Mesenchymal Stem and Stromal Cells Harness Macrophage-Derived Amphiregulin to Maintain Tissue Homeostasis

Amphiregulin orchestrates the paracrine immune-suppressive function of amniotic-derived cells through its interplay with COX-2/PGE2/EP4 axis

The paracrine crosstalk between amniotic-derived membranes (AMs)/epithelial cells (AECs) and immune cells is pivotal in tissue healing following inflammation. Despite evidence collected to date, gaps in understanding the underlying molecular mechanisms have hindered clinical applications. The present study represents a significant step forward demonstrating that amphiregulin (AREG) orchestrates the native immunomodulatory functions of amniotic derivatives via the COX-2/PGE2/EP4 axis. The results highlight the immunosuppressive efficacy of PGE2-dependent AREG release, dampening PBMCs' activation, and NFAT pathway in Jurkat reporter cells via TGF-β signaling. Moreover, AREG emerges as a key protein mediator by attenuating acute inflammatory response in Tg(lysC:DsRed2) zebrafish larvae. Notably, the interplay of diverse COX-2/PGE2 pathway activators enables AM/AEC to adapt rapidly to external stimuli (LPS and/or stretching) through a responsive positive feedback loop on the AREG/EGFR axis. These findings offer valuable insights for developing innovative cell-free therapies leveraging the potential of amniotic derivatives in immune-mediated diseases and regenerative medicine.

Amphiregulin secreted by umbilical cord multipotent stromal cells protects against ferroptosis of macrophages via the activating transcription factor 3-CD36 axis to alleviate endometrial fibrosis

Endometrium fibrosis is the leading cause of uterine infertility. Macrophages participated in the occurrence and development of endometrial fibrosis. We previously reported that human umbilical cord multipotent stromal cells (hUC-MSCs) exerted their therapeutic effect in a macrophage-dependent manner in endometrial fibrosis. However precise mechanisms by which hUC-MSCs may influence macrophages in endometrial fibrosis remain largely unexplored. Here, we demonstrated that abnormal iron and lipid metabolism occurred in patients with intrauterine adhesions (IUA) and murine models. Ferroptosis has been proven to contribute to the progression of fibrotic diseases. Our results revealed that pharmacological activation of ferroptosis by Erastin aggravated endometrial fibrosis, while inhibition of ferroptosis by Ferrostatin-1 ameliorated endometrial fibrosis in vivo. Moreover, ferroptosis of macrophages was significantly upregulated in endometria of IUA murine models. Of note, transcriptome profiles revealed that CD36 gene expression was significantly increased in patients with IUA and immunofluorescence analysis showed CD36 protein was mainly located in macrophages. Silencing CD36 in macrophages could reverse cell ferroptosis. Dual luciferase reporter assay revealed that CD36 was the direct target of activation transcription factor 3 (ATF3). Furthermore, through establishing coculture system and IUA murine models, we found that hUC-MSCs had a protective role against macrophage ferroptosis and alleviated endometrial fibrosis related to decreased CD36 and ATF3. The effect of hUC-MSCs on macrophage ferroptosis was attributed to the upregulation of amphiregulin (AREG). Our data highlighted that macrophage ferroptosis occurred in endometrial fibrosis via the ATF3-CD36 pathway and hUC-MSCs protected against macrophage ferroptosis to alleviate endometrial fibrosis via secreting AREG. These findings provided a potential target for therapeutic implications of endometrial fibrosis.

Extracellular vesicles meet mitochondria: Potential roles in regenerative medicine

Extracellular vesicles (EVs), secreted by most cells, act as natural cell-derived carriers for delivering proteins, nucleic acids, and organelles between cells. Mitochondria are highly dynamic organelles responsible for energy production and cellular physiological processes. Recent evidence has highlighted the pivotal role of EVs in intercellular mitochondrial content transfer, including mitochondrial DNA (mtDNA), proteins, and intact mitochondria. Intriguingly, mitochondria are crucial mediators of EVs release, suggesting an interplay between EVs and mitochondria and their potential implications in physiology and pathology. However, in this expanding field, much remains unknown regarding the function and mechanism of crosstalk between EVs and mitochondria and the transport of mitochondrial EVs. Herein, we shed light on the physiological and pathological functions of EVs and mitochondria, potential mechanisms underlying their interactions, delivery of mitochondria-rich EVs, and their clinical applications in regenerative medicine.

Toxicity and efficacy of type I interferons on the ocular surface: in vitro, animal, and clinical studies

PURPOSE

To investigate the toxicity of type I interferons (IFNs) on the ocular surface and assess their efficacy in ocular surface tumors.

METHODS

We examined the effects of IFN-α2a, IFN-α2b and IFN-β on corneal epithelial cells and stromal fibroblasts in vitro as well as the impact of IFN-α2a on the ocular surface in mice. Additionally, we analyzed the therapeutic and adverse effects of topically administered IFN-α2a and IFN-α2b in patients with ocular surface tumors. Risk factors contributing to side effects were explored.

RESULTS

IFN-α2a, IFN-α2b or IFN-β reduced cell viability and induced pro-inflammatory cytokines in corneal epithelial cells and stromal fibroblasts. Furthermore, IFNs enhanced the expression of major histocompatibility complex class II and CD40 in corneal epithelial cells. In mice, subconjunctival IFN-α2a injection did not induce corneal epithelial defects or opacity, nor did it reduce aqueous tears or conjunctival goblet cells. In patients, topical IFN-α2a or IFN-α2b administration decreased tumor size and prevented recurrence; however, it was associated with mild side effects, including corneal epitheliopathy and conjunctival hyperemia. These complications were associated with longer IFN use, the presence of underlying ocular surface disease and concurrent use of mitomycin C or anti-glaucoma eye drops.

