CCR7 guides migration of mesenchymal stem cell to secondary lymphoid organs: a novel approach to separate GvHD from GvL effect

CXCL12+ fibroblastic reticular cells in lymph nodes facilitate immune tolerance by regulating T cell-mediated alloimmunity

Fibroblastic reticular cells (FRCs) are the master regulators of the lymph node (LN) microenvironment. However, the role of specific FRC subsets in controlling alloimmune responses remains to be studied. Single-cell RNA sequencing (scRNA-Seq) of naive and draining LNs (DLNs) of heart-transplanted mice and human LNs revealed a specific subset of CXCL12hi FRCs that expressed high levels of lymphotoxin-β receptor (LTβR) and are enriched in the expression of immunoregulatory genes. CXCL12hi FRCs had high expression of CCL19, CCL21, indoleamine 2,3-dioxygenase (IDO), IL-10, and TGF-β1. Adoptive transfer of ex vivo-expanded FRCs resulted in their homing to LNs and induced immunosuppressive environments in DLNs to promote heart allograft acceptance. Genetic deletion of LTβR and Cxcl12 in FRCs increased alloreactivity, abrogating the effect of costimulatory blockade in prolonging heart allograft survival. As compared with WT recipients, CXCL12+ FRC-deficient recipients exhibited increased differentiation of CD4+ T cells into Th1 cells. Nano delivery of CXCL12 to DLNs improved allograft survival in heart-transplanted mice. Our study highlights the importance of DLN CXCL12hi FRCs in promoting transplant tolerance.

Immunoregulatory iPSC-derived non-lymphoid progeny in autoimmunity and GVHD alloimmunity

Non-lymphoid immunoregulatory cells, including mesenchymal stem cells (MSCs), myeloid-derived suppressor cells (MDSCs), regulatory macrophages (Mregs), and tolerogenic dendritic cells (Tol-DCs), play critical roles in maintaining immune homeostasis. However, their therapeutic application in autoimmune diseases and graft-versus-host disease (GVHD) has received comparatively less attention. Induced pluripotent stem cells (iPSCs) offer a promising platform for cell engineering, enabling superior quality control, scalable production, and large-scale in vitro expansion of iPSC-derived non-lymphoid immunoregulatory cells. These advances pave the way for their broader application in autoimmune disease and GVHD therapy. Recent innovations in iPSC differentiation protocols have facilitated the generation of these cell types with functional characteristics akin to their primary counterparts. This review explores the unique features and generation processes of iPSC-derived non-lymphoid immunoregulatory cells, their therapeutic potential in GVHD and autoimmune disease, and their progress toward clinical translation. It emphasizes the phenotypic and functional diversity within each cell type and their distinct effects on disease modulation. Despite these advancements, challenges persist in optimizing differentiation efficiency, ensuring functional stability, and bridging the gap to clinical application. By synthesizing current methodologies, preclinical findings, and translational efforts, this review underscores the transformative potential of iPSC-derived non-lymphoid immunoregulatory cells in advancing cell-based therapies for alloimmune and autoimmune diseases.

Chemokines Signature and T Cell Dynamics in Leishmaniasis: Molecular insight and therapeutic application

Leishmaniasis, caused by obligate intracellular Leishmania parasites, poses a significant global health burden. The control of Leishmania infection relies on an effective T cell-dependent immune response; however, various factors impede the host’s ability to mount a successful defence. Alterations in the chemokine profile, responsible for cell trafficking to the infection site, can disrupt optimal immune responses and influence the outcome of pathogenesis by facilitating parasite persistence. This review aims to emphasize the significance of the chemokine system in T cell responses and to summarize the current knowledge on the dysregulation of chemokines and their receptors associated with different subsets of T lymphocytes during Leishmaniasis. A comprehensive understanding of the dynamic nature of the chemokine system during Leishmaniasis is crucial for the development of successful immunotherapeutic approaches.

The Role of Mesenchymal Stem Cells in Modulating Adaptive Immune Responses in Multiple Sclerosis

Multiple sclerosis (MS) is a chronic autoimmune disease of the central nervous system, leading to significant disability through neurodegeneration. Despite advances in the understanding of MS pathophysiology, effective treatments remain limited. Mesenchymal stem cells (MSCs) have gained attention as a potential therapeutic option due to their immunomodulatory and regenerative properties. This review examines MS pathogenesis, emphasizing the role of immune cells, particularly T cells, in disease progression, and explores MSCs' therapeutic potential. Although preclinical studies in animal models show MSC efficacy, challenges such as donor variability, culture conditions, migratory capacity, and immunological compatibility hinder widespread clinical adoption. Strategies like genetic modification, optimized delivery methods, and advanced manufacturing are critical to overcoming these obstacles. Further research is needed to validate MSCs' clinical application in MS therapy.

Pharmacokinetic characteristics of mesenchymal stem cells in translational challenges

Over the past two decades, mesenchymal stem/stromal cell (MSC) therapy has made substantial strides, transitioning from experimental clinical applications to commercial products. MSC therapies hold considerable promise for treating refractory and critical conditions such as acute graft-versus-host disease, amyotrophic lateral sclerosis, and acute respiratory distress syndrome. Despite recent successes in clinical and commercial applications, MSC therapy still faces challenges when used as a commercial product. Current detection methods have limitations, leaving the dynamic biodistribution, persistence in injured tissues, and ultimate fate of MSCs in patients unclear. Clarifying the relationship between the pharmacokinetic characteristics of MSCs and their therapeutic effects is crucial for patient stratification and the formulation of precise therapeutic regimens. Moreover, the development of advanced imaging and tracking technologies is essential to address these clinical challenges. This review provides a comprehensive analysis of the kinetic properties, key regulatory molecules, different fates, and detection methods relevant to MSCs and discusses concerns in evaluating MSC druggability from the perspective of integrating pharmacokinetics and efficacy. A better understanding of these challenges could improve MSC clinical efficacy and speed up the introduction of MSC therapy products to the market.

Mesenchymal stromal cells restrain the Th17 cell response via L-amino-acid oxidase within lymph nodes

Mesenchymal stromal/stem cells (MSC) have emerged as a promising therapeutic avenue for treating autoimmune diseases, eliciting considerable interest and discussion regarding their underlying mechanisms. This study revealed the distinctive ability of human umbilical cord MSC to aggregate within the lymph nodes of mice afflicted with autoimmune diseases, but this phenomenon was not observed in healthy mice. The specific distribution is driven by the heightened expression of the CCL21-CCR7 axis in mice with autoimmune diseases, facilitating the targeted homing of MSC to the lymph nodes. Within the lymph nodes, MSC exhibit a remarkable capacity to modulate Th17 cell function, exerting a pronounced anti-inflammatory effect. Transplanted MSC stimulates the secretion of L-amino-acid oxidase (LAAO), a response triggered by elevated levels of tumor necrosis factor-α (TNF-α) in mice with autoimmune diseases through the NF-κB pathway. The presence of LAAO is indispensable for the efficacy of MSC, as it significantly contributes to the inhibition of Th17 cells. Furthermore, LAAO-derived indole-3-pyruvic acid (I3P) serves as a potent suppressor of Th17 cells by activating the aryl hydrocarbon receptor (AHR) pathway. These findings advance our understanding of the global immunomodulatory effects exerted by MSC, providing valuable information for optimizing therapeutic outcomes.

CCR5-overexpressing mesenchymal stem cells protect against experimental autoimmune uveitis: insights from single-cell transcriptome analysis

Autoimmune uveitis is a leading cause of severe vision loss, and animal models provide unique opportunities for studying its pathogenesis and therapeutic strategies. Here we employ scRNA-seq, RNA-seq and various molecular and cellular approaches to characterize mouse models of classical experimental autoimmune uveitis (EAU), revealing that EAU causes broad retinal neuron degeneration and marker downregulation, and that Müller glia may act as antigen-presenting cells. Moreover, EAU immune response is primarily driven by Th1 cells, and results in dramatic upregulation of CC chemokines, especially CCL5, in the EAU retina. Accordingly, overexpression of CCR5, a CCL5 receptor, in mesenchymal stem cells (MSCs) enhances their homing capacity and improves their immunomodulatory outcomes in preventing EAU, by reducing infiltrating T cells and activated microglia and suppressing Nlrp3 inflammasome activation. Taken together, our data not only provide valuable insights into the molecular characteristics of EAU but also open an avenue for innovative MSC-based therapy.

CFL1 restores the migratory capacity of bone marrow mesenchymal stem cells in primary Sjögren's syndrome by regulating CCR1 expression

BACKGROUND

Primary Sjögren's syndrome (pSS) is a chronic systemic autoimmune disease. There is no relevant research on whether the migratory ability of bone marrow mesenchymal stem cells (BM-MSC) is impaired in patients with pSS (pSS-BMMSC).

