The Role of Mesenchymal Stem Cells in Atherosclerosis: Prospects for Therapy via the Modulation of Inflammatory Milieu

Understanding the intricacies of cellular senescence in atherosclerosis: Mechanisms and therapeutic implications

Cardiovascular disease is currently the largest cause of mortality and disability globally, surpassing communicable diseases, and atherosclerosis is the main contributor to this epidemic. Aging is intimately linked to atherosclerosis development and progression, however, the mechanism of aging in atherosclerosis is not well known. To emphasize the significant research on the involvement of senescent cells in atherosclerosis, we begin by outlining compelling evidence that indicates various types of senescent cells and SASP factors linked to atherosclerotic phenotypes. We subsequently provide a comprehensive summary of the existing knowledge, shedding light on the intricate mechanisms through which cellular senescence contributes to the pathogenesis of atherosclerosis. Further, we cover that senescence can be identified by both structural changes and several senescence-associated biomarkers. Finally, we discuss that preventing accelerated cellular senescence represents an important therapeutic potential, as permanent changes may occur in advanced atherosclerosis. Together, the review summarizes the relationship between cellular senescence and atherosclerosis, and inspects the molecular knowledge, and potential clinical significance of senescent cells in developing senescent-based therapy, thus providing crucial insights into their biology and potential therapeutic exploration.

Therapeutic potentials of mesenchymal stem cells in the treatment of inflammatory bowel disease in rats

Interleukin-1beta (IL-1β) and interleukin-17A (IL-17A) have strong pro-inflammatory activities that are involved in inflammatory bowel diseases (IBDs). Mesenchymal stem cell (MSC) therapy is considered a promising treatment for IBD. This study was performed to understand the role of rat Nlrp3 inflammasome, Hmgb1, and pro-inflammatory cytokines (IL-1β and IL-17a) in the pathogenesis of IBD. Also, to evaluate the role of human umbilical cord blood-MSCs (hUCB-MSCs) in the management of IBD. The rats were in four groups: normal controls, indomethacin-induced IBD group, indomethacin-induced IBD rats that received phosphate-buffered saline (PBS), and the IBD group that received hUCB-MSCs as a treatment. The messenger RNA (mRNA) expression levels of rat Nlrp3, Hmgb1, IL-1β, and IL-17a were evaluated by quantitative real-time polymerase chain reaction. Histopathological examination of the small intestinal tissues of the studied rats was performed. There was a significant upregulation of the rat Nlrp3, IL-1β, IL-17a mRNA expression (p < 0.001 for the three parameters), and Hmgb1 (p < 0.05) in the untreated IBD group compared to the normal control group. In the MSC-treated group, IL-1β, IL-17a, and rat Nlrp3 mRNA expression significantly decreased compared to both the untreated IBD group and PBS group (p < 0.05 for all). hUCB-MSCs ameliorated IBD in rats by downregulating the pro-inflammatory cytokines (IL-1β and IL-17a) and other inflammatory mediators such as Hmgb1 and rat Nlrp3.

Exploring the mechanism of atherosclerosis and the intervention of traditional Chinese medicine combined with mesenchymal stem cells based on inflammatory targets

Atherosclerosis (AS) is a chronic inflammatory vascular disease, which is the common pathological basis of cardiovascular and cerebrovascular diseases. The immune inflammatory response throughout the course of AS has been evidenced by studies, in which a large number of immune cells and inflammatory factors play a crucial role in the pathogenesis of AS. The inflammation related to AS is mainly mediated by inflammatory cytokines (IL-1β, IL-6, IL-18, TNF-α, hs-CRP, SAA), inflammatory enzymes (Lp-PLA2, sPLA2-IIA, MMPs), and inflammatory signaling pathways (P38 MAPK signaling pathway, NF-κB signaling pathway, TLR2/4 signaling pathway). It is involved in the pathophysiological process of AS, and the degree of inflammation measured by it can be used to evaluate the risk of progression of AS plaque instability. In recent years, traditional Chinese medicine (TCM) has shown the advantage of minimal side effects in immune regulation and has made some progress in the prevention and treatment of AS. Mesenchymal stem cells (MSCs), as self-renewal, highly differentiated, and pluripotent stem cells with anti-inflammatory properties and immune regulation, have been widely used for AS treatment. They also play an important inflammation-immune regulatory function in AS. Notably, in terms of regulating immune cells and inflammatory factors, compared with TCM and its compound, the combination therapy has obvious anti-inflammatory advantages over the use of MSCs alone. It is an important means to further improve the efficacy of AS and provides a new way for the prevention and treatment of AS.