CONCLUSION

Although type I IFNs cause direct toxicity on corneal cells, they do not induce significant side effects on the healthy ocular surface. Considering its therapeutic and preventive effects, topical type I IFN is safe and effective for treating ocular surface tumors. The potential for ocular side effects should be considered in eyes with identified risk factors.

Shape-Versatile Fixed Cellular Materials for Multiple Target Immunomodulation

Therapeutic cells are usually administered as living agents, despite the risks of undesired cell migration and acquisition of unpredictable phenotypes. Additionally, most cell-based therapies rely on the administration of single cells, often associated with rapid in vivo clearance. 3D cellular materials may be useful to prolong the effect of cellular therapies and offer the possibility of creating structural volumetric constructs. Here, the manufacturing of shape-versatile fixed cell-based materials with immunomodulatory properties is reported. Living cell aggregates with different shapes (spheres and centimeter-long fibers) are fixed using a method compatible with maintenance of structural integrity, robustness, and flexibility of 3D constructs. The biological properties of living cells can be modulated before fixation, rendering an in vitro anti-inflammatory effect toward human macrophages, in line with a decreased activation of the nuclear factor kappa B (NF-κB) pathway that preponderantly correlated with the surface area of the materials. These findings are further corroborated in vivo in mouse skin wounds. Contact with fixed materials also reduces the proliferation of activated primary T lymphocytes, while promoting regulatory populations. The fixation of cellular constructs is proposed as a versatile phenotypic stabilization method that can be easily implemented to prepare immunomodulatory materials with therapeutic potential.

Prostanoid signaling in retinal vascular diseases

The vasculature of the retina is exposed to systemic and local factors that have the capacity to induce several retinal vascular diseases, each of which may lead to vision loss. Prostaglandin signaling has arisen as a potential therapeutic target for several of these diseases due to the diverse manners in which these lipid mediators may affect retinal blood vessel function. Previous reports and clinical practices have investigated cyclooxygenase (COX) inhibition by nonsteroidal anti-inflammatory drugs (NSAIDs) to address retinal diseases with varying degrees of success; however, targeting individual prostanoids or their distinct receptors affords more signaling specificity and poses strong potential for therapeutic development. This review offers a comprehensive view of prostanoid signaling involved in five key retinal vascular diseases: retinopathy of prematurity, diabetic retinopathy, age-related macular degeneration, retinal occlusive diseases, and uveitis. Mechanistic and clinical studies of these lipid mediators provide an outlook for therapeutic development with the potential to reduce vision loss in each of these conditions.

Defining mesenchymal stem/stromal cell-induced myeloid-derived suppressor cells using single-cell transcriptomics

Mesenchymal stem/stromal cells (MSCs) modulate the immune response through interactions with innate immune cells. We previously demonstrated that MSCs alleviate ocular autoimmune inflammation by directing bone marrow cell differentiation from pro-inflammatory CD11bhiLy6ChiLy6Glo cells into immunosuppressive CD11bmidLy6CmidLy6Glo cells. Herein, we analyzed MSC-induced CD11bmidLy6Cmid cells using single-cell RNA sequencing and compared them with CD11bhiLy6Chi cells. Our investigation revealed seven distinct immune cell types including myeloid-derived suppressor cells (MDSCs) in the CD11bmidLy6Cmid cells, while CD11bhiLy6Chi cells included mostly monocytes/macrophages with a small cluster of neutrophils. These MSC-induced MDSCs highly expressed Retnlg, Cxcl3, Cxcl2, Mmp8, Cd14, and Csf1r as well as Arg1. Comparative analyses of CSF-1RhiCD11bmidLy6Cmid and CSF-1RloCD11bmidLy6Cmid cells demonstrated that the former had a homogeneous monocyte morphology and produced elevated levels of interleukin-10. Functionally, these CSF-1RhiCD11bmidLy6Cmid cells, compared with the CSF-1RloCD11bmidLy6Cmid cells, inhibited CD4+ T cell proliferation and promoted CD4+CD25+Foxp3+ Treg expansion in culture and in a mouse model of experimental autoimmune uveoretinitis. Resistin-like molecule (RELM)-γ encoded by Retnlg, one of the highly upregulated genes in MSC-induced MDSCs, had no direct effects on T cell proliferation, Treg expansion, or splenocyte activation. Together, our study revealed a distinct transcriptional profile of MSC-induced MDSCs and identified CSF-1R as a key cell-surface marker for detection and therapeutic enrichment of MDSCs.

MSCs promote the efferocytosis of large peritoneal macrophages to eliminate ferroptotic monocytes/macrophages in the injured endometria

BACKGROUND

Endometria are one of the important components of the uterus, which is located in the peritoneal cavity. Endometrial injury usually leads to intrauterine adhesions (IUA), accompanied by inflammation and cell death. We previously reported that both the endometrial ferroptosis was increased and monocytes/macrophages were involved in endometrial injury of IUA. Large peritoneal macrophages (LPMs) are recently reported to migrate into the injured tissues and phagocytose dead cells to repair the tissues. We previously demonstrated that mesenchymal stromal cells (MSCs) had made excellent progress in the repair of endometrial injury. However, it is unclear whether MSCs regulate the LPM efferocytosis against ferroptotic monocytes/macrophages in the injured endometria.

