PDGFRα/Sca-1 Sorted Mesenchymal Stromal Cells Reduce Liver Injury in Murine Models of Hepatic Ischemia-Reperfusion Injury.

Liver transplantation is an effective therapy, but increasing demand for donor organs has led to the use of marginal donor organs with increased complication rates. Mesenchymal stromal cells (MSC) pleiotropically modulate aberrant immune-mediated responses and represent a potential therapy to target the inflammation seen post-transplant with marginal donor livers. To avoid the confounding effects of xenotransplantation seen in studies with human MSC, a PDGFRα/Sca-1 (PaS) sorted MSC population was used which was analogous to human MSC populations (LNGFR+Thy-1+VCAM-1Hi). PaS MSC are a well-described population that demonstrate MSC properties without evidence of clonal mutation during expansion. We demonstrate their anti-inflammatory properties herein through their suppression of T-lymphocyte proliferation in vitro and secretion of anti-inflammatory cytokines (IL-10 and OPG) after stimulation (P = .004 and P = .003). The MDR2-/- model of biliary injury and hepatic ischemia-reperfusion (HIR) injury models were used to replicate the non-anastomotic biliary complications seen following liver transplantation. Systemic MSC therapy in MDR2-/- mice led to reduced liver injury with an increase in restorative macrophages (5913 ± 333.9 vs 12 597 ± 665.8, P = .002, n = 7) and a change in lymphocyte ratios (3.55 ± 0.37 vs 2.59 ± 0.139, P = .023, n = 17), whereas subcutaneous administration of MSC showed no beneficial effect. MSC also reduced cell death in the HIR model assessed by Periodic acid-Schiff (PAS) staining (91.7% ± 2.8 vs 80.1% ± 4.6, P = .03). Systemically administered quantum dot-labeled MSC were tracked using single-cell resolution CryoViz imaging which demonstrated their sequestration in the lungs alongside retention/redistribution to injured liver tissue. MSC represent a potential novel therapy in marginal organ transplantation which warrants further study.

Efficacy of mesenchymal stromal cells intraspinal transplantation for patients with different degrees of spinal cord injury: A systematic review and meta-analysis.

BACKGROUND AIMS: Several studies have reported that mesenchymal stromal cells (MSCs) may improve neurological functions in patients with spinal cord injury (SCI). In this study, we conducted a systematic review and meta-analysis to summarize the effects of MSC treatment on different degrees of severity of SCI. METHODS: Systematic searching of studies reporting outcomes of MSCs on specific injury severities of patients with SCI was performed in The National Library of Medicine (MEDLINE), Embase and Cochrane for published articles up to the 6 July 2022. Two investigators independently reviewed the included studies and extracted the relevant data. The standardized mean differences of American Spinal Injury Association (ASIA) motor score, ASIA light touch scores, ASIA pinprick scores and the Barthel index between baseline and follow-ups were pooled. RESULTS: A total of eight studies were included. A large majority focused on patients with ASIA grade A classification. The pooled mean differences of ASIA motor scores, ASIA light touch scores, ASIA pinprick scores and the Barthel index were -2.78 (95% confidence interval [CI] -5.12 to -0.43, P = 0.02), -18.26 (95% CI -26.09 to -10.43, P < 0.01), -17.08 (95% CI -24.10 to -10.07, P < 0.01) and -4.37 (95% CI -10.96 to 2.22, P = 0.19), respectively. CONCLUSIONS: MSC transplantation was a significantly effective therapy for patients with SCI with ASIA grade A. In the future, further studies are warranted to confirm the potential beneficial effects of MSC therapy.

A roadmap from research to clinical testing of mesenchymal stromal cell exosomes in the treatment of psoriasis.

