Novel cell-free strategy for therapeutic angiogenesis: in vitro generated conditioned medium can replace progenitor cell transplantation

The role of cardiac microenvironment in cardiovascular diseases: implications for therapy

Due to aging populations and changes in lifestyle, cardiovascular diseases including cardiomyopathy, hypertension, and atherosclerosis, are the leading causes of death worldwide. The heart is a complicated organ composed of multicellular types, including cardiomyocytes, fibroblasts, endothelial cells, vascular smooth muscle cells, and immune cells. Cellular specialization and complex interplay between different cell types are crucial for the cardiac tissue homeostasis and coordinated function of the heart. Mounting studies have demonstrated that dysfunctional cells and disordered cardiac microenvironment are closely associated with the pathogenesis of various cardiovascular diseases. In this paper, we discuss the composition and the homeostasis of cardiac tissues, and focus on the role of cardiac environment and underlying molecular mechanisms in various cardiovascular diseases. Besides, we elucidate the novel treatment for cardiovascular diseases, including stem cell therapy and targeted therapy. Clarification of these issues may provide novel insights into the prevention and potential targets for cardiovascular diseases.

Analysis of endothelial progenitor cell subtypes as clinical biomarkers for elderly patients with ischaemic stroke

Endothelial progenitor cells (EPCs), expressing markers for stemness (CD34), immaturity (CD133) and endothelial maturity (KDR), may determine the extent of post-stroke vascular repair. Given the prevalence of stroke in elderly, this study explored whether variations in plasmatic availability of certain EPC subtypes could predict the severity and outcome of disease in older patients. Blood samples were collected from eighty-one consented patients (≥ 65 years) at admission and days 7, 30 and 90 post-stroke. EPCs were counted with flow cytometry. Stroke severity and outcome were assessed using the National Institutes of Health Stroke Scale, Barthel Index and modified Rankin Scale. The levels of key elements known to affect EPC characteristics were measured by ELISA. Diminished total antioxidant capacity and CD34 + KDR + and CD133 + KDR + counts in early phases of stroke were associated with disease severity and worse functional outcome at day 90 post-stroke. Baseline levels of angiogenic agent PDGF-BB, but not VEGF, positively correlated with CD34 + KDR + numbers at day 90. Baseline LDL-cholesterol levels were inversely correlated with CD34 + KDR+, CD133 + KDR + and CD34 + CD133 + KDR + numbers at day 90. Close correlation between baseline CD34 + KDR + and CD133 + KDR + counts and the outcome of stroke proposes these particular EPC subtypes as potential prognostic markers for ischaemic stroke.

Conditioned Medium Derived From the Human Amniotic Membrane Prevents Brain Damage Against Cerebral Ischemia/Reperfusion in Subacute, Acute, and Chronic Phases in a Rat Model of Stroke

Introduction

Stem cells isolated from the amniotic membrane can produce and release substances that can regenerate damaged tissues and contain proteins and other factors that via numerous major and minor mechanisms lead to increasing angiogenesis and tissue survival. This research was conducted to prove the defensive characteristics of the secretome in the face of temporary focal cerebral ischemia in mouse stroke models.

Methods

Cerebral ischemia protocol in a specific area was implemented in rats with middle cerebral artery occlusion for 60 minutes and then reperfusion was given for 6, 20, and 30 minutes. Within 30 minutes after the start of reperfusion, conditioned medium derived from the human amniotic membrane (AMSC-CM) was poured into the right ventricle (ICV) at a dose of 0.5 μL. Finally, the volume of the injury, cerebral tissue water, sensorimotor activity, and the strength of the blood-brain barrier integrity were evaluated 24 hours after drug injection.

Results

ICV injection of conditioned medium at the start of reperfusion phase considerably decreased the volume of the injury 6, 20, and 30 hours after reperfusion compared to the MCAO-operated group (P<0.01). Cerebral tissue water in the treatment group decreased considerably after the intervention in comparison with the MCAO group in the core and penumbral area not in the subcortical area (P<0.05). Also, the amount of Evans blue infiltration at all times in the core and half-foot area in the AMSC-CM group was significantly reduced in parallel with the MCAO group (P<0.05).

Conclusion

Treatment with AMSC-CM during 6-30 h after ischemia-reperfusion insult exerts some beneficial effects against ischemia-reperfusion injury. These findings provide an important vision for more complementary research and treatment of stroke.

Highlights

During ischemia, the brain undergoes a series of harmful pathological events.Mesenchymal stem cells culture medium is called condition medium (CM).CM contains substances that have neuroprotective properties.The use of CM reduces the damage caused by cerebral ischemia.

Plain Language Summary

The stem cell culture medium is called condition medium (CM). CM contains substances that have neuroprotective properties. This study aims to investigate the effect of CM on injuries caused by stroke. After causing a stroke in rats by closing the artery, the CM was injected into the injury site. The results showed that CM reduced the severity of the injury.

An optimized procedure for preparation of conditioned medium from Wharton's jelly mesenchymal stromal cells isolated from umbilical cord

Cell-free therapy based on conditioned medium derived from mesenchymal stromal cells (MSCs) has gained attention in the field of protective and regenerative medicine. However, the exact composition and properties of MSC-derived conditioned media can vary greatly depending on multiple parameters, which hamper standardization. In this study, we have optimized a procedure for preparation of conditioned medium starting from efficient isolation, propagation and characterization of MSCs from human umbilical cord, using a culture medium supplemented with human platelet lysate as an alternative source to fetal bovine serum. Our procedure successfully maximizes the yield of viable MSCs that maintain canonical key features. Importantly, under these conditions, the compositional profile and biological effects elicited by the conditioned medium preparations derived from these MSC populations do not depend on donor individuality. Moreover, approximately 120 L of conditioned medium could be obtained from a single umbilical cord, which provides a suitable framework to produce industrial amounts of toxic-free conditioned medium with predictable composition.

Neuroprotective Effects of Conditioned Medium of Mesenchymal Stem Cells (MSC-CM) as a Therapy for Ischemic Stroke Recovery: A Systematic Review

It has been reported that the therapeutic potential of stem cells is mainly mediated by their paracrine factors. In order to identify the effects of conditioned medium of mesenchymal stem cells (MSC-CM) against stroke, a systematic review was conducted. We searched PubMed, Scopus, and ISI Web of Science databases for all available articles relevant to the effects of MSC-CM against the middle cerebral artery occlusion (MCAO) model of ischemic stroke until August 2022. The quality of the included studies was evaluated using The STAIR scale. During the systematic search, a total of 356 published articles were found. A total of 15 datasets were included following screening for eligibility. The type of cerebral ischemia was the MCAO model and CM was obtained from MSCs. The results showed that the therapeutic time window can be considered a crucial factor when researchers use MSC-CM for stroke therapy. In addition, MSC-CM therapy contributes to functional recovery and reduces infarct volume after stroke by targeting different cellular signaling pathways. Our findings showed that MSC-CM therapy has the ability to improve functional recovery and attenuate brain infarct volume after ischemic stroke in preclinical studies. We hope our study accelerates needed progress towards clinical trials.

Endothelial Progenitor Cells in Neurovascular Disorders—A Comprehensive Overview of the Current State of Knowledge

Endothelial progenitor cells (EPCs) are a population of cells that circulate in the blood looking for areas of endothelial or vascular injury in order to repair them. Endothelial dysfunction is an important component of disorders with neurovascular involvement. Thus, the subject of involvement of EPCs in such conditions has been gaining increasing scientific interest in recent years. Overall, decreased levels of EPCs are associated with worse disease outcome. Moreover, their functionalities appear to decline with severity of disease. These findings inspired the application of EPCs as therapeutic targets and agents. So far, EPCs appear safe and promising based on the results of pre-clinical studies conducted on their use in the treatment of Alzheimer’s disease and ischemic stroke. In the case of the latter, human clinical trials have recently started to be performed in this subject and provided optimistic results thus far. Whereas in the case of migraine, existing findings pave the way for testing EPCs in in vitro studies. This review aims to thoroughly summarize current knowledge on the role EPCs in four disorders with neurovascular involvement, which are Alzheimer’s disease, cerebral small vessel disease, ischemic stroke and migraine, with a particular focus on the potential practical use of these cells as a treatment remedy.