METHODS

Trajectories and velocities of BM-MSC were analyzed. Transwell migration assay and wound healing assay were used to investigate the migratory capacity of BM-MSC. The proliferative capacity of BM-MSC was evaluated by EDU and CCK8 assay. RNA-seq analysis was then performed to identify the underlying mechanism of lentivirus-mediated cofilin-1 overexpression BM-MSC (BMMSCCFL1). The therapeutic efficacy of BMMSCCFL1 was evaluated in NOD mice.

RESULTS

The migratory capacity of pSS-BMMSC was significantly reduced compared to normal volunteers (HC-BMMSC). The expression of the motility-related gene CFL1 was decreased in pSS-BMMSC. Lentivirus-mediated CFL1 overexpression of pSS-BMMSC promoted the migration capacity of pSS-BMMSC. Furthermore, RNA-seq revealed that CCR1 was the downstream target gene of CFL1. To further elucidate the mechanism of CFL1 in regulating BM-MSC migration and proliferation via the CCL5/CCR1 axis, we performed a rescue experiment using BX431 (a CCR1-specific inhibitor) to inhibit CCR1. The results showed that CCR1 inhibitors suppressed the migration and proliferation capacity of MSC induced by CFL1.

CONCLUSION

The pSS-BMMSC leads to impaired migration and proliferation, and overexpression of CFL1 can rescue the functional deficiency and alleviate disease symptoms in NOD mice. Mechanically, CFL1 can regulate the expression level of the downstream CCL5/CCR1 axis to enhance the migration and proliferation of BM-MSC.

Mesenchymal stromal cells ameliorate chronic GVHD by boosting thymic regeneration in a CCR9-dependent manner in mice

Chronic graft-versus-host disease (cGVHD) is a major cause of morbidity and mortality after allogeneic hematopoietic stem cell transplantation. Mature donor T cells within the graft contribute to severe damage of thymic epithelial cells (TECs), which are known as key mediators in the continuum of acute GVHD (aGVHD) and cGVHD pathology. Mesenchymal stromal cells (MSCs) are reportedly effective in the prevention and treatment of cGVHD. In our previous pilot clinical trial in patients with refractory aGVHD, the incidence and severity of cGVHD were decreased, along with an increase in levels of blood signal joint T-cell receptor excision DNA circles after MSCs treatment, which indicated an improvement in thymus function of patients with GVHD, but the mechanisms leading to these effects remain unknown. Here, we show in a murine GVHD model that MSCs promoted the quantity and maturity of TECs as well as elevated the proportion of Aire-positive medullary TECs, improving both CD4+CD8+ double-positive thymocytes and thymic regulatory T cells, balancing the CD4:CD8 ratio in the blood. In addition, CCL25-CCR9 signaling axis was found to play an important role in guiding MSC homing to the thymus. These studies reveal mechanisms through which MSCs ameliorate cGVHD by boosting thymic regeneration and offer innovative strategies for improving thymus function in patients with GVHD.

Assessment of therapeutic role of mesenchymal stromal cells in mouse models of graft-versus-host disease using cryo-imaging

Insights regarding the biodistribution and homing of mesenchymal stromal cells (MSCs), as well as their interaction with alloreactive T-cells are critical for understanding how MSCs can regulate graft-versus-host disease (GVHD) following allogeneic (allo) bone marrow transplantation (BMT). We developed novel assays based on 3D, microscopic, cryo-imaging of whole-mouse-sized volumes to assess the therapeutic potential of human MSCs using an established mouse GVHD model. Following infusion, we quantitatively tracked fluorescently labeled, donor-derived, T-cells and third party MSCs in BMT recipients using multispectral cryo-imaging. Specific MSC homing sites were identified in the marginal zones in the spleen and the lymph nodes, where we believe MSC immunomodulation takes place. The number of MSCs found in spleen of the allo BMT recipients was about 200% more than that observed in the syngeneic group. To more carefully define the effects MSCs had on T cell activation and expansion, we developed novel T-cell proliferation assays including secondary lymphoid organ (SLO) enlargement and Carboxyfluoescein succinimidyl ester (CFSE) dilution. As anticipated, significant SLO volume enlargement and CFSE dilution was observed in allo but not syn BMT recipients due to rapid proliferation and expansion of labeled T-cells. MSC treatment markedly attenuated CFSE dilution and volume enlargement of SLO. These assays confirm evidence of potent, in vivo, immunomodulatory properties of MSC following allo BMT. Our innovative platform includes novel methods for tracking cells of interest as well as assessing therapeutic function of MSCs during GVHD induction. Our results support the use of MSCs treatment or prevention of GVHD and illuminate the wider adoption of MSCs as a standard medicinal cell therapy.

Effects of Low-Intensity Pulsed Ultrasound on the Migration and Homing of Human Amnion-Derived Mesenchymal Stem Cells to Ovaries in Rats With Premature Ovarian Insufficiency

Premature ovarian insufficiency (POI) can cause multiple sequelae and is currently incurable. Mesenchymal stem cell (MSC) transplantation might provide an effective treatment method for POI. However, the clinical application of systemic MSC transplantation is limited by the low efficiency of cell homing to target tissue in vivo, including systemic MSC transplantation for POI treatment. Thus, exploration of methods to promote MSC homing is necessary. This study was to investigate the effects of low-intensity pulsed ultrasound (LIPUS) on the migration and homing of transplanted human amnion–derived MSCs (hAD-MSCs) to ovaries in rats with chemotherapy-induced POI. For LIPUS treatment, hAD-MSCs were exposed to LIPUS or sham irradiation. Chemokine receptor expressions in hAD-MSCs were detected by polymerase chain reaction (PCR), Western blot, and immunofluorescence assays. hAD-MSC migration was detected by wound healing and transwell migration assays. Cyclophosphamide-induced POI rat models were established to evaluate the effects of LIPUS on the homing of systemically transplanted hAD-MSCs to chemotherapy-induced POI ovaries in vivo. We found that hAD-MSCs expressed chemokine receptors. The LIPUS promoted the expression of chemokine receptors, especially CXCR4, in hAD-MSCs. SDF-1 induced hAD-MSC migration. The LIPUS promoted hAD-MSC migration induced by SDF-1 through SDF-1/CXCR4 axis. SDF-1 levels significantly increased in ovaries induced by chemotherapy in POI rats. Pretreating hAD-MSCs with LIPUS increased the number of hAD-MSCs homing to ovaries in rats with chemotherapy-induced POI to some extent. However, the difference was not significant. Both hAD-MSC and LIPUS-pretreated hAD-MSC transplantation reduced ovarian injuries and improved ovarian function in rats with chemotherapy-induced POI. CXCR4 antagonist significantly reduced the number of hAD-MSCs- and LIPUS-pretreated hAD-MSCs homing to POI ovaries, and further reduced their efficacy in POI treatment. According to these findings, pretreating MSCs with LIPUS before transplantation might provide a novel, convenient, and safe technique to explore for improving the homing of systemically transplanted MSCs to target tissue.

Secondary Lymphoid Organs in Mesenchymal Stromal Cell Therapy: More Than Just a Filter

Mesenchymal stromal cells (MSCs) have demonstrated therapeutic potential in inflammatory models of human disease. However, clinical translation has fallen short of expectations, with many trials failing to meet primary endpoints. Failure to fully understand their mechanisms of action is a key factor contributing to the lack of successful commercialisation. Indeed, it remains unclear how the long-ranging immunomodulatory effects of MSCs can be attributed to their secretome, when MSCs undergo apoptosis in the lung shortly after intravenous infusion. Their apoptotic fate suggests that efficacy is not based solely on their viable properties, but also on the immune response to dying MSCs. The secondary lymphoid organs (SLOs) orchestrate immune responses and play a key role in immune regulation. In this review, we will discuss how apoptotic cells can modify immune responses and highlight the importance of MSC-immune cell interactions in SLOs for therapeutic outcomes.

Infusion of haploidentical HSCs combined with allogenic MSCs for the treatment of ALL patients

Although haploidentical stem cell transplantation (haplo-HSCT) offers almost all acute lymphoblastic leukaemia (ALL) patients an opportunity for immediate transplantation, it exhibits a higher incidence of graft failure and graft versus host disease (GVHD). Mesenchymal stem cells (MSCs) are characterised by their haematopoiesis-promoting and immunomodulatory capacity. Thus, we designed a combination of haplo-HSCT and MSCs for ALL patients. ALL patients (n = 110) were given haploidentical HSCs combined with allogenic MSCs, and ALL patients without MSC infusion (n = 56) were included as controls. The 100-day cumulative incidences of grade ≥2 acute GVHD (aGVHD) and grade ≥3 aGVHD were 40.00% and 9.09% compared to 42.32% (P = 0.79) and 22.79% (P = 0.03) in patients without MSC infusion, respectively. The 3-year cumulative incidences of chronic GVHD (cGVHD) and extensive cGVHD were 22.27% and 10.27% compared to 32.14% (P = 0.19) and 22.21% (P = 0.04) in patients without MSC infusion, respectively. No significant differences in the 3-year relapse incidence, nonrelapse mortality, leukaemia-free survival or overall survival in groups with and without MSC cotransplantation were observed. Multivariate analysis showed that MSC infusion contributed to a lower risk of developing extensive cGVHD. Our data suggested that haplo-HSCT combined with MSCs may provide an effective and safe treatment for ALL patients.