The most clinically trialed cells, mesenchymal stromal cells (MSCs), are now known to mainly exert their therapeutic activity through paracrine secretions, which include exosomes. To mitigate potential regulatory concerns on the scalability and reproducibility in the preparations of MSC exosomes, MSC exosomes were produced using a highly characterized MYC-immortalized monoclonal cell line. These cells do not form tumors in athymic nude mice or exhibit anchorage-independent growth, and their exosomes do not carry MYC protein or promote tumor growth. Unlike intra-peritoneal injections, topical applications of MSC exosomes in a mouse model of IMQ-induced psoriasis alleviate interleukin (IL)-17, IL-23 and terminal complement complex, C5b9 in psoriatic skin. When applied on human skin explants, fluorescence from covalently labeled fluorescent MSC exosomes permeated and persisted in the stratum corneum for about 24 hours with negligible exit out of the stratum corneum into the underlying epidermis. As psoriatic stratum corneums are uniquely characterized by activated complements and Munro microabscesses, we postulated that topically applied exosomes permeate the psoriatic stratum corneum to inhibit C5b9 complement complex through CD59, and this inhibition attenuated neutrophil secretion of IL-17. Consistent with this, we demonstrated that assembly of C5b9 on purified human neutrophils induced IL-17 secretion and this induction was abrogated by MSC exosomes, which was in turn abrogated by a neutralizing anti-CD 59 antibody. We thus established the mechanism of action for the alleviation of psoriatic IL-17 by topically applied exosomes.

Extracellular Matrix Synthesis and Remodeling by Mesenchymal Stromal Cells Is Context-Sensitive.

Matrix remodeling could be an important mode of action of multipotent mesenchymal stromal cells (MSC) in extracellular matrix (ECM) disease, but knowledge is limited in this respect. As MSC are well-known to adapt their behavior to their environment, we aimed to investigate if their mode of action would change in response to healthy versus pathologically altered ECM. Human MSC-derived ECM was produced under different culture conditions, including standard culture, culture on Matrigel-coated dishes, and stimulation with the pro-fibrotic transforming growth factor-ß1 (TGFß1). The MSC-ECM was decellularized, characterized by histochemistry, and used as MSC culture substrate reflecting different ECM conditions. MSC were cultured on the different ECM substrates or in control conditions for 2 days. Culture on ECM increased the presence of surface molecules with ECM receptor function in the MSC, demonstrating an interaction between MSC and ECM. In MSC cultured on Matrigel-ECM and TGFß1-ECM, which displayed a fibrosis-like morphology, gene expression of collagens and decorin, as well as total matrix metalloproteinase (MMP) activity in the supernatant were decreased as compared with control conditions. These results demonstrated that MSC adapt to their ECM environment, which may include pathological adaptations that could compromise therapeutic efficacy.

Beneficial effects of autologous mesenchymal stem cell transplantation in active progressive multiple sclerosis.

In this study (trial registration: NCT02166021), we aimed to evaluate the optimal way of administration, the safety and the clinical efficacy of mesenchymal stem cell (MSC) transplantation in patients with active and progressive multiple sclerosis. Forty-eight patients (28 males and 20 females) with progressive multiple sclerosis (Expanded Disability Status Scale: 3.0-6.5, mean : 5.6 ± 0.8, mean age: 47.5 ± 12.3) and evidence of either clinical worsening or activity during the previous year, were enrolled (between 2015 and 2018). Patients were randomized into three groups and treated intrathecally (IT) or intravenously (IV) with autologous MSCs (1 × 106/kg) or sham injections. After 6 months, half of the patients from the MSC-IT and MSC-IV groups were retreated with MSCs, and the other half with sham injections. Patients initially assigned to sham treatment were divided into two subgroups and treated with either MSC-IT or MSC-IV. The study duration was 14 months. No serious treatment-related safety issues were detected. Significantly fewer patients experienced treatment failure in the MSC-IT and MSC-IV groups compared with those in the sham-treated group (6.7%, 9.7%, and 41.9%, respectively, P = 0.0003 and P = 0.0008). During the 1-year follow-up, 58.6% and 40.6% of patients treated with MSC-IT and MSC-IV, respectively, exhibited no evidence of disease activity compared with 9.7% in the sham-treated group (P < 0.0001 and P < 0.0048, respectively). MSC-IT transplantation induced additional benefits on the relapse rate, on the monthly changes of the T2 lesion load on MRI, and on the timed 25-foot walking test, 9-hole peg test, optical coherence tomography, functional MRI and cognitive tests. Treatment with MSCs was well-tolerated in progressive multiple sclerosis and induced short-term beneficial effects regarding the primary end points, especially in the patients with active disease. The intrathecal administration was more efficacious than the intravenous in several parameters of the disease. A phase III trial is warranted to confirm these findings.