Increasing angiogenic efficacy of conditioned medium using light stimulation of human adipose-derived stem cells

Conditioned medium (CM) contains various therapeutic molecules produced by cells. However, the low concentration of therapeutic molecules in CM is a major challenge for successful tissue regeneration. Here, we aim to develop a CM enriched in angiogenic paracrine factors for the treatment of ischemic diseases. Combining spheroidal culture and light irradiation significantly upregulates the angiogenic factor expression in human adipose-derived stem cells (hADSCs). Spheroids of light-irradiated hADSCs (SR group) show significantly enhanced expression of angiogenic paracrine factors compared with spheroids without light stimulation. Enhanced viability, migration, and angiogenesis are observed in cells treated with CM derived from the SR group. Furthermore, we performed in vivo experiments using a mouse hindlimb ischemia model; the results demonstrate that CM derived from densely cultured spheroids of light-irradiated hADSCs induced increased angiogenesis in vivo. In conclusion, our proposed approach of using light to stimulate stem cells may overcome the major drawbacks of CM-based therapies.

Combining spheroidal culture of human adipose-derived stem cells with light irradiation enhances angiogenic growth factor secretion in conditioned media, which can improve angiogenesis in a mouse hindlimb ischemia model.

The Role of Blood-Derived Factors in Protection and Regeneration of Aged Tissues

Tissue regeneration substantially relies on the functionality of tissue-resident endogenous adult stem cell populations. However, during aging, a progressive decline in organ function and regenerative capacities impedes endogenous repair processes. Especially the adult human heart is considered as an organ with generally low regenerative capacities. Interestingly, beneficial effects of systemic factors carried by young blood have been described in diverse organs including the heart, brain and skeletal muscle of the murine system. Thus, the interest in young blood or blood components as potential therapeutic agents to target age-associated malignancies led to a wide range of preclinical and clinical research. However, the translation of promising results from the murine to the human system remains difficult. Likewise, the establishment of adequate cellular models could help to study the effects of human blood plasma on the regeneration of human tissues and particularly the heart. Facing this challenge, this review describes the current knowledge of blood plasma-mediated protection and regeneration of aging tissues. The current status of preclinical and clinical research examining blood borne factors that act in stem cell-based tissue maintenance and regeneration is summarized. Further, examples of cellular model systems for a more detailed examination of selected regulatory pathways are presented.

Aerobic exercise-induced circulating extracellular vesicle combined decellularized dermal matrix hydrogel facilitates diabetic wound healing by promoting angiogenesis

Background: Insufficient blood supply results in unsatisfactory wound healing, especially for challenging wound repair such as diabetic wound defects. Regular exercise training brings a lot of benefits to cardiovascular fitness and metabolic health including attenuation of T2DM progression. Circulating extracellular vesicles (EVs) are postulated to carry a variety of signals involved in tissue crosstalk by their modified cargoes, representing novel mechanisms for the effects of exercise. Prominently, both acute and chronic aerobic exercise training can promote the release of exercise-induced cytokines and enhance the angiogenic function of circulating angiogenic cell–derived EVs.

Methods: We investigated the possible angiogenesis potential of aerobic exercise-induced circulating EVs (EXE-EVs) on diabetic wound healing. Circulating EVs were isolated from the plasma of rats subjected to 4 weeks of moderate aerobic exercise or sedentariness 24 h after the last training session. The therapeutic effect of circulating EVs was evaluated in vitro by proliferation, migration, and tube formation assays of human umbilical vein endothelial cells (HUVECs), as well as in vivo by quantification of angiogenesis and cutaneous wound healing in diabetic rats.

Results: The number of circulating EVs did not change significantly in exercised rats 24 h post-exercise in comparison with the sedentary rats. Nevertheless, EXE-EVs showed remarkable pro-angiogenic effect by augmenting proliferation, migration, and tube formation of HUVECs. Furthermore, the findings of animal experiments revealed that the EXE-EVs delivered by decellularized dermal matrix hydrogel (DDMH) could significantly promote the repair of skin defects through stimulating the regeneration of vascularized skin.

Discussion: The present study is the first attempt to demonstrate that aerobic exercise-induced circulating EVs could be utilized as a cell-free therapy to activate angiogenesis and promote diabetic wound healing. Our findings suggest that EXE-EVs may stand for a potential strategy for diabetic soft tissue wound repair.

A Review Into the Insights of the Role of Endothelial Progenitor Cells on Bone Biology

In addition to its important transport functions, the skeletal system is involved in complex biological activities for the regulation of blood vessels. Endothelial progenitor cells (EPCs), as stem cells of endothelial cells (ECs), possess an effective proliferative capacity and a powerful angiogenic capacity prior to their differentiation. They demonstrate synergistic effects to promote bone regeneration and vascularization more effectively by co-culturing with multiple cells. EPCs demonstrate a significant therapeutic potential for the treatment of various bone diseases by secreting a combination of growth factors, regulating cellular functions, and promoting bone regeneration. In this review, we retrospect the definition and properties of EPCs, their interaction with mesenchymal stem cells, ECs, smooth muscle cells, and immune cells in bone regeneration, vascularization, and immunity, summarizing their mechanism of action and contribution to bone biology. Additionally, we generalized their role and potential mechanisms in the treatment of various bone diseases, possibly indicating their clinical application.

Exploring Endothelial Colony-Forming Cells to Better Understand the Pathophysiology of Disease: An Updated Review

Endothelial cell (EC) dysfunction has been implicated in a variety of pathological conditions. The collection of ECs from patients is typically conducted postmortem or through invasive procedures, such as surgery and interventional procedures, hampering efforts to clarify the role of ECs in disease onset and progression. In contrast, endothelial colony-forming cells (ECFCs), also termed late endothelial progenitor cells, late outgrowth endothelial cells, blood outgrowth endothelial cells, or endothelial outgrowth cells, are obtained in a minimally invasive manner, namely, by the culture of human peripheral blood mononuclear cells in endothelial growth medium. ECFCs resemble mature ECs phenotypically, genetically, and functionally, making them excellent surrogates for ECs. Numerous studies have been performed that examined ECFC function in conditions such as coronary artery disease, diabetes mellitus, hereditary hemorrhagic telangiectasia, congenital bicuspid aortic valve disease, pulmonary arterial hypertension, venous thromboembolic disease, and von Willebrand disease. Here, we provide an updated review of studies using ECFCs that were performed to better understand the pathophysiology of disease. We also discuss the potential of ECFCs as disease biomarkers and the standardized methods to culture, quantify, and evaluate ECFCs and suggest the future direction of research in this field.

Advancing Regenerative Cellular Therapies in Non-Scarring Alopecia

Alopecia or baldness is a common diagnosis in clinical practice. Alopecia can be scarring or non-scarring, diffuse or patchy. The most prevalent type of alopecia is non-scarring alopecia, with the majority of cases being androgenetic alopecia (AGA) or alopecia areata (AA). AGA is traditionally treated with minoxidil and finasteride, while AA is treated with immune modulators; however, both treatments have significant downsides. These drawbacks compel us to explore regenerative therapies that are relatively devoid of adverse effects. A thorough literature review was conducted to explore the existing proven and experimental regenerative treatment modalities in non-scarring alopecia. Multiple treatment options compelled us to classify them into growth factor-rich and stem cell-rich. The growth factor-rich group included platelet-rich plasma, stem cell-conditioned medium, exosomes and placental extract whereas adult stem cells (adipose-derived stem cell-nano fat and stromal vascular fraction; bone marrow stem cell and hair follicle stem cells) and perinatal stem cells (umbilical cord blood-derived mesenchymal stem cells (hUCB-MSCs), Wharton jelly-derived MSCs (WJ-MSCs), amniotic fluid-derived MSCs (AF-MSCs), and placental MSCs) were grouped into the stem cell-rich group. Because of its regenerative and proliferative capabilities, MSC lies at the heart of regenerative cellular treatment for hair restoration. A literature review revealed that both adult and perinatal MSCs are successful as a mesotherapy for hair regrowth. However, there is a lack of standardization in terms of preparation, dose, and route of administration. To better understand the source and mode of action of regenerative cellular therapies in hair restoration, we have proposed the "À La Mode Classification". In addition, available evidence-based cellular treatments for hair regrowth have been thoroughly described.

Preconditioning with secretome of neural crest-derived stem cells enhanced neurotrophic expression in mesenchymal stem cells

During the last 20 years, stem cell therapy has been considered as an effective approach for regenerative medicine. Due to poor ability of stem cells to survive following transplantation, it has been proposed that beneficial effects of stem cells mainly depend on paracrine function. Therefore, the present study was designed to reinforce mesenchymal stem cells (MSCs) to express higher levels of trophic factors especially the ones with the neurotrophic properties. Here, bone marrow (BM)-MSCs and adipose-MSCs were treated with conditioned medium (CM) of dental pulp stem cells (DPSCs) or hair follicle stem cells (HFSCs) for up to three days. The relative expression of five key trophic factors that have critical effects on the central nervous system regeneration were evaluated using qRT-PCR technique. Furthermore, to assess the impacts of conditioned mediums on the fate of MSCs, expression of seven neuronal/glial markers were evaluated 3 days after the treatments. The obtained data revealed priming of BM-MSCs with HFSC-CM or DPSC-CM increases the BDNF expression over time. Such effect was also observed in adipose-MSCs following DPSC-CM treatment. Secretome preconditioning remarkably increased NGF expression in the adipose-MSCs. In addition, although priming of adipose-MSCs with HFSC-CM increased GDNF expression one day after the treatment, DPSC-CM enhanced GDNF mRNA in BM-MSCs at a later time point. It seemed priming of BM-MSCs with HFSC-CM, promoted differentiation into the glial lineage. Our findings showed that MSCs preconditioning with secretome of neural crest-derived stem cells could be a promising approach to enhance the neurotrophic potential of these stem cells.

