Mesenchymal stem cells: a new strategy for immunosuppression and tissue repair. Cell Res. 2010;20:510-518. [PMID: 20368733 DOI: 10.1038/cr.2010.44]

Engineered mesenchymal stem/stromal cells against cancer

Mesenchymal stem/stromal cells (MSCs) have garnered attention for their potential in cancer therapy due to their ability to home to tumor sites. Engineered MSCs have been developed to deliver therapeutic proteins, microRNAs, prodrugs, chemotherapy drugs, and oncolytic viruses directly to the tumor microenvironment, with the goal of enhancing therapeutic efficacy while minimizing off-target effects. Despite promising results in preclinical studies and clinical trials, challenges such as variability in delivery efficiency and safety concerns persist. Ongoing research aims to optimize MSC-based cancer eradication and immunotherapy, enhancing their specificity and efficacy in cancer treatment. This review focuses on advancements in engineering MSCs for tumor-targeted therapy.

Integrated GelMA and liposome composite hydrogel with effective coupling of angiogenesis and osteogenesis for promoting bone regeneration

In clinical scenarios, bone defects stemming from trauma, infections, degenerative diseases, or hereditary conditions necessitate considerable bone grafts. Researchers ardently focus on creating diverse biomaterials to expedite and enhance these intricate restorative processes. These biomaterials play a pivotal role in aiding osteogenesis and angiogenesis factors for reconstructing stable, fully developed bone tissue. We observed the utilization of Desferoxamine (DFO) facilitated angiogenesis, thereby enabling Kartogenin (KGN) to activate the β-catenin/Runx-2 pathway. Our study introduces a composite hydrogel loaded with KGN and DFO via liposomes to enhance the coupling of angiogenesis and osteogenesis. Within this composite hydrogel system, KGN and DFO undergo effective release. This controlled release substantially promotes a conducive microenvironment for angiogenesis and osteogenesis. Our in vitro studies provide compelling evidence of the synergistic impact between KGN and DFO on osteogenic processes. Moreover, the composite hydrogel exhibits the capability to enhance the expression of proteins and genes associated with both angiogenesis and osteogenesis. In rat skull defect model, the composite hydrogel notably stimulates vascularization and osteogenic differentiation without infection or mortality. In summary, results underscore the potential of this composite hydrogel as an alternative to autografts for bone defect repair, offering a promising approach for future clinical and regenerative applications.

Placenta-derived mesenchymal stem cells protect against diabetic kidney disease by upregulating autophagy-mediated SIRT1/FOXO1 pathway

Diabetic kidney disease (DKD) is a common chronic microvascular complication of diabetes mellitus. Although studies have indicated the therapeutic potential of mesenchymal stem cells (MSCs) for DKD, the underlying molecular mechanisms remain unclear. Herein, we explored the renoprotective effect of placenta-derived MSCs (P-MSCs) and the potential mechanism of SIRT1/FOXO1 pathway-mediated autophagy in DKD. The urine microalbumin/creatinine ratio was determined using ELISA, and renal pathological changes were detected by special staining techniques. Immunofluorescence was used for detecting the renal tissue expression of podocin and nephrin; immunohistochemistry for the renal expression of autophagy-related proteins (LC3, Beclin-1, SIRT1, and FOXO1); and western blotting and PCR for the expression of podocyte autophagy- and pathway-related indicators. We found that P-MSCs ameliorated renal tubular injury and glomerular mesangial matrix deposition and alleviated podocyte damage in DKD rats. PMSCs enhanced autophagy levels and increased SIRT1 and FOXO1 expression in DKD rat renal tissue, whereas the autophagy inhibitor 3-methyladenine significantly attenuated the renoprotective effect of P-MSCs. P-MSCs improved HG-induced Mouse podocyte clone5(MPC5)injury, increased podocyte autophagy, and upregulated SIRT1 and FOXO1 expression. Moreover, downregulation of SIRT1 expression blocked the P-MSC-mediated enhancement of podocyte autophagy and improvement of podocyte injury. Thus, P-MSCs can significantly improve renal damage and reduce podocyte injury in DKD rats by modulating the SIRT1/FOXO1 pathway and enhancing podocyte autophagy.

Roles of extracellular vesicles from mesenchymal stem cells in regeneration

Mesenchymal stem cells (MSCs) are highly valued in regenerative medicine due to their ability to self-renew and differentiate into various cell types. Their therapeutic benefits are primarily due to their paracrine effects, in particular through extracellular vesicles (EVs), which are related to intercellular communication. Recent advances in EV production and extraction technologies highlight the potential of MSC-derived EVs (MSC-EVs) in tissue engineering and regenerative medicine. MSC-EVs offer several advantages over traditional cell therapies, including reduced toxicity and immunogenicity compared with whole MSCs. EVs carrying functional molecules such as growth factors, cytokines, and miRNAs play beneficial roles in tissue repair, fibrosis treatment, and scar prevention by promoting angiogenesis, skin cell migration, proliferation, extracellular matrix remodeling, and reducing inflammation. Despite the potential of MSC-EVs, there are several limitations to their use, including variability in quality, the need for standardized methods, low yield, and concerns about the composition of EVs and the potential risks. Overall, MSC-EVs are a promising alternative to cell-based therapies, and ongoing studies aim to understand their actions and optimize their use for better clinical outcomes in wound healing and skin regeneration.

Dental pulp mesenchymal stem cell (DPSCs)-derived soluble factors, produced under hypoxic conditions, support angiogenesis via endothelial cell activation and generation of M2-like macrophages

BACKGROUND

Cell therapy has emerged as a revolutionary tool to repair damaged tissues by restoration of an adequate vasculature. Dental Pulp stem cells (DPSC), due to their easy biological access, ex vivo properties, and ability to support angiogenesis have been largely explored in regenerative medicine.

METHODS

Here, we tested the capability of Dental Pulp Stem Cell-Conditioned medium (DPSC-CM), produced in normoxic (DPSC-CM Normox) or hypoxic (DPSC-CM Hypox) conditions, to support angiogenesis via their soluble factors. CMs were characterized by a secretome protein array, then used for in vivo and in vitro experiments. In in vivo experiments, DPSC-CMs were associated to an Ultimatrix sponge and injected in nude mice. After excision, Ultimatrix were assayed by immunohistochemistry, electron microscopy and flow cytometry, to evaluate the presence of endothelial, stromal, and immune cells. For in vitro procedures, DPSC-CMs were used on human umbilical-vein endothelial cells (HUVECs), to test their effects on cell adhesion, migration, tube formation, and on their capability to recruit human CD14+ monocytes.

RESULTS

We found that DPSC-CM Hypox exert stronger pro-angiogenic activities, compared with DPSC-CM Normox, by increasing the frequency of CD31+ endothelial cells, the number of vessels and hemoglobin content in the Ultimatrix sponges. We observed that Utimatrix sponges associated with DPSC-CM Hypox or DPSC-CM Normox shared similar capability to recruit CD45- stromal cells, CD45+ leukocytes, F4/80+ macrophages, CD80+ M1-macrophages and CD206+ M2-macropages. We also observed that DPSC-CM Hypox and DPSC-CM Normox have similar capabilities to support HUVEC adhesion, migration, induction of a pro-angiogenic gene signature and the generation of capillary-like structures, together with the ability to recruit human CD14+ monocytes.

CONCLUSIONS

Our results provide evidence that DPSCs-CM, produced under hypoxic conditions, can be proposed as a tool able to support angiogenesis via macrophage polarization, suggesting its use to overcome the issues and restrictions associated with the use of staminal cells.

Mesenchymal stromal cells alleviate APAP-induced liver injury via extracellular vesicle-mediated regulation of the miR-186-5p/CXCL1 axis

BACKGROUND

Acetaminophen (APAP) overdose is a significant cause of drug-induced liver injury (DILI). N-acetylcysteine (NAC) is the first-line agent used in the clinic. However, it rarely benefits patients with advanced APAP toxicity. Mesenchymal stromal cells (MSCs) have demonstrated potential in treating DILI. However, the specific mechanism by which MSCs protect against APAP-induced liver injury remains unclear.

METHODS

APAP was injected intraperitoneally to induce a liver injury model. We then detected histopathology, biochemical indices, and inflammatory cytokine levels to assess the efficacy of MSCs and MSC extracellular vesicles (MSC-EVs). Flow cytometry was performed to reveal the immunoregulatory effects of MSCs and MSC-EVs on the neutrophils. RNA sequencing (RNA-Seq) of liver tissues was used to identify critical target genes for MSC treatment.

