed by CD31 immunostaining.

RESULTS

Although no detectable quantities of soluble VEGF-A were produced by UC-MSCs, the culture medium, conditioned by the UC-MSCs, effectively stimulated proliferation, motility, and directed migration of EA.hy926 cells. In 2D culture, UC-MSCs were able to acquire CD31(+) endothelial cell-like phenotype when stimulated by EA.hy926-conditioned media supplemented with VEGF-A165. UC-MSCs were capable of forming unstable 2D tubular networks either by themselves or in combinations with EA.hy926 cells. Active spontaneous sprouting from cell clusters, resulting from disassembling of such networks, was observed only in the mixed cultures, not in pure UC-MSC cultures. In 3D mode of sprouting experimentation, structural support of newly formed capillary-like structures was provided by UC-MSCs that acquired the CD31(+) phenotype in the absence of exogenous VEGF-A.

CONCLUSION

These data suggest that a VEGF-A-independent paracrine mechanism and at least partially VEGF-A-independent differentiation mechanism are involved in the pro-angiogenic activity of UC-MSCs.

Adipose-derived stem cell differentiation as a basic tool for vascularized adipose tissue engineering

The development of in vitro adipose tissue constructs is highly desired to cope with the increased demand for substitutes to replace damaged soft tissue after high graded burns, deformities or tumor removal. To achieve clinically relevant dimensions, vascularization of soft tissue constructs becomes inevitable but still poses a challenge. Adipose-derived stem cells (ASCs) represent a promising cell source for the setup of vascularized fatty tissue constructs as they can be differentiated into adipocytes and endothelial cells in vitro and are thereby available in sufficiently high cell numbers. This review summarizes the currently known characteristics of ASCs and achievements in adipogenic and endothelial differentiation in vitro. Further, the interdependency of adipogenesis and angiogenesis based on the crosstalk of endothelial cells, stem cells and adipocytes is addressed at the molecular level. Finally, achievements and limitations of current co-culture conditions for the construction of vascularized adipose tissue are evaluated.

Effect of Endothelial Cells on Angiogenic Properties of Multipotent Stromal Cells from the Umbilical Cord during Angiogenesis Modeling in the Basement Membrane Matrix

Short-term cell culturing on basement membrane matrix is a common and very convenient in vitro model of angiogenesis. We studied the possibility of interaction of multipotent stromal cells from the umbilical cord and Ea.hy926 endothelial cells on this model at the early and late periods of the experiment. Multipotent stromal cells alone and in combination with endothelial cells formed an unstable tubular network. Clusters formed after its disassembling later became the sprouting centers in co-culture of the two cell types, but not in pure culture of multipotent stromal cells. Multipotent stromal cells with CD31+ phenotype constitute the structural basis of newly formed stable 3D capillary-like network. Prolongation of the time of culturing and combination of the two in vitro models of angiogenesis (tubulogenesis and sprouting) allowed more complete assessment of the angiogenic potential of multipotent stromal cells.

Inhibition of Rho-Associated Protein Kinase Increases the Angiogenic Potential of Mesenchymal Stem Cell Aggregates via Paracrine Effects

The aggregation of multiple cells, such as mesenchymal condensation, is an important biological process in skeletal muscle development, osteogenesis, and adipogenesis. Due to limited in vivo study model systems, a simple and effective in vitro three-dimensional (3D) aggregation system is required to study the mechanisms of multicellular aggregation and its applications. We first generated controlled mesenchymal stem cell (MSC) aggregates using a bioprinting technique to monitor their aggregation and sprouting. We induced the angiogenic potential of the MSCs through chemical inhibition of the Rho/Rho-associated protein kinase (ROCK) pathway, which led to hairy sprouting in the aggregates. The angiogenic potential of this 3D construct was then tested by subcutaneously implanting the Matrigel with 3D MSC aggregates in a rat. Treatment of 3D MSCs with the ROCK inhibitor, Y27632, increased their angiogenic activity in vivo. The gene expressions and histological staining indicated that angiogenesis and neovascularization were mainly regulated by the paracrine factors secreted from human 3D MSC constructs. Our results demonstrate the enhancement of the angiogenic potential of the MSC constructs through the secretion of vascular endothelial growth factor (VEGF) and epidermal growth factor (EGF) by the inhibition of the Rho/ROCK pathway.