METHODS

Here, endometrial injury in IUA mouse model was conducted by uterine curettage and LPS injection surgery and the samples were collected at different times to detect the changes of LPMs and ferroptotic monocytes/macrophages. We conducted LPMs depletion assay in vivo and LPMs and Erastin-induced ferroptotic THP-1 cells coculture systems in vitro to detect the LPM efferocytosis against ferroptotic monocytes/macrophages. The IUA model was treated with MSCs, and their effects on LPMs and endometrial repair were analyzed. Flow cytometry, western blotting, quantitative real-time PCR, immunohistochemical analysis, ELISA, and RNA-sequencing were performed.

RESULTS

We found that LPMs migrated to the injured uteri in response to the damage in early phase (3 h), and sustained to a later stage (7 days). Astonishingly, we found that ferroptotic monocytes/macrophages were significantly increased in the injured uteri since 12 h after injury. Moreover, LPMs cocultured with Erastin-induced ferroptotic THP-1 cells in vitro, efferocytosis of LPMs against ferroptotic monocytes/macrophages was emerged. The mRNA expression profiles revealed that LPM efferocytosis against ferroptotic monocytes/macrophages was an induction of glycolysis program and depended on the PPARγ-HK2 pathway. Importantly, we validated that MSCs promoted the efferocytic capability and migration of LPMs to the injured uteri via secreting stanniocalcin-1 (STC-1).

CONCLUSION

The data collectively demonstrated first the roles of LPMs via removal of ferroptotic monocytes/macrophages and provided a novel mechanism of MSCs in repairing the endometrial injury.

Trained innate immunity modulates osteoblast and osteoclast differentiation

Macrophages are key regulators in bone repair and regeneration. Recent studies have shown that long-term epigenetic changes and metabolic shifts occur during specific immune training of macrophages that affect their functional state, resulting in heightened (trained) or reduced (tolerant) responses upon exposure to a second stimulus. This is known as innate immune memory. Here, we study the impact of macrophages' memory trait on osteoblast differentiation of human mesenchymal stromal cells (hMSCs) and osteoclast differentiation. An in vitro trained immunity protocol of monocyte-derived macrophages was employed using inactivated Candida albicans and Bacillus Calmette-Guérin (BCG) to induce a 'trained' state and Pam3CSK4 (PAM) and Lipopolysaccharides (LPS) to induce a 'tolerance' state. Macrophages were subsequently cocultured with hMSCs undergoing osteogenic differentiation during either resting (unstimulated) or inflammatory conditions (restimulated with LPS). Alkaline phosphatase activity, mineralization, and cytokine levels (TNF, IL-6, oncostatin M and SDF-1α) were measured. In addition, macrophages underwent osteoclast differentiation. Our findings show that trained and tolerized macrophages induced opposing results. Under resting conditions, BCG-trained macrophages enhanced ALP levels (threefold), while under inflammatory conditions this was found in the LPS-tolerized macrophages (fourfold). Coculture of hMSCs with trained macrophages showed mineralization while tolerized macrophages inhibited the process under both resting and inflammatory conditions. While osteoclast differentiation was not affected in trained-macrophages, this ability was significantly loss in tolerized ones. This study further confirms the intricate cross talk between immune cells and bone cells, highlighting the need to consider this interaction in the development of personalized approaches for bone regenerative medicine.

Spatiotemporal immune atlas of a clinical-grade gene-edited pig-to-human kidney xenotransplant

Pig-to-human xenotransplantation is rapidly approaching the clinical arena; however, it is unclear which immunomodulatory regimens will effectively control human immune responses to pig xenografts. Here, we transplant a gene-edited pig kidney into a brain-dead human recipient on pharmacologic immunosuppression and study the human immune response to the xenograft using spatial transcriptomics and single-cell RNA sequencing. Human immune cells are uncommon in the porcine kidney cortex early after xenotransplantation and consist of primarily myeloid cells. Both the porcine resident macrophages and human infiltrating macrophages express genes consistent with an alternatively activated, anti-inflammatory phenotype. No significant infiltration of human B or T cells into the porcine kidney xenograft is detectable. Altogether, these findings provide proof of concept that conventional pharmacologic immunosuppression may be able to restrict infiltration of human immune cells into the xenograft early after compatible pig-to-human kidney xenotransplantation.

Mitochondria in Mesenchymal Stem Cells: Key to Fate Determination and Therapeutic Potential

Mesenchymal stem cells (MSCs) have become popular tool cells in the field of transformation and regenerative medicine due to their function of cell rescue and cell replacement. The dynamically changing mitochondria serve as an energy metabolism factory and signal transduction platform, adapting to different cell states and maintaining normal cell activities. Therefore, a clear understanding of the regulatory mechanism of mitochondria in MSCs is profit for more efficient clinical transformation of stem cells. This review highlights the cutting-edge knowledge regarding mitochondrial biology from the following aspects: mitochondrial morphological dynamics, energy metabolism and signal transduction. The manuscript mainly focuses on mitochondrial mechanistic insights in the whole life course of MSCs, as well as the potential roles played by mitochondria in MSCs treatment of transplantation, for seeking pivotal targets of stem cell fate regulation and stem cell therapy.