CCR2-overexpressing mesenchymal stem cells targeting damaged liver enhance recovery of acute liver failure

Background

Mesenchymal stem cell (MSC) transplantation is emerging as a promising cell therapeutic strategy in acute liver failure (ALF) clinical research. The potency of MSCs to migrate and engraft into targeted lesions could largely determine their clinical efficacy, in which chemokine/receptor axes play a crucial role. Unfortunately, the downregulation of chemokine receptors expression after in vitro expansion results in a poor homing capacity of MSCs.

Methods

By evaluating the chemokine expression profile in the liver of ALF patients and ALF mice, we found that CCL2 expression was highly upregulated in damaged livers, while the corresponding receptor, CCR2, was lacking in cultured MSCs. Thus, we genetically modified MSCs to overexpress CCR2 and investigated the targeted homing capacity and treatment efficacy of MSC^CCR2 compared to those of the MSC^vector control.

Results

In vivo and ex vivo near-infrared fluorescence imaging showed that MSC^CCR2 rapidly migrated and localized to injured livers in remarkably greater numbers following systemic infusion, and these cells were retained in liver lesions for a longer time than MSC^vector. Furthermore, MSC^CCR2 exhibited significantly enhanced efficacy in the treatment of ALF in mice, which was indicated by a dramatically improved survival rate, the alleviation of liver injury with reduced inflammatory infiltration and hepatic apoptosis, and the promotion of liver regeneration.

Conclusions

Altogether, these results indicate that CCR2 overexpression enhances the targeted migration of MSCs to damaged livers, improves their treatment effect, and may provide a novel strategy for improving the efficacy of cell therapy for ALF.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02729-y.

Infusion of haploidentical hematopoietic stem cells combined with mesenchymal stem cells for treatment of severe aplastic anemia in adult patients yields curative effects

BACKGROUND AIMS

Despite the great advances in immunosuppressive therapy for severe aplastic anemia (SAA), most patients are not completely cured. Haploidentical hematopoietic stem cell transplantation (haplo-HSCT) has been recommended as an alternative treatment in adult SAA patients. However, haplo-HSCT presents a higher incidence of graft failure and graft-versus-host disease (GVHD). The authors designed a combination of haplo-HSCT and umbilical cord-derived mesenchymal stem cells (UC-MSCs) for treatment of SAA in adult patients and evaluated its effects.

METHODS

Adult patients (≥18 years) with SAA (N = 25) were given HLA-haploidentical hematopoietic stem cells (HSCs) combined with UC-MSCs after a conditioning regimen consisting of busulfan, cyclophosphamide, fludarabine and anti-thymocyte globulin and intensive GVHD prophylaxis, including cyclosporine, basiliximab, mycophenolate mofetil and short-term methotrexate. Additionally, the effects of the protocol in adult SSA patients were compared with those observed in juvenile SAA patients (N = 75).

RESULTS

All patients achieved myeloid engraftment after haplo-HSCT at a median of 16.12 days (range, 11-26). The median time of platelet engraftment was 28.30 days (range, 13-143). The cumulative incidence of grade II acute GVHD (aGVHD) at day +100 was 32.00 ± 0.91%. No one had grade III-IV aGVHD at day +100. The cumulative incidence of total chronic GVHD was 28.00 ± 0.85%. The overall survival was 71.78 ± 9.05% at a median follow-up of 42.08 months (range, 2.67-104). Promisingly, the protocol yielded a similar curative effect in both young and adult SAA patients.

CONCLUSIONS

The authors' data suggest that co-transplantation of HLA-haploidentical HSCs and UC-MSCs may provide an effective and safe treatment for adult SAA.

Mesenchymal stromal cells in hematopoietic cell transplantation

Mesenchymal stromal cells (MSCs) are widely recognized to possess potent immunomodulatory activity, as well as to stimulate repair and regeneration of diseased or damaged tissue. These fundamental properties suggest important applications in hematopoietic cell transplantation. Although the mechanisms of therapeutic activity in vivo are yet to be fully elucidated, MSCs seem to suppress lymphocytes by paracrine mechanisms, including secreted mediators and metabolic modulators. Most recently, host macrophage engulfment of apoptotic MSCs has emerged as an important contributor to the immune suppressive microenvironment. Although bone marrow-derived MSCs are the most commonly studied, the tissue source of MSCs may be a critical determinant of immunomodulatory function. The key application of MSC therapy in hematopoietic cell transplantation is to prevent or treat graft-versus-host disease (GVHD). The pathogenesis of GVHD reveals multiple potential targets. Moreover, the recently proposed concept of tissue tolerance suggests a new possible mechanism of MSC therapy for GVHD. Beyond GVHD, MSCs may facilitate hematopoietic stem cell engraftment, which could gain greater importance with increasing use of haploidentical transplantation. Despite many challenges and much doubt, commercial MSC products for pediatric steroid-refractory GVHD have been licensed in Japan, conditionally licensed in Canada and New Zealand, and have been recommended for approval by an FDA Advisory Committee in the United States. Here, we review key historical data in the context of the most salient recent findings to present the current state of MSCs as adjunct cell therapy in hematopoietic cell transplantation.

Chemokines and their receptors: predictors of the therapeutic potential of mesenchymal stromal cells

Multipotent mesenchymal stromal cells (MSCs) are promising cellular therapeutics for the treatment of inflammatory and degenerative disorders due to their anti-inflammatory, immunomodulatory and regenerative potentials. MSCs can be sourced from a variety of tissues within the body, but bone marrow is the most frequently used starting material for clinical use. The chemokine family contains many regulators of inflammation, cellular function and cellular migration-all critical factors in understanding the potential potency of a novel cellular therapeutic. In this review, we focus on expression of chemokine receptors and chemokine ligands by MSCs isolated from different tissues. We discuss the differential migratory, angiogenetic and immunomodulatory potential to understand the role that tissue source of MSC may play within a clinical context. Furthermore, this is strongly associated with leukocyte recruitment, immunomodulatory potential and T cell inhibition potential and we hypothesize that chemokine profiling can be used to predict the in vivo therapeutic potential of MSCs isolated from new sources and compare them to BM MSCs.

Ferulic acid promotes bone defect repair after radiation by maintaining the stemness of skeletal stem cells

The reconstruction of irradiated bone defects after settlement of skeletal tumors remains a significant challenge in clinical applications. In this study, we explored radiation‐induced skeletal stem cell (SSC) stemness impairments and rescuing effects of ferulic acid (FA) on SSCs in vitro and in vivo. The immunophenotype, cell renewal, cell proliferation, and differentiation of SSCs in vitro after irradiation were investigated. Mechanistically, the changes in tissue regeneration‐associated gene expression and MAPK pathway activation in irradiated SSCs were evaluated. The regenerative capacity of SSCs in the presence of FA in an irradiated bone defect mouse model was also investigated. We found that irradiation reduced CD140a‐ and CD105‐positive cells in skeletal tissues and mouse‐derived SSCs. Additionally, irradiation suppressed cell proliferation, colony formation, and osteogenic differentiation of SSCs. The RNA‐Seq results showed that tissue regeneration‐associated gene expression decreased, and the Western blotting results demonstrated the suppression of phosphorylated p38/MAPK and ERK/MAPK in irradiated SSCs. Notably, FA significantly rescued the radiation‐induced impairment of SSCs by activating the p38/MAPK and ERK/MAPK pathways. Moreover, the results of imaging and pathological analyses demonstrated that FA enhanced the bone repair effects of SSCs in an irradiated bone defect mouse model substantially. Importantly, inhibition of the p38/MAPK and ERK/MAPK pathways in SSCs by specific chemical inhibitors partially abolished the promotive effect of FA on SSC‐mediated bone regeneration. In summary, our findings reveal a novel function of FA in repairing irradiated bone defects by maintaining SSC stemness and suggest that the p38/MAPK and ERK/MAPK pathways contribute to SSC‐mediated tissue regeneration postradiation.