Mesenchymal Stromal Cells Adapt to Chronic Tendon Disease Environment with an Initial Reduction in Matrix Remodeling.

Tendon lesions are common sporting injuries in humans and horses alike. The healing process of acute tendon lesions frequently results in fibrosis and chronic disease. In horses, local mesenchymal stromal cell (MSC) injection is an accepted therapeutic strategy with positive influence on acute lesions. Concerning the use of MSCs in chronic tendon disease, data are scarce but suggest less therapeutic benefit. However, it has been shown that MSCs can have a positive effect on fibrotic tissue. Therefore, we aimed to elucidate the interplay of MSCs and healthy or chronically diseased tendon matrix. Equine MSCs were cultured either as cell aggregates or on scaffolds from healthy or diseased equine tendons. Higher expression of tendon-related matrix genes and tissue inhibitors of metalloproteinases (TIMPs) was found in aggregate cultures. However, the tenogenic transcription factor scleraxis was upregulated on healthy and diseased tendon scaffolds. Matrix metalloproteinase (MMPs) expression and activity were highest in healthy scaffold cultures but showed a strong transient decrease in diseased scaffold cultures. The release of glycosaminoglycan and collagen was also higher in scaffold cultures, even more so in those with tendon disease. This study points to an early suppression of MSC matrix remodeling activity by diseased tendon matrix, while tenogenic differentiation remained unaffected.

Secretory Activity of Mesenchymal Stromal Cells with Different Degree of Commitment under Conditions of Simulated Microgravity.

Microgravity negatively affects the bone tissue which manifested in a decrease in mineral density of the bones during long-term space flights. Impairments of bone homeostasis are determined among other things by changes in secretory activity of heterogeneous populations of low-committed precursors, such as mesenchymal stromal cells (MSC) and osteoblasts. We studied the effect of microgravity modeling during 10 days on paracrine activity of osteogenically committed and intact MSC. Cell response to simulated microgravity depended on the degree of commitment. The response of osteogenically committed MSC was less pronounced and manifested in increased production of sclerostin. In intact MSC, an increase in IL-8 and VEGF secretion and a decrease in osteoprotegerin level were detected. These changes can underlie the shift of bone homeostasis towards bone resorption.

Osteogenic Commitment of MSC Is Enhanced after Interaction with Umbilical Cord Blood Mononuclear Cells In Vitro.

The effectiveness of stroma-dependent expansion of hematopoietic cells ex vivo may depend on the level of commitment of multipotent mesenchymal stromal cells (MSC). Markers of MSC osteodifferentiation and the level of soluble hematopoiesis regulators were determined during their interaction with umbilical cord blood mononuclears. After 72-h co-culturing, an increase in the expression of ALPL and alkaline phosphatase activity was revealed. In conditioned medium of co-cultures, the levels of osteopontin and osteoprotegerin were elevated and the levels of osteocalcin and sclerostin were reduced. Co-culturing of umbilical cord blood mononuclears with osteocommitted MSC was accompanied by more pronounced increase in the concentration of both positive (GM-CSF and G-CSF) and negative (IP-10, MIP-1α, and MCP-3) regulators of hematopoiesis. Thus, umbilical cord blood mononuclears induced the formation of early osteogenic progenitor phenotype in MSC ex vivo, providing the microenvironmental conditions necessary to support hematopoiesis. Preliminary osteocommitted MSC were more sensitive to the effect of umbilical cord blood mononuclears.

Modulation of the in vitro angiogenic potential of human mesenchymal stromal cells from different tissue sources.