Nestin Positive Bone Marrow Derived Cells Responded to Injury Mobilize into Peripheral Circulation and Participate in Skin Defect Healing

Exogenously infused mesenchymal stem cells (MSCs) are thought to migrate to injury site through peripheral blood stream and participate in tissue repair. However, whether and how endogenous bone marrow MSCs mobilized to circulating and targeted to tissue injury has raised some controversy, and related studies were restricted by the difficulty of MSCs identifying in vivo. Nestin, a kind of intermediate filament protein initially identified in neuroepithelial stem cells, was recently reported as a credible criteria for MSCs in bone marrow. In this study, we used a green fluorescent protein (GFP) labeled bone marrow replacement model to trace the nestin positive bone marrow derived cells (BMDCs) of skin defected-mice. We found that after skin injured, numbers of nestin⁺ cells in peripheral blood and bone marrow both increased. A remarkable concentration of nestin⁺ BMDCs around skin wound was detected, while few of these cells could be observed in uninjured skin or other organs. This recruitment effect could not be promoted by granulocyte colony-stimulating factor (G-CSF), suggests a different mobilization mechanism from ones G-CSF takes effect on hematopoietic cells. Our results proposed nestin⁺ BMDCs as mobilized candidates in skin injury repair, which provide a new insight of endogenous MSCs therapy.

Chorion Mesenchymal Stem Cells Show Superior Differentiation, Immunosuppressive, and Angiogenic Potentials in Comparison With Haploidentical Maternal Placental Cells

Mesenchymal stem cells (MSCs) of placental origin have become increasingly translational owing to their abundance and accessibility. MSCs of different origin share several features but also present biological differences that might point to distinct clinical properties. Hence, mixing fetal and maternal cells from the same placenta can lead to contradicting results. We analyzed the biological characteristics of haploidentical MSCs isolated from fetal sources, including the umbilical cord (UC-MSCs) and chorion (Ch-MSCs), compared with maternal decidua MSCs (Dc-MSCs). All MSCs were analyzed for general stem cell properties. In addition, immunosuppressive capacity was assessed by the inhibition of T-cell proliferation, and angiogenic potential was evaluated in a Matrigel transplantation assay. The comparison between haploidentical MSCs displayed several distinct features, including (a) marked differences in the expression of CD56, (b) a higher proliferative capacity for Dc-MSCs and UC-MSCs than for Ch-MSCs, (c) a diversity of mesodermal differentiation potential in favor of fetal MSCs, (d) a higher capacity for Ch-MSCs to inhibit T-cell proliferation, and (e) superior angiogenic potential of Ch-MSCs evidenced by a higher capability to form tubular vessel-like structures and an enhanced release of hepatocyte growth factor and vascular endothelial growth factor under hypoxic conditions. Our results suggest that assessing the prevalence of fetomaternal contamination within placental MSCs is necessary to increase robustness and limit side effects in their clinical use. Finally, our work presents evidence positioning fetoplacental cells and notably Ch-MSCs in the forefront of the quest for cell types that are superior for applications in regenerative medicine.

SIGNIFICANCE

This study analyzed the biological characteristics of mesenchymal stem cells (MSCs) isolated from fetal and maternal placental origins. The findings can be summarized as follows: (a) important differences were found in the expression of CD56, (b) a different mesodermal differentiation potential was found in favor of fetal MSCs, (c) a higher immunosuppressive capacity for chorion MSCs was noted, and (d) superior angiogenic potential of Ch-MSCs was observed. These results suggest that assessing the prevalence of fetomaternal contamination within placental MSCs is necessary to increase robustness and limit side effects in their clinical use. The evidence should allow clinicians to view fetoplacental cells, notably Ch-MSCs, favorably as candidates for use in regenerative medicine.