Challenges and advances in clinical applications of mesenchymal stromal cells

Mesenchymal stromal cells (MSCs), also known as mesenchymal stem cells, have been intensely investigated for clinical applications within the last decades. However, the majority of registered clinical trials applying MSC therapy for diverse human diseases have fallen short of expectations, despite the encouraging pre-clinical outcomes in varied animal disease models. This can be attributable to inconsistent criteria for MSCs identity across studies and their inherited heterogeneity. Nowadays, with the emergence of advanced biological techniques and substantial improvements in bio-engineered materials, strategies have been developed to overcome clinical challenges in MSC application. Here in this review, we will discuss the major challenges of MSC therapies in clinical application, the factors impacting the diversity of MSCs, the potential approaches that modify MSC products with the highest therapeutic potential, and finally the usage of MSCs for COVID-19 pandemic disease.

IFN-γ gene loaded human umbilical mesenchymal stromal cells targeting therapy for Graft-versus-host disease

Graft-versus-host disease (GVHD) is a frequent complication following allogeneic hematopoietic stem cell transplantation (allo-HSCT). The application of mesenchymal stromal cells (MSCs) to treat GVHD patients refractory to initial steroid treatment has led to impressive results. In this study, we explored the potential of human umbilical mesenchymal stem cells (HUMSCs) transfected with the IFN-γ gene of human (h)/mice (m) (HUMSCs + Ad-h/mIFN-γ) carried by a recombinant adenoviral vector in the prevention and treatment of GVHD. We demonstrated that HUMSCs + Ad-h/mIFN-γ efficiently suppressed T lymphocyte proliferation and activation, induced G1 cell cycle arrest and apoptosis in vitro. To assess the in vivo efficacy of HUMSCs + Ad-h/mIFN-γ, Balb/c mice were induced to develop GVHD symptoms by tail vein injection of C57BL/6 splenocytes after irradiation. Weight, hair, survival, hemogram, and chimera condition of GVHD model mice were monitored before and after treatment, respectively. The results showed that HUMSCs + Ad-h/mIFN-γ reduced GVHD's incidence and severity on the model mice and provided a significant survival benefit. In conclusion, this study may provide validated evidence that the introduction of IFN-γ into HUMSCs would help ameliorate GVHD after allo-HSCT.

A Phase I Study to Evaluate Two Doses of Wharton's Jelly-Derived Mesenchymal Stromal Cells for the Treatment of De Novo High-Risk or Steroid-Refractory Acute Graft Versus Host Disease

BACKGROUND

Because of their well-described immunosuppressive properties, allogeneic adult human mesenchymal stromal cells (MSC) derived from bone marrow have demonstrated safety and efficacy in steroid refractory acute graft versus host disease (SR aGVHD). Clinical trials have resulted in variable success and an optimal source of MSC has yet to be defined. Based on the importance of maternal-fetal interface immune tolerance, extraembryonic fetal tissues, such as the umbilical cord, may provide an superior tissue source of MSC to mediate immunomodulation in aGVHD.

METHODS

A two-dose cohort trial allogeneic Wharton's Jelly-derived mesenchymal stromal cells (WJMSC, referred to as MSCTC-0010, here) were tested in 10 patients with de novo high risk (HR) or SR aGVHD post allogeneic hematopoietic stem cell transplantation (allo-HCT). Following Good Manufacturing Practices isolation, expansion and cryostorage, WJMSC were thawed and administered via intravenous infusions on days 0 and 7 at one of two doses (low dose cohort, 2 × 106/kg, n = 5; high dose cohort, 10 × 106/kg, n = 5). To evaluate safety, patients were monitored for infusion related toxicity, Treatment Related Adverse Events (TRAE) til day 42, or ectopic tissue formation at day 90. Clinical responses were monitored at time points up to 180 days post infusion. Serum biomarkers ST2 and REG3α were acquired 1 day prior to first MSCTC-0010 infusion and on day 14.

RESULTS

Safety was indicated, e.g., no infusion-related toxicity, no development of TRAE, nor ectopic tissue formation in either low or high dose cohort was observed. Clinical response was suggested at day 28: the overall response rate (ORR) was 70%, 4 of 10 patients had a complete response (CR) and 3 had a partial response (PR). By study day 90, the addition of escalated immunosuppressive therapy was necessary in 2 of 9 surviving patients. Day 100 and 180 post infusion survival was 90% and 60%, respectively. Serum biomarker REG3α decreased, particularly in the high dose cohort, and with REG3α decrease correlated with clinical response.

CONCLUSIONS

Treatment of patients with de novo HR or SR aGVHD with low or high dose MSCTC-0010 was safe: the infusion was well-tolerated, and no TRAEs or ectopic tissue formation was observed. A clinical improvement was seen in about 70% patients, with 4 of 10 showing a complete response that may have been attributable to MSCTC-0010 infusions. These observations indicate safety of two different doses of MSCTC-0010, and suggest that the 10 × 106 cells/ kg dose be tested in an expanded randomized, controlled Phase 2 trial. Graphical abstract.

A study of human leukocyte antigen-haploidentical hematopoietic stem cells transplantation combined with allogenic mesenchymal stem cell infusion for treatment of severe aplastic anemia in pediatric and adolescent patients

The clinical applications of human leukocyte antigen (HLA) haploidentical hematopoietic stem cells transplantation (haplo‐HSCT) have offered most of the young severe aplastic anemia (SAA) patients an opportunity to accept curative therapy at the early stage of bone marrow lesions. However, the outcome of juvenile SAA patients received haplo‐HSCT remain to be improved due to high incidence of graft failure and graft vs host disease (GVHD). Mesenchymal stem cells (MSCs) have been characterized by their hematopoiesis‐supporting and immunomodulatory properties. In the current study, we designed a combination of haplo‐HSCT with allogenic MSC for treatment of SAA in pediatric and adolescent patients and evaluated its effects. Juvenile patients (<18 years) with SAA (n = 103) were given HLA‐haploidentical HSC combined with allogenic MSC after a conditioning regimen consisting of busulfan, cyclophosphamide, fludarabine, and antithymocyte globulin and an intensive GVHD prophylaxis, including cyclosporine, short‐term methotrexate, mycophenolate mofetil, and basiliximab. Neutrophil engraftment was achieved in 102 of 103 patients in a median time of 14.3 days (range 9‐25 days). The median time of platelet engraftment was 25.42 days (range 8‐93 days). The cumulative incidence of II‐IV acute GVHD at day +100 was 26.32% ± 0.19% and III‐IV acute GVHD was 6.79% ± 0.06% at day +100, respectively. The cumulative incidence of chronic GVHD was 25.56% ± 0.26%. The overall survival was 87.15% ± 3.3% at a median follow‐up of 40 (1.3‐98) months. Our data suggest that cotransplantation of HLA‐haploidentical HSC and allogenic mesenchymal stem cell may provide an effective and safe treatment for children and adolescents with SAA who lack matched donors.

Effect of Timing and Complement Receptor Antagonism on Intragraft Recruitment and Protolerogenic Effects of Mesenchymal Stromal Cells in Murine Kidney Transplantation

BACKGROUND

Mesenchymal stromal cells (MSCs) have protolerogenic effects in renal transplantation, but they induce long-term regulatory T cells (Treg)-dependent graft acceptance only when infused before transplantation. When given posttransplant, MSCs home to the graft where they promote engraftment syndrome and do not induce Treg. Unfortunately, pretransplant MSC administration is unfeasible in deceased-donor kidney transplantation.

METHODS

To make MSCs a therapeutic option also for deceased organ recipients, we tested whether MSC infusion at the time of transplant (day 0) or posttransplant (day 2) together with inhibition of complement receptors prevents engraftment syndrome and allows their homing to secondary lymphoid organs for promoting tolerance. We analyzed intragraft and splenic MSC localization, graft survival, and alloimmune response in mice recipients of kidney allografts and syngeneic MSCs given on day 0 or on posttransplant day 2. C3a receptor (C3aR) or C5a receptor (C5aR) antagonists were administered to mice in combination with the cells or were used together to treat MSCs before infusion.

RESULTS

Syngeneic MSCs given at day 0 homed to the spleen increased Treg numbers and induced long-term graft acceptance. Posttransplant MSC infusion, combined with a short course of C3aR or C5aR antagonist or administration of MSCs pretreated with C3aR and C5aR antagonists, prevented intragraft recruitment of MSCs and graft inflammation, inhibited antidonor T-cell reactivity, but failed to induce Treg, resulting in mild prolongation of graft survival.

CONCLUSIONS

These data support testing the safety/efficacy profile of administering MSCs on the day of transplant in deceased-donor transplant recipients and indicate that complement is crucial for MSC recruitment into the kidney allograft.