Application of mesenchymal stem cells for anti-senescence and clinical challenges

Senescence is a hot topic nowadays, which shows the accumulation of senescent cells and inflammatory factors, leading to the occurrence of various senescence-related diseases. Although some methods have been identified to partly delay senescence, such as strengthening exercise, restricting diet, and some drugs, these only slow down the process of senescence and cannot fundamentally delay or even reverse senescence. Stem cell-based therapy is expected to be a potential effective way to alleviate or cure senescence-related disorders in the coming future. Mesenchymal stromal cells (MSCs) are the most widely used cell type in treating various diseases due to their potentials of self-replication and multidirectional differentiation, paracrine action, and immunoregulatory effects. Some biological characteristics of MSCs can be well targeted at the pathological features of aging. Therefore, MSC-based therapy is also a promising strategy to combat senescence-related diseases. Here we review the recent progresses of MSC-based therapies in the research of age-related diseases and the challenges in clinical application, proving further insight and reference for broad application prospects of MSCs in effectively combating senesce in the future.

TNF-α Preconditioning Improves the Therapeutic Efficacy of Mesenchymal Stem Cells in an Experimental Model of Atherosclerosis

Atherosclerosis (AS) is an inflammatory disease involving multiple factors in its initiation and development. In recent years, the potential application of mesenchymal stem cells (MSCs) for treating AS has been investigated. This study examined the effect of TNF-α preconditioning on MSCs' therapeutic efficacy in treating AS in ApoE KO mice. TNF-α-treated MSCs were administered to high-fat diet-treated ApoE KO mice. Cytokine and serum lipid levels were measured before and after treatment. Cryosections of the atherosclerotic aorta were stained with Oil-Red-O, and the relative areas of atherosclerotic lesions were measured. The level of Tregs were increased in TNF-α-MSC-treated animals compared to the MSCs group. In addition, the systemic administration of TNF-α-MSCs to ApoE KO mice reduced the level of proinflammatory cytokines such as TNF-α and IFN-γ and increased the level of the immunosuppressive IL-10 in the blood serum. Total cholesterol and LDL levels were decreased, and HDL levels were increased in the TNF-α-MSCs group of ApoE KO mice. A histological analysis showed that TNF-α-MSCs decreased the size of the atherosclerotic lesion in the aorta of ApoE KO mice by 38%, although there was no significant difference when compared with untreated MSCs. Thus, our data demonstrate that TNF-α-MSCs are more effective at treating AS than untreated MSCs.

The effect of lncRNA MIR155HG-modified MSCs and exosome delivery to synergistically attenuate vein graft intimal hyperplasia

Background

The mesenchymal stem cells (MSCs) were used to repair tissue injury. However, the treatment effect was not satisfactory. We investigated whether lncRNA MIR155HG could promote survival and migration of MSCs under oxidative stress, which mimics in vivo environments. Furthermore, we studied the protective effect of exosomes secreted by MSCs transfected with MIR155HG on endothelial cells. This study aimed to determine whether exploiting MSCs and exosomes modified with lncRNA MIR155HG would exert synergistic therapeutic effect to attenuate vein graft intimal hyperplasia more effectively.