Therapeutic Effect of Human Mesenchymal Stem Cell-Conditioned Medium on Erectile Dysfunction

Purpose

Owing to the safety and cost effectiveness of conditioned medium (CM), its therapeutic effects have attracted significant attention from many researchers. To date, numerous studies have been conducted on CM; however, little has been done with regard to erectile dysfunction (ED). In this research, the potential of human mesenchymal stem cell-derived CM (MSC-CM) for the treatment of ED was investigated.

Materials and Methods

A high concentration of MSC-CM was prepared through 3D spheroid culturing with bone marrow-derived MSCs and cut-off filtering. The composition of CM was analyzed using biochemical assays, and the effect of the preparation process on the quality of CM was investigated. The therapeutic effects of MSC-CM were evaluated through animal studies using a cavernous nerve (CN) injury rat model.

Results

3D spheroid culturing afforded a 278-fold increase in the total protein content of CM, as compared to that from 2D cultures; the protein concentration increased by 19 times on increasing the centrifugation time for cut-off filtering. Biochemical assays indicated that the CM contains various xlink:types of angiogenic, neurotrophic, and anti-inflammatory factors. Histological assay results showed that MSC-CM has angio- and neuro-trophic effect in a CN injury rat model in vivo, and these therapeutic effects appear in a dose-dependent manner.

Conclusions

The experimental results confirmed the therapeutic effect of MSC-CM in healing damaged cavernosal tissue and restoring erectile function. These results successfully demonstrated that MSC-CM has significant potential for the treatment of ED.

Secretome Analysis of Rabbit and Human Mesenchymal Stem and Endothelial Progenitor Cells: A Comparative Study

Human adipose tissue-derived mesenchymal stem cells (AT-MSCs) have been studied several years for their immunomodulatory effect through the paracrine mechanism and cytokine secretion. In combination with endothelial progenitor cells (EPCs), MSCs have great therapeutical potential for the repair of endothelium and wound healing. However, little is known about the cytokine profile of rabbit AT-MSCs or even EPCs. The aim of this study was to analyze the secretomes of these rabbit stem/progenitor cells. A large-scale human cytokine array (up to 80 cytokines) was used to identify and compare cytokines secreted into conditioned media of human and rabbit AT-MSCs as well as HUVECs and rabbit EPCs. Few cytokines were highly expressed by human AT-MSCs (TIMP-2, TIMP-1), HUVECs (MCP-1, TIMP-2, GRO, Angiogenin, IL-8, TIMP-1), or by rabbit EPCs (TIMP-2). Several cytokines have moderate expression by human (MCP-1, GRO, Angiogenin, TGF-β 2, IL-8, LIF, IL-6, Osteopontin, Osteoprotegerin) and rabbit AT-MSCs (TIMP-2, TGF-β 2, LIF, Osteopontin, IL-8, IL-5, IL-3) or by HUVECs (IL-6, MIF, TGF-β 2, GCP-2, IGFBP-2, Osteoprotegerin, EGF, LIF, PDGF-BB, MCP-3, Osteopontin, Leptin, IL-5, ENA-78, TNF-β) and rabbit EPCs (TGF-β 2, Osteopontin, GRO, LIF, IL-8, IL-5, IL-3). In conclusion, the proposed method seems to be useful for the secretome analysis of rabbit stem/progenitor cells.

Endothelial Progenitor Cells Modulate the Phenotype of Smooth Muscle Cells and Increase Their Neointimal Accumulation Following Vascular Injury

BACKGROUND

 Smooth muscle cells (SMCs) are the main driver of neointima formation and restenosis following vascular injury. In animal models, endothelial progenitor cells (EPCs) accelerate endothelial regeneration and reduce neointima formation after arterial injury; however, EPC-capture stents do not reduce target vessel failure compared with conventional stents. Here we examined the influence of EPCs on features of SMCs pivotal for their impact on injury-induced neointima formation including proliferation, migration, and phenotype switch.

METHODS AND RESULTS

 EPCs, their conditioned medium, and EPC-derived microparticles induced proliferation of SMCs while limiting their apoptosis. In transwell membrane experiments and scratch assays, EPCs stimulated migration of SMCs and accelerated their recovery from scratch-induced injury. Treatment of SMCs with an EPC-derived conditioned medium or microparticles triggered transformation of SMCs toward a synthetic phenotype. However, co-cultivation of EPCs and SMCs enabling direct cell-cell contacts preserved their original phenotype and protected from the transformative effect of SMC cholesterol loading. Adhesion of EPCs to SMCs was stimulated by SMC injury and reduced by blocking CXCR2 and CCR5. Interaction of EPCs with SMCs modulated their secretory products and synergistically increased the release of selected chemokines. Following carotid wire injury in athymic mice, injection of EPCs resulted not only in reduced neointima formation but also in altered cellular composition of the neointima with augmented accumulation of SMCs.

CONCLUSION

 EPCs stimulate proliferation and migration of SMCs and increase their neointimal accumulation following vascular injury. Furthermore, EPCs context-dependently modify the SMC phenotype with protection from the transformative effect of cholesterol when a direct cell-cell contact is established.

Endothelial Progenitor Cell-Derived Factors Exert Neuroprotection in Cultured Cortical Neuronal Progenitor Cells

There is substantial evidence that stem and progenitor cells secrete trophic factors that have potential for repairing injured tissues. We have previously reported that the conditioned medium (CM) obtained from endothelial progenitor cells (EPC) cultures protects striatal neurons against 3-nitropropionic acid-induced toxicity. In the present study we tested the hypothesis that EPC-CM may support cortical neuronal cell function and/or survival. EPC were isolated from the peripheral blood of healthy human donors and cultured in hypoxic conditions (1.5% O₂) to stimulate the secretion of growth factors. The supernatant or conditioned medium (EPC-CM) was then collected and used for the various experiments. Primary cultures of cerebral cortex from fetal rat embryonic day 14 were treated with EPC-CM and challenged by glucose and serum deprivation. We observed that EPC-CM treatment significantly increased total cell number and cell viability in the cultures. Similarly, the number of lba1-expressing cells was significantly upregulated by EPC-CM, while western blot analyses for the astroglial marker glial fibrillary acidic protein did not show a marked difference. Importantly, the number of beta-lll-tubulin-positive neurons in the cultures was significantly augmented after EPC-CM treatment. Similarly, western blot analyses for beta-III-tubulin showed significant higher signal intensities. Furthermore, EPC-CM administration protected neurons against glucose- and serum deprivation-induced cell loss.

In sum, our findings identified EPC-CM as a means to promote viability and/or differentiation of cortical neurons and suggest that EPC-CM might be useful for neurorestorative approaches.

Tyrosine-Protein Phosphatase Non-receptor Type 9 (PTPN9) Negatively Regulates the Paracrine Vasoprotective Activity of Bone-Marrow Derived Pro-angiogenic Cells: Impact on Vascular Degeneration in Oxygen-Induced Retinopathy

Background and Aim

Insufficient post-ischemic neovascularization is an initial key step in the pathogenesis of Oxygen-Induced Retinopathy (OIR). During neovascularization, pro-angiogenic cells (PACs) are mobilized from the bone marrow and integrate into ischemic tissues to promote angiogenesis. However, the modulation of PAC paracrine activity during OIR and the specific mechanisms involved remain to be explored. Because Tyrosine-protein phosphatase non-receptor type 9 (PTPN9) is reported to be a negative regulator of stem cell differentiation and angiogenesis signaling, we investigated its effect on PAC activity in the context of OIR.

Methods and Results

In a rat model of OIR, higher levels of PTPN9 in the retina and in bone marrow derived PACs are associated with retinal avascular areas, lower levels of the mobilization factor SDF-1 and decreased number of CD34⁺/CD117⁺/CD133⁺ PACs. PACs exposed ex vivo to hyperoxia display increased PTPN9 expression, which is associated with impaired ability of PAC secretome to promote angiogenesis ex vivo (choroidal vascular sprouting) and in vitro (endothelial cell tubule formation) compared to the secretome of PACs maintained in normoxia. Suppression of PTPN9 (using siRNA) increases VEGF and SDF-1 expression to normalize PAC secretome during hyperoxia, leading to restored angiogenic ability of PAC secretome. Moreover, endothelial cells exposed to the secretome of siPTPN9-treated PACs expressed increased levels of activated form of VEGF receptor 2 (VEGFR2). In the rat model of OIR, intravitreal injection of secretome from siPTPN9-treated PACs significantly reduced retinal vaso-obliteration; this was associated with higher retinal levels of VEGF/SDF-1, and increased recruitment of PACs (CD34⁺ cells) to the retinal and choroidal vessels.