RESULTS

MSC and MSC-EV treatment effectively alleviated APAP-induced liver injury and inhibited neutrophil infiltration. RNA-Seq analysis and ELISA data indicated that C-X-C motif chemokine 1 (CXCL1), a chemoattractant for neutrophils, was a key molecule in the MSC-mediated amelioration of APAP-induced liver damage. In addition, neutralization of CXCL1 reduced APAP-induced liver damage, which was accompanied by decreased neutrophil infiltration. Importantly, we verified that MSC-EV-derived miR-186-5p directly binds to the 3'-UTR of Cxcl1 to inhibit its expression in hepatocytes. The agomir miR-186-5p showed excellent potential for the treatment of DILI.

CONCLUSIONS

Our findings suggest that MSCs and MSC-EVs are an effective approach to mitigate DILI. Targeting the miR-186-5p/CXCL1 axis is a promising approach to improve the efficacy of MSCs and MSC-EVs in the treatment of DILI.

Stimuli-Responsive Substrates to Control the Immunomodulatory Potential of Stromal Cells

Mesenchymal stromal cells (MSCs) have broad immunomodulatory properties that range from regulation, proliferation, differentiation, and immune cell activation to secreting bioactive molecules that inhibit inflammation and regulate immune response. These properties provide MSCs with high therapeutic potency that has been shown to be relevant to tissue engineering and regenerative medicine. Hence, researchers have explored diverse strategies to control the immunomodulatory potential of stromal cells using polymeric substrates or scaffolds. These substrates alter the immunomodulatory response of MSCs, especially through biophysical cues such as matrix mechanical properties. To leverage these cell-matrix interactions as a strategy for priming MSCs, emerging studies have explored the use of stimuli-responsive substrates to enhance the therapeutic value of stromal cells. This review highlights how stimuli-responsive materials, including chemo-responsive, microenvironment-responsive, magneto-responsive, mechano-responsive, and photo-responsive substrates, have specifically been used to promote the immunomodulatory potential of stromal cells by controlling their secretory activity.

Differential effects of TLR3 and TLR4 activation on MSC-mediated immune regulation

Mesenchymal stromal cells (MSCs) have evolved as an invaluable therapeutic cell type due to their broad therapeutic properties. Bone marrow-derived MSCs are currently being applied in numerous clinical trials, and the initial results have been encouraging. However, heterogeneous responsiveness amongst patients is also being experienced; therefore, the efficacy of MSCs in vivo is still debatable. Host microenvironment plays an essential role in determining the fate of MSCs in vivo. Recent studies have indicated the role of toll-like receptors (TLR) in modulating the biological properties of MSCs. TLRs are expressed by MSCs, and activation of TLR3 and TLR4 can alter the functionality of MSCs. While MSCs can suppress the effector and memory T cell function by promoting regulatory T cells, the effect of TLR activation on MSC-mediated immune cell induction is still not well understood. This study was performed to understand the TLR licensing of MSCs and its impact on MSC-mediated immunomodulation. We found that TLR3 mediated activation of MSCs (TLR3-MSCs) increased the expression of G-CSF & IL-10 while TLR4-mediated activation of MSCs led to an increase in CXCL-1, CXCL-10, and CXCL-12. To study the immunological aspect, an in vitro co-culture model was established-to imitate the brief in vivo interaction of MSCs and immune cells. We found that TLR3-MSCs led to increase in CD4 and CD8 naive T (TNAI) cells and vice versa for effector (TEFF) and memory T (TMEM) cells, while TLR4-MSCs did not show any effect. Moreover, only TLR3-MSCs led to a non-significant increase in the regulatory T cells (TREGS) and Double negative regulatory cells. No change in B cell profile was evident while TLR3-MSCs depicted an increasing trend in regulatory B cells which was not statistically significant. TLR3 MSCs also inhibited the T cell proliferation in our setup. Our data indicate that TLR3 priming may regulate the function of MSCs through immunomodulation. Understanding the role of TLRs and other microenvironmental factors causing subdued responses of MSCs in vivo would allow the uninhibited use of MSCs for many diseased conditions.

CXCL3: A key player in tumor microenvironment and inflammatory diseases

CXCL3 (C-X-C Motif Chemokine 3), a member of the C-X-C chemokine subfamily, operates as a potent chemoattractant for neutrophils, thereby orchestrating the recruitment and migration of leukocytes alongside eliciting an inflammatory response. Recent inquiries have shed light on the pivotal roles of CXCL3 in the context of carcinogenesis. In the tumor microenvironment, CXCL3 emanating from both tumor and stromal cells intricately modulates cellular behaviors through autocrine and paracrine actions, primarily via interaction with its receptor CXCR2. Activation of signaling cascades such as ERK/MAPK, AKT, and JAK2/STAT3 underscores CXCL3's propensity to favor tumorigenic processes. However, CXCL3 exhibits dualistic behaviors, as evidenced by its capacity to exert anti-tumor effects under specific conditions. Additionally, the involvement of CXCL3 extends to inflammatory disorders like eclampsia, obesity, and asthma. This review encapsulates the structural attributes, biological functionalities, and molecular underpinnings of CXCL3 across both tumorigenesis and inflammatory diseases.

WTAP/YTHDF1-mediated m6A modification amplifies IFN-γ-induced immunosuppressive properties of human MSCs

INTRODUCTION

The immunosuppressive capacity of mesenchymal stem cells (MSCs) is dependent on the "license" of several pro-inflammatory factors to express immunosuppressive molecular profiles, which determines the therapeutic efficacy of MSCs in immune-mediated inflammatory diseases. Of those, interferon-γ (IFN-γ) is a key inducer for the expression of immunosuppressive molecular profiles; however, the mechanism underlying this effect is unknown.

OBJECTIVES

To elucidate the regulation mechanism and biological functions of N6-methyladenosine (m6A) modification in the immunosuppressive functions by the IFN-γ-licensing MSCs.

METHODS

Epitranscriptomic microarray analysis and MeRIP-qPCR assay were performed to identify the regulatory effect of WTAP in the IFN-γ-licensing MSCs. RIP-qPCR, western blot, qRT-PCR and RNA stability assays were used to determine the regulation of WTAP/m6A/YTHDF1 signaling axis in the expression of immunosuppressive molecules. Further, functional capacity of T cells was tested using flow cytometry, and both DSS-induced colitis mice and CIA mice were constructed to clarify the effect of WTAP and YTHDF1 in MSC-mediated immunosuppression.

RESULTS

We identified that IFN-γ increased the m6A methylation levels of immunosuppressive molecules, while WTAP deficiency abolished the IFN-γ-induced promotion of m6A modification. IFN-γ activated ERK signaling, which induced WTAP phosphorylation. Additionally, the stabilization of WTAP post-transcriptionally increased the mRNA expression of immunosuppressive molecules (IDO1, PD-L1, ICAM1, and VCAM1) in an m6A-YTHDF1-dependent manner; this effect further impacted the immunosuppressive capacity of IFN-γ licensing MSCs on activated T cells. Notably, WTAP/YTHDF1 overexpression enhanced the therapeutic efficacy of IFN-γ licensing MSCs and restructures the ecology of inflammation in both colitis and arthritis models.

CONCLUSION

Our results showed that m6A modification of IDO1, PD-L1, ICAM1, and VCAM1 mRNA mediated by WTAP-YTHDF1 is involved in the regulation of IFN-γ licensing MSCs immunosuppressive abilities, and shed a light to enhance the clinical therapeutic potential of IFN-γ-licensing MSCs.

Multilineage-differentiating stress-enduring cells: a powerful tool for tissue damage repair

Multilineage-differentiating stress-enduring (Muse) cells are a type of pluripotent cell with unique characteristics such as non-tumorigenic and pluripotent differentiation ability. After homing, Muse cells spontaneously differentiate into tissue component cells and supplement damaged/lost cells to participate in tissue repair. Importantly, Muse cells can survive in injured tissue for an extended period, stabilizing and promoting tissue repair. In addition, it has been confirmed that injection of exogenous Muse cells exerts anti-inflammatory, anti-apoptosis, anti-fibrosis, immunomodulatory, and paracrine protective effects in vivo. The discovery of Muse cells is an important breakthrough in the field of regenerative medicine. The article provides a comprehensive review of the characteristics, sources, and potential mechanisms of Muse cells for tissue repair and regeneration. This review serves as a foundation for the further utilization of Muse cells as a key clinical tool in regenerative medicine.