Identifying the Therapeutic Significance of Mesenchymal Stem Cells

The pleiotropic behavior of mesenchymal stem cells (MSCs) has gained global attention due to their immense potential for immunosuppression and their therapeutic role in immune disorders. MSCs migrate towards inflamed microenvironments, produce anti-inflammatory cytokines and conceal themselves from the innate immune system. These signatures are the reason for the uprising in the sciences of cellular therapy in the last decades. Irrespective of their therapeutic role in immune disorders, some factors limit beneficial effects such as inconsistency of cell characteristics, erratic protocols, deviating dosages, and diverse transfusion patterns. Conclusive protocols for cell culture, differentiation, expansion, and cryopreservation of MSCs are of the utmost importance for a better understanding of MSCs in therapeutic applications. In this review, we address the immunomodulatory properties and immunosuppressive actions of MSCs. Also, we sum up the results of the enhancement, utilization, and therapeutic responses of MSCs in treating inflammatory diseases, metabolic disorders and diabetes.

Gene-based Therapeutic Tools in the Treatment of Cornea Disease

BACKGROUND

As one of the main blinding ocular diseases, corneal blindness resulted from neovascularization that disrupts the angiogenic privilege of corneal avascularity. Following neovascularization, inflammatory cells are infiltrating into cornea to strengthen corneal injury. How to maintain corneal angiogenic privilege to treat corneal disease has been investigated for decades.

METHODOLOGY

Local administration of viral and non-viral-mediated anti-angiogenic factors reduces angiogenic protein expression in situ with limited or free of off-target effects upon gene delivery. Recently, Mesenchymal Stem Cells (MSCs) have been studied to treat corneal diseases. Once MSCs are manipulated to express certain genes of interest, they could achieve superior therapeutic efficacy after transplantation.

DISCUSSION

In the text, we first introduce the pathological development of corneal disease in the aspects of neovascularization and inflammation. We summarize how MSCs become an ideal candidate in cell therapy for treating injured cornea, focusing on cell biology, property and features. We provide an updated review of gene-based therapies in animals and preclinical studies in the aspects of controlling target gene expression, safety and efficacy. Gene transfer vectors are potent to induce candidate protein expression. Delivered by vectors, MSCs are equipped with certain characters by expressing a protein of interest, which facilitates better for MSC-mediated therapeutic intervention for the treatment of corneal disease.

CONCLUSION

As the core of this review, we discuss how MSCs could be engineered to be vector system to achieve enhanced therapeutic efficiency after injection.

Targeted Migration of Human Adipose-Derived Stem Cells to Secondary Lymphoid Organs Enhances Their Immunomodulatory Effect and Prolongs the Survival of Allografted Vascularized Composites

The targeted delivery of therapeutic agents to secondary lymphoid organs (SLOs), which are the niches for immune initiation, provides an unprecedented opportunity for immune intolerance induction. The alloimmune rejection postvascularized composite allotransplantation (VCA) is mediated by T lymphocytes. Human adipose-derived stem cells (hASCs) possess the superiority of convenient availability and potent immunoregulatory property, but their therapeutic results in the VCA are unambiguous thus far. Chemokine receptor 7 (CCR7) can specifically guide immune cells migrating into SLOs. There, the genes of CCR7-GFP or GFP alone were introduced into hASCs by lentivirus. hASCs/CCR7 maintained the multidifferentiation and immunoregulatory abilities, but it gained the migration capacity elicited by secondary lymphoid organ chemokine (SCL) (CCR7 ligand) in vitro. Noteworthily, intravenously infused hASCs/CCR7 targetedly relocated in the T-cell aggression area in SLOs. In a rat VCA model, hASCs/GFP transfusion had a rare effect on the allografted vascularized composite. However, hASCs/CCR7 infusion potently prolonged the grafts' survival time. The ameliorated pathologic exhibition and the regulated inflammatory cytokines in the peripheral blood were also observed. The altered axis of Th1/Th2 and Tregs/Th17 in SLOs may underlie the downregulated rejection response. Moreover, the proteomic examination of splenic T lymphocytes also confirmed that hASCs/CCR7 decreased the proteins related to cytokinesis, lymphocyte proliferation, differentiation, and apoptotic process. In conclusion, our present study demonstrated that targeted migration of hASCs/CCR7 to SLOs highly intensifies their in vivo immunomodulatory effect in the VCA model for the first time. We believe this SLO-targeting strategy may improve the clinical therapeutic efficacy of hASC for allogeneic and autogenic immune disease. Stem Cells 2019;37:1581-1594.

Alpha-1 Antitrypsin-Expressing Mesenchymal Stromal Cells Confer a Long-Term Survival Benefit in a Mouse Model of Lethal GvHD

Acute graft-versus-host disease is a frequent complication associated with allogeneic hematopoietic stem cell transplantation. Patients that become refractory to initial steroid treatment have a poor prognosis. apceth-201 consists of human allogeneic mesenchymal stromal cells, engineered by lentiviral transduction to express the protease inhibitor alpha-1 antitrypsin, to augment the anti-inflammatory potential of the mesenchymal stromal cells. We show that apceth-201 mesenchymal stromal cells efficiently suppress T cell proliferation and polarize macrophages to an anti-inflammatory M2 type, in vitro. To assess the in vivo efficacy of apceth-201, it was tested in two different mouse models of acute graft-versus-host disease. Control animals in a humanized model succumbed quickly to disease, whereas median survival was doubled in apceth-201-treated animals. The product was also tested in a graft-versus-host disease model system that closely mimics haploidentical hematopoietic stem cell transplantation, an approach that is now being evaluated for use in the clinic. Control animals succumbed quickly to disease, whereas treatment with apceth-201 resulted in long-term survival of 57% of the animals. Within 25 days after the second injection, clinical scores returned to baseline in responding animals, indicating complete resolution of graft-versus-host disease. These promising data have led to planning of a phase I study using apceth-201.

[Brain derived neurotrophic factor enhances the role of mesenchymal stem cells in inhibiting follicular helper T cells]

目的

探讨脑源性神经营养因子（BDNF）增强间充质干细胞（MSC）抑制滤泡辅助性T细胞（Tfh细胞）的作用及机制。

方法

ELISA法检测MSC培养上清中吲哚胺2,3-二加氧酶（IDO）、IL-10、TGF-β和IL-21的含量；采集健康志愿者的外周血标本，采用人淋巴细胞分离液分离外周血中的淋巴细胞；采用Transwell小室进行MSC和淋巴细胞共培养，流式细胞术检测CD4⁺CXCR5⁺ Tfh细胞及其亚群的比例。

结果

①BDNF组（BDNF刺激的MSC）培养上清IL-10、TGF-β、IDO浓度均高于对照组（加入等体积磷酸盐缓冲液）[IL-10：（42.1±4.4）ng/ml对（19.3±2.1）ng/ml，t=4.761，P=0.009；TGF-β：（13.9±1.7）ng/ml对（5.3±0.6）ng/ml，t=5.129，P=0.008；IDO：（441.3±56.9）ng/ml对（226.7±37.6）ng/ml，t=3.130，P=0.035]；②BDNF组（淋巴细胞与BDNF刺激的MSC共培养）与MSC组（淋巴细胞与MSC共培养）比较：CD4⁺CXCR5⁺Tfh细胞比例降低[（3.37±0.21）%对（6.51±0.27）%，t=9.353，P<0.001]，CD4⁺ CXCR5⁺ CXCR3⁺ CCR6⁻Tfh1细胞比例升高[（41.14±2.04）%对（26.72±2.57）%，t=4.383，P=0.012]，CD4⁺CXCR5⁺CXCR3⁻CCR6⁻Tfh2细胞和CD4⁺CXCR5⁺CXCR3⁻CCR6⁺Tfh17细胞比例降低[Tfh2：（30.16±5.38）%对（43.26±4.11）%，t=4.426，P=0.012；Tfh17：（15.61±1.52）%对（22.32±0.72）%，t=4.202，P=0.014]，CD4⁺CXCR5⁺Foxp3⁺ Tfr细胞比例升高[（4.95±0.22）%对（2.32±0.16）%，t=10.241，P<0.001]，淋巴细胞培养上清中IL-21浓度降低[（0.28±0.03）ng/ml对（0.85±0.08）ng/ml，t=6.675，P=0.003]。

结论

BDNF能够增强MSC抑制Tfh细胞的作用，机制是抑制淋巴细胞中Tfh细胞比例升高及其向Tfh2和Tfh17亚群的分化。

Strategies for Enhancing and Preserving Anti-leukemia Effects Without Aggravating Graft-Versus-Host Disease

Allogeneic stem cell transplantation (allo-SCT) is a curable method for the treatment of hematological malignancies. In the past two decades, the establishment of haploidentical transplant modalities make “everyone has a donor” become a reality. However, graft-versus-host disease (GVHD) and relapse remain the major two causes of death either in the human leukocyte antigen (HLA)-matched transplant or haploidentical transplant settings, both of which restrict the improvement of transplant outcomes. Preclinical mice model showed that both donor-derived T cells and natural killer (NK) cells play important role in the pathogenesis of GVHD and the effects of graft-versus-leukemia (GVL). Hence, understanding the immune mechanisms of GVHD and GVL would provide potential strategies for the control of leukemia relapse without aggravating GVHD. The purpose of the current review is to summarize the biology of GVHD and GVL responses in preclinical models and to discuss potential novel therapeutic strategies to reduce the relapse rate after allo-SCT. We will also review the approaches, including optimal donor selection and, conditioning regimens, donor lymphocyte infusion, BCR/ABL-specific CTL, and chimeric antigen receptor-modified T cells, which have been successfully used in the clinic to enhance and preserve anti-leukemia activity, especially GVL effects, without aggravating GVHD or alleviate GVHD.