Investigating the impact of antibiotic-induced dysbiosis on protection from Clostridium difficile colitis by mouse colonic innate lymphoid cells

Innate lymphoid cells (ILCs) play a critical role in maintaining intestinal health in homeostatic and diseased conditions. During Clostridium difficile infection (CDI), IL-33 activates ILC2 to protect from colonic damage and mortality. The function of IL-33 and ILC is tightly regulated by the intestinal microbiota. We set out to determine the impact of antibiotic-induced disruption of the microbiome on ILC function. Our goal was to understand antibiotic-induced changes in ILC function on susceptibility to C. difficile colitis in a mouse model. We utilized high-throughput single-cell RNAseq to investigate the phenotypic features of colonic ILC at baseline, after antibiotic administration with or without IL-33 treatment. We identified a heterogeneous landscape of colonic ILCs with gene signatures of inflammatory, anti-inflammatory, migratory, progenitor, plastic, and antigen-presenting ILCs. Antibiotic treatment decreased ILC2 while coordinately increasing ILC1 and ILC3 phenotypes. Notably, Ifng+, Ccl5+, and Il23r+ ILC increased after antibiotics. IL-33 treatment counteracted the antibiotic effect by downregulating ILC1 and ILC3 and activating ILC2. In addition, IL-33 treatment markedly induced the expression of type 2 genes, including Areg and Il5. Finally, we identified amphiregulin, produced by ILC2, as protective during C. difficile infection. Together, our data expand our understanding of how antibiotics induce susceptibility to C. difficile colitis through their impact on ILC subsets and function.IMPORTANCEClostridium difficile infection (CDI) accounts for around 500,000 symptomatic cases and over 20,000 deaths annually in the United States alone. A major risk factor of CDI is antibiotic-induced dysbiosis of the gut. Microbiota-regulated IL-33 and innate lymphoid cells (ILCs) are important in determining the outcomes of C. difficile infection. Understanding how antibiotic and IL-33 treatment alter the phenotype of colon ILCs is important to identify potential therapeutics. Here, we performed single-cell RNAseq of mouse colon ILCs collected at baseline, after antibiotic treatment, and after IL-33 treatment. We identified heterogeneous subpopulations of all three ILC subtypes in the mouse colon. Our analysis revealed several potential pathways of antibiotic-mediated increased susceptibility to intestinal infection. Our discovery that Areg is abundantly expressed by ILCs, and the protection of mice from CDI by amphiregulin treatment, suggests that the amphiregulin-epidermal growth factor receptor pathway is a potential therapeutic target for treating intestinal colitis.

Regulation of inflammation during wound healing: the function of mesenchymal stem cells and strategies for therapeutic enhancement

A wound takes a long time to heal and involves several steps. Following tissue injury, inflammation is the primary cause of tissue regeneration and repair processes. As a result, the pathophysiological processes involving skin damage, healing, and remodeling depend critically on the control of inflammation. The fact that it is a feasible target for improving the prognosis of wound healing has lately become clear. Mesenchymal stem cells (MSCs) are an innovative and effective therapeutic option for wound healing due to their immunomodulatory and paracrine properties. By controlling the inflammatory milieu of wounds through immunomodulation, transplanted MSCs have been shown to speed up the healing process. In addition to other immunomodulatory mechanisms, including handling neutrophil activity and modifying macrophage polarization, there may be modifications to the activation of T cells, natural killer (NK) cells, and dendritic cells (DCs). Furthermore, several studies have shown that pretreating MSCs improves their ability to modulate immunity. In this review, we summarize the existing knowledge about how MSCs influence local inflammation in wounds by influencing immunity to facilitate the healing process. We also provide an overview of MSCs optimizing techniques when used to treat wounds.

Mesenchymal stromal cells (MSCs) as a therapeutic agent of inflammatory disease and infectious COVID-19 virus: live or dead mesenchymal?

The COVID-19 infection is a worldwide disease that causes numerous immune-inflammatory disorders, tissue damage, and lung dysfunction. COVID-19 vaccines, including those from Pfizer, AstraZeneca, and Sinopharm, are available globally as effective interventions for combating the disease. The severity of COVID-19 can be most effectively reduced by mesenchymal stromal cells (MSCs) because they possess anti-inflammatory activity and can reverse lung dysfunction. MSCs can be harvested from various sources, such as adipose tissue, bone marrow, peripheral blood, inner organs, and neonatal tissues. The regulation of inflammatory cytokines is crucial in inhibiting inflammatory diseases and promoting the presence of anti-inflammatory cytokines for infectious diseases. MSCs have been employed as therapeutic agents for tissue damage, diabetes, autoimmune diseases, and COVID-19 patients. Our research aimed to determine whether live or dead MSCs are more suitable for the treatment of COVID-19 patients. Our findings concluded that dead MSCs, when directly administered to the patient, offer advantages over viable MSCs due to their extended presence and higher levels of immune regulation, such as T-reg, B-reg, and IL-10, compared to live MSCs. Additionally, dead and apoptotic MSCs are likely to be more readily captured by monocytes and macrophages, prolonging their presence compared to live MSCs.

Engineered Extracellular Vesicles in Wound Healing: Design, Paradigms, and Clinical Application

The severe quality of life and economic burden imposed by non-healing skin wounds, infection risks, and treatment costs are affecting millions of patients worldwide. To mitigate these challenges, scientists are relentlessly seeking effective treatment measures. In recent years, extracellular vesicles (EVs) have emerged as a promising cell-free therapy strategy, attracting extensive attention from researchers. EVs mediate intercellular communication, possessing excellent biocompatibility and stability. These features make EVs a potential tool for treating a plethora of diseases, including those related to wound repair. However, there is a growing focus on the engineering of EVs to overcome inherent limitations such as low production, relatively fixed content, and targeting capabilities of natural EVs. This engineering could improve both the effectiveness and specificity of EVs in wound repair treatments. In light of this, the present review will introduce the latest progress in the design methods and experimental paradigms of engineered EVs applied in wound repair. Furthermore, it will comprehensively analyze the current clinical research status and prospects of engineered EVs within this field.