Mesenchymal Stromal Cells: New Generation Treatment of Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a chronic inflammatory disease of the gastrointestinal tract, which has a high recurrence rate and is incurable due to a lack of effective treatment. Mesenchymal stromal cells (MSCs) are a class of pluripotent stem cells that have recently received a lot of attention due to their strong self-renewal ability and immunomodulatory effects, and a large number of experimental and clinical models have confirmed the positive therapeutic effect of MSCs on IBD. In preclinical studies, MSC treatment for IBD relies on MSCs paracrine effects, cell-to-cell contact, and its mediated mitochondrial transfer for immune regulation. It also plays a therapeutic role in restoring the intestinal mucosal barrier through the homing effect, regulation of the intestinal microbiome, and repair of intestinal epithelial cells. In the latest clinical trials, the safety and efficacy of MSCs in the treatment of IBD have been confirmed by transfusion of autologous or allogeneic bone marrow, umbilical cord, and adipose MSCs, as well as their derived extracellular vesicles. However, regarding the stable and effective clinical use of MSCs, several concerns emerge, including the cell sources, clinical management (dose, route and frequency of administration, and pretreatment of MSCs) and adverse reactions. This article comprehensively summarizes the effects and mechanisms of MSCs in the treatment of IBD and its advantages over conventional drugs, as well as the latest clinical trial progress of MSCs in the treatment of IBD. The current challenges and future directions are also discussed. This review would add knowledge into the understanding of IBD treatment by applying MSCs.

Mesenchymal stem cells pretreated with interferon-gamma attenuate renal fibrosis by enhancing regulatory T cell induction

Mesenchymal stem cells (MSCs) exert their anti-inflammatory and anti-fibrotic effects by secreting various humoral factors. Interferon-gamma (IFN-γ) can enhance these effects of MSCs, and enhancement of regulatory T (Treg) cell induction is thought to be an underlying mechanism. However, the extent to which Treg cell induction by MSCs pretreated with IFN-γ (IFN-γ MSCs) ameliorates renal fibrosis remains unknown. In this study, we investigated the effects of Treg cell induction by IFN-γ MSCs on renal inflammation and fibrosis using an siRNA knockdown system. Administration of IFN-γ MSCs induced Treg cells and inhibited infiltration of inflammatory cells in ischemia reperfusion injury (IRI) rats more drastically than control MSCs without IFN-γ pretreatment. In addition, administration of IFN-γ MSCs more significantly attenuated renal fibrosis compared with control MSCs. Indoleamine 2,3-dioxygenase (IDO) expression levels in conditioned medium from MSCs were enhanced by IFN-γ pretreatment. Moreover, IDO1 knockdown in IFN-γ MSCs reduced their anti-inflammatory and anti-fibrotic effects in IRI rats by reducing Treg cell induction. Our findings suggest that the increase of Treg cells induced by enhanced secretion of IDO by IFN-γ MSCs played a pivotal role in their anti-fibrotic effects. Administration of IFN-γ MSCs may potentially be a useful therapy to prevent renal fibrosis progression.

A comprehensive review on the role of mesenchymal stromal/stem cells in the management of rheumatoid arthritis

INTRODUCTION

Rheumatoid arthritis (RA) is a chronic autoimmune inflammatory disease with systemic manifestations. Although the success of immune modulatory drug therapy is considerable, about 40% of patients do not respond to treatment. Mesenchymal stromal/stem cells (MSCs) have been demonstrated to have therapeutic potential for inflammatory diseases.

AREAS COVERED

This review provides an update on RA disease and on pre-clinical and clinical studies using MSCs from bone marrow, umbilical cord, adipose tissue, and dental pulp, to regulate the immune response. Moreover, the clinical use, safety, limitations, and future perspective of MSCs in RA are discussed. Using the PubMed database and ClincalTrials.gov, peer-reviewed full-text papers, abstracts and clinical trials were identified from 1985 through to April 2023.

EXPERT OPINION

MSCs demonstrated a satisfactory safety profile and potential for clinical efficacy. However, it is mandatory to deepen the investigations on how MSCs affect the proinflammatory deregulated RA patients' cells. MSCs are potentially good candidates for severe RA patients not responding to conventional therapies but a long-term follow-up after stem cells treatment and standardized protocols are needed. Future research should focus on well-designed multicenter randomized clinical trials with adequate sample sizes and properly selected patients satisfying RA criteria for a valid efficacy evaluation.

Exosomes Derived from Bone Marrow Mesenchymal Stem Cells Alleviate Rheumatoid Arthritis Symptoms via Shuttling Proteins

Our prior investigations have evidenced that bone marrow mesenchymal stem cell (BMSC) therapy can significantly improve the outcomes of rheumatoid arthritis (RA). This study aims to conduct a comprehensive analysis of the proteomics between BMSCs and BMSCs-Exos, and to further elucidate the potential therapeutic effect of BMSCs-Exos on RA, so as to establish a theoretical framework for the prevention and therapy of BMSCs-Exos on RA. The 4D label-free LC-MS/MS technique was used for comparative proteomic analysis of BMSCs and BMSCs-Exos. Collagen-induced arthritis (CIA) rat model was used to investigate the therapeutic effect of BMSCs-Exos on RA. Our results showed that some homology and differences were observed between BMSCs and BMSCs-Exos proteins, among which proteins highly enriched in BMSCs-Exos were related to extracellular matrix and extracellular adhesion. BMSCs-Exos can be taken up by chondrocytes, promoting cell proliferation and migration. In vivo results revealed that BMSCs-Exos significantly improved the clinical symptoms of RA, showing a certain repair effect on the injury of articular cartilage. In short, our study revealed, for the first time, that BMSCs-Exos possess remarkable efficacy in alleviating RA symptoms, probably through shuttling proteins related to cell adhesion and tissue repair ability in CIA rats, suggesting that BMSCs-Exos carrying expressed proteins may become a useful biomaterial for RA treatment.

Mesenchymal stromal cells with chimaeric antigen receptors for enhanced immunosuppression

Allogeneic mesenchymal stromal cells (MSCs) are a safe treatment option for many disorders of the immune system. However, clinical trials using MSCs have shown inconsistent therapeutic efficacy, mostly owing to MSCs providing insufficient immunosuppression in target tissues. Here we show that antigen-specific immunosuppression can be enhanced by genetically modifying MSCs with chimaeric antigen receptors (CARs), as we show for E-cadherin-targeted CAR-MSCs for the treatment of graft-versus-host disease in mice. CAR-MSCs led to superior T-cell suppression and localization to E-cadherin+ colonic cells, ameliorating the animals' symptoms and survival rates. On antigen-specific stimulation, CAR-MSCs upregulated the expression of immunosuppressive genes and receptors for T-cell inhibition as well as the production of immunosuppressive cytokines while maintaining their stem cell phenotype and safety profile in the animal models. CAR-MSCs may represent a widely applicable therapeutic technology for enhancing immunosuppression.

Recombinant human collagen I/carboxymethyl chitosan hydrogel loaded with long-term released hUCMSCs derived exosomes promotes skin wound repair

BACKGROUND

Stem cell exosomes are beneficial in accelerating wound repair. However, the therapeutic function is limited due to its rapid clearance in vivo. To improve the functionality of exosomes in cutaneous wound healing, a novel hydrogel was designed and fabricated by recombinant human collagen I and carboxymethyl chitosan loaded with exosomes derived from human umbilical cord mesenchymal stem cells (hUCMSCs), named as the rhCol I/CMC-Exos hydrogel.

METHODS

Exosomes were extracted from hUCMSCs and were characterizated by TEM (Transmission Electron Microscopy), and biomarker detection. The rhCol I hydrogel, rhCol I/carboxymethyl chitosan (rhCol I/CMC) hydrogel and the rhCol I/CMC-Exos hydrogel composites were cross-linked by genipin. These materials were assessed and compared for their physical characteristics, including cross-sectional morphology, porosity, pore distribution, and hydrophilicity. Cell biocompatibility on biomaterials was investigated using scanning electron microscopy and CFDA staining, as well as assessed in vivo through histological examination of major organs in mice. Effects of the hydrogel composite on wound healing were further evaluated by using the full-thickness skin defect mice model.

RESULTS

Successful extraction of hUCMSCs-derived exosomes was confirmed by TEM，Western Blotting and flow cytometry. The synthesized rhCol I/CMC-Exos hydrogel composite exhibited cytocompatibility and promoted cell growth in vitro. The rhCol I/CMC-Exos hydrogel showed sustained release of exosomes. In the mice full skin-defects model, the rhCol I/CMC-Exos-treated group showed superior wound healing efficiency, with 15 % faster wound closure compared to controls. Histological examinations revealed thicker dermis formation and more balanced collagen deposition in wounds treated with rhCol I/CMC-Exos hydrogel. Mechanistically, the application of rhCol I/CMC-Exos hydrogel increased fibroblasts proliferation, alleviated inflammation responses as well as promoted angiogenesis, thereby was beneficial in promoting skin wound healing and regeneration.

CONCLUSION

Our study, for the first time, introduced recombinant human Collagen I in fabricating a novel hydrogel loaded with hUCMSCs-derived exosomes, which effectively promoted skin wound closure and regeneration, demonstrating a great potential in severe skin wound healing treatment.