Various strategies to improve efficacy of stem cell transplantation in multiple sclerosis: Focus on mesenchymal stem cells and neuroprotection

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system (CNS) which predominantly affect young adults and undergo heavy socioeconomic burdens. Conventional therapeutic modalities for MS mostly downregulate aggressive immune responses and are almost insufficient for management of progressive course of the disease. Mesenchymal stem cells (MSCs), due to both immunomodulatory and neuroprotective properties have been known as practical cells for treatment of neurodegenerative diseases like MS. However, clinical translation of MSCs is associated with some limitations such as short-life engraftment duration, little in vivo trans-differentiation and restricted accessibility into damaged sites. Therefore, laboratory manipulation of MSCs can improve efficacy of MSCs transplantation in MS patients. In this review, we discuss several novel approaches, which can potentially enhance MSCs capabilities for treating MS.

Targeted homing of CCR2-overexpressing mesenchymal stromal cells to ischemic brain enhances post-stroke recovery partially through PRDX4-mediated blood-brain barrier preservation

Rationale: Mesenchymal stromal cells (MSCs) are emerging as a novel therapeutic strategy for the acute ischemic stroke (AIS). However, the poor targeted migration and low engraftment in ischemic lesions restrict their treatment efficacy. The ischemic brain lesions express a specific chemokine profile, while cultured MSCs lack the set of corresponding receptors. Thus, we hypothesize that overexpression of certain chemokine receptor might help in MSCs homing and improve therapeutic efficacy. Methods: Using the middle cerebral artery occlusion (MCAO) model of ischemic stroke, we identified that CCL2 is one of the most highly expressed chemokines in the ipsilateral hemisphere. Then, we genetically transduced the corresponding receptor, CCR2 to the MSCs and quantified the cell retention of MSCCCR2 compared to the MSCdtomato control. Results: MSCCCR2 exhibited significantly enhanced migration to the ischemic lesions and improved the neurological outcomes. Brain edema and blood-brain barrier (BBB) leakage levels were also found to be much lower in the MSCCCR2-treated rats than the MSCdtomato group. Moreover, this BBB protection led to reduced inflammation infiltration and reactive oxygen species (ROS) generation. Similar results were also confirmed using the in vitro BBB model. Furthermore, genome-wide RNA sequencing (RNA-seq) analysis revealed that peroxiredoxin4 (PRDX4) was highly expressed in MSCs, which mainly contributed to their antioxidant impacts on MCAO rats and oxygen-glucose deprivation (OGD)-treated endothelium. Conclusion: Taken together, this study suggests that overexpression of CCR2 on MSCs enhances their targeted migration to the ischemic hemisphere and improves the therapeutic outcomes, which is attributed to the PRDX4-mediated BBB preservation.

Bioengineered cellular and cell membrane-derived vehicles for actively targeted drug delivery: So near and yet so far

Cellular carriers for drug delivery are attractive alternatives to synthetic nanoparticles owing to their innate homing/targeting abilities. Here, we review molecular interactions involved in the homing of Mesenchymal stem cells (MSCs) and other cell types to understand the process of designing and engineering highly efficient, actively targeting cellular vehicles. In addition, we comprehensively discuss various genetic and non-genetic strategies and propose futuristic approaches of engineering MSC homing using micro/nanotechnology and high throughput small molecule screening. Most of the targeting abilities of a cell come from its plasma membrane, thus, efforts to harness cell membranes as drug delivery vehicles are gaining importance and are highlighted here. We also recognize and report the lack of detailed characterization of cell membranes in terms of safety, structural integrity, targeting functionality, and drug transport. Finally, we provide insights on future development of bioengineered cellular and cell membrane-derived vesicles for successful clinical translation.

Efficacy and safety of mesenchymal stromal cells for the prophylaxis of chronic graft-versus-host disease after allogeneic hematopoietic stem cell transplantation: a meta-analysis of randomized controlled trials

A meta-analysis of randomized controlled trials (RCTs) was conducted to evaluate the efficacy and safety of mesenchymal stromal cells (MSCs) for the prophylaxis of chronic graft-versus-host disease (cGVHD) in patients with hematological malignancies undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT). Six studies involving 365 patients were included. The pooled results showed that MSCs significantly reduced the incidence of cGVHD (risk ratio [RR] 0.63, 95% confidence interval [CI] 0.46 to 0.86, P = 0.004). Favorable prophylactic effects of MSCs on cGVHD were observed with umbilical cord-derived, high-dose, and late-infusion MSCs, while bone marrow-derived, low-dose, and coinfused MSCs did not confer beneficial prophylactic effects. In addition, MSC infusion did not increase the risk of primary disease relapse and infection (RR 1.02, 95% CI 0.70 to 1.50, P = 0.913; RR 0.89, 95% CI 0.44 to 1.81, P = 0.752; respectively). Moreover, there was an apparent trend toward increased overall survival (OS) in the MSC group compared with that in the control group (RR 1.13, 95% CI 0.98 to 1.29, P = 0.084). In conclusion, this meta-analysis demonstrated that MSC infusion is an effective and safe prophylactic strategy for cGVHD in patients with hematological malignancies undergoing allo-HSCT.

Mesenchymal stem cells provide prophylaxis against acute graft-versus-host disease following allogeneic hematopoietic stem cell transplantation: A meta-analysis of animal models

A meta-analysis of animal models was conducted to evaluate the prophylactic effects of mesenchymal stem cells (MSCs) on acute graft-versus-host disease (aGVHD) after allogeneic hematopoietic stem cell transplantation. A total of 50 studies involving 1848 animals were included. The pooled results showed that MSCs significantly reduced aGVHD-associated mortality (risk ratio = 0.70, 95% confidence interval 0.62 to 0.79, P = 2.73×10⁻⁹) and clinical scores (standardized mean difference = −3.60, 95% confidence interval −4.43 to −2.76, P = 3.61×10⁻¹⁷). In addition, MSCs conferred robust favorable prophylactic effects on aGVHD across recipient species, MSC doses, and administration times, but not MSC sources. Our meta-analysis showed that MSCs significantly prevented mortality and alleviated the clinical manifestations of aGVHD in animal models. These data support further clinical trials aimed at evaluating the efficacy of using MSCs to prevent aGVHD.

Genetic modification to induce CXCR2 overexpression in mesenchymal stem cells enhances treatment benefits in radiation-induced oral mucositis

Radiation-induced oral mucositis affects patient quality of life and reduces tolerance to cancer therapy. Unfortunately, traditional treatments are insufficient for the treatment of mucositis and might elicit severe side effects. Due to their immunomodulatory and anti-inflammatory properties, the transplantation of mesenchymal stem cells (MSCs) is a potential therapeutic strategy for mucositis. However, systemically infused MSCs rarely reach inflamed sites, impacting their clinical efficacy. Previous studies have demonstrated that chemokine axes play an important role in MSC targeting. By systematically evaluating the expression patterns of chemokines in radiation/chemical-induced oral mucositis, we found that CXCL2 was highly expressed, whereas cultured MSCs negligibly express the CXCL2 receptor CXCR2. Thus, we explored the potential therapeutic benefits of the transplantation of CXCR₂-overexpressing MSCs (MSCs^CXCR2) for mucositis treatment. Indeed, MSCs^CXCR2 exhibited enhanced targeting ability to the inflamed mucosa in radiation/chemical-induced oral mucositis mouse models. Furthermore, we found that MSC^CXCR2 transplantation accelerated ulcer healing by suppressing the production of pro-inflammatory chemokines and radiogenic reactive oxygen species (ROS). Altogether, these findings indicate that CXCR2 overexpression in MSCs accelerates ulcer healing, providing new insights into cell-based therapy for radiation/chemical-induced oral mucositis.