Methods

Lentivirus containing lncRNA MIR155HG overexpressing vector was packaged and used to infect MSCs. Then, CCK-8 assay, flow cytometry, Transwell assay, and Elisa assay were used to assess the functional changes of MSCs with overexpressed MIR155HG (OE-MSCs). Furthermore, the associated pathways were screened by Western blot. MIR155HG-MSCs-derived exosomes (OE-exo) were collected and co-cultured with human umbilicus vein endothelial cell (HUVEC). We validated the protective effect of OE-exo on HUVEC. In vivo, both MSCs and exosomes modified with MIR155HG were injected into a vein graft rat model via tail vein. We observed MSCs homing and intimal hyperplasia of vein graft using a fluorescent microscope and histological stain.

Results

Our study found that lncRNA MIR155HG promoted proliferation, migration, and anti-apoptosis of MSCs. NF-κB pathway took part in the regulation process induced by MIR155HG. OE-exo could enhance the activity and healing ability of HUVEC and reduce apoptosis. In vivo, OE-MSCs had a higher rate of homing to vascular endothelium. The combined treatment with OE-MSCs and OE-exo protected vascular endothelial integrity, reduced inflammatory cell proliferation, and significantly attenuated intimal hyperplasia of vein graft.

Conclusion

LncRNA MIR155HG could promote the survival and activity of MSCs, and reduce the apoptosis of HUVECs using exosome delivery. Exploiting MSCs and exosomes modified with MIR155HG could attenuate vein graft intimal hyperplasia more effectively and maximize the surgical effect.

Mechanotransduction through adhesion molecules: Emerging roles in regulating the stem cell niche

Stem cells have been shown to play an important role in regenerative medicine due to their proliferative and differentiation potential. The challenge, however, lies in regulating and controlling their potential for this purpose. Stem cells are regulated by growth factors as well as an array of biochemical and mechanical signals. While the role of biochemical signals and growth factors in regulating stem cell homeostasis is well explored, the role of mechanical signals has only just started to be investigated. Stem cells interact with their niche or to other stem cells via adhesion molecules that eventually transduce mechanical cues to maintain their homeostatic function. Here, we present a comprehensive review on our current understanding of the influence of the forces perceived by cell adhesion molecules on the regulation of stem cells. Additionally, we provide insights on how this deeper understanding of mechanobiology of stem cells has translated toward therapeutics.

EndMT-derived mesenchymal stem cells: a new therapeutic target to atherosclerosis treatment

Cardiovascular diseases, such as coronary artery disease and stroke, are the main threats to human health worldwide. Atherosclerosis, a chronic inflammatory disorder, plays a role as an initiator of all of the above-mentioned diseases. Cell therapy for diseases has attracted widespread attention. Mesenchymal stem cells (MSCs) are a type of stem cell that still exist in adults and have the characteristics of self-renewal ability, pluripotent differentiation potential, immunomodulation, tissue regeneration, anti-inflammation and low immunogenicity. In light of the properties of MSCs, some researchers have begun to target MSCs to create a possible way to alleviate atherosclerosis. Most of these studies are focused on MSC transplantation, injecting MSCs to modulate macrophages, the key inflammatory cell in atherosclerosis plaque. According to recent studies, researchers found that endothelial-to-mesenchymal transition (EndMT) has something to do with atherosclerosis development. A new cell type MSC might also appear during the EndMT process. In this article, we summarize the characteristics of MSCs, the latest progress of MSC research and its application prospects, and in view of the process of EndMT occurring in atherosclerosis, we propose some new ideas for the treatment of atherosclerosis by targeting MSCs.

Mesenchymal stem cell transplantation alleviated atherosclerosis in systemic lupus erythematosus through reducing MDSCs

Objective

The mechanism by which mesenchymal stem cell (MSC) transplantation alleviates atherosclerosis in systemic lupus erythematosus (SLE) remains elusive. In this study, we aim to explore the efficacy and mechanism of MSC in ameliorating atherosclerosis in SLE.

Methods

ApoE^−/− and Fas^−/− mice on the B6 background were cross-bred to generate SLE mice with atherosclerosis. Myeloid-derived suppressor cells (MDSCs) were sorted and quantified. The apoE^−/−Fas^−/− mice were either treated with anti-Gr antibody or injected with MDSCs. The lupus-like autoimmunity and atherosclerotic lesions were evaluated. Furthermore, the apoE^−/−Fas^−/− mice were transplanted with MSCs and lupus-like autoimmunity and atherosclerotic lesions were assessed.