Mesenchymal stem cells alleviate mouse liver fibrosis by inhibiting pathogenic function of intrahepatic B cells

BACKGROUND AND AIMS

The immunomodulatory characteristics of mesenchymal stem cells (MSCs) make them a promising therapeutic approach for liver fibrosis (LF). Here, we postulated that MSCs could potentially suppress the pro-fibrotic activity of intrahepatic B cells, thereby inhibiting LF progression.

APPROACH AND RESULTS

Administration of MSCs significantly ameliorated LF as indicated by reduced myofibroblast activation, collagen deposition, and inflammation. The treatment efficacy of MSCs can be attributed to decreased infiltration, activation, and pro-inflammatory cytokine production of intrahepatic B cells. Single-cell RNA sequencing revealed a distinct intrahepatic B cell atlas, and a subtype of naive B cells (B-II) was identified, which were markedly abundant in fibrotic liver, displaying mature features with elevated expression of several proliferative and inflammatory genes. Transcriptional profiling of total B cells revealed that intrahepatic B cells displayed activation, proliferation, and pro-inflammatory gene profile during LF. Fibrosis was attenuated in mice ablated with B cells (μMT) or in vivo treatment with anti-CD20. Moreover, fibrosis was recapitulated in μMT after adoptive transfer of B cells, which in turn could be rescued by MSC injection, validating the pathogenic function of B cells and the efficacy of MSCs on B cell-promoted LF progression. Mechanistically, MSCs could inhibit the proliferation and cytokine production of intrahepatic B cells through exosomes, regulating the Mitogen-activated protein kinase and Nuclear factor kappa B signaling pathways.

CONCLUSIONS

Intrahepatic B cells serve as a target of MSCs, play an important role in the process of MSC-induced amelioration of LF, and may provide new clues for revealing the novel mechanisms of MSC action.

Advances in cell-based delivery of oncolytic viruses as therapy for lung cancer

Lung cancer's intractability is enhanced by its frequent resistance to (chemo)therapy and often high relapse rates that make it the leading cause of cancer death worldwide. Improvement of therapy efficacy is a crucial issue that might lead to a significant advance in the treatment of lung cancer. Oncolytic viruses are desirable combination partners in the developing field of cancer immunotherapy due to their direct cytotoxic effects and ability to elicit an immune response. Systemic oncolytic virus administration through intravenous injection should ideally lead to the highest efficacy in oncolytic activity. However, this is often hampered by the prevalence of host-specific, anti-viral immune responses. One way to achieve more efficient systemic oncolytic virus delivery is through better protection against neutralization by several components of the host immune system. Carrier cells, which can even have innate tumor tropism, have shown their appropriateness as effective vehicles for systemic oncolytic virus infection through circumventing restrictive features of the immune system and can warrant oncolytic virus delivery to tumors. In this overview, we summarize promising results from studies in which carrier cells have shown their usefulness for improved systemic oncolytic virus delivery and better oncolytic virus therapy against lung cancer.

Therapeutic and immunomodulatory potentials of mesenchymal stromal/stem cells and immune checkpoints related molecules

Mesenchymal stromal/stem cells (MSCs) are used in many studies due to their therapeutic potential, including their differentiative ability and immunomodulatory properties. These cells perform their therapeutic functions by using various mechanisms, such as the production of anti-inflammatory cytokines, growth factors, direct cell-to-cell contact, extracellular vesicles (EVs) production, and mitochondrial transfer. However, mechanisms related to immune checkpoints (ICPs) and their effect on the immunomodulatory ability of MSCs are less discussed. The main function of ICPs is to prevent the initiation of unwanted responses and to regulate the immune system responses to maintain the homeostasis of these responses. ICPs are produced by various types of immune system regulatory cells, and defects in their expression and function may be associated with excessive responses that can ultimately lead to autoimmunity. Also, by expressing different types of ICPs and their ligands (ICPLs), tumor cells prevent the formation and durability of immune responses, which leads to tumors' immune escape. ICPs and ICPLs can be produced by MSCs and affect immune cell responses both through their secretion into the microenvironment or direct cell-to-cell interaction. Pre-treatment of MSCs in inflammatory conditions leads to an increase in their therapeutic potential. In addition to the effect that inflammatory environments have on the production of anti-inflammatory cytokines by MSCs, they can increase the expression of various types of ICPLs. In this review, we discuss different types of ICPLs and ICPs expressed by MSCs and their effect on their immunomodulatory and therapeutic potential.

Human dental pulp stem cell-derived exosomes decorated titanium scaffolds for promoting bone regeneration

Exosomes, nanoscale extracellular vesicles crucial for intercellular communication, hold great promise as a therapeutic avenue in cell-free tissue regeneration. In this study, we identified and utilized exosomes to adorn anodized titanium scaffolds, inducing osteogenic differentiation in human dental pulp stem cells (hDPSCs). The osteogenesis of hDPSCs was stimulated by exosomes derived from hDPSCs that underwent various periods of osteogenic differentiation. After purification, these exosomes were loaded onto anodized titanium scaffolds. Notably, the scaffolds loaded with exosomes deriving from osteogenic differentiated hDPSCs demonstrated superior bone tissue regeneration compared to those loaded with exosomes deriving from hDPSCs within 10-week. RNA-sequencing analysis shed light on the underlying mechanism, revealing that the osteogenic exosomes carried specific cargo, which is due to upregulated miRNAs (Hsa-miR-29c-5p, Hsa-miR-378a-5p, Hsa-miR-10b-5p and Hsa-miR-9-3p) associated with osteogenesis. And down-regulated anti-osteogenic miRNA (Hsa-miR-31-3p, Hsa-miR-221-3p, Hsa-miR-183-5p and Hsa-miR-503-5p). In conclusion, the identification and utilization of exosomes derived from osteogenic differentiated stem cells offer a novel and promising strategy for achieving cell-free bone regeneration.

Dual-Targeting Nanovesicles Carrying CSF1/CD47 Identified from Single-Cell Transcriptomics of Innate Immune Cells in Heart Transplant for Alleviating Acute Rejection

Although immunosuppressive drugs for targeting T cells are the standard of care in acute transplantation rejection, the role of innate immune cells should not be ignored. Here, single-cell RNA sequencing (scRNA-seq) and flow cytometry are performed to reveal the dynamic changes of innate immune cells within the acute rejection time and find a significantly-increased presence of Ly6G- Ly6C+ inflammatory macrophages and decreased presence of neutrophils among all types of immune cells. Next, to further explore potential targets regulating Ly6G- Ly6C+ inflammatory macrophages, scRNA-seq is used to analyze the reciprocal signaling of both neutrophils and macrophages, along with the surface genes of macrophages. It is found that activating colony-stimulating factor 1/ colony-stimulating factor 1 receptor (CSF1/CSF1R) andcluster of differentiation 47/signal regulatory protein α (CD47/SIRPα) signaling may serve as a strategy to relieve Ly6G- Ly6C+ inflammatory macrophage-mediated early graft rejection. To investigate this hypothesis, CSF1/CD47 dual-targeting nanovesicles (NVs) derived from IFN-γ-stimulated induced pluripotent stem cell-derived mesenchymal stem cells ( iPSC-MSCs )are designed and constructed. It is confirmed that CSF1/CD47 NVs synergistically induce the differentiation of Ly6G- Ly6C- M2 inhibitory macrophages by the CSF1/CSF1R pathway, and inhibit the phagocytosis of inflammatory macrophages and inflammatory response by the CD47/SIRPα pathway, ultimately relieving immune rejection. This study highlights the power of dual-targeting CSF1/CD47 NVs as an immunosuppressant against early innate immune responses with the potential for broad clinical applications.

ASC-expressing pyroptotic extracellular vesicles alleviate sepsis by protecting B cells

Pyroptosis is an inflammatory programmed cell death process characterized by membrane rupture. Interestingly, pyroptotic cells can generate plenty of nanosized vesicles. Non-inflammatory apoptotic cell death-derived apoptotic vesicles (apoVs) were systemically characterized and displayed multiple physiological functions and therapeutic potentials. However, the characteristics of pyroptotic cell-generated extracellular vesicles (EVs) are largely unknown. Here, we identified a group of pyroptotic EVs (pyroEVs) from in vitro cultured pyroptotic mesenchymal stem cells (MSCs), as well as from septic mouse blood. Compared with apoVs, pyroEVs express similar levels of annexin V, calreticulin, and common EV markers, but express a decreased level of apoptotic marker cleave caspase-3. PyroEVs, but not apoVs and exosomes, specifically express pyroptotic maker apoptosis-associated speck-like protein containing CARD (ASC). More importantly, MSC-derived pyroEVs protect B cells in the spleen and bone marrow to relieve inflammatory responses and enhance the survival rate of the septic mice. Mechanistically, pyroEV membrane-expressed ASC binds to B cells to repress cell death by repressing Toll-like receptor 4. This study uncovered the characteristics of pyroEVs and their therapeutic role in sepsis and B cell-mediated immune response.