CXCR3 blockade combined with cyclosporine A alleviates acute graft-versus-host disease by inhibiting alloreactive donor T cell responses in a murine model

Chemotaxis of T cells to acute graft-versus-host disease (aGvHD) target tissues directed by chemokines and their receptors plays a key role in the pathogenesis of aGvHD. Blockade of lymphocyte migration by targeting chemokine receptors may be a viable strategy for the prevention and treatment of aGvHD, which is quite distinguishable from typical efforts to use immunosuppressive medications that have been associated with some side effects. CXCR3 and its ligands have been reported to be correlated with aGvHD pathogenesis. Using the small-molecule CXCR3 antagonist AMG487, we demonstrated that AMG487 combined with cyclosporine A (CsA) effectively alleviated aGvHD with a prolonged mean survival time and significantly inhibited the infiltration of inflammatory cells in aGvHD target tissues in a murine aGvHD model. In addition, AMG487 combined with CsA inhibited the activation, proliferation and differentiation of donor-derived T cells in the spleens. Further results showed that the concentrations of Th1 cells associated with pro-inflammatory cytokines such as IFN-γ and TNFα in serum were decreased. In addition, AMG487 treatment did not alter CXCR3 and CCR5 expression in donor-derived T cells but elevated the serum CXCL9 and CXCL10 levels. This novel and effective approach has the potential to develop a new clinical method to prevent and treat aGvHD.

CTLA4-CD28 chimera gene modification of T cells enhances the therapeutic efficacy of donor lymphocyte infusion for hematological malignancy

Donor lymphocyte infusion (DLI) followed by hematopoietic stem cell transplantation has served as an effective prevention/treatment modality against the relapse of some hematologic tumors, such as chronic myeloid leukemia (CML). However, the therapeutic efficacies of DLI for other types of leukemia, including acute lymphocytic leukemia (ALL), have been limited thus far. Therefore, we examined whether increasing the reactivity of donor T cells by gene modification could enhance the therapeutic efficacy of DLI in a murine model of ALL. When a CTLA4-CD28 chimera gene (CTC28) in which the intracellular signaling domain of CTLA4 was replaced with the CD28 signaling domain was introduced into CD4 and CD8 T cells in DLI, the graft-versus-tumor (GVT) effect was significantly increased. This effect was correlated with an increased expansion of donor CD8 T cells in vivo, and the depletion of CD8 T cells abolished this effect. The CD8 T cell expansion and the enhanced GVT effect were dependent on the transduction of both CD4 and CD8 T cells with CTC28, which emphasizes the role of dual modification in this therapeutic effect. The CTC28-transduced T cells that expanded in vivo also exhibited enhanced functionality. Although the potentiation of the GVT effect mediated by the CTC28 gene modification of T cells was accompanied by an increase of graft-versus-host disease (GVHD), the GVHD was not lethal and was mitigated by treatment with IL-10 gene-modified third-party mesenchymal stem cells. Thus, the combined genetic modification of CD4 and CD8 donor T cells with CTC28 could be a promising strategy for enhancing the therapeutic efficacy of DLI.

CXCR5-Overexpressing Mesenchymal Stromal Cells Exhibit Enhanced Homing and Can Decrease Contact Hypersensitivity

Mesenchymal stromal cells (MSCs) can modulate inflammation and contribute to tissue regeneration and, thus, have emerged as a promising option for cell-based therapy. However, the ability of MSCs to migrate to injured tissues still needs to be improved. In this study, we investigated whether genetically engineered MSCs could exhibit increased migratory properties and improved therapeutic efficacy. Using a mouse model of contact hypersensitivity (CHS), chemokine gene expression screening revealed that CXCL13 changed most significantly in injured tissue. Unfortunately, MSCs hardly express the corresponding receptor, CXCR5. Thus, CXCR5-overexpressing MSCs (MSCCXCR5) were generated that retained their abilities of proliferation, differentiation, and immunomodulation. Furthermore, MSCCXCR5 showed significantly increased migrating ability toward CXCL13. Importantly, systemic infusion of MSCCXCR5 dramatically suppressed CHS in mice, as evidenced by decreased levels of inflammatory cell infiltration and pro-inflammatory cytokine production. Numerous MSCCXCR5 migrated into inflamed ears, localized with T cells, inhibited T cell proliferation, promoted T cell apoptosis, and suppressed the production of T cell-derived pro-inflammatory factors. Collectively, these findings demonstrate that CXCR5 overexpression increases the ability of MSCs to respond to migratory stimuli and highly intensifies their immunomodulatory effects in vivo. This strategy for enhancing targeted stem/progenitor cell homing may improve the efficacy of MSC-based therapies.

LL-37 boosts immunosuppressive function of placenta-derived mesenchymal stromal cells

BACKGROUND

Although promising for graft-versus-host disease (GvHD) treatment, MSC therapy still faces important challenges. For instance, increasing MSC migratory capacity as well as potentializing immune response suppression are of interest. For GvHD management, preventing opportunistic infections is also a valuable strategy, since immunocompromised patients are easy targets for infections. LL-37 is a host defense peptide (HDP) that has been deeply investigated due to its immunomodulatory function. In this scenario, the combination of MSC and LL-37 may result in a robust combination to be clinically used.

METHODS

In the present study, the effects of LL-37 upon the proliferation and migratory capacity of human placenta-derived MSCs (pMSCs) were assessed by MTT and wound scratch assays. The influence of LL-37 over the immunosuppressive function of pMSCs was then investigated using CFSE cell division kit. Flow cytometry and real-time PCR were used to investigate the molecular mechanisms involved in the effects observed.

RESULTS

LL-37 had no detrimental effects over MSC proliferation and viability, as assessed by MTT assay. Moreover, the peptide promoted increased migratory behavior of pMSCs and enhanced their immunomodulatory function over activated human PBMCs. Strikingly, our data shows that LL-37 treatment leads to increased TLR3 levels, as shown by flow cytometry, and to an increased expression of factors classically related to immunosuppression, namely IDO, IL-10, TGF-β, IL-6, and IL-1β.

CONCLUSIONS

Taken together, our observations may serve as groundwork for the development of new therapeutic strategies based on the combined use of LL-37 and MSCs, which may provide patients not only with an enhanced immunosuppression regime, but also with an agent to prevent opportunistic infections.

Upregulation of CC Chemokine Receptor 7 (CCR7) Enables Migration of Xenogeneic Human Adipose-Derived Mesenchymal Stem Cells to Rat Secondary Lymphoid Organs

Background

CC chemokine receptor 7 (CCR7) expression is vital for cell migration to secondary lymphoid organs (SLOs). Our previous work showed that inducing CCR7 expression enabled syngeneic mesenchymal stem cells (MSCs) to migrate into SLOs, resulting in enhanced immunosuppressive performance in mice. Given that human adipose-derived stem cells (hASCs) are widely used in clinical therapy, we further investigated whether upregulation of CCR7 enables xenogeneic hASCs to migrate to rat SLOs.

Material/Methods

hASCs rarely express CCR7; therefore, hASCs were transfected with lentivirus encoding rat CCR7 (rCCR7) plus green fluorescence protein (GFP) or GFP alone. CCR7 mRNA and cell surface expression of rCCR7-hASCs and GFP-hASCs were examined by reverse transcription-polymerase chain reaction (RT-PCR) and flow cytometry (FCM), respectively. The phenotype, differentiation, and proliferation capacity of each cell type was also determined. To examine migration, rCCR7-hASCs and GFP-hASCs were injected intravenously into Lewis rats, and the proportion of GFP-positive cells in the spleen and lymph nodes was determined with FCM.

Results

mRNA and cell surface protein expression of CCR7 was essentially undetectable in hASCs and GFP-ASCs; however, CCR7 was highly expressed in rCCR7-ASCs. rCCR7-hASCs, GFP-hASCs, and hASCs shared a similar immunophenotype, and maintained the ability of multilineage differentiation and proliferation. In addition, the average proportion of GFP-positive cells was significantly higher following transplantation of rCCR7-hASCs compared with GFP-hASCs (p<0.01).

Conclusions

These results suggest that upregulation of rat CCR7 expression does not change the phenotype, differentiation, or proliferation capacity of hASCs, but does enable efficient migration of hASCs to rat SLOs.

Immunomodulatory effects of bone marrow versus adipose tissue-derived mesenchymal stromal cells on NK cells: implications in the transplantation setting

INTRODUCTION

The ability of mesenchymal stromal cells (MSC) to suppress T-cell function has prompted their therapeutic use for graft-versus-host disease (GVHD) control. However, as MSC also modulate the activity of NK cells, which play an important role in graft-versus-leukemia (GVL) reaction, their administration could hamper this beneficial effect of allogeneic hematopoietic stem cell transplantation. MSC can be expanded from several sources, especially bone marrow and fat, but it is not well established if the cell source makes a difference in their immunoregulatory capacity.

OBJECTIVE

The aim of this study was to compare the immunomodulatory effect of MSC derived from bone marrow (BM-CSM) or adipose tissue (AT-MSC) on NK cells, to determine whether the use of MSC from one or the other origin could be more favorable to preserve NK cell activity and, therefore, GVL.

METHODS

Human NK cells were stimulated with IL-15 in the presence of BM-MSC or AT-MSC. The effect of both MSC populations on NK cell proliferation, cell cycle progression, and CD56 expression was analyzed by flow cytometry. Cytokine secretion was measured by ELISA, and cytotoxic activity was assessed by calcein release assays.