Results

MDSCs in peripheral blood, spleen, draining lymph nodes increased in apoE^−/−Fas^−/− mice compared with B6 mice. Moreover, the adoptive transfer of MDSCs aggravated both atherosclerosis and SLE pathologies, whereas depleting MDSCs ameliorated those pathologies in apoE^−/−Fas^−/− mice. MSC transplantation in apoE^−/−Fas^−/− mice decreased the percentage of MDSCs, alleviated the typical atherosclerotic lesions, including atherosclerotic lesions in aortae and liver, and reduced serum cholesterol, triglyceride and low-density lipoprotein levels. MSC transplantation also reduced SLE pathologies, including splenomegaly, glomerular lesions, anti-dsDNA antibody in serum, urine protein and serum creatinine. Moreover, MSC transplantation regulated the generation and function of MDSCs through secreting prostaglandin E 2 (PGE2).

Conclusion

Taken together, these results indicated that the increased MDSCs contributed to atherosclerosis in SLE. MSC transplantation ameliorated the atherosclerosis and SLE through reducing MDSCs by secreting PGE2.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-03002-y.

Stem Cell Based Approaches to Modulate the Matrix Milieu in Vascular Disorders

The extracellular matrix (ECM) represents a complex and dynamic framework for cells, characterized by tissue-specific biophysical, mechanical, and biochemical properties. ECM components in vascular tissues provide structural support to vascular cells and modulate their function through interaction with specific cell-surface receptors. ECM–cell interactions, together with neurotransmitters, cytokines, hormones and mechanical forces imposed by blood flow, modulate the structural organization of the vascular wall. Changes in the ECM microenvironment, as in post-injury degradation or remodeling, lead to both altered tissue function and exacerbation of vascular pathologies. Regeneration and repair of the ECM are thus critical toward reinstating vascular homeostasis. The self-renewal and transdifferentiating potential of stem cells (SCs) into other cell lineages represents a potentially useful approach in regenerative medicine, and SC-based approaches hold great promise in the development of novel therapeutics toward ECM repair. Certain adult SCs, including mesenchymal stem cells (MSCs), possess a broader plasticity and differentiation potential, and thus represent a viable option for SC-based therapeutics. However, there are significant challenges to SC therapies including, but not limited to cell processing and scaleup, quality control, phenotypic integrity in a disease milieu in vivo, and inefficient delivery to the site of tissue injury. SC-derived or -inspired strategies as a putative surrogate for conventional cell therapy are thus gaining momentum. In this article, we review current knowledge on the patho-mechanistic roles of ECM components in common vascular disorders and the prospects of developing adult SC based/inspired therapies to modulate the vascular tissue environment and reinstate vessel homeostasis in these disorders.

Wnt2 Contributes to the Development of Atherosclerosis

Atherosclerosis, is a chronic inflammatory disease, characterized by the narrowing of the arteries resulting from the formation of intimal plaques in the wall of arteries. Yet the molecular mechanisms responsible for maintaining the development and progression of atherosclerotic lesions have not been fully defined. In this study, we show that TGF-β activates the endothelial-to-mesenchymal transition (EndMT) in cultured human aortic endothelial cells (HAECs) and this transition is dependent on the key executor of the Wnt signaling pathway in vitro. This study presents the first evidence describing the mechanistic details of the TGF-β-induced EndMT signaling pathway in HAECs by documenting the cellular transition to the mesenchymal phenotype including the expression of mesenchymal markers α-SMA and PDGFRα, and the loss of endothelial markers including VE-cadherin and CD31. Furthermore, a short hairpin RNA (shRNA) screening revealed that Wnt2 signaling is required for TGF-β-mediated EndMT of HAECs. Also, we found that LDLR^−/− mice fed on a high-fat western-type diet (21% fat, 0.2% cholesterol) expressed high levels of Wnt2 protein in atherosclerotic lesions, confirming that this signaling pathway is involved in atherosclerosis in vivo. These findings suggest that Wnt2 may contribute to atherosclerotic plaque development and this study will render Wnt2 as a potential target for therapeutic intervention aiming at controlling atherosclerosis.