Advances in treatment of inflammatory bowel disease

Because of varied clinical manifestations, long duration and recurrence, and lack of diagnostic criteria, the treatment of inflammatory bowel disease (IBD) is very complicated. The treatment should be aimed at its diverse pathogenesis and be multimodal, including controlling active inflammation, regulating immune function, use of biological agents, and stem cell transplantation. Some cases even require surgical treatment.

Radio-resistant mesenchymal stem cells: mechanisms of resistance and potential implications for the clinic

Mesenchymal stem cells (MSCs) comprise a heterogeneous population of multipotent stromal cells and can be isolated from various tissues and organs. Due to their regenerative potential, they have been subject to intense research efforts, and they may provide an efficient means for treating radiation-induced tissue damage. MSCs are relatively resistant to ionizing radiation and retain their stem cell characteristics even after high radiation doses. The underlying mechanisms for the observed MSC radioresistance have been extensively studied and may involve efficient DNA damage recognition, double strand break repair and evasion of apoptosis. Here, we present a concise review of the published scientific data on the radiobiological features of MSCs. The involvement of different DNA damage recognition and repair pathways in the creation of a radioresistant MSC phenotype is outlined, and the roles of apoptosis, senescence and autophagy regarding the reported radioresistance are summarized. Finally, potential influences of the radioresistant MSCs for the clinic are discussed with respect to the repair and radioprotection of irradiated tissues.

Characterization of Nestin, a Selective Marker for Bone Marrow Derived Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) are multipotent cells capable of differentiating into multiple cell lineages and contributing to tissue repair and regeneration. Characterization of the physiological function of MSCs has been largely hampered by lack of unique markers. Nestin, originally found in neuroepithelial stem cells, is an intermediate filament protein expressed in the early stages of development. Increasing studies have shown a particular association between Nestin and MSCs. Nestin could characterize a subset of bone marrow perivascular MSCs which contributed to bone development and closely contacted with hematopoietic stem cells (HSCs). Nestin expressing (Nes(+)) MSCs also play a role in the progression of various diseases. However, Nes(+) cells were reported to participate in angiogenesis as MSCs or endothelial progenitor cells (EPCs) in several tissues and be a heterogeneous population comprising mesenchymal cells and endothelial cells in the developing bone marrow. In this review article, we will summarize the progress of the research on Nestin, particularly the function of Nes(+) cells in bone marrow, and discuss the feasibility of using Nestin as a specific marker for MSCs.

Application of mesenchymal stem cells in digestive system diseases

Mesenchymal stem cells (MSCs) have the capacity of multipotent differentiation and the property of immunomodulation. MSCs have been widely used in digestive system disease research because of their advantageous characteristics such as homing to areas of inflammation or tumour tissue, anti-inflammation, high plasticity, absence of immunologic rejection, being easy to be isolated, and being convenient for the expression of exogenous genes. In this article, we will review the application of mesenchymal stem cells in digestive system diseases including caustic esophagus injury, reflux esophagitis, gastric ulcer, radioactive intestinal injury, severe acute pancreatitis, inflammatory bowel disease, nonalcoholic steatohepatitis, acute liver failure, hepatic fibrosis, autoimmune liver diseases, liver cirrhosis, esophageal cancer, gastric cancer, colon cancer, liver cancer, and pancreatic cancer.

Do Vascular Pericytes Contribute to Neurovasculogenesis in the Central Nervous System as Multipotent Vascular Stem Cells?

Increasing evidence suggests that multipotent stem cells are harbored within a vascular niche inside various organs. Although a precise phenotype of resident vascular stem cells (VSCs) that can function as multipotent stem cells remains unclear, accumulating evidence shows that multipotent VSCs are likely vascular pericytes (PCs) that localize within blood vessels. These PCs are multipotent, possessing the ability to differentiate into various cell types, including vascular lineage cells. In addition, brain PCs are unique: They are derived from neural crest and can differentiate into neural lineage cells. Because PCs in the central nervous system (CNS) can contribute to both neurogenesis and vasculogenesis, they may mediate the reparative process of neurovascular units that are constructed by neural and vascular cells. Here, we describe the activity of PCs when viewed as multipotent VSCs, primarily regarding their neurogenic and vasculogenic potential in the CNS. We also discuss similarities between PCs and other candidates for multipotent VSCs, including perivascular mesenchymal stem cells, neural crest-derived stem cells, adventitial progenitor cells, and adipose-derived stem cells.