Mesenchymal stromal cells (MSCs) have been widely exploited for the treatment of several conditions due to their intrinsic regenerative and immunomodulatory properties. MSC have demonstrated to be particularly relevant for the treatment of ischemic diseases, where MSC-based therapies can stimulate angiogenesis and induce tissue regeneration. Regardless of the condition targeted, recent analyses of MSC-based clinical trials have demonstrated limited benefits indicating a need to improve the efficacy of this cell product. Preconditioning MSC ex vivo through microenvironment modulation was found to improve MSC survival rate and thus prolong their therapeutic effect. This workstudy aims at enhancing the in vitro angiogenic capacity of a potential MSC-based medicinal product by comparing different sources of MSC and culture conditions. MSC from three different sources (bone marrow [BM], adipose tissue [AT], and umbilical cord matrix [UCM]) were cultured with xenogeneic-/serum-free culture medium under static conditions and their angiogenic potential was studied. Results indicated a higher in vitro angiogenic capacity of UCM MSC, compared with cells derived from BM and AT. Physicochemical preconditioning of UCM MSC through a microcarrier-based culture platform and low oxygen concentration (2% O2 , compared with atmospheric air) increased the in vitro angiogenic potential of the cultured cells. Envisaging the clinical manufacturing of an allogeneic, off-the-shelf MSC-based product, preconditioned UCM MSC maintain the angiogenic gene expression profile upon cryopreservation and delivery processes in the conditions of our study. These results are expected to contribute to the development of MSC-based therapies in the context of angiogenesis.

Mesenchymal stromal cells for osteonecrosis.

Osteonecrosis (ON) is an acquired debilitating skeletal disorder, which is caused by a multitude of traumatic and non-traumatic etiological factors. Vascular damage, mechanical stress and increased intraosseous pressure have been discussed as contributors to ON. The optimal treatment of ON remains to be determined, since the current gold standard, core decompression, is insufficiently effective. Specific properties of mesenchymal stromal cells (MSCs) provide the rationale for their assessment in advanced stages of ON: Osteoinductive potential has been demonstrated and MSC preparations of suitable quality for use as medicinal products have been developed. Here we review the scant information on the use of allogeneic or autologous MSCs in advanced ON as well as potentially supportive data from pre-clinical studies with autologous bone marrow mononuclear cells (auto BM-MNCs), which have been studied quite extensively and the presumed therapeutic effect of which was attributed to the rare MSCs contained in these cell products. Outcomes in clinical trials with MSCs and auto-BM-MNCs remain preliminary and non-definitive, at best promising, with respect to their pharmacological effect. Clearly, though, the application of any of these cell therapies was technically feasible and safe in that it was associated with low complication rates. The heterogeneity of cell type and source, study protocols, cell manufacturing, cell properties, cell doses and surgical techniques might contribute to inconsistent results.

Transforming Growth Factor Beta 3-Loaded Decellularized Equine Tendon Matrix for Orthopedic Tissue Engineering.

Transforming growth factor beta 3 (TGFß3) promotes tenogenic differentiation and may enhance tendon regeneration in vivo. This study aimed to apply TGFß3 absorbed in decellularized equine superficial digital flexor tendon scaffolds, and to investigate the bioactivity of scaffold-associated TGFß3 in an in vitro model. TGFß3 could effectively be loaded onto tendon scaffolds so that at least 88% of the applied TGFß3 were not detected in the rinsing fluid of the TGFß3-loaded scaffolds. Equine adipose tissue-derived multipotent mesenchymal stromal cells (MSC) were then seeded on scaffolds loaded with 300 ng TGFß3 to assess its bioactivity. Both scaffold-associated TGFß3 and TGFß3 dissolved in the cell culture medium, the latter serving as control group, promoted elongation of cell shapes and scaffold contraction (p < 0.05). Furthermore, scaffold-associated and dissolved TGFß3 affected MSC musculoskeletal gene expression in a similar manner, with an upregulation of tenascin c and downregulation of other matrix molecules, most markedly decorin (p < 0.05). These results demonstrate that the bioactivity of scaffold-associated TGFß3 is preserved, thus TGFß3 application via absorption in decellularized tendon scaffolds is a feasible approach.