Modification of the inflammatory profile of mesenchymal stem cells using different culture conditions

Aim: Mesenchymal stem cells (MSCs) are pluripotent cells with significant therapeutic potential. The objective of this study was to examine the inflammatory profile of MSCs cultured under different conditions. Methods: MSCs were cultured by three strategies: seeding on an extracellular matrix (ECM), spheroids in static culture and spheroids in a bioreactor. Paracrine factors and CD206, a marker of M2 macrophage phenotype, were measured. Results: MSCs grown as spheroids in a bioreactor produced more IL-6 and IL-8 (p < 0.05). Supernatant collected from spheroids under both culture conditions increased the M2 macrophage phenotype almost twofold. Conclusion: Results indicate that the inflammatory profile of the supernatant collected from MSCs can be modified through culture conditions which has impacts for the future of regenerative medicine.

The Role of Mesenchymal Stem/Stromal Cells Secretome in Macrophage Polarization: Perspectives on Treating Inflammatory Diseases

Mesenchymal stem/stromal cells (MSCs) have exhibited potential for treating multiple inflammation- related diseases (IRDs) due to their easy acquisition, unique immunomodulatory and tissue repair properties, and immune-privileged characteristics. It is worth mentioning that MSCs release a wide array of soluble bioactive components in the secretome that modulate host innate and adaptive immune responses and promote the resolution of inflammation. As the first line of defense, macrophages exist throughout the entire inflammation process. They continuously switch their molecular phenotypes accompanied by complementary functional regulation ranging from classically activated pro-inflammatory M1-type (M1) to alternatively activated anti-inflammatory M2-type macrophages (M2). Recent studies have shown that the active intercommunication between MSCs and macrophages is indispensable for the immunomodulatory and regenerative behavior of MSCs in pharmacological cell therapy products. In this review, we systematically summarized the emerging capacities and detailed the molecular mechanisms of the MSC-derived secretome (MSC-SE) in immunomodulating macrophage polarization and preventing excessive inflammation, providing novel insights into the clinical applications of MSC-based therapy in IRD management.

Magnesium-Organic Framework-Loaded Bisphosphonate-Functionalized Gel Scaffolds for Enhanced Bone Regeneration

The development of magnesium-derived biomaterials is one of the most promising research in bone tissue engineering, and related strategies have been extensively used for tendon, skull, cartilage, and bone regeneration. Also, alendronate, a well-recognized drug for osteoporosis treatment, has recently attracted a great deal of attention for bone repair. However, rapid corrosion in vivo of Mg2+ and low systemic bioavailability of alendronate are the main limitations hampering their full exploitation. In this work, by means of physical and chemical cross-linking conjugating magnesium-metal-organic frameworks (Mg-MOFs) and bone-targeting alendronate to biocompatible gelatin scaffolds, a facile method is developed for the preparation of organic/inorganic nanocomposite gel scaffolds. The results affirmed that the nanocomposite gel scaffolds possessed excellent biocompatibility, continuous slow release of Mg2+ and alendronate, strong bone affinity, and bone regeneration. It is noteworthy that the continuous slow release of Mg2+ and alendronate could induce the macrophage switch to the M2 phenotype and promote osteogenic differentiation in the early stage, resulting in improved bone regeneration during implanting the scaffolds into the distal femoral. In summary, Mg-MOFs-loaded alendronate-modified gelatin gel scaffolds have been developed, exhibiting great potential for bone regenerative.

Exploring therapeutic avenues: mesenchymal stem/stromal cells and exosomes in confronting enigmatic biofilm-producing fungi

Fungal infections concomitant with biofilms can demonstrate an elevated capacity to withstand substantially higher concentrations of antifungal agents, contrasted with infectious diseases caused by planktonic cells. This inherent resilience intrinsic to biofilm-associated infections engenders a formidable impediment to effective therapeutic interventions. The different mechanisms that are associated with the intrinsic resistance of Candida species encompass drug sequestration by the matrix, drug efflux pumps, stress response cell density, and the presence of persister cells. These persisters, a subset of fungi capable of surviving hostile conditions, pose a remarkable challenge in clinical settings in virtue of their resistance to conventional antifungal therapies. Hence, an exigent imperative has arisen for the development of novel antifungal therapeutics with specific targeting capabilities focused on these pathogenic persisters. On a global scale, fungal persistence and their resistance within biofilms generate an urgent clinical need for investigating recently introduced therapeutic strategies. This review delves into the unique characteristics of Mesenchymal stem/stromal cells (MSCs) and their secreted exosomes, which notably exhibit immunomodulatory and regenerative properties. By comprehensively assessing the current literature and ongoing research in this field, this review sheds light on the plausible mechanisms by which MSCs and their exosomes can be harnessed to selectively target fungal persisters. Additionally, prospective approaches in the use of cell-based therapeutic modalities are examined, emphasizing the importance of further research to overcome the enigmatic fungal persistence.

New era of mesenchymal stem cell-based medicine: basis, challenges and prospects

Stem cells of mesenchymal origin (MSC) arouse special interest due to their regenerative, anti-inflammatory, anti-apoptotic, anti-oxidative stress, antitumor or antimicrobial properties. However, its implementation in the clinic runs into drawbacks of cell therapy (immunological incompatibility, tumor formation, possible transmission of infections, entry into cellular senescence, difficult evaluation of safety, dose and potency; complex storage conditions, high economic cost or impractical clinical use). Considering that the positive effects of MSC are due, to a large extent, to the paracrine effects mediated by the set of substances they secrete (growth factors, cytokines, chemokines or microvesicles), the in vitro obtaining of these biological products makes possible a medicine cell-free regenerative therapy without the drawbacks of cell therapy. However, this new therapeutic innovation implies challenges, such as the recognition of the biological heterogeneity of MSC and the optimization and standardization of their secretome.

Differential response of mesenchymal stromal cells (MSCs) to type 1 ex vivo cytokine priming: implications for MSC therapy

BACKGROUND AIMS

Mesenchymal stromal cells (MSCs) are polymorphic, adherent cells with the capability to stimulate tissue regeneration and modulate immunity. MSCs have been broadly investigated for potential therapeutic applications, particularly immunomodulatory properties, wound healing and tissue regeneration. The exact physiologic role of MSCs, however, remains poorly understood, and this gap in knowledge significantly impedes the rational development of therapeutic cells. Here, we considered interferon γ (IFN-γ) and tumor necrosis factor alpha (TNF-α), two cytokines likely encountered physiologically and commonly used in cell manufacturing. For comparison, we studied interleukin-10 (IL-10) (anti-inflammatory) and interleukin-4 (IL-4) (type 2 cytokine).

METHODS

We directly assessed the effects of these cytokines on bone marrow MSCs by comparing RNA Seq transcriptional profiles. Western blotting and flow cytometry were also used to evaluate effects of cytokine priming.

RESULTS

The type 1 cytokines (IFN-γ and TNF-α) induced striking changes in gene expression and remarkably different profiles from one another. Importantly, priming MSCs with either of these cytokines did not increase variability among multiple donors beyond what is intrinsic to non-primed MSCs from different donors. IFN-γ-primed MSCs expressed IDO1 and chemokines that recruit activated T cells. In contrast, TNF-α-primed MSCs expressed genes in alternate pathways, namely PGE2 and matrix metalloproteinases synthesis, and chemokines that recruit neutrophils. IL-10 and IL-4 priming had little to no effect.

CONCLUSIONS

Our data suggest that IFN-γ-primed MSCs may be a more efficacious immunosuppressive therapy aimed at diseases that target T cells (ie, graft-versus-host disease) compared with TNF-α-primed or non-primed MSCs, which may be better suited for therapies in other disease settings. These results contribute to our understanding of MSC bioactivity and suggest rational ex vivo cytokine priming approaches for MSC manufacturing and therapeutic applications.

Protective effects of EVs/exosomes derived from permanently growing human MSC on primary murine ALS motor neurons

In recent years, the neuroprotective potential of mesenchymal stroma-/stem-like cells (MSC) as well as of MSC-derived extracellular vesicles (EVs) like exosomes has been intensively explored. This included preclinical evaluation regarding treatment of neurodegenerative disorders such as the fatal motor neuron disease amyotrophic Lateral Sclerosis (ALS). Several studies have reported that MSC-derived exosomes can stimulate tissue regeneration and reduce inflammation. MSC release EVs and trophic factors and thereby modify cell-to-cell communication. These cell-free products may protect degenerating motor neurons (MNs) and represent a potential therapeutic approach for ALS. In the present study we investigated the effects of exosomes derived from a permanently growing MSC line on both, wild type and ALS (SOD1G93A transgenic) primary motor neurons. Following application in a normal and stressed environment we could demonstrate beneficial effects of MSC exosomes on neurite growth and morphology indicating the potential for further preclinical evaluation and clinical therapeutic development. Investigation of gene expression profiles detected transcripts of several antioxidant and anti-inflammatory genes in MSC exosomes. Characterization of their microRNA (miRNA) content revealed miRNAs capable of regulating antioxidant and anti-apoptotic pathways.