Exosome-eluting stents for vascular healing after ischaemic injury

Drug-eluting stents implanted after ischaemic injury reduce the proliferation of endothelial cells and vascular smooth muscle cells and thus neointimal hyperplasia. However, the eluted drug also slows down the re-endothelialization process, delays arterial healing and can increase the risk of late restenosis. Here we show that stents releasing exosomes derived from mesenchymal stem cells in the presence of reactive oxygen species enhance vascular healing in rats with renal ischaemia-reperfusion injury, promoting endothelial cell tube formation and proliferation, and impairing the migration of smooth muscle cells. Compared with drug-eluting stents and bare-metal stents, the exosome-coated stents accelerated re-endothelialization and decreased in-stent restenosis 28 days after implantation. We also show that exosome-eluting stents implanted in the abdominal aorta of rats with unilateral hindlimb ischaemia regulated macrophage polarization, reduced local vascular and systemic inflammation, and promoted muscle tissue repair.

Mesenchymal stem cells ameliorate silica-induced pulmonary fibrosis by inhibition of inflammation and epithelial-mesenchymal transition

Silicosis is a devastating occupational disease caused by long-term inhalation of silica particles, inducing irreversible lung damage and affecting lung function, without effective treatment. Mesenchymal stem cells (MSCs) are a heterogeneous subset of adult stem cells that exhibit excellent self-renewal capacity, multi-lineage differentiation potential and immunomodulatory properties. The aim of this study was to explore the effect of bone marrow-derived mesenchymal stem cells (BMSCs) in a silica-induced rat model of pulmonary fibrosis. The rats were treated with BMSCs on days 14, 28 and 42 after perfusion with silica. Histological examination and hydroxyproline assays showed that BMSCs alleviated silica-induced pulmonary fibrosis in rats. Results from ELISA and qRT-PCR indicated that BMSCs inhibited the expression of inflammatory cytokines TNF-α, IL-1β and IL-6 in lung tissues and bronchoalveolar lavage fluid of rats exposed to silica particles. We also performed qRT-PCR, Western blot and immunohistochemistry to examine epithelial-mesenchymal transition (EMT)-related indicators and demonstrated that BMSCs up-regulate E-cadherin and down-regulate vimentin and extracellular matrix (ECM) components such as fibronectin and collagen Ⅰ. Additionally, BMSCs inhibited the silica-induced increase in TGF-β1, p-Smad2 and p-Smad3 and decrease in Smad7. These results suggested that BMSCs can inhibit inflammation and reverse EMT through the inhibition of the TGF-β/Smad signalling pathway to exhibit an anti-fibrotic effect in the rat silicosis model. Our study provides a new and meaningful perspective for silicosis treatment strategies.

Initiation of Post-Primary Tuberculosis of the Lungs: Exploring the Secret Role of Bone Marrow Derived Stem Cells

Mycobacterium tuberculosis (Mtb), the causative organism of pulmonary tuberculosis (PTB) now infects more than half of the world population. The efficient transmission strategy of the pathogen includes first remaining dormant inside the infected host, next undergoing reactivation to cause post-primary tuberculosis of the lungs (PPTBL) and then transmit via aerosol to the community. In this review, we are exploring recent findings on the role of bone marrow (BM) stem cell niche in Mtb dormancy and reactivation that may underlie the mechanisms of PPTBL development. We suggest that pathogen's interaction with the stem cell niche may be relevant in potential inflammation induced PPTBL reactivation, which need significant research attention for the future development of novel preventive and therapeutic strategies for PPTBL, especially in a post COVID-19 pandemic world. Finally, we put forward potential animal models to study the stem cell basis of Mtb dormancy and reactivation.