The Role of Prep1 in the Regulation of Mesenchymal Stromal Cells.

Molecular mechanisms governing cell fate decision events in bone marrow mesenchymal stromal cells (MSC) are still poorly understood. Herein, we investigated the homeobox gene Prep1 as a candidate regulatory molecule, by adopting Prep1 hypomorphic mice as a model to investigate the effects of Prep1 downregulation, using in vitro and in vivo assays, including the innovative single cell RNA sequencing technology. Taken together, our findings indicate that low levels of Prep1 are associated to enhanced adipogenesis and a concomitant reduced osteogenesis in the bone marrow, suggesting Prep1 as a potential regulator of the adipo-osteogenic differentiation of mesenchymal stromal cells. Furthermore, our data suggest that in vivo decreased Prep1 gene dosage favors a pro-adipogenic phenotype and induces a "browning" effect in all fat tissues.

In situ detection of CD73+ CD90+ CD105+ lineage: Mesenchymal stromal cells in human placenta and bone marrow specimens by chipcytometry.

Mesenchymal stromal cells (MSCs) support endogenous regeneration and present therefore promising opportunities for in situ tissue engineering. They can be isolated and expanded from various tissues, for example, bone marrow, adipose tissue, or placenta. The minimal consensus definition criteria of ex vivo expanded MSCs requires them to be positive for CD73, CD90, and CD105 expression, while being negative for CD34, CD45, CD14, CD19, and HLA-DR. This study aimed to compare the in situ phenotype of MSCs with that of their culture-expanded progeny. We report for the first time in situ detection of cells expressing this marker combination in human placenta cryosections as well as in bone marrow aspirates using multiplex-immunohistology (Chipcytometry), a technique that allows staining of more than 100 biomarkers consecutively on the same cell. © 2018 International Society for Advancement of Cytometry.

Tenogenic Properties of Mesenchymal Progenitor Cells Are Compromised in an Inflammatory Environment.

Transplantation of multipotent mesenchymal progenitor cells is a valuable option for treating tendon disease. Tenogenic differentiation leading to cell replacement and subsequent matrix modulation may contribute to the regenerative effects of these cells, but it is unclear whether this occurs in the inflammatory environment of acute tendon disease. Equine adipose-derived stromal cells (ASC) were cultured as monolayers or on decellularized tendon scaffolds in static or dynamic conditions, the latter represented by cyclic stretching. The impact of different inflammatory conditions, as represented by supplementation with interleukin-1ß and/or tumor necrosis factor-α or by co-culture with allogeneic peripheral blood leukocytes, on ASC functional properties was investigated. High cytokine concentrations increased ASC proliferation and osteogenic differentiation, but decreased chondrogenic differentiation and ASC viability in scaffold culture, as well as tendon scaffold repopulation, and strongly influenced musculoskeletal gene expression. Effects regarding the latter differed between the monolayer and scaffold cultures. Leukocytes rather decreased ASC proliferation, but had similar effects on viability and musculoskeletal gene expression. This included decreased expression of the tenogenic transcription factor scleraxis by an inflammatory environment throughout culture conditions. The data demonstrate that ASC tenogenic properties are compromised in an inflammatory environment, with relevance to their possible mechanisms of action in acute tendon disease.

Physiological Hypoxia (Physioxia) Impairs the Early Adhesion of Single Lymphoma Cell to Marrow Stromal Cell and Extracellular Matrix. Optical Tweezers Study.