RESULTS

Although both BM-MSC and AT-MSC induced a similar inhibition of NK cell proliferation, only BM-MSC decreased significantly NK cell cytotoxic activity and showed a trend for a higher reduction of IFN-γ secretion.

CONCLUSION

These results suggest that, in the context of GVHD inhibition, the use of AT-MSC rather than BM-MSC could further preserve NK cell activity and, thus, favor GVL.

Biodistribution of in vitro-derived microglia applied intranasally and intravenously to mice: effects of aging

BACKGROUND AIMS

The age of both the donor and the recipient has a potential influence on the efficacy of various cell therapies, but the underlying mechanisms are still being charted. We studied the effect of donor and recipient age in the context of microglia migration.

METHODS

Microglia were in vitro--differentiated from bone marrow of young (3 months) and aged (12 months) mice and transplanted into young (∼ 3 months) and aged (∼ 17 months) C57BL/6 mice (n = 25) through intravenous and intranasal application routes. Recipients were not immune-suppressed or irradiated. Transplanted microglia were tracked through the use of a sex-mismatched setup or histologically with the use of cells from enhanced green fluorescent protein enhanced green fluorescent protein transgenic mice.

RESULTS

No acute rejections or transplant-associated toxicity was observed. After 10 days, both intravenously and intranasally transplanted cells were detected in the brain. Transplanted cells were also found in the blood and the lymph system. The applied cells were also tracked in lungs and kidney but only after intravenous injection subjected to a "pulmonary first-pass effect." After 28 days, intravenously delivered cells were also found in the bone marrow and other organs, especially in aged recipients. Whereas in young recipients the transplanted microglia did not appear to persist, in aged brains the transplanted cells could still be identified up to 28 days after transplantation. However, when cells from aged donors were used, no signals of transplanted cells could be detected in the recipients.

CONCLUSIONS

This study establishes proof of principle that in vitro--derived microglia from young but not from aged donors, intravenously or intranasally transplanted, migrate to the brain in young and aged recipients.

Genetic Engineering of Mesenchymal Stem Cells to Induce Their Migration and Survival

Mesenchymal stem cells (MSCs) are very attractive for regenerative medicine due to their relatively easy derivation and broad range of differentiation capabilities, either naturally or induced through cell engineering. However, efficient methods of delivery to diseased tissues and the long-term survival of grafted cells still need improvement. Here, we review genetic engineering approaches designed to enhance the migratory capacities of MSCs, as well as extend their survival after transplantation by the modulation of prosurvival approaches, including prevention of senescence and apoptosis. We highlight some of the latest examples that explore these pivotal points, which have great relevance in cell-based therapies.

A20 plays a critical role in the immunoregulatory function of mesenchymal stem cells

Mesenchymal stem cells (MSCs) possess an immunoregulatory capacity and are a therapeutic target for many inflammation‐related diseases. However, the detailed mechanisms of MSC‐mediated immunosuppression remain unclear. In this study, we provide new information to partly explain the molecular mechanisms of immunoregulation by MSCs. Specifically, we found that A20 expression was induced in MSCs by inflammatory cytokines. Knockdown of A20 in MSCs resulted in increased proliferation and reduced adipogenesis, and partly reversed the suppressive effect of MSCs on T cell proliferation in vitro and inhibited tumour growth in vivo. Mechanistic studies indicated that knockdown of A20 in MSCs inhibited activation of the p38 mitogen‐activated protein kinase (MAPK) pathway, which potently promoted the production of tumour necrosis factor (TNF)‐α and inhibited the production of interleukin (IL)‐10. Collectively, these data reveal a crucial role of A20 in regulating the immunomodulatory activities of MSCs by controlling the expression of TNF‐α and IL‐10 in an inflammatory environment. These findings provide novel insights into the pathogenesis of various inflammatory‐associated diseases, and are a new reference for the future development of treatments for such afflictions.

Mesenchymal stem cells and immunomodulation: current status and future prospects

The unique immunomodulatory properties of mesenchymal stem cells (MSCs) make them an invaluable cell type for the repair of tissue/ organ damage caused by chronic inflammation or autoimmune disorders. Although they hold great promise in the treatment of immune disorders such as graft versus host disease (GvHD) and allergic disorders, there remain many challenges to overcome before their widespread clinical application. An understanding of the biological properties of MSCs will clarify the mechanisms of MSC-based transplantation for immunomodulation. In this review, we summarize the preclinical and clinical studies of MSCs from different adult tissues, discuss the current hurdles to their use and propose the future development of pluripotent stem cell-derived MSCs as an approach to immunomodulation therapy.

International Society for Cellular Therapy perspective on immune functional assays for mesenchymal stromal cells as potency release criterion for advanced phase clinical trials

Mesenchymal stromal cells (MSCs) as a pharmaceutical for ailments characterized by pathogenic autoimmune, alloimmune and inflammatory processes now cover the spectrum of early- to late-phase clinical trials in both industry and academic sponsored studies. There is a broad consensus that despite different tissue sourcing and varied culture expansion protocols, human MSC-like cell products likely share fundamental mechanisms of action mediating their anti-inflammatory and tissue repair functionalities. Identification of functional markers of potency and reduction to practice of standardized, easily deployable methods of measurements of such would benefit the field. This would satisfy both mechanistic research as well as development of release potency assays to meet Regulatory Authority requirements for conduct of advanced clinical studies and their eventual registration. In response to this unmet need, the International Society for Cellular Therapy (ISCT) addressed the issue at an international workshop in May 2015 as part of the 21st ISCT annual meeting in Las Vegas. The scope of the workshop was focused on discussing potency assays germane to immunomodulation by MSC-like products in clinical indications targeting immune disorders. We here provide consensus perspective arising from this forum. We propose that focused analysis of selected MSC markers robustly deployed by in vitro licensing and metricized with a matrix of assays should be responsive to requirements from Regulatory Authorities. Workshop participants identified three preferred analytic methods that could inform a matrix assay approach: quantitative RNA analysis of selected gene products; flow cytometry analysis of functionally relevant surface markers and protein-based assay of secretome. We also advocate that potency assays acceptable to the Regulatory Authorities be rendered publicly accessible in an "open-access" manner, such as through publication or database collection.

Human mesenchymal stromal cells attenuate graft-versus-host disease and maintain graft-versus-leukemia activity following experimental allogeneic bone marrow transplantation

We sought to define the effects and underlying mechanisms of human, marrow-derived mesenchymal stromal cells (hMSCs) on graft-versus-host disease (GvHD) and graft-versus-leukemia (GvL) activity. Irradiated B6D2F1 mice given C57BL/6 BM and splenic T cells and treated with hMSCs had reduced systemic GvHD, donor T-cell expansion, and serum TNFα and IFNγ levels. Bioluminescence imaging demonstrated that hMSCs redistributed from lungs to abdominal organs within 72 hours, and target tissues harvested from hMSC-treated allogeneic BMT (alloBMT) mice had less GvHD than untreated controls. Cryoimaging more precisely revealed that hMSCs preferentially distributed to splenic marginal zones and regulated T-cell expansion in the white pulp. Importantly, hMSCs had no effect on in vitro cytotoxic T-cell activity and preserved potent GvL effects in vivo. Mixed leukocyte cultures containing hMSCs exhibited decreased T-cell proliferation, reduced TNFα, IFNγ, and IL-10 but increased PGE2 levels. Indomethacin and E-prostanoid 2 (EP2) receptor antagonisms both reversed while EP2 agonism restored hMSC-mediated in vitro T-cell suppression, confirming the role for PGE2 . Furthermore, cyclo-oxygenase inhibition following alloBMT abrogated the protective effects of hMSCs. Together, our data show that hMSCs preserve GvL activity and attenuate GvHD and reveal that hMSC biodistribute to secondary lymphoid organs wherein they attenuate alloreactive T-cell proliferation likely through PGE2 induction.

Mesenchymal Stromal Cell Therapy in Hematology: From Laboratory to Clinic and Back Again

There is currently major interest to use mesenchymal stromal cells (MSCs) for a very diverse range of therapeutic applications. This stems mainly from the immunosuppressive qualities and differentiation capacity of these cells. In this review, we focus on cell therapy applications for MSCs in hematology. In this domain, MSCs are used for the treatment or prevention of graft-versus-host disease, support of hematopoiesis, or repair of tissue toxicities after hematopoietic cell transplantation. We critically review the accumulating clinical data and elaborate on complications that might arise from treatment with MSCs. In addition, we assume that the real clinical benefit of using MSCs for these purposes can only be estimated by a better understanding of the influence of in vitro expansion on the biological properties of these cells as well as by more harmonization of the currently used expansion protocols.