Neglected No More: Emerging Cellular Therapies in Traumatic Injury

Traumatic injuries are a leading cause of death and disability in both military and civilian populations. Given the complexity and diversity of traumatic injuries, novel and individualized treatment strategies are required to optimize outcomes. Cellular therapies have potential benefit for the treatment of acute or chronic injuries, and various cell-based pharmaceuticals are currently being tested in preclinical studies or in clinical trials. Cellular therapeutics may have the ability to complement existing therapies, especially in restoring organ function lost due to tissue disruption, prolonged hypoxia or inflammatory damage. In this article we highlight the current status and discuss future directions of cellular therapies for the treatment of traumatic injury. Both published research and ongoing clinical trials are discussed here.

Autologous adipose mesenchymal stem cell administration in arteriosclerosis and potential for anti-aging application: a retrospective cohort study

Objective

Arteriosclerosis is an age-related disease and a leading cause of cardiovascular disease. In animal experiments, mesenchymal stem cells and its culture-conditioned medium have been shown to be promising tools for prevention or treatment of arteriosclerosis. On the basis of these evidences, we aimed to assess whether administration of autologous adipose-derived mesenchymal stem cells (Ad-MSC) is safe and effective for treatment of arteriosclerosis.

Methods

We retrospectively reviewed clinical records of patients with arteriosclerosis who had received autologous Ad-MSC administration at our clinic. Patients’ characteristics were recorded and data on lipid profile, intimal-media thickness (IMT), cardio-ankle vascular index (CAVI), and ankle-brachial index (ABI) before and after Ad-MSC administration were collected and compared.

Results

Treatment with Ad-MSC significantly improved HDL, LDL, and remnant-like particle (RLP) cholesterol levels. No adverse effect or toxicity was observed in relation to the treatment. Of the patients with abnormal HDL values before treatment, the vast majority showed improvement in the values. Overall, the measurements after treatment were significantly increased compared with those before treatment (p < 0.01). In addition, decreases in LDL cholesterol and RLP levels were observed after treatment in patients who had abnormal LDL cholesterol or RLP levels before treatment. The majority of patients with pre-treatment abnormal CAVI values had improved values after treatment. In patients with available IMT values, a significant decrease in the IMT values was found after therapy (p < 0.01). All patients with borderline arteriosclerosis disease had improved laboratory findings after treatment. In general, post-treatment values were significantly decreased as compared with pre-treatment values. Of the patients with normal ABI values before treatment at the same time as CAVI, the vast majority remained normal after treatment.

Conclusions

These findings suggest that Ad-MSC administration is safe and effective in patients developing arteriosclerosis, thereby providing an attractive tool for anti-aging application.

Fibroblasts in atherosclerosis: heterogeneous and plastic participants

PURPOSE OF REVIEW

Fibroblasts are very heterogeneous and plastic cells in the vasculature. A growing interest in fibroblasts in healthy and atherosclerotic vasculature is observed, next to macrophages, endothelial cells, and smooth muscle cells (SMCs). In this review, we discuss fibroblast presence, heterogeneity, origin, and plasticity in health and atherosclerosis based on latest literature.

RECENT FINDINGS

With help of single cell sequencing (SCS) techniques, we have gained more insight into presence and functions of fibroblasts in atherosclerosis. Next to SMCs, fibroblasts are extracellular matrix-producing cells abundant in the vasculature and involved in atherogenesis. Fibroblasts encompass a heterogeneous population and SCS data reveal several fibroblast clusters in healthy and atherosclerotic tissue with varying gene expression and function. Moreover, recent findings indicate interesting similarities between adventitial stem and/or progenitor cells and fibroblasts. Also, communication with inflammatory cells opens up a new therapeutic avenue.

SUMMARY

Because of their highly plastic and heterogeneous nature, modulating fibroblast cell function and communication in the atherosclerotic vessel might be useful in battling atherosclerosis from within the plaque.