Adhesion is critical for the maintenance of cellular structures as well as intercellular communication, and its dysfunction occurs prevalently during cancer progression. Recently, a growing number of studies indicated the ability of oxygen to regulate adhesion molecules expression, however, the influence of physiological hypoxia (physioxia) on cell adhesion remains elusive. Thus, here we aimed: (i) to develop an optical tweezers based assay to precisely evaluate single diffuse large B-cell lymphoma (DLBCL) cell adhesion to neighbor cells (mesenchymal stromal cells) and extracellular matrix (Matrigel) under normoxia and physioxia; and, (ii) to explore the role of integrins in adhesion of single lymphoma cell. We identified the pronouncedly reduced adhesive properties of lymphoma cell lines and primary lymphocytes B under physioxia to both stromal cells and Matrigel. Corresponding effects were shown in bulk adhesion assays. Then we emphasized that impaired ß1, ß2 integrins, and cadherin-2 expression, studied by confocal microscopy, account for reduction in lymphocyte adhesion in physioxia. Additionally, the blockade studies conducted with anti-integrin antibodies have revealed the critical role of integrins in lymphoma adhesion. To summarize, the presented approach allows for precise confirmation of the changes in single cell adhesion properties provoked by physiological hypoxia. Thus, our findings reveal an unprecedented role of using physiologically relevant oxygen conditioning and single cell adhesion approaches when investigating tumor adhesion in vitro.

Individual Differences of Multipotent Mesenchymal Stromal Cells Manifesting in during Interaction with Lymphocytes.

Analysis of changes in lymphocyte subpopulations during co-culturing with multipotent mesenchymal stromal cells (MSC) revealed two distinct MSC groups: one group (A) increased HLA-DR expression on lymphocytes during co-culturing and the other (B) did not change it in comparison with lymphocyte monoculture. In stromal cells interacting with lymphocytes, expression of HLA-DR molecules was initiated, but only in samples that induced enhanced expression on lymphocytes and irrespectively of whether allogeneic or autologous lymphocytes were used for co-culturing with MSC. In group A, the relative expression of IDO1 significantly increased in comparison with group B. The revealed individual differences in MSC can explain why not all MSC samples are effective in the treatment of autoimmune diseases, acute "graft-versus-host" disease, and other pathologies.

Sequential third-party mesenchymal stromal cell therapy for refractory acute graft-versus-host disease.

We evaluated the feasibility, safety, and efficacy of the administration of 4 sequential doses (intravenously administered on days 1, 4, 11, and 18) of cryopreserved bone marrow-derived mesenchymal stromal cells (MSC) expanded with platelet lysate and obtained from third-party donors as a second-line treatment for steroid-refractory acute graft-versus-host (aGVHD) disease in a series of 25 patients. All patients received at least 2 doses of MSC, whereas 21 received 3 doses and 18 received the initially planned 4 doses. Because of the achievement of partial response, 4 patients received additional doses of MSC. Median single cell dose administered was 1.1 × 10(6) MSC/kg of recipient body weight. There were no adverse events related to the MSC infusion in the 99 procedures performed, with the exception of a cardiac ischemic event that occurred twice in a patient with prior history of cardiac ischemia. Response to MSC at 60 days after the first dose was evaluable in 24 patients. Seventeen patients (71%) responded (11 complete and 6 partial responses), with a median time to response of 28 days after the first MSC dose, whereas 7 patients did not respond. In summary, we can conclude that sequential cryopreserved third-party MSC therapy administered on days 1, 4, 11, and 18 is a safe procedure for patients with steroid-refractory aGVHD. This strategy may provide a high rate of overall responses of aGVHD with a low toxicity profile.

Transplantation of autologous mesenchymal stromal cells in complete cervical spinal cord injury: a pilot study.