Conclusion

Our results suggest that hyperoxia alters the paracrine proangiogenic activity of BM-PACs by inducing PTPN9, which can contribute to impair post-ischemic revascularization in the context of OIR. Targeting PTPN9 restores PAC angiogenic properties, and provide a new target for vessel integrity in ischemic retinopathies.

Hypertension impairs hypoxia-induced angiogenesis in men

OBJECTIVE

The inability of the organism to appropriately respond to hypoxia results in abnormal cell metabolism and function. Hypoxia-induced angiogenesis seems to be suppressed in experimental models of hypertension; however, this hypothesis has not been tested in humans. We examined changes in endothelial biomarkers and vascular chemoattraction/angiogenic capacity in response to isocapnic hypoxia in hypertensive men.

METHODS

Twelve normotensive (38 ± 10 years) and nine hypertensive men (45 ± 11 years) were exposed to 5-min trials of normoxia (21% O2) and isocapnic hypoxia (10% O2). During the last minute of each trial, venous blood was drawn. Endothelial progenitor cells (EPCs; CD45/CD34/VEGFR2), endothelial microvesicles (apoptotic EMVs, CD42b/CD31/AnnexinV; endothelial activation, CD62E/CD144), nitrite, vascular endothelial growth factor (VEGF), and stromal cell-derived factor 1 (SDF-1) were measured.

RESULTS

During normoxia, EPCs, nitrite, endothelial activation, and SDF-1 were similar between groups, whereas VEGF was lower (P = 0.02) and apoptotic EMVs tended to increase (P = 0.07) in hypertensive men. During isocapnic hypoxia, endothelial activation increased in both groups (normotensive, P = 0.007 vs. normoxia; hypertensive, P = 0.006 vs. normoxia), whereas EMVs were higher only in the hypertensive group (P = 0.03 vs. normotensive). EPCs (P = 0.01 vs. normoxia; P = 0.03 vs. hypertensive men), NO (P = 0.01 vs. normoxia; P = 0.04 vs. hypertensive), and VEGF (P = 0.02 vs. normoxia; P = 0.0005 vs. hypertensive) increased only in normotensive individuals in response to isocapnic hypoxia. SDF-1 did not change in either group.

CONCLUSION

These results suggest that hypertension-induced impairment in angiogenesis in response to isocapnic hypoxia is related to disrupted NO bioavailability, VEGF chemotactic signaling, and EPC mobilization.

An In Vitro Comparison of Anti-Tumoral Potential of Wharton's Jelly and Bone Marrow Mesenchymal Stem Cells Exhibited by Cell Cycle Arrest in Glioma Cells (U87MG)

The therapeutic potential of mesenchymal stem cells (MSCs) for various malignancies is currently under investigation due to their unique properties. However, many discrepancies regarding their anti-tumoral or pro-tumoral properties have raised uncertainty about their application for anti-cancer therapies. To investigate, if the anti-tumoral or pro-tumoral properties are subjective to the type of MSCs under different experimental conditions we set out these experiments. Three treatments namely cell lysates (CL), serum-free conditioned media and FBS conditioned media (FBSCM) from each of Wharton’s Jelly MSCs and Bone Marrow-MSCs were applied to evaluate the anti-tumoral or pro-tumoral effect on the glioma cells (U87MG). The functional analysis included; Morphological evaluation, proliferation and migration potential, cell cycle analysis, and apoptosis for glioma cells. The fibroblast cell line was added to investigate the stimulatory or inhibitory effect of treatments on the proliferation of the normal cell. We found that cell lysates induced a generalized inhibitory effect on the proliferation of the glioma cells and the fibroblasts from both types of MSCs. Similarly, both types of conditioned media from two types of MSCs exerted the same inhibitory effect on the proliferation of the glioma cells. However, the effect of two types of conditioned media on the proliferation of fibroblasts was stimulatory from BM-MSCs and variable from WJ-MSCs. Moreover, all three treatments exerted a likewise inhibitory effect on the migration potential of the glioma cells. Furthermore, we found that the cell cycle was arrested significantly at the G1 phase after treating cells with conditioned media which may have led to inhibit the proliferative and migratory abilities of the glioma cells (U87MG). We conclude that cell extracts of MSCs in the form of secretome can induce specific anti-tumoral properties in serum-free conditions for the glioma cells particularly the WJ-MSCs and the effect is mediated by the cell cycle arrest at the G1 phase.

Conditioned media derived from mesenchymal stem cells induces apoptosis and decreases cell viability and proliferation in squamous carcinoma cell lines

Squamous cell carcinoma (SCC) is a relatively common cancer with a low survival rate, poor prognosis and no effective treatment strategy. The use of cell-free conditioned media derived from mesenchymal stem cells (CM-MSCs) has shown promising results in treating various diseases. This study aimed to evaluate the effects of CM-MSCs on proliferation and apoptosis of CAL-27 and FaDu SCC cell lines. CM derived from human bone marrow and human amniotic membrane MSCs (BM-MSCs and AM-MSCs) was used in this investigation. MTT assay demonstrated that CM-BMMSC decreased the viability of CAL-27 and FaDu cell lines, 24, 48, and 72 h after treatment. Quantitative real-time PCR indicated that mRNA expression of PCNA as a proliferative marker, and BCL-2 as an anti-apoptotic protein, decreased in both cell lines treated with CM-BMMSC. Based on the flow cytometry results, the number of positive proliferative Ki67 cells and apoptotic Annexin-V cells decreased and increased in both cell lines treated with CM-BMMSC, respectively. However, CM-AMMSC treatment had both pro-and anti-neoplastic effects in our samples and showed considerable differences between the two cell lines. Taken together, our findings demonstrated that CM-BMMSC and, to a lesser degree, CM-AMMSC decrease cell viability and proliferation and increase cell apoptosis in SCC cell lines in a time-dependent manner. However, further studies are needed, especially to evaluate the anti-tumor potential of CM-BMMSC in vivo.

Current Status of Angiogenic Cell Therapy and Related Strategies Applied in Critical Limb Ischemia

Critical limb ischemia (CLI) constitutes the most severe form of peripheral arterial disease (PAD), it is characterized by progressive blockade of arterial vessels, commonly correlated to atherosclerosis. Currently, revascularization strategies (bypass grafting, angioplasty) remain the first option for CLI patients, although less than 45% of them are eligible for surgical intervention mainly due to associated comorbidities. Moreover, patients usually require amputation in the short-term. Angiogenic cell therapy has arisen as a promising alternative for these "no-option" patients, with many studies demonstrating the potential of stem cells to enhance revascularization by promoting vessel formation and blood flow recovery in ischemic tissues. Herein, we provide an overview of studies focused on the use of angiogenic cell therapies in CLI in the last years, from approaches testing different cell types in animal/pre-clinical models of CLI, to the clinical trials currently under evaluation. Furthermore, recent alternatives related to stem cell therapies such as the use of secretomes, exosomes, or even microRNA, will be also described.

Extracellular Vesicle-Derived microRNAs of Human Wharton's Jelly Mesenchymal Stromal Cells May Activate Endogenous VEGF-A to Promote Angiogenesis

Despite low levels of vascular endothelial growth factor (VEGF)-A, the secretome of human Wharton’s jelly (WJ) mesenchymal stromal cells (MSCs) effectively promoted proangiogenic responses in vitro, which were impaired upon the depletion of small (~140 nm) extracellular vesicles (EVs). The isolated EVs shared the low VEGF-A profile of the secretome and expressed five microRNAs, which were upregulated compared to fetal dermal MSC-derived EVs. These upregulated microRNAs exclusively targeted the VEGF-A gene within 54 Gene Ontology (GO) biological processes, 18 of which are associated with angiogenesis. Moreover, 15 microRNAs of WJ-MSC-derived EVs were highly expressed (Ct value ≤ 26) and exclusively targeted the thrombospondin 1 (THBS1) gene within 75 GO biological processes, 30 of which are associated with the regulation of tissue repair. The relationship between predicted microRNA target genes and WJ-MSC-derived EVs was shown by treating human umbilical-vein endothelial cells (HUVECs) with appropriate doses of EVs. The exposure of HUVECs to EVs for 72 h significantly enhanced the release of VEGF-A and THBS1 protein expression compared to untreated control cells. Finally, WJ-MSC-derived EVs stimulated in vitro tube formation along with the migration and proliferation of HUVECs. Our findings can contribute to a better understanding of the molecular mechanisms underlying the proangiogenic responses induced by human umbilical cord-derived MSCs, suggesting a key regulatory role for microRNAs delivered by EVs.