Mitochondria as secretory organelles and therapeutic cargos

Mitochondria have been primarily considered intracellular organelles that are responsible for generating energy for cell survival. However, accumulating evidence suggests that mitochondria are secreted into the extracellular space under physiological and pathological conditions, and these secreted mitochondria play diverse roles by regulating metabolism, the immune response, or the differentiation/maturation in target cells. Furthermore, increasing amount of research shows the therapeutic effects of local or systemic administration of mitochondria in various disease models. These findings have led to growing interest in exploring mitochondria as potential therapeutic agents. Here, we discuss the emerging roles of mitochondria as extracellularly secreted organelles to shed light on their functions beyond energy production. Additionally, we provide information on therapeutic outcomes of mitochondrial transplantation in animal models of diseases and an update on ongoing clinical trials, underscoring the potential of using mitochondria as a novel therapeutic intervention.

Current Advances in Corneal Stromal Stem Cell Biology and Therapeutic Applications

Corneal stromal stem cells (CSSCs) are of particular interest in regenerative ophthalmology, offering a new therapeutic target for corneal injuries and diseases. This review provides a comprehensive examination of CSSCs, exploring their anatomy, functions, and role in maintaining corneal integrity. Molecular markers, wound healing mechanisms, and potential therapeutic applications are discussed. Global corneal blindness, especially in more resource-limited regions, underscores the need for innovative solutions. Challenges posed by corneal defects, emphasizing the urgent need for advanced therapeutic interventions, are discussed. The review places a spotlight on exosome therapy as a potential therapy. CSSC-derived exosomes exhibit significant potential for modulating inflammation, promoting tissue repair, and addressing corneal transparency. Additionally, the rejuvenation potential of CSSCs through epigenetic reprogramming adds to the evolving regenerative landscape. The imperative for clinical trials and human studies to seamlessly integrate these strategies into practice is emphasized. This points towards a future where CSSC-based therapies, particularly leveraging exosomes, play a central role in diversifying ophthalmic regenerative medicine.

Adipose Stromal Cell-Derived Secretome Attenuates Cisplatin-Induced Injury In Vitro Surpassing the Intricate Interplay between Proximal Tubular Epithelial Cells and Macrophages

(1) Background: The chemotherapeutic drug cisplatin exerts toxic side effects causing acute kidney injury. Mesenchymal stromal cells can ameliorate cisplatin-induced kidney injury. We hypothesize that the MSC secretome orchestrates the vicious cycle of injury and inflammation by acting on proximal tubule epithelial cells (PTECs) and macrophages individually, but further by counteracting their cellular crosstalk. (2) Methods: Conditioned medium (CM) from adipose stromal cells was used, first assessing its effect on cisplatin injury in PTECs. Second, the effects of cisplatin and the CM on macrophages were measured. Lastly, in an indirect co-culture system, the interplay between the two cell types was assessed. (3) Results: First, the CM rescued PTECs from cisplatin-induced apoptosis by reducing oxidative stress and expression of nephrotoxicity genes. Second, while cisplatin exerted only minor effects on macrophages, the CM skewed macrophage phenotypes to the anti-inflammatory M2-like phenotype and increased phagocytosis. Finally, in the co-culture system, the CM suppressed PTEC death by inhibiting apoptosis and nuclei fragmentation. The CM lowered TNF-α release, while cisplatin inhibited macrophage phagocytosis, PTECs, and the CM to a greater extent, thus enhancing it. The CM strongly dampened the inflammatory macrophage cytokine secretion triggered by PTECs. (4) Conclusions: ASC-CM surpasses the PTEC-macrophage crosstalk in cisplatin injury. The positive effects on reducing cisplatin cytotoxicity, on polarizing macrophages, and on fine-tuning cytokine secretion underscore MSCs' CM benefit to prevent kidney injury progression.

Amphiregulin in infectious diseases: Role, mechanism, and potential therapeutic targets

Amphiregulin (AREG) serves as a ligand for the epidermal growth factor receptor (EGFR) and is involved in vital biological functions, including inflammatory responses, tissue regeneration, and immune system function. Upon interaction with the EGFR, AREG initiates a series of signaling cascades necessary for several physiological activities, such as metabolism, cell cycle regulation, and cellular proliferation. Recent findings have provided evidence for the substantial role of AREG in maintaining the equilibrium of homeostasis in damaged tissues and preserving epithelial cell structure in the context of viral infections affecting the lungs. The development of resistance to influenza virus infection depends on the presence of type 1 cytokine responses. Following the eradication of the pathogen, the lungs are subsequently colonized by several cell types that are linked with type 2 immune responses. These cells contribute to the process of repairing and resolving the tissue injury and inflammation caused by infections. Following influenza infection, the activation of AREG promotes the regeneration of bronchial epithelial cells, enhancing the tissue's structural integrity and increasing the survival rate of infected mice. In the same manner, mice afflicted with influenza experience rapid mortality due to a subsequent bacterial infection in the pulmonary region when both bacterial and viral infections manifest concurrently inside the same host. The involvement of AREG in bacterial infections has been demonstrated. The gene AREG experiences increased transcriptional activity inside host cells in response to bacterial infections caused by pathogens such as Escherichia coli and Neisseria gonorrhea. In addition, AREG has been extensively studied as a mitogenic stimulus in epithelial cell layers. Consequently, it is regarded as a prospective contender that might potentially contribute to the observed epithelial cell reactions in helminth infection. Consistent with this finding, mice that lack the AREG gene exhibit a delay in the eradication of the intestinal parasite Trichuris muris. The observed delay is associated with a reduction in the proliferation rate of colonic epithelial cells compared to the infected animals in the control group. The aforementioned findings indicate that AREG plays a pivotal role in facilitating the activation of defensive mechanisms inside the epithelial cells of the intestinal tissue. The precise cellular sources of AREG in this specific context have not yet been determined. However, it is evident that the increased proliferation of the epithelial cell layer in infected mice is reliant on CD4+ T cells. The significance of this finding lies in its demonstration of the crucial role played by the interaction between immunological and epithelial cells in regulating the AREG-EGFR pathway. Additional research is necessary to delve into the cellular origins and signaling mechanisms that govern the synthesis of AREG and its tissue-protective properties, independent of infection.