Objective: Spinal cord injury (SCI) is a serious condition that can lead to partial or complete paraplegia or tetraplegia. Currently, there are few therapeutic options for these conditions, which are mainly directed toward the acute phase, such as surgical intervention and high-dose steroid administration. Mesenchymal stromal cells (MSC) have been shown to improve neurological function following spinal cord injury. The aim of the study was to evaluate the safety, feasibility, and potential efficacy of MSC transplantation in patients with cervical traumatic SCI. Methods: We included seven subjects with chronic traumatic SCI (> 1 year) at the cervical level, classified as American Spinal Cord Injury Association impairment scale (AIS) grade A. Subjects received two doses of autologous bone marrow derived MSC, the first by direct injection into the lesion site after hemilaminectomy and the second three months later by intrathecal injection. Neurologic evaluation, spinal magnetic resonance imaging (MRI), urodynamics, and life quality questionnaires were assessed before and after treatment. Results: Cell transplantation was safe without severe or moderate adverse effects, and the procedures were well tolerated. Neurological evaluation revealed discrete improvements in sensitivity below the lesion level, following treatment. Five subjects showed some degree of bilateral sensory improvement for both superficial and deep mechanical stimuli compared to the pretreatment profile. No significant alterations in bladder function were observed during this study. Conclusion: Transplantation of autologous MSC in patients with chronic cervical SCI is a safe and feasible procedure. Further studies are required to confirm the efficacy of this therapeutic approach. Clinical trial registration: https://clinicaltrials.gov/study/NCT02574572, identifier NCT02574572.

Mitigation of acute radiation syndrome (ARS) with human umbilical cord blood.

PURPOSE: The growing concern over potential unintended nuclear accidents or malicious activities involving nuclear/radiological devices cannot be overstated. Exposure to whole-body doses of radiation can result in acute radiation syndrome (ARS), colloquially known as "radiation sickness," which can severely damage various organ systems. Long-term health consequences, such as cancer and cardiovascular disease, can develop many years post-exposure. Identifying effective medical countermeasures and devising a strategic medical plan represents an urgent, unmet need. Various clinical studies have investigated the therapeutic use of umbilical cord blood (UCB) for a range of illnesses, including ARS. The objective of this review is to thoroughly discuss ARS and its sub-syndromes, and to highlight recent findings regarding the use of UCB for radiation injury. UCB, a rich source of stem cells, boasts numerous advantages over other stem cell sources, like bone marrow, owing to its ease of collection and relatively low risk of severe graft-versus-host disease. Preclinical studies suggest that treatment with UCB, and often UCB-derived mesenchymal stromal cells (MSCs), results in improved survival, accelerated hematopoietic recovery, reduced gastrointestinal tract damage, and mitigation of radiation-induced pneumonitis and pulmonary fibrosis. Interestingly, recent evidence suggests that UCB-derived exosomes and their microRNAs (miRNAs) might assist in treating radiation-induced damage, largely by inhibiting fibrotic pathways. CONCLUSION: UCB holds substantial potential as a radiation countermeasure, and future research should focus on establishing treatment parameters for ARS victims.

Native characterization and QC profiling of human amniotic mesenchymal stromal cell vesicular fractions for secretome-based therapy.

Human amniotic mesenchymal stromal cells (hAMSCs) have unique immunomodulatory properties making them attractive candidates for regenerative applications in inflammatory diseases. Most of their beneficial properties are mediated through their secretome. The bioactive factors concurring to its therapeutic activity are still unknown. Evidence suggests synergy between the two main components of the secretome, soluble factors and vesicular fractions, pivotal in shifting inflammation and promoting self-healing. Biological variability and the absence of quality control (QC) protocols hinder secretome-based therapy translation to clinical applications. Moreover, vesicular secretome contains a multitude of particles with varying size, cargos and functions whose complexity hinders full characterization and comprehension. This study achieved a significant advancement in secretome characterization by utilizing native, FFF-based separation and characterizing extracellular vesicles derived from hAMSCs. This was accomplished by obtaining dimensionally homogeneous fractions then characterized based on their protein content, potentially enabling the identification of subpopulations with diverse functionalities. This method proved to be successful as an independent technique for secretome profiling, with the potential to contribute to the standardization of a qualitative method. Additionally, it served as a preparative separation tool, streamlining populations before ELISA and LC-MS characterization. This approach facilitated the categorization of distinctive and recurring proteins, along with the identification of clusters associated with vesicle activity and functions. However, the presence of proteins unique to each fraction obtained through the FFF separation tool presents a challenge for further analysis of the protein content within these cargoes.