Endothelial Progenitor Cell-Derived Microvesicles Promote Angiogenesis in Rat Brain Microvascular Endothelial Cells In vitro

Brain microvascular endothelial cells (BMECs) are a major component of the blood-brain barrier that maintains brain homeostasis. Preserving and restoring the normal biological functions of BMECs can reverse or reduce brain injury. Endothelial progenitor cells (EPCs) may promote brain vascular remodeling and restore normal endothelial function. As a novel vehicle for cell-cell communication, microvesicles (MVs) have varied biological functions. The present study investigated the biological effects of EPC-derived MVs (EPC-MVs) on BMECs in vitro. We isolated MVs from the supernatant of EPCs in a serum-depleted medium. BMECs were cultured alone or in the presence of EPC-MVs. BMEC viability and proliferation were evaluated with the Cell Counting Kit-8 and by flow cytometry, and the proangiogenic effect of EPC-MVs on BMECs was assessed with the transwell migration, wound healing, and tube formation assays. Our results showed that EPC-derived MVs labeled with DiI were internalized by cultured BMECs; this enhanced BMEC viability and promoted their proliferation. EPC-MVs also stimulated migration and tube formation in BMECs. These results demonstrate that EPC-derived MVs exert a proangiogenic effect on BMECs, which has potential applications in cell-free therapy for brain injury.

The Effect of Conditioned Media From Human Adipocyte-Derived Mesenchymal Stem Cells on Androgenetic Alopecia After Nonablative Fractional Laser Treatment

BACKGROUND

The conditioned media from adipocyte-derived mesenchymal stem cells-conditioned media (ADSC-CM) contains cytokines and growth factors that stimulate hair regeneration.

OBJECTIVE

We evaluated the efficacy and safety of human ADSC-CM treatment on patients who underwent nonablative fractional laser for the treatment of androgenetic alopecia (AGA).

MATERIALS AND METHODS

Thirty patients who underwent nonablative fractional laser treatment were topically administered either ADSC-CM or placebo solution. As a primary outcome, phototrichograms were taken to measure changes in hair density at each visit. In addition, global improvement scores (GISs) were compared by clinical digital photographs, which were taken at the initial and final visits, and assessed by 2 independent dermatologists. Finally, the investigator's improvement score was measured by questionnaire response during the final visit.

RESULTS

Hair density comparisons during the treatment period revealed that the ADSC-CM group had significantly higher final densities compared with the placebo group. The GIS of the ADSC-CM group was also significantly higher than the placebo group. Finally, no adverse effects associated with the application of ADSC-CM were noted during the study.

CONCLUSION

The application of ADSC-CM after nonablative fractional laser treatment accelerated increases in hair density and volume in AGA patients.

Conditioned media from endothelial progenitor cells cultured in simulated microgravity promote angiogenesis and bone fracture healing

Background

Paracrine signaling from endothelial progenitor cells (EPCs) is beneficial for angiogenesis and thus promotes tissue regeneration. Microgravity (MG) environment is found to facilitate the functional potentials of various stem or progenitor cells. The present study aimed to elucidate the effects of MG on pro-angiogenic properties and fracture repair capacities of conditioned media (CM) from EPCs.

Methods

Human peripheral blood-derived EPCs were cultured under MG or normal gravity (NG) followed by analysis for angiogenic gene expression. Furthermore, the serum-free CM under MG (MG-CM) or NG (NG-CM) were collected, and their pro-angiogenic properties were examined in human umbilical vein endothelial cells (HUVECs). In order to investigate the effects of MG-CM on fracture healing, they were injected into the fracture gaps of rat models, and radiography, histology, and mechanical test were performed to evaluate neovascularization and fracture healing outcomes.

Results

MG upregulated the expression of hypoxia-induced factor-1α (HIF-1α) and endothelial nitric oxide synthase (eNOS) and promoted NO release. Comparing to NG-CM, MG-CM significantly facilitated the proliferation, migration, and angiogenesis of HUVECs through NO-induced activation of FAK/Erk1/2-MAPK signaling pathway. In addition, MG-CM were verified to improve angiogenic activities in fracture area in a rat tibial fracture model, accelerate fracture healing, and well restore the biomechanical properties of fracture bone superior to NG-CM.

Conclusion

These findings provided insight into the use of MG bioreactor to enhance the angiogenic properties of EPCs’ paracrine signals via HIF-1α/eNOS/NO axis, and the administration of MG-CM favored bone fracture repair.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-020-02074-y.

The secretome of endothelial progenitor cells: a potential therapeutic strategy for ischemic stroke

Ischemic stroke continues to be a leading cause of mortality and morbidity in the world. Despite recent advances in the field of stroke medicine, thrombolysis with recombinant tissue plasminogen activator remains as the only pharmacological therapy for stroke patients. However, due to short therapeutic window (4.5 hours of stroke onset) and increased risk of hemorrhage beyond this point, each year globally less than 1% of stroke patients receive this therapy which necessitate the discovery of safe and efficacious therapeutics that can be used beyond the acute phase of stroke. Accumulating evidence indicates that endothelial progenitor cells (EPCs), equipped with an inherent capacity to migrate, proliferate and differentiate, may be one such therapeutics. However, the limited availability of EPCs in peripheral blood and early senescence of few isolated cells in culture conditions adversely affect their application as effective therapeutics. Given that much of the EPC-mediated reparative effects on neurovasculature is realized by a wide range of biologically active substances released by these cells, it is possible that EPC-secretome may serve as an important therapeutic after an ischemic stroke. In light of this assumption, this review paper firstly discusses the main constituents of EPC-secretome that may exert the beneficial effects of EPCs on neurovasculature, and then reviews the currently scant literature that focuses on its therapeutic capacity.

Stem cell secretome, regeneration, and clinical translation: a narrative review

Regenerative medicine is a field growing in popularity due to high hopes for stimulating in situ tissue restoration. Stem cell therapy remain at the center of regenerative medicine, due to early reports on its pluripotent differentiating capability. However, more recent reports suggest the paracrine activity of stem cells, and not direct differentiation, as the cause of its therapeutic effects. This paracrine activity can be harnessed in the form of conditioned media. Despite these capabilities, the clinical translation of stem cell conditioned media (i.e., secretome) is precluded by a variety of factors. These limitations include standardization of stem cell-conditioned media formulation, characterization of bioactive factors in conditioned media and dosing, optimizing modes of delivery, and uncovering of mechanisms of action of stem cell conditioned media. The purpose of this review is to provide a focused narration on the aforementioned preclusions pertaining to the clinical translation of stem cell conditioned media. Specifically, we will report on commonly use methodologies for the development of stem cell conditioned media, modalities for conditioned media characterization, modes of delivery, and postulated mechanisms of action for stem cell conditioned media in regenerative medicine.

Santalum album extract exhibits neuroprotective effect against the TLR3-mediated neuroinflammatory response in human SH-SY5Y neuroblastoma cells

Neuroinflammation is an inflammatory response in the nervous system that is associated with various neurological diseases including Alzheimer's diseases and others. Many studies evaluated the anti-inflammatory potential of Santalum album (S. album) extract, but none of them analyzed its effects against neuroinflammatory response in vitro. In addition, the precise mechanism underlying the anti-inflammatory effect of the extract has not yet been elucidated. Therefore, in this study, we investigated the effect of S. album extract on modulation of toll-like receptor 3 (TLR3) agonist polyinosnic-polycytidylic acid (PolyI:C)-induced neuroinflammatory response in human neuroblastoma cells. The TLR3-mediated immune response was differentially modulated by S. album extract in SH-SY5Y cells. In addition, treatment of cells with the conditioned medium (CM) of S. album extract significantly increased the mRNA levels of IFN-β, IFN-α, MxA and OAS-1 and decreased IL-6, CXCL8, CCL2 and IP-10. S. album extract has indirectly affected the expression of IFNs and inflammatory cytokines in SH-SY5Y cells. Furthermore, the extract was able to modulate PolyI:C-induced inflammatory response in Caco2 cells. Overall, S. album was capable to attenuate PolyI:C-induced neuroinflammatory effect through the induction of TLR2, TLR4 and the modulation of TLR negative regulators of the TRAF3, IRF3 and NF-κB pathways.