A new generation of mesenchymal stromal/stem cells differentially trained by immunoregulatory probiotics in a lupus microenvironment

BACKGROUND

Increasing evidence suggests that multipotent mesenchymal stem/stromal cells (MSCs) are a promising intervention strategy in treating autoimmune inflammatory diseases. It should be stated that systemic immunoregulation is increasingly recognized among the beneficial effects of MSCs and probiotics in treating morbid autoimmune disorders such as lupus. This study aimed to determine if immunoregulatory probiotics L. rhamnosus or L. delbrueckii can change the immunomodulatory effects of MSCs in lupus-like disease.

METHODS

Pristane-induced lupus (PIL) mice model was created via intraperitoneal injection of Pristane and then confirmed. Naïve MSCs (N-MSCs) were coincubated with two Lactobacillus strains, rhamnosus (R-MSCs) or delbrueckii (D-MSCs), and/or a combination of both (DR-MSCs) for 48 h, then administrated intravenously in separate groups. Negative (PBS-treated normal mice) and positive control groups (PBS-treated lupus mice) were also investigated. At the end of the study, flow cytometry and enzyme-linked immunosorbent assay (ELISA) analysis were used to determine the percentage of Th cell subpopulations in splenocytes and the level of their master cytokines in sera, respectively. Moreover, lupus nephritis was investigated and compared. Analysis of variance (ANOVA) was used for multiple comparisons.

RESULTS

Abnormalities in serum levels of anti-dsDNA antibodies, creatinine, and urine proteinuria were significantly suppressed by MSCs transplantation, whereas engrafted MSCs coincubation with both L. strains did a lesser effect on anti-dsDNA antibodies. L. rhamnosus significantly escalated the ability of MSCs to scale down the inflammatory cytokines (IFN-ɣ, IL-17), while L. delbrueckii significantly elevated the capacity of MSCs to scale down the percentage of Th cell subpopulations. However, incubation with both strains induced MSCs with augmented capacity in introducing inflammatory cytokines (IFN-ɣ, IL-17). Strikingly, R-MSCs directly restored the serum level of TGF-β more effectively and showed more significant improvement in disease parameters than N-MSCs. These results suggest that R-MSCs significantly attenuate lupus disease by further skew the immune phenotype of MSCs toward increased immunoregulation.

CONCLUSIONS

Results demonstrated that Lactobacillus strains showed different capabilities in training/inducing new abilities in MSCs, in such a way that pretreated MSCs with L. rhamnosus might benefit the treatment of lupus-like symptoms, given their desirable properties.

Identification and validation of an immune-relevant risk signature predicting survival outcome and immune infiltration in uveal melanoma

PURPOSE

The current study aimed to reveal a novel immune-related signature to evaluate immune infiltration status and the survival outcome for patients with uveal melanoma (UM).

METHODS

Based on 80 UM samples from the Cancer Genome Atlas, the transcriptome gene expression and clinical characteristics were analyzed to identify immune-related genes that contributed most to prognosis based on LASSO Cox regression. By combining the gene expression level with the corresponding regression coefficient, a risk score was calculated and all patients were divided into high- and low-risk groups. Survival, tumor-infiltrating immune cell abundance, dysregulated signaling pathways, immunophenoscore and tumor mutation burden were compared between two groups. Validation of the risk signature was performed in GSE22138 and GSE44295 cohort. For evaluating the immunotherapy efficacy, 348 advanced urothelial cancer patients treated with immune checkpoint inhibitor (ICI) were used for external validation.

RESULTS

Nine immune-related prognostic genes were identified under the LASSO Cox regression in the TCGA cohort; they are ACKR2, AREG, CCL5, CLEC11A, IGKV1-33, IL36B, NROB1, TRAV8-4 and TRBV28. Better prognosis, elevated immune cell infiltration, decreased immune-suppressive cell infiltration, immune response-related pathways and higher immunophenoscore were found in low-risk patients, with better ICI treatment response rate.

CONCLUSION

The identified immune risk signature was demonstrated to be associated with the favorable immune infiltration, prognosis and immunotherapeutic efficacy, which may provide clues for survival evaluation and immune treatment.