Human Mesenchymal Stem Cell Transplantation Improved Functional Outcomes Following Spinal Cord Injury Concomitantly with Neuroblast Regeneration

Purpose

Spinal cord injury (SCI) is damage to the spinal cord that resulted in irreversible neuronal loss, glial scar formation and axonal injury. Herein, we used the human amniotic fluid mesenchymal stem cells (hAF-MSCs) and their conditioned medium (CM), to investigate their ability in neuroblast and astrocyte production as well as functional recovery following SCI.

Methods

Fifty-four adult rats were randomly divided into nine groups (n=6), included: Control, SCI, (SCI + DMEM), (SCI + CM), (SCI + MSCs), (SCI + Astrocyte), (SCI + Astrocyte + DMEM), (SCI + Astrocyte + CM) and (SCI + Astrocyte + MSCs). Following laminectomy and SCI induction, DMEM, CM, MSCs, and astrocytes were injected. Western blot was performed to explore the levels of the Sox2 protein in the MSCs-CM. The immunofluorescence staining against doublecortin (DCX) and glial fibrillary acidic protein (GFAP) was done. Finally, Basso-Beattie-Brenham (BBB) locomotor test was conducted to assess the neurological outcomes.

Results

Our results showed that the MSCs increased the number of endogenous DCX-positive cells and decreased the number of GFAP-positive cells by mediating juxtacrine and paracrine mechanisms (P<0.001). Transplanted human astrocytes were converted to neuroblasts rather than astrocytes under influence of MSCs and CM in the SCI. Moreover, functional recovery indexes were promoted in those groups that received MSCs and CM.

Conclusion

Taken together, our data indicate the MSCs via juxtacrine and paracrine pathways could direct the spinal cord endogenous neural stem cells (NSCs) to the neuroblasts lineage which indicates the capability of the MSCs in the increasing of the number of DCX-positive cells and astrocytes decline.

The role and mechanisms of microvascular damage in the ischemic myocardium

Following myocardial ischemic injury, the most effective clinical intervention is timely restoration of blood perfusion to ischemic but viable myocardium to reduce irreversible myocardial necrosis, limit infarct size, and prevent cardiac insufficiency. However, reperfusion itself may exacerbate cell death and myocardial injury, a process commonly referred to as ischemia/reperfusion (I/R) injury, which primarily involves cardiomyocytes and cardiac microvascular endothelial cells (CMECs) and is characterized by myocardial stunning, microvascular damage (MVD), reperfusion arrhythmia, and lethal reperfusion injury. MVD caused by I/R has been a neglected problem compared to myocardial injury. Clinically, the incidence of microvascular angina and/or no-reflow due to ineffective coronary perfusion accounts for 5-50% in patients after acute revascularization. MVD limiting drug diffusion into injured myocardium, is strongly associated with the development of heart failure. CMECs account for > 60% of the cardiac cellular components, and their role in myocardial I/R injury cannot be ignored. There are many studies on microvascular obstruction, but few studies on microvascular leakage, which may be mainly due to the lack of corresponding detection methods. In this review, we summarize the clinical manifestations, related mechanisms of MVD during myocardial I/R, laboratory and clinical examination means, as well as the research progress on potential therapies for MVD in recent years. Better understanding the characteristics and risk factors of MVD in patients after hemodynamic reconstruction is of great significance for managing MVD, preventing heart failure and improving patient prognosis.

Advanced micro-/nanotechnologies for exosome encapsulation and targeting in regenerative medicine

Exosomes, a subset of vesicles generated from cell membranes, are crucial for cellular communication. Exosomes' innate qualities have been used in recent studies to create nanocarriers for various purposes, including medication delivery and immunotherapy. As a result, a wide range of approaches has been designed to utilize their non-immunogenic nature, drug-loading capacity, or targeting ability. In this study, we aimed to review the novel methods and approaches in exosome engineering for encapsulation and targeting in regenerative medicine. We have assessed and evaluated each method's efficacy, advantages, and disadvantages and discussed the results of related studies. Even though the therapeutic role of non-allogenic exosomes has been demonstrated in several studies, their application has certain limitations as these particles are neither fully specific to target tissue nor tissue retainable. Hence, there is a strong demand for developing more efficient encapsulation methods along with more accurate and precise targeting methods, such as 3D printing and magnetic nanoparticle loading in exosomes, respectively.

NAD+ salvage governs the immunosuppressive capacity of mesenchymal stem cells

Mesenchymal stem/stromal cells (MSCs) possess robust immunoregulatory functions and are promising therapeutics for inflammatory disorders. This capacity is not innate but is activated or 'licensed' by inflammatory cytokines. The licensing mechanism remains unclear. Here, we examined whether inflammatory cytokines metabolically reprogrammed MSCs to confer this immunoregulatory capacity. In response to stimulation by inflammatory cytokines, MSCs exhibited a dramatic increase in the consumption of glucose, which was accompanied by an enhanced use of nicotinamide adenine dinucleotide (NAD+) and increased expression of nicotinamide phosphoribosyltransferase (NAMPT), a central enzyme in the salvage pathway for NAD+ production. When NAD+ synthesis was blocked by inhibiting or depleting NAMPT, the immunosuppressive function of MSCs induced by inflammatory cytokines was greatly attenuated. Consequently, when NAD+ metabolism in MSCs was perturbed, their therapeutic benefit was decreased in mice suffering from inflammatory bowel disease and acute liver injury. Further analysis revealed that NAMPT-driven production of NAD+ was critical for the inflammatory cytokine-induced increase in glycolysis in MSCs. Furthermore, the increase in glycolysis led to succinate accumulation in the tricarboxylic acid cycle, which led to hypoxia-inducible factor 1α (HIF-1α) stabilization and subsequently increased the transcription of key glycolytic genes, thereby persistently maintaining glycolytic flux. This study demonstrated that unlike its proinflammatory role in immune cells, NAD+ metabolism governs the anti-inflammatory function of MSCs during inflammation.

Orchestration of Mesenchymal Stem/Stromal Cells and Inflammation During Wound Healing

Wound healing is a complex process and encompasses a number of overlapping phases, during which coordinated inflammatory responses following tissue injury play dominant roles in triggering evolutionarily highly conserved principals governing tissue repair and regeneration. Among all nonimmune cells involved in the process, mesenchymal stem/stromal cells (MSCs) are most intensely investigated and have been shown to play fundamental roles in orchestrating wound healing and regeneration through interaction with the ordered inflammatory processes. Despite recent progress and encouraging results, an informed view of the scope of this evolutionarily conserved biological process requires a clear understanding of the dynamic interplay between MSCs and the immune systems in the process of wound healing. In this review, we outline current insights into the ways in which MSCs sense and modulate inflammation undergoing the process of wound healing, highlighting the central role of neutrophils, macrophages, and T cells during the interaction. We also draw attention to the specific effects of MSC-based therapy on different pathological wound healing. Finally, we discuss how ongoing scientific advances in MSCs could be efficiently translated into clinical strategies, focusing on the current limitations and gaps that remain to be overcome for achieving preferred functional tissue regeneration.

Reconditioned monocytes are immunomodulatory and regulate inflammatory environment in sepsis

Sepsis is caused by dysregulated immune response to severe infection and hyper inflammation plays a central role in worsening the disease. The immunomodulatory properties of mesenchymal stem cells (MSCs) have been evaluated as a therapeutic candidate for sepsis. Reconditioned monocytes (RM), generated from healthy human peripheral blood mononuclear cells (PBMCs) exhibit both macrophage and MSCs-like properties. RM were administered at different stages of sepsis in a mouse model. It reduced serum levels of IL6, MCP-1, IL-10, improved hypothermia, increased survival, and recovery from 0 to 66% when combined with antibiotics in the mouse model. The reduced human leucocyte antigen DR molecules expression on RM enables their co-culture with PBMCs of sepsis patients which resulted in reduced ROS production, and up-regulated TGF-β while down-regulating IL6, IL8, and IL-10 in-vitro. RM are potentially immunomodulatory, enhance survival in sepsis mouse model and modulate inflammatory behaviour of sepsis patient's PBMCs.