The involving progress of MSCs based therapy in atherosclerosis

Atherosclerosis is a chronic progressive vascular inflammation characterized by lipid deposition and plaque formation, for which vascular cell dysfunction and impaired immune responses are involved. Up to now, lipid-lowering drugs remain the main therapy for treating atherosclerosis; however, the surgical or interventional therapy is often applied, and yet, morbidity and mortality of such cardiovascular disease remain high worldwide. Over the past decades, an anti-inflammatory approach has become an important therapeutic target for dealing with atherosclerosis, as altered immune responses have been regarded as an essential player in the pathological process of vascular abnormality induced by hyperlipidemia. Interestingly, mesenchymal stem cells, one type of stem cells with the capabilities of self-renewal and multi-potential, have demonstrated their unique immunomodulatory function in the various pathological process, especially in atherosclerosis. While some controversies remain regarding their therapeutic efficacy and working mechanisms, our present review aims to summarize the current research progress on stem cell-based therapy, focusing on its immunomodulatory effects on the pathogenesis of atherosclerosis and how endothelial cells, smooth muscle cells, and other immune cells are regulated by MSC-based therapy.

Umbilical Cord-derived Mesenchymal Stem Cells for COVID-19 Patients with Acute Respiratory Distress Syndrome (ARDS)

The coronavirus SARS-CoV-2 is cause of a global pandemic of a pneumonia-like disease termed Coronavirus Disease 2019 (COVID-19). COVID-19 presents a high mortality rate, estimated at 3.4%. More than 1 out of 4 hospitalized COVID-19 patients require admission to an Intensive Care Unit (ICU) for respiratory support, and a large proportion of these ICU-COVID-19 patients, between 17% and 46%, have died. In these patients COVID-19 infection causes an inflammatory response in the lungs that can progress to inflammation with cytokine storm, Acute Lung Injury (ALI), Acute Respiratory Distress Syndrome (ARDS), thromboembolic events, disseminated intravascular coagulation, organ failure, and death. Mesenchymal Stem Cells (MSCs) are potent immunomodulatory cells that recognize sites of injury, limit effector T cell reactions, and positively modulate regulatory cell populations. MSCs also stimulate local tissue regeneration via paracrine effects inducing angiogenic, anti-fibrotic and remodeling responses. MSCs can be derived in large number from the Umbilical Cord (UC). UC-MSCs, utilized in the allogeneic setting, have demonstrated safety and efficacy in clinical trials for a number of disease conditions including inflammatory and immune-based diseases. UC-MSCs have been shown to inhibit inflammation and fibrosis in the lungs and have been utilized to treat patients with severe COVID-19 in pilot, uncontrolled clinical trials, that reported promising results. UC-MSCs processed at our facility have been authorized by the FDA for clinical trials in patients with an Alzheimer's Disease, and in patients with Type 1 Diabetes (T1D). We hypothesize that UC-MSC will also exert beneficial therapeutic effects in COVID-19 patients with cytokine storm and ARDS. We propose an early phase controlled, randomized clinical trial in COVID-19 patients with ALI/ARDS. Subjects in the treatment group will be treated with two doses of UC-MSC (l00 × 10⁶ cells). The first dose will be infused within 24 hours following study enrollment. A second dose will be administered 72 ± 6 hours after the first infusion. Subject in the control group will receive infusion of vehicle (DPBS supplemented with 1% HSA and 70 U/kg unfractionated Heparin, delivered IV) following the same timeline. Subjects will be evaluated daily during the first 6 days, then at 14, 28, 60, and 90 days following enrollment (see Schedule of Assessment for time window details). Safety will be determined by adverse events (AEs) and serious adverse events (SAEs) during the follow-up period. Efficacy will be defined by clinical outcomes, as well as a variety of pulmonary, biochemical and immunological tests. Success of the current study will provide a framework for larger controlled, randomized clinical trials and a means of accelerating a possible solution for this urgent but unmet medical need. The proposed early phase clinical trial will be performed at the University of Miami (UM), in the facilities of the Diabetes Research Institute (DRI), UHealth Intensive Care Unit (ICU) and the Clinical Translational Research Site (CTRS) at the University of Miami Miller School of Medicine and at the Jackson Memorial Hospital (JMH).