Immunomodulatory function of licensed human bone marrow mesenchymal stromal cell-derived apoptotic bodies

BACKGROUND

Mesenchymal stromal cells (MSCs) show great potential for immunomodulatory and anti-inflammatory treatments. Clinical trials have been performed for the treatment of Type 1 diabetes, graft-versus-host disease and organ transplantation, which offer a promise of MSCs as an immunomodulatory therapy. Nevertheless, their unstable efficacy and immunogenicity concerns present challenges to clinical translation. It has emerged that the MSC-derived secretome, which includes secreted proteins, exosomes, apoptotic bodies (ABs) and other macromolecules, may have similar therapeutic effects to parent MSCs. Among all of the components of the MSC-derived secretome, most interest thus far has been garnered by exosomes for their therapeutic potential. However, since MSCs were reported to undergo apoptosis after in vivo transplantation and release ABs, we speculated as to whether ABs have immunomodulatory effects. In this study, cytokine licensing was used to enhance the immunomodulatory potency of MSCs and ABs derived from licensed MSCs in vitro were isolated to explore their immunomodulatory effects as an effective non-viable cell therapy.

RESULTS

IFN-γ and IFN-γ/TGF-β1 licensing enhanced the immunomodulatory effect of MSCs on T cell proliferation. Further, TGF-β1 and IFN-γ licensing strengthened the immunomodulatory effect of MSC on reducing the TNF-α and IL-1β expression by M1 macrophage-like THP-1 cells. Additionally, we discovered the immunomodulatory effect mediated by MSC-derived apoptotic bodies. Licensing impacted the uptake of ABs by recipient immune cells and importantly altered their phenotypes.

CONCLUSION

ABs derived from IFN-γ/TGF-β1-licensed apoptotic MSCs significantly inhibited T cell proliferation, induced more regulatory T cells, and maintained immunomodulatory T cells but reduced pro-inflammatory T cells.

LepR+ niche cell-derived AREG compromises hematopoietic stem cell maintenance under conditions of DNA repair deficiency and aging

The cross talk between extrinsic niche-derived and intrinsic hematopoietic stem cell (HSC) factors controlling HSC maintenance remains elusive. Here, we demonstrated that amphiregulin (AREG) from bone marrow (BM) leptin receptor (LepR+) niche cells is an important factor that mediates the cross talk between the BM niche and HSCs in stem cell maintenance. Mice deficient of the DNA repair gene Brca2, specifically in LepR+ cells (LepR-Cre;Brca2fl/fl), exhibited increased frequencies of total and myeloid-biased HSCs. Furthermore, HSCs from LepR-Cre;Brca2fl/fl mice showed compromised repopulation, increased expansion of donor-derived, myeloid-biased HSCs, and increased myeloid output. Brca2-deficient BM LepR+ cells exhibited persistent DNA damage-inducible overproduction of AREG. Ex vivo treatment of wild-type HSCs or systemic treatment of C57BL/6 mice with recombinant AREG impaired repopulation, leading to HSC exhaustion. Conversely, inhibition of AREG by an anti-AREG-neutralizing antibody or deletion of the Areg gene in LepR-Cre;Brca2fl/fl mice rescued HSC defects caused by AREG. Mechanistically, AREG activated the phosphoinositide 3-kinases (PI3K)/AKT/mammalian target of rapamycin (mTOR) pathway, promoted HSC cycling, and compromised HSC quiescence. Finally, we demonstrated that BM LepR+ niche cells from other DNA repair-deficient and aged mice also showed persistent DNA damage-associated overexpression of AREG, which exerts similar negative effects on HSC maintenance. Therefore, we identified an important factor that regulates HSCs function under conditions of DNA repair deficiency and aging.

Exploring the role of growth factors as potential regulators in psoriatic plaque formation

Psoriasis is a chronic inflammatory skin disease in which growth activity is more prominent than inflammatory activity at the centre of lesional skin (CE skin). This growth activity is partly influenced by growth factors (GFs) that play an important role in cell growth and inflammation during the plaque development. In this study, we identified potential GFs in CE skin and predicted their regulatory functions and biological activity in mediating transcripts in the plaques. Samples of uninvolved skin (UN skin) and CE skin were biopsied from patients with psoriasis vulgaris for RNA-sequencing analysis in order to identify differentially expressed genes (DEGs). Our finding revealed that epidermal growth factor (EGF), fibroblast growth factor (FGF), platelet-derived growth factor (PDGF) and hepatocyte growth factor (HGF) signalling were enriched by CE/UN skin-derived DEGs. Additionally, several EGFR ligands, namely EGF, heparin-binding EGF like growth factor (HB-EGF), amphiregulin (AREG) and transforming growth factor (TGF)-α, as well as TGF-β1, TGF-β2, vascular endothelial growth factor-A, FGFs, PDGF-B and HGF, were predicted to be GF regulators. The regulatory pattern and biological activity of these GF regulators on mediating the CE/UN skin-derived DEGs was demonstrated. This study provides a novel hypothesis regarding the overall regulatory function of GFs, which appear to modulate the expression of the transcripts involved in inflammation and growth in the CE skin. In addition, some GFs may exert anti-inflammatory effects. Further investigations on the mechanisms underlying this regulation may contribute to a deeper understanding of psoriasis and the identification of potential therapeutic targets for patients with psoriasis.