Effects of Exercise Training on the Paracrine Function of Circulating Angiogenic Cells

Exercise training has various benefits on cardiovascular health, and circulating angiogenic cells have been proposed as executing these changes. Work from the late 1990s supported an important role of these circulating post-natal cells in contributing to the maintenance and repair of the endothelium and vasculature. It was later found that circulating angiogenic cells were a heterogenous population of cells and primarily functioned in a paracrine manner by adhering to damaged endothelium and releasing growth factors. Many studies have discovered novel circulating angiogenic cell secreted proteins, microRNA and extracellular vesicles that mediate their angiogenic potential, and some studies have shown that both acute and chronic aerobic exercise training have distinct benefits. This review highlights work establishing an essential role of secreted factors from circulating angiogenic cells and summarizes studies regarding the effects of exercise training on these factors. Finally, we highlight the various gaps in the literature in hopes of guiding future work.

Conditioned Medium from Canine Amniotic Membrane-Derived Mesenchymal Stem Cells Improved Dog Sperm Post-Thaw Quality-Related Parameters

Simple Summary

Mesenchymal stem cells and their derivatives are used in clinical studies for their anti-apoptotic, anti-oxidant, immunomodulatory, and regenerative properties. Their use in reproductive medicine is increasing as they have been proved to be beneficial for infertility treatment. Mesenchymal stem cells can secrete factors that influence biological processes in target tissues or cells; these factors are either directly secreted by the cells or mediated through their derivatives. Although the amniotic membrane is easy to obtain and is a good source of stem cells, clinical trials using amniotic membrane-derived mesenchymal stem cells are still uncommon, especially in reproductive medicine or artificial reproductive technologies. The objective of the present study was to demonstrate the effects of conditioned medium prepared from amniotic membrane-derived stem cells on dog sperm cryopreservation. Our results showed that 10% of the conditioned medium enhanced the quality-related parameters of frozen–thawed sperm cells because of the presence of antioxidants and growth factors in the medium, which probably protected spermatozoa during the freeze–thaw process. These results suggest that conditioned media prepared from amniotic membrane-derived mesenchymal stem cells might have clinical applications in assisted reproductive technologies.

Abstract

This study investigated the effects of conditioned medium (CM) from canine amniotic membrane-derived MSCs (cAMSCs) on dog sperm cryopreservation. For this purpose, flow cytometry analysis was performed to characterize cAMSCs. The CM prepared from cAMSCs was subjected to proteomic analysis for the identification of proteins present in the medium. Sperm samples were treated with freezing medium supplemented with 0%, 5%, 10%, and 15% of the CM, and kinetic parameters were evaluated after 4–6 h of chilling at 4 °C to select the best concentration before proceeding to cryopreservation. Quality-related parameters of frozen–thawed sperm were investigated, including motility; kinetic parameters; viability; integrity of the plasma membrane, chromatin, and acrosome; and mitochondrial activity. The results showed that 10% of the CM significantly enhanced motility, viability, mitochondrial activity, and membrane integrity (p < 0.05); however, the analysis of chromatin and acrosome integrity showed no significant differences between the treatment and control groups. Therefore, we concluded that the addition of 10% CM derived from cAMSC in the freezing medium protected dog sperm during the cryopreservation process.

Outgrowth endothelial cells form a functional cerebral barrier and restore its integrity after damage

Breakdown of blood-brain barrier, formed mainly by brain microvascular endothelial cells (BMECs), represents the major cause of mortality during early phases of ischemic strokes. Hence, discovery of novel agents that can effectively replace dead or dying endothelial cells to restore blood-brain barrier integrity is of paramount importance in stroke medicine. Although endothelial progenitor cells (EPCs) represent one such agents, their rarity in peripheral blood severely limits their adequate isolation and therapeutic use for acute ischemic stroke which necessitate their ex vivo expansion and generate early EPCs and outgrowth endothelial cells (OECs) as a result. Functional analyses of these cells, in the present study, demonstrated that only OECs endocytosed DiI-labelled acetylated low-density lipoprotein and formed tubules on matrigel, prominent endothelial cell and angiogenesis markers, respectively. Further analyses by flow cytometry demonstrated that OECs expressed specific markers for stemness (CD34), immaturity (CD133) and endothelial cells (CD31) but not for hematopoietic cells (CD45). Like BMECs, OECs established an equally tight in vitro model of human BBB with astrocytes and pericytes, suggesting their capacity to form tight junctions. Ischemic injury mimicked by concurrent deprivation of oxygen and glucose (4 hours) or deprivation of oxygen and glucose followed by reperfusion (20 hours) affected both barrier integrity and function in a similar fashion as evidenced by decreases in transendothelial electrical resistance and increases in paracellular flux, respectively. Wound scratch assays comparing the vasculoreparative capacity of cells revealed that, compared to BMECs, OECs possessed a greater proliferative and directional migratory capacity. In a triple culture model of BBB established with astrocytes, pericytes and BMEC, exogenous addition of OECs effectively repaired the damage induced on endothelial layer in serum-free conditions. Taken together, these data demonstrate that OECs may effectively home to the site of vascular injury and repair the damage to maintain (neuro)vascular homeostasis during or after a cerebral ischemic injury.

Migration Inhibitory Factor in Conditioned Medium from Human Umbilical Cord Blood-Derived Mesenchymal Stromal Cells Stimulates Hair Growth

Conventional therapeutic applications of mesenchymal stromal cells (MSCs) focus on cell replacement and differentiation; however, increasing evidence suggests that most of their therapeutic effects are carried out by their various secretions. This study investigated the application of conditioned medium (CM) from human umbilical cord blood-derived MSCs (hUCB-MSCs) to improve hair growth and developed a method to reliably produce this optimized CM. Primed MSC-derived CM (P-CM) with combinations of TGF-β1 and LiCl was optimized by comparing its effects on the cell viability of dermal papilla cells (DPCs). P-CM significantly increased the viability of DPCs compared to CM. The secretion of vascular endothelial growth factor (VEGF) in DPCs was regulated by the macrophage migration inhibitory factor (MIF) in the P-CM secreted by MSCs. These findings suggest that P-CM can improve the efficacy in hair growth via a paracrine mechanism and that MIF in P-CM exerts hair growth-promoting effects via a VEGF-related β-catenin and p-GSK-3β [SER9] signaling pathway. Furthermore, clinical trials have shown that 5% P-CM improved androgenetic alopecia through producing an increased hair density, thickness, and growth rate, suggesting that this topical agent may be a novel and effective treatment option for patients with androgenetic alopecia.

Biological activity of mesenchymal stem cells secretome as a basis for cell-free therapeutic approach

Mesenchymal stem (stromal) cells (MSCs) are self-renewing, cultured adult stem cells which secrete a complex set of multiple soluble biologically active molecules such as chemokines, and cytokines, cell adhesion molecules, lipid mediators, interleukins (IL), growth factors (GFs), hormones, micro RNAs (miRNAs), long non-coding RNAs (lncRNAs), messenger RNAs (mRNAs), exosomes, as well as microvesicles, the secretome. MSCs of various origin, including adipose-derived stem cells (ASCs), bone marrow derived mesenchymal stem cells (BM-MSCs), human uterine cervical stem cells (hUCESCs), may be good candidates for obtaining secretome-derived products. Different population of MSCs can secret different factors which could have anti-inflammatory, anti-apoptotic, anti-fibrotic activities, a neuroprotective effect, could improve bone, muscle, liver regeneration and wound healing. Therefore, the paracrine activity of conditioned medium obtained when cultivating MSCs, due to a plethora of bioactive factors, was assumed to have the most prominent cell-free therapeutic impact and can serve as a better option in the field of regenerative medicine in future.

Anti-CD3 Antibody Treatment Reduces Scar Formation in a Rat Model of Myocardial Infarction

Introduction: Antibody treatment with anti-thymocyte globulin (ATG) has been shown to be cardioprotective. We aimed to evaluate which single anti-T-cell epitope antibody alters chemokine expression at a level similar to ATG and identified CD3, which is a T-cell co-receptor mediating T-cell activation. Based on these results, the effects of anti-CD3 antibody treatment on angiogenesis and cardioprotection were tested in vitro and in vivo. Methods: Concentrations of IL-8 and MCP-1 in supernatants of human peripheral blood mononuclear cell (PBMC) cultures following distinct antibody treatments were evaluated by Enzyme-linked Immunosorbent Assay (ELISA). In vivo, anti-CD3 antibodies or vehicle were injected intravenously in rats subjected to acute myocardial infarction (AMI). Chemotaxis and angiogenesis were evaluated using tube and migration assays. Intracellular pathways were assessed using Western blot. Extracellular vesicles (EVs) were quantitatively evaluated using fluorescence-activated cell scanning, exoELISA, and nanoparticle tracking analysis. Also, microRNA profiles were determined by next-generation sequencing. Results: Only PBMC stimulation with anti-CD3 antibody led to IL-8 and MCP-1 changes in secretion, similar to ATG. In a rat model of AMI, systemic treatment with an anti-CD3 antibody markedly reduced infarct scar size (27.8% (Inter-quartile range; IQR 16.2–34.9) vs. 12.6% (IQR 8.3–27.2); p < 0.01). The secretomes of anti-CD3 treated PBMC neither induced cardioprotective pathways in cardiomyocytes nor pro-angiogenic mechanisms in human umbilical vein endothelial cell (HUVECs) in vitro. While EVs quantities remained unchanged, PBMC incubation with an anti-CD3 antibody led to alterations in EVs miRNA expression. Conclusion: Treatment with an anti-CD3 antibody led to decreased scar size in a rat model of AMI. Whereas cardioprotective and pro-angiogenetic pathways were unaltered by anti-CD3 treatment, qualitative changes in the EVs miRNA expression could be observed, which might be causal for the observed cardioprotective phenotype. We provide evidence that EVs are a potential cardioprotective treatment target. Our findings will also provide the basis for a more detailed analysis of putatively relevant miRNA candidates.