Genetic Landscape of Masticatory Muscle Tendon-Aponeurosis Hyperplasia

Limited mouth opening is a characteristic of masticatory muscle tendon-aponeurosis hyperplasia (MMTAH). Although genetic involvement is suspected where familial onset is frequently observed, the genetic background of MMTAH is yet to be elucidated. In this study, we conducted whole genome sequencing of 10 patients with MMTAH and their family members when available. We also conducted RNA sequencing of normal temporal tendon (as disease region) and Achilles tendon (as control region) from commercially available pig samples. We identified 51 genes that had rare variants in patients with MMTAH and were highly expressed in the temporal tendons of pigs. Among the 51 genes, 37 genes have not been reported to be causative for human genetic diseases so far. As an implication of genetic involvement in the pathogenesis of MMTAH, 21 of these 37 genes were identified in two independent families. In particular, PCDH1 and BAIAP3 were identified in one affected individual in a family and consistently segregated in unrelated family, indicating they could be candidate causative genes of MMTAH. Our findings will help elucidate the genetic landscape of MMTAH and provide insights into future possibilities for tendon regeneration treatment.

Preparation of Fibrinogen-Depleted Human Platelet Lysate to Support Heparin-Free Expansion of Umbilical Cord-Derived Mesenchymal Stem Cells

Human platelet lysate (hPL) has high levels of fibrinogen and coagulation factors, which can lead to gel and precipitate formation during storage and cell culture. Heparin derived from animals is commonly added to minimize these risks, but cannot completely eliminate them. Thus, this study proposes an alternative method to prepare fibrinogen-depleted hPL (Fd-hPL) that supports heparin-free expansion of mesenchymal stem cells (MSCs). hPL was added to heparin to prepare heparin-hPL (H-hPL), whilst Fd-hPL was prepared by adding calcium salt to hPL to remove the fibrin clot. The concentrations of calcium, fibrinogen, and growth factors in H-hPL and Fd-hPL were compared. The effects of H-hPL and Fd-hPL on umbilical cord-derived MSCs (UC-MSCs) were assessed. The results showed that Fd-hPL possessed a significantly higher calcium concentration and a lower fibrinogen level than H-hPL. The concentrations of BDNF, TGF-β1, and PDGF-BB showed no significant difference between H-hPL and Fd-hPL, but Fd-hPL had a lower VEGF concentration. Fd-hPL retained the characteristics of UC-MSCs, as it did not affect the cell viability, proliferation, multilineage differentiation potential, or surface marker expression. In conclusion, Fd-hPL effectively supported the in vitro expansion of MSCs without compromising their characteristics, positioning it as a potential substitute for FBS in MSC culture.

Wharton's jelly mesenchymal stem cells: a concise review of their secretome and prospective clinical applications

Accumulating evidence indicates that most primary Wharton's jelly mesenchymal stem cells (WJ-MSCs) therapeutic potential is due to their paracrine activity, i.e., their ability to modulate their microenvironment by releasing bioactive molecules and factors collectively known as secretome. These bioactive molecules and factors can either be released directly into the surrounding microenvironment or can be embedded within the membrane-bound extracellular bioactive nano-sized (usually 30-150 nm) messenger particles or vesicles of endosomal origin with specific route of biogenesis, known as exosomes or carried by relatively larger particles (100 nm-1 μm) formed by outward blebbing of plasma membrane called microvesicles (MVs); exosomes and MVs are collectively known as extracellular vesicles (EVs). The bioactive molecules and factors found in secretome are of various types, including cytokines, chemokines, cytoskeletal proteins, integrins, growth factors, angiogenic mediators, hormones, metabolites, and regulatory nucleic acid molecules. As expected, the secretome performs different biological functions, such as immunomodulation, tissue replenishment, cellular homeostasis, besides possessing anti-inflammatory and anti-fibrotic effects. This review highlights the current advances in research on the WJ-MSCs' secretome and its prospective clinical applications.

Efficacy of Rectal Systemic Administration of Mesenchymal Stem Cells to Injury Sites via the CXCL12/CXCR4 Axis to Promote Regeneration in a Rabbit Skeletal Muscle Injury Model

Mesenchymal stem cells (MSCs) have been transplanted directly into lesions or injected intravenously. The administration of MSCs using these delivery methods requires specialized knowledge, techniques, and facilities. Here, we describe intrarectal systemic administration of MSCs, a simple, non-invasive route for homing to the injury sites to promote the regeneration of skeletal muscle injuries. Using a cardiotoxin (CTX)-induced rabbit skeletal muscle injury model, homing to the site of muscle injury was confirmed by intrarectal administration of MSCs; the time required for homing after intrarectal administration was approximately 5 days. In addition, the C-X-C chemokine ligand 12 (CXCL12)/C-X-C chemokine receptor-4 (CXCR4) axis was found to be involved in the homing process. Histopathological examinations showed that skeletal muscle regeneration was promoted in the MSCs-administered group compared to the CTX-only group. Myosin heavy polypeptide 3 (Myh3) expression, an indicator of early muscle regeneration, was detected earlier in the intrarectal MSCs group compared to the CTX-only group. These findings indicate that intrarectal administration of MSCs is effective in homing to the injured area, where they promote injury repair. Since intrarectal administration is a simple and non-invasive delivery route, these findings may be valuable in future research on stem cell therapy.

Inflammatory auxo-action in the stem cell division theory of cancer

Acute inflammation is a beneficial response to the changes caused by pathogens or injuries that can eliminate the source of damage and restore homeostasis in damaged tissues. However, chronic inflammation causes malignant transformation and carcinogenic effects of cells through continuous exposure to pro-inflammatory cytokines and activation of inflammatory signaling pathways. According to the theory of stem cell division, the essential properties of stem cells, including long life span and self-renewal, make them vulnerable to accumulating genetic changes that can lead to cancer. Inflammation drives quiescent stem cells to enter the cell cycle and perform tissue repair functions. However, as cancer likely originates from DNA mutations that accumulate over time via normal stem cell division, inflammation may promote cancer development, even before the stem cells become cancerous. Numerous studies have reported that the mechanisms of inflammation in cancer formation and metastasis are diverse and complex; however, few studies have reviewed how inflammation affects cancer formation from the stem cell source. Based on the stem cell division theory of cancer, this review summarizes how inflammation affects normal stem cells, cancer stem cells, and cancer cells. We conclude that chronic inflammation leads to persistent stem cells activation, which can accumulate DNA damage and ultimately promote cancer. Additionally, inflammation not only facilitates the progression of stem cells into cancer cells, but also plays a positive role in cancer metastasis.

Revisiting the role of mesenchymal stem cells in tuberculosis and other infectious diseases

Mesenchymal stem cells (MSCs) play diverse roles ranging from regeneration and wound healing to immune signaling. Recent investigations have indicated the crucial role of these multipotent stem cells in regulating various aspects of the immune system. MSCs express unique signaling molecules and secrete various soluble factors that play critical roles in modulating and shaping immune responses, and in some other cases, MSCs can also exert direct antimicrobial effects, thereby helping with the eradication of invading organisms. Recently, it has been demonstrated that MSCs are recruited at the periphery of the granuloma containing Mycobacterium tuberculosis and exert "Janus"-like functions by harboring pathogens and mediating host protective immune responses. This leads to the establishment of a dynamic balance between the host and the pathogen. MSCs function through various immunomodulatory factors such as nitric oxide (NO), IDO, and immunosuppressive cytokines. Recently, our group has shown that M.tb uses MSCs as a niche to evade host protective immune surveillance mechanisms and establish dormancy. MSCs also express a large number of ABC efflux pumps; therefore, dormant M.tb residing in MSCs are exposed to a suboptimal dose of drugs. Therefore, it is highly likely that drug resistance is coupled with dormancy and originates within MSCs. In this review, we discussed various immunomodulatory properties of MSCs, their interactions with important immune cells, and soluble factors. We also discussed the possible roles of MSCs in the outcome of multiple infections and in shaping the immune system, which may provide insight into therapeutic approaches using these cells in different infection models.

Different priming strategies improve distinct therapeutic capabilities of mesenchymal stromal/stem cells: Potential implications for their clinical use

Mesenchymal stromal/stem cells (MSCs) have shown significant therapeutic potential, and have therefore been extensively investigated in preclinical studies of regenerative medicine. However, while MSCs have been shown to be safe as a cellular treatment, they have usually been therapeutically ineffective in human diseases. In fact, in many clinical trials it has been shown that MSCs have moderate or poor efficacy. This inefficacy appears to be ascribable primarily to the heterogeneity of MSCs. Recently, specific priming strategies have been used to improve the therapeutic properties of MSCs. In this review, we explore the literature on the principal priming approaches used to enhance the preclinical inefficacy of MSCs. We found that different priming strategies have been used to direct the therapeutic effects of MSCs toward specific pathological processes. Particularly, while hypoxic priming can be used primarily for the treatment of acute diseases, inflammatory cytokines can be used mainly to prime MSCs in order to treat chronic immune-related disorders. The shift in approach from regeneration to inflammation implies, in MSCs, a shift in the production of functional factors that stimulate regenerative or anti-inflammatory pathways. The opportunity to fine-tune the therapeutic properties of MSCs through different priming strategies could conceivably pave the way for optimizing their therapeutic potential.