Deterministic and stochastic approaches in the clinical application of mesenchymal stromal cells (MSCs)

Mesenchymal stromal cells (MSCs) have enormous intrinsic clinical value due to their multi-lineage differentiation capacity, support of hemopoiesis, immunoregulation and growth factors/cytokines secretion. MSCs have thus been the object of extensive research for decades. After completion of many pre-clinical and clinical trials, MSC-based therapy is now facing a challenging phase. Several clinical trials have reported moderate, non-durable benefits, which caused initial enthusiasm to wane, and indicated an urgent need to optimize the efficacy of therapeutic, platform-enhancing MSC-based treatment. Recent investigations suggest the presence of multiple in vivo MSC ancestors in a wide range of tissues, which contribute to the heterogeneity of the starting material for the expansion of MSCs. This variability in the MSC culture-initiating cell population, together with the different types of enrichment/isolation and cultivation protocols applied, are hampering progress in the definition of MSC-based therapies. International regulatory statements require a precise risk/benefit analysis, ensuring the safety and efficacy of treatments. GMP validation allows for quality certification, but the prediction of a clinical outcome after MSC-based therapy is correlated not only to the possible morbidity derived by cell production process, but also to the biology of the MSCs themselves, which is highly sensible to unpredictable fluctuation of isolating and culture conditions. Risk exposure and efficacy of MSC-based therapies should be evaluated by pre-clinical studies, but the batch-to-batch variability of the final medicinal product could significantly limit the predictability of these studies. The future success of MSC-based therapies could lie not only in rational optimization of therapeutic strategies, but also in a stochastic approach during the assessment of benefit and risk factors.

Nestin expression in mesenchymal stromal cells: regulation by hypoxia and osteogenesis

Background

The intermediate filament protein nestin is used as a marker for neural stem cells, and its expression is inversely correlated with cellular differentiation. More recently, nestin expression has also been described in other cell types including multipotential mesenchymal stromal cells (MSCs). In this study, we examined the expression of nestin in equine, canine and human bone marrow-derived MSCs undergoing osteogenic differentiation, to determine whether nestin levels were attenuated as the cells acquired a more mature phenotype. In addition, the expression of nestin may be under the influence of cellular hypoxia, as nestin expression is known to increase in areas of ischemic tissue damage. Therefore, we also examined the effects of hypoxia on expression of nestin in human MSCs and examined a role for hypoxia inducible factor 1-alpha (HIF-1α) and vascular endothelial growth factor (VEGF) in the response. Additionally, we quantified the temporal expression of nestin in the fracture callus during bone regeneration, a site that has been characterized as hypoxic.

Results

There were no significant changes in nestin expression in MSCs during osteogenic differentiation. There was a significant increase in expression of nestin mRNA and protein in human MSCs in response to hypoxia (1% O₂) or the chemical hypoxia mimetic desferroxamine. This may be due to upregulation of VEGF under hypoxia, as treatment of cells with the VEGF receptor antagonist CPO-P11 attenuated hypoxia-induced nestin expression. A significant increase in nestin mRNA expression was observed in the fracture callus of mice three and seven days post fracture.

Conclusions

Nestin was not a selective marker for MSCs, as its expression was maintained during osteogenic differentiation, in all species examined. Furthermore our data suggest that nestin expression can be induced by hypoxia, and that this increase in nestin is partially regulated by HIF-1α and VEGF. Interestingly, nestin levels were significantly upregulated at the fracture site. Further studies are required to understand the role of nestin in bone cell biology and ultimately bone regeneration.