Mechanisms Underlying Cell Therapy in Liver Fibrosis: An Overview

Fibrosis is a common feature in most pathogenetic processes in the liver, and usually results from a chronic insult that depletes the regenerative capacity of hepatocytes and activates multiple inflammatory pathways, recruiting resident and circulating immune cells, endothelial cells, non-parenchymal hepatic stellate cells, and fibroblasts, which become activated and lead to excessive extracellular matrix accumulation. The ongoing development of liver fibrosis results in a clinically silent and progressive loss of hepatocyte function, demanding the constant need for liver transplantation in clinical practice, and motivating the search for other treatments as the chances of obtaining compatible viable livers become scarcer. Although initially cell therapy has emerged as a plausible alternative to organ transplantation, many factors still challenge the establishment of this technique as a main or even additional therapeutic tool. Herein, the authors discuss the most recent advances and point out the corners and some controversies over several protocols and models that have shown promising results as potential candidates for cell therapy for liver fibrosis, presenting the respective mechanisms proposed for liver regeneration in each case.

Another win for endothelial progenitor cells: Endothelial progenitor cell-derived conditioned medium promotes proliferation and exerts neuroprotection in cultured neuronal progenitor cells

Progress in stem cell research demonstrates stem cells' potential for treating neurodegenerative diseases. Stem cells have proliferative/differentiative properties and produce a variety of paracrine factors that can potentially be used to regenerate nervous tissue. Previous studies have shown the positive regenerative effects of endothelial progenitor cells (EPCs), and thus, they may be used as a tool for regeneration. A study by Di Santo et al. explored whether EPC-derived conditioned medium (EPC-CM) promotes the survival of cultured striatal progenitor cells and attempted to find the paracrine factors and signaling pathways involved with EPC-CM's effects. The neuronal progenitor cells that were cultured with EPC-CM had much higher densities of GABA-immunoreactive (GABA-ir) neurons. It was shown that phosphatidylinositol-3-kinase/AKT and mitogen-activated protein kinase/ERK signaling pathways are involved in the proliferation of GABAergic neurons, as inhibition of these pathways decreased GABAergic densities. In addition, the results suggest that paracrine factors from EPC, both proteinaceous and lipidic, significantly elevated the viability and/or differentiation in the cultures. Importantly, it was found that EPC-CM provided neuroprotection against toxins from 3-nitropropionic acid. In sum, EPC-CM engendered proliferation and regeneration of the cultured striatal cells through paracrine factors and imparted neuroprotection. Furthermore, the effects of EPC-CM may generate a cell-free therapeutic strategy to address neurodegeneration.

Extracellular vesicles as a novel therapeutic tool for cell-free regenerative medicine in oral rehabilitation

Oral maxillofacial defects may always lead to complicated hard and soft tissue loss, including bone, nerve, blood vessels, teeth and skin, which are difficult to restore and severely influence the life quality of patients. Extracellular vesicles (EVs), including exosomes, microvesicles and apoptotic bodies, are emerging as potential solutions for complex tissue regeneration through cell-free therapies. In this review, we highlight the functional roles of EVs in the regenerative medicine for oral maxillofacial rehabilitation, specifically bone, skin, blood vessels, peripheral nerve and tooth-related tissue regeneration. Publications were reviewed by two researchers independently basing on three databases (PubMed, MEDLINE and Web of Science), until 31 December 2018. Basing on current researches, we classified the origin of EVs for regenerative medicine into four categories: related cells in the regenerative niche, mesenchymal stem cells, immune cells and body fluids. The secretome of different cells are distinct, while the same cells secrete different EVs under varied conditions; therefore, the content profiles of EVs and regulatory mechanisms on target cells are compared and emphasised. By unravelling the regulatory mechanisms of EVs in tissue regeneration, modified cells and tailored EVs with specific target may be produced for precision medicine with high efficacy.

Conditioned medium from Endothelial Progenitor Cells promotes number of dopaminergic neurons and exerts neuroprotection in cultured ventral mesencephalic neuronal progenitor cells

Transplantation of stem and progenitor cells offers a promising tool for brain repair in the context of neuropathological disorders including Parkinson's disease. There is growing proof that the capacity of adult stem and progenitor cells for tissue regeneration relies rather on the release of paracrine factors than on their cell replacement properties. In line with this notion, we have previously reported that conditioned medium (CM) collected from cultured Endothelial Progenitor Cells (EPC) stimulated survival of striatal neurons. In the present study we investigated whether EPC-CM promotes survival of cultured midbrain progenitor cells. For that purpose primary cultures from fetal rat embryonic ventral mesencephalon (VM) were prepared and grown for 7 days in vitro (DIV). EPC-CM was administered from DIV5-7. First, we found that EPC-CM treatment resulted in significantly increased cell densities of TH-ir neurons. Interestingly, this effect was no longer seen after proteolytic digestion of the EPC-CM. EPC-CM also significantly increased densities of beta-III-tubulin positive neurons and lba-1-ir microglial cells. The effect on dopaminergic neurons was not due to higher cell proliferation as no incorporation of EdU was observed in TH-ir cells. Importantly, EPC-CM exerted neuroprotection against MPP+ induced toxicity as in vitro model of Parkinson's disease. Taken together, our findings identified EPC-CM as a powerful tool to promote survival of cultured VM neurons and further support the importance of paracrine factors in the actions of stem and progenitor cells for brain repair.

Local pharmacological induction of angiogenesis: Drugs for cells and cells as drugs

The past decades have seen significant advances in pro-angiogenic strategies based on delivery of molecules and cells for conditions such as coronary artery disease, critical limb ischemia and stroke. Currently, three major strategies are evolving. Firstly, various pharmacological agents (growth factors, interleukins, small molecules, DNA/RNA) are locally applied at the ischemic region. Secondly, preparations of living cells with considerable bandwidth of tissue origin, differentiation state and preconditioning are delivered locally, rarely systemically. Thirdly, based on the notion, that cellular effects can be attributed mostly to factors secreted in situ, the cellular secretome (conditioned media, exosomes) has come into the spotlight. We review these three strategies to achieve (neo)angiogenesis in ischemic tissue with focus on the angiogenic mechanisms they tackle, such as transcription cascades, specific signalling steps and cellular gases. We also include cancer-therapy relevant lymphangiogenesis, and shall seek to explain why there are often conflicting data between in vitro and in vivo. The lion's share of data encompassing all three approaches comes from experimental animal work and we shall highlight common technical obstacles in the delivery of therapeutic molecules, cells, and secretome. This plethora of preclinical data contrasts with a dearth of clinical studies. A lack of adequate delivery vehicles and standardised assessment of clinical outcomes might play a role here, as well as regulatory, IP, and manufacturing constraints of candidate compounds; in addition, completed clinical trials have yet to reveal a successful and efficacious strategy. As the biology of angiogenesis is understood well enough for clinical purposes, it will be a matter of time to achieve success for well-stratified patients, and most probably with a combination of compounds.

Exosomes secreted by endothelial progenitor cells improve the bioactivity of pulmonary microvascular endothelial cells exposed to hyperoxia in vitro

Background

Paracrine factors secreted by endothelial progenitor cells (EPCs) are suggested to be responsible, in part, for the improved microvascular development in bronchopulmonary dysplasia (BPD) models. This study aims to investigate the potential role of exosomes derived from EPCs (EPC-EXOs), a component of paracrine secretion, in angiogenesis by mediating the activity of PMVECs exposed to hyperoxia.