Adipose mesenchymal stem cell-derived soluble factors, produced under hypoxic condition, efficiently support in vivo angiogenesis

Tissue regeneration or healing both require efficient vascularization within a tissue-damaged area. Based on this concept, a remarkable number of strategies, aimed at developing new tools to support re-vascularization of damaged tissue have emerged. Among the strategies proposed, the use of pro-angiogenic soluble factors, as a cell-free tool, appears as a promising approach, able to overcome the issues concerning the direct use of cells for regenerative medicine therapy. Here, we compared the effectiveness of adipose mesenchymal stem cells (ASCs), use as cell suspension, ASC protein extract or ASC-conditioned-medium (i.e., soluble factors), combined with collagenic scaffold, in supporting in vivo angiogenesis. We also tested the capability of hypoxia in increasing the efficiency of ASC to promote angiogenesis, via soluble factors, both in vivo and in vitro. In vivo studies were performed using the Integra® Flowable Wound Matrix, and the Ultimatrix in sponge assay. Flow cytometry was used to characterize the scaffold- and sponge-infiltrating cells. Real-time PCR was used to evaluate the expression of pro-angiogenic factors by stimulating Human Umbilical-Vein Endothelial Cells with ASC-conditioned media, obtained in hypoxic and normoxic conditions. We found that, in vivo, ACS-conditioned media can support angiogenesis similar to ASCs and ASC protein extract. Also, we observed that hypoxia increases the pro-angiogenic activities of ASC-conditioned media, compared to normoxia, by generating a secretome enriched in pro-angiogenic soluble factors, with bFGF, Adiponectine, ENA78, GRO, GRO-a, and ICAM1-3, as most regulated factors. Finally, ASC-conditioned media, produced in hypoxic condition, induce the expression of pro-angiogenic molecules in HUVECs. Our results provide evidence that ASC-conditioned-medium can be proposed as a cell-free preparation able to support angiogenesis, thus providing a relevant tool to overcome the issues and restrictions associated with the use of cells.

Mesenchymal stem cells and allergic airway inflammation; a therapeutic approach to induce immunoregulatory responses

Allergic airway inflammations are among the essential disorders worldwide that are already considered a significant concern. Mesenchymal stem cells (MSCs) are stromal cells with regenerative potential and immunomodulatory characteristics and are widely administered for tissue repair as an immunoregulatory agent in different inflammatory diseases. The current review summarized primary studies conducted to evaluate the therapeutic potential of MSCs for allergic airway disorders. In this case, modulation of airway pathologic inflammation and infiltration of inflammatory cells were examined, and modulation of the Th1/Th2 cellular balance and humoral responses. Also, the effects of MSCs on the Th17/Treg ratio and inducing Treg immunoregulatory responses along with macrophage and dendritic cell function were evaluated.

Therapeutic effects of MSCs, genetically modified MSCs, and NFĸB-inhibitor on chronic inflammatory osteolysis in aged mice

The number of total joint replacements is increasing, especially in elderly patients, and so too are implant-related complications such as prosthesis loosening. Wear particles from the prosthesis induce a chronic inflammatory reaction and subsequent osteolysis, leading to the need for revision surgery. This study investigated the therapeutic effect of NF-ĸB decoy oligodeoxynucleotides (ODN), mesenchymal stem cells (MSCs), and genetically-modified NF-ĸB sensing interleukin-4 over-secreting MSCs (IL4-MSCs) on chronic inflammation in aged mice. The model was generated by continuous infusion of contaminated polyethylene particles into the intramedullary space of the distal femur of aged mice (15-17 months old) for 6 weeks. Local delivery of ODN showed increased bone mineral density (BMD), decreased osteoclast-like cells, increased alkaline phosphatase (ALP)-positive area, and increased M2/M1 macrophage ratio. Local injection of MSCs and IL4-MSCs significantly decreased osteoclast-like cells and increased the M2/M1 ratio, with a greater trend for IL4-MSCs than MSCs. MSCs significantly increased ALP-positive area and BMD values compared with the control. The IL4-MSCs demonstrated higher values for both ALP-positive area and BMD. These findings demonstrated the therapeutic effects of ODN, MSCs, and IL4-MSCs on chronic inflammatory osteolysis in aged mice. The two MSC-based therapies were more effective than ODN in increasing the M2/M1 macrophage ratio, reducing bone resorption, and increasing bone formation. Specifically, MSCs were more effective in increasing bone formation, and IL4-MSCs were more effective in mitigating inflammation. This study suggests potential therapeutic strategies for treating wear particle-associated inflammatory osteolysis after arthroplasty in the elderly.

Immunomodulatory properties of mesenchymal stromal/stem cells: The link with metabolism

BACKGROUND

Mesenchymal stromal/stem cells (MSCs) are the most promising stem cells for the treatment of multiple inflammatory and immune diseases due to their easy acquisition and potent immuno-regulatory capacities. These immune functions mainly depend on the MSC secretion of soluble factors. Recent studies have shown that the metabolism of MSCs plays critical roles in immunomodulation, which not only provides energy and building blocks for macromolecule synthesis but is also involved in the signaling pathway regulation.

AIM OF REVIEW

A thorough understanding of metabolic regulation in MSC immunomodulatory properties can provide new sights to the enhancement of MSC-based therapy.

KEY SCIENTIFIC CONCEPTS OF REVIEW

MSC immune regulation can be affected by cellular metabolism (glucose, adenosine triphosphate, lipid and amino acid metabolism), which further mediates MSC therapy efficiency in inflammatory and immune diseases. The enhancement of glycolysis of MSCs, such as signaling molecule activation, inflammatory cytokines priming, or environmental control can promote MSC immune functions and therapeutic potential. Besides glucose metabolism, inflammatory stimuli also alter the lipid molecular profile of MSCs, but the direct link with immunomodulatory properties remains to be further explored. Arginine metabolism, glutamine-glutamate metabolism and tryptophan-kynurenine via indoleamine 2,3-dioxygenase (IDO) metabolism all contribute to the immune regulation of MSCs. In addition to the metabolism dictating the MSC immune functions, MSCs also influence the metabolism of immune cells and thus determine their behaviors. However, more direct evidence of the metabolism in MSC immune abilities as well as the underlying mechanism requires to be uncovered.

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

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

Glucose Metabolism: Optimizing Regenerative Functionalities of Mesenchymal Stromal Cells Postimplantation

Mesenchymal stromal cells (MSCs) are considered promising candidates for regenerative medicine applications. Their clinical performance postimplantation, however, has been disappointing. This lack of therapeutic efficacy is most likely due to suboptimal formulations of MSC-containing material constructs. Tissue engineers, therefore, have developed strategies addressing/incorporating optimized cell, microenvironmental, biochemical, and biophysical cues/stimuli to enhance MSC-containing construct performance. Such approaches have had limited success because they overlooked that maintenance of MSC viability after implantation for a sufficient time is necessary for MSCs to develop their regenerative functionalities fully. Following a brief overview of glucose metabolism and regulation in MSCs, the present literature review includes recent pertinent findings that challenge old paradigms and notions. We hereby report that glucose is the primary energy substrate for MSCs, provides precursors for biomass generation, and regulates MSC functions, including proliferation and immunosuppressive properties. More importantly, glucose metabolism is central in controlling in vitro MSC expansion, in vivo MSC viability, and MSC-mediated angiogenesis postimplantation when addressing MSC-based therapies. Meanwhile, in silico models are highlighted for predicting the glucose needs of MSCs in specific regenerative medicine settings, which will eventually enable tissue engineers to design viable and potent tissue constructs. This new knowledge should be incorporated into developing novel effective MSC-based therapies. Impact statement The clinical use of mesenchymal stromal cells (MSCs) has been unsatisfactory due to the inability of MSCs to survive and be functional after implantation for sufficient periods to mediate directly or indirectly a successful regenerative tissue response. The present review summarizes the endeavors in the past, but, most importantly, reports the latest findings that elucidate underlying mechanisms and identify glucose metabolism as the crucial parameter in MSC survival and the subsequent functions pertinent to new tissue formation of importance in tissue regeneration applications. These latest findings justify further basic research and the impetus for developing new strategies to improve the modalities and efficacy of MSC-based therapies.