Methods

EPCs were isolated from bone marrow of rats. EPC-EXOs were isolated by ExoQuick-TC kits from the conditioned media of EPCs. The PMVECs were divided into three groups, including the normal group, the hyperoxia group (exposed to 85% O₂) and the EPC-EXOs treatment group (exposed to 85% O₂ and EPC-EXOs with the concentration of 100 µg/mL). The activities of proliferation, migration and tube formation of PMVECs were detected at the endpoint. The mRNA and protein expression levels of VEGF, VEGFR2 and eNOS in different groups were detected by real-time quantitative PCR and western blot.

Results

We found EPC-EXOs exhibited a cup or biconcave morphology, with the size ranging from 30 to 150 nm, and positive for the characteristic exosomal surface marker proteins, CD63 and TSG101. Comparing to the control group, Hyperoxic stress impaired the proliferation, migration, and tubule formation of PMVECs, and decreased the expression of endothelial nitric oxide synthase (eNOS), vascular endothelial growth factor (VEGF), and vascular endothelial growth factor receptor 2 (VEGFR-2) of PMVECs. Comparing to the hyperoxia group, EPC-EXOs treatment enhanced the bioactivity of PMVECs in vitro, and increased the expression of eNOS, VEGF and VEGFR2.

Conclusions

Our data demonstrate EPCs secrete exosomes that have independent angiogenic activity in vitro. This may help explain in part the protective effects of EPCs on hyperoxic injury in the developing lung vasculature and may represent a promising therapeutic strategy for BPD.

Dental derived stem cell conditioned media for hair growth stimulation

Alopecia is a clinical condition caused by excessive hair loss which may result in baldness, the causes of which still remain elusive. Conditioned media (CM) from stem cells shows promise in regenerative medicine. Our aim was to evaluate the potential CM of dental pulp stem cells obtained from human deciduous teeth (SHED-CM) to stimulate hair growth under in vitro and in vivo conditions. SHED and hair follicle stem cells (HFSCs) (n = 3) were cultured in media combinations; i) STK2, ii) DMEM-KO+10% FBS, iii) STK2+2% FBS and profiled for the presence of positive hair growth-regulatory paracrine factors; SDF-1, HGF, VEGF-A, PDGF-BB and negative hair growth-regulatory paracrine factors; IL-1α, IL-1β, TGF-β, bFGF, TNF-α, and BDNF. The potential of CM from both cell sources to stimulate hair growth was evaluated based on the paracrine profile and measured dynamics of hair growth under in vitro conditions. The administration of CM media to telogen-staged synchronized 7-week old C3H/HeN female mice was carried out to study the potential of the CM to stimulate hair growth in vivo. SHED and HFSCs cultured in STK2 based media showed a shorter population doubling time, higher viability and better maintenance of MSC characteristics in comparison to cells cultured in DMEM-KO media. STK2 based CM contained only two negative hair growth-regulatory factors; TNF-α, IL-1 while DMEM-KO CM contained all negative hair growth-regulatory factors. The in vitro study confirmed that treatment with STK2 based media CM from passage 3 SHED and HFSCs resulted in a significantly higher number of anagen-staged hair follicles (p<0.05) and a significantly lower number of telogen-staged hair follicles (p<0.05). Administration of SHED-CM to C3H/HeN mice resulted in a significantly faster stimulation of hair growth in comparison to HFSC-CM (p<0.05), while the duration taken for complete hair coverage was similar for both CM sources. Thus, SHED-CM carries the potential to stimulate hair growth which can be used as a treatment tool for alopecia.

Endothelial Progenitor Cells Conditioned Medium Supports Number of GABAergic Neurons and Exerts Neuroprotection in Cultured Striatal Neuronal Progenitor Cells

There is growing evidence that stem and progenitor cells exert regenerative actions by means of paracrine factors. In line with these notions, we recently demonstrated that endothelial progenitor cell (EPC)-derived conditioned medium (EPC-CM) substantially increased viability of brain microvascular cells. In the present study, we aimed at investigating whether EPC-CM supports cell survival of cultured striatal progenitor cells. For that purpose, primary cultures from fetal rat embryonic (E14) ganglionic eminence were prepared and grown for 7 days in vitro (DIV). EPC-CM was administered from DIV5–7. Treatment of the striatal cultures with EPC-CM resulted in significantly increased densities of GABA-immunoreactive (-ir) neurons. Inhibition of mitogen-activated protein kinase and phosphatidylinositol-3-kinase, but not of the ROCK pathway, significantly attenuated the EPC-CM induced increase in GABA-ir cell densities. Similar results were observed when EPC-CM was subjected to proteolytic digestion and lipid extraction. Furthermore, inhibition of translation abolished the EPC-CM induced effects. Importantly, EPC-CM displayed neuroprotection against 3-nitropropionic acid induced toxicity. These findings demonstrate that EPC-derived paracrine factors substantially promote survival and/or differentiation of cultured striatal progenitor cells involving both proteinaceous factors and lipidic factors. In sum, EPC-CM constituents might lead to a novel cell-free therapeutic strategy to challenge neuronal degeneration.

Regenerative Cardiovascular Therapies: Stem Cells and Beyond

Although reperfusion therapy has improved outcomes, acute myocardial infarction (AMI) is still associated with both significant mortality and morbidity. Once irreversible myocardial cell death due to ischemia and reperfusion sets in, scarring leads to reduction in left ventricular function and subsequent heart failure. Regenerative cardiovascular medicine experienced a boost in the early 2000s when regenerative effects of bone marrow stem cells in a murine model of AMI were described. Translation from an animal model to stem cell application in a clinical setting was rapid and the first large trials in humans suffering from AMI were conducted. However, high initial hopes were early shattered by inconsistent results of randomized clinical trials in patients suffering from AMI treated with stem cells. Hence, we provide an overview of both basic science and clinical trials carried out in regenerative cardiovascular therapies. Possible pitfalls in specific cell processing techniques and trial design are discussed as these factors influence both basic science and clinical outcomes. We address possible solutions. Alternative mechanisms and explanations for effects seen in both basic science and some clinical trials are discussed here, with special emphasis on paracrine mechanisms via growth factors, exosomes, and microRNAs. Based on these findings, we propose an outlook in which stem cell therapy, or therapeutic effects associated with stem cell therapy, such as paracrine mechanisms, might play an important role in the future. Optimizing stem cell processing and a better understanding of paracrine signaling as well as its effect on cardioprotection and remodeling after AMI might improve not only AMI research, but also our patients' outcomes.

Conditioned media derived from mesenchymal stem cell cultures: The next generation for regenerative medicine

Recent studies suggest that the main driving force behind the therapeutic activity observed in mesenchymal stem cells (MSCs) are the paracrine factors secreted by these cells. These biomolecules also trigger antiapoptotic events to prevent further degeneration of the diseased organ through paracrine signalling mechanisms. In comparison with the normal physiological conditions, an increased paracrine gradient is observed within the peripheral system of diseased organs that enhances the migration of tissue-specific MSCs towards the site of infection or injury to promote healing. Thus, upon administration of conditioned media derived from mesenchymal stem cell cultures (MSC-CM) could contribute in maintaining the increased paracrine factor gradient between the diseased organ and the stem cell niche in order to speed up the process of recovery. Based on the principle of the paracrine signalling mechanism, MSC-CM, also referred as the secretome of the MSCs, is a rich source of the paracrine factors and are being studied extensively for a wide range of regenerative therapies such as myocardial infarction, stroke, bone regeneration, hair growth, and wound healing. This article highlights the current technological applications and advances of MSC-CM with the aim to appraise its future potential as a regenerative therapeutic agent.

Exercise and Cardiovascular Progenitor Cells

Autologous stem/progenitor cell-based methods to restore blood flow and function to ischemic tissues are clinically appealing for the substantial proportion of the population with cardiovascular diseases. Early preclinical and case studies established the therapeutic potential of autologous cell therapies for neovascularization in ischemic tissues. However, trials over the past ∼15 years reveal the benefits of such therapies to be much smaller than originally estimated and a definitive clinical benefit is yet to be established. Recently, there has been an emphasis on improving the number and function of cells [herein generally referred to as circulating angiogenic cells (CACs)] used for autologous cell therapies. CACs include of several subsets of circulating cells, including endothelial progenitor cells, with proangiogenic potential that is largely exerted through paracrine functions. As exercise is known to improve CV outcomes such as angiogenesis and endothelial function, much attention is being given to exercise to improve the number and function of CACs. Accordingly, there is a growing body of evidence that acute, short-term, and chronic exercise have beneficial effects on the number and function of different subsets of CACs. In particular, recent studies show that aerobic exercise training can increase the number of CACs in circulation and enhance the function of isolated CACs as assessed in ex vivo assays. This review summarizes the roles of different subsets of CACs and the effects of acute and chronic exercise on CAC number and function, with a focus on the number and paracrine function of circulating CD34+ cells, CD31+ cells, and CD62E+ cells. © 2019 American Physiological Society. Compr Physiol 9:767-797, 2019.