Umbilical cord mesenchymal stromal cell-derived extracellular vesicles lack the potency to immunomodulate human monocyte-derived macrophages in vitro

Mesenchymal stromal cells (MSCs) have been reported to display efficacy in a variety of preclinical models, but without long-term engraftment, suggesting a role for secreted factors, such as MSC-derived extracellular vesicles (EVs). MSCs are known to elicit immunomodulatory effects, an important aspect of which is their ability to affect macrophage phenotype. However, it is not clear if these effects are mediated by MSC-derived EVs, or other factors secreted by the MSCs. Here, we use flow cytometry to assess the effects of human umbilical cord (hUC) MSC-derived EVs on the expression of pro-inflammatory (CD80) and anti-inflammatory (CD163) surface markers in human monocyte-derived macrophages (hMDMs). hUC-MSC-derived EVs did not change the surface marker expression of the hMDMs. In contrast, when hMDMs were co-incubated with hUC-MSCs in indirect co-cultures, changes were observed in the expression of CD14, CD80 and CD163, particularly in M1 macrophages, suggesting that soluble factors are necessary to elicit a shift in phenotype. However, even though EVs did not alter the surface marker expression of macrophages, they promoted angiogenesis and phagocytic capacity increased proportionally to increases in EV concentration. Taken together, these results suggest that hUC-MSC-derived EVs are not sufficient to alter macrophage phenotype and that additional MSC-derived factors are needed.

Secretome profile of TNF-α-induced human umbilical cord mesenchymal stem cells unveils biological processes relevant to skin wound healing

Aim: To profile and study the proteins responsible for the beneficial effect of the TNF-α-induced human umbilical cord mesenchymal stem cells (hUCMSCs) secretome in wound healing. Methods: The hUCMSCs secretome was generated with (induced) or without (uninduced) TNF-α and was subsequently analyzed by liquid chromatography-mass spectrometry, immunoassay and in vitro scratch assay. Results: Proteomic analysis revealed approximately 260 proteins, including 51 and 55 unique proteins in the induced and uninduced secretomes, respectively. Gene ontology analysis disclosed that differential proteins in the induced secretome mainly involved inflammation-related terms. The induced secretome, consisting of higher levels of FGFb, VEGF, PDGF and IL-6, significantly accelerated wound closure and enhanced MMP-13 secretion in HaCaT keratinocytes. Conclusion: The secretome from induced hUCMSCs includes factors that promote wound closure.

Therapeutic Effects of Mesenchymal Stromal Cells Require Mitochondrial Transfer and Quality Control

Due to their beneficial effects in an array of diseases, Mesenchymal Stromal Cells (MSCs) have been the focus of intense preclinical research and clinical implementation for decades. MSCs have multilineage differentiation capacity, support hematopoiesis, secrete pro-regenerative factors and exert immunoregulatory functions promoting homeostasis and the resolution of injury/inflammation. The main effects of MSCs include modulation of immune cells (macrophages, neutrophils, and lymphocytes), secretion of antimicrobial peptides, and transfer of mitochondria (Mt) to injured cells. These actions can be enhanced by priming (i.e., licensing) MSCs prior to exposure to deleterious microenvironments. Preclinical evidence suggests that MSCs can exert therapeutic effects in a variety of pathological states, including cardiac, respiratory, hepatic, renal, and neurological diseases. One of the key emerging beneficial actions of MSCs is the improvement of mitochondrial functions in the injured tissues by enhancing mitochondrial quality control (MQC). Recent advances in the understanding of cellular MQC, including mitochondrial biogenesis, mitophagy, fission, and fusion, helped uncover how MSCs enhance these processes. Specifically, MSCs have been suggested to regulate peroxisome proliferator-activated receptor-gamma coactivator 1 alpha (PGC1α)-dependent biogenesis, Parkin-dependent mitophagy, and Mitofusins (Mfn1/2) or Dynamin Related Protein-1 (Drp1)-mediated fission/fusion. In addition, previous studies also verified mitochondrial transfer from MSCs through tunneling nanotubes and via microvesicular transport. Combined, these effects improve mitochondrial functions, thereby contributing to the resolution of injury and inflammation. Thus, uncovering how MSCs affect MQC opens new therapeutic avenues for organ injury, and the transplantation of MSC-derived mitochondria to injured tissues might represent an attractive new therapeutic approach.

Mitochondrial-Derived Vesicles: The Good, the Bad, and the Ugly

Mitophagy is crucial for maintaining mitochondrial quality. However, its assessment in vivo is challenging. The endosomal-lysosomal system is a more accessible pathway through which subtypes of extracellular vesicles (EVs), which also contain mitochondrial constituents, are released for disposal. The inclusion of mitochondrial components into EVs occurs in the setting of mild mitochondrial damage and during impairment of lysosomal function. By releasing mitochondrial-derived vesicles (MDVs), cells limit the unload of mitochondrial damage-associated molecular patterns with proinflammatory activity. Both positive and negative effects of EVs on recipient cells have been described. Whether this is due to the production of EVs other than those containing mitochondria, such as MDVs, holding specific biological functions is currently unknown. Evidence on the existence of different MDV subtypes has been produced. However, their characterization is not always pursued, which would be relevant to exploring the dynamics of mitochondrial quality control in health and disease. Furthermore, MDV classification may be instrumental in understanding their biological roles and promoting their implementation as biomarkers in clinical studies.

Mesenchymal stromal cells regulate THP-1-differentiated macrophage cytokine production by activating Akt/mammalian target of rapamycin complex 1 pathway

BACKGROUND AIMS

The Akt/mammalian target of rapamycin (mTOR) pathway in macrophages converges inflammatory and metabolic signals from multiple receptors to regulate a cell's survival, metabolism and activation. Although mesenchymal stromal cells (MSCs) are well known to modulate macrophage activation, the effects of MSCs on the Akt/mTOR pathway in macrophages have not been elucidated.

METHODS

We herein investigated whether MSCs affect the Akt/mTOR complex 1 (mTORC1) pathway to regulate macrophage polarization.

RESULTS

Results showed that human bone marrow-derived MSCs induced activation of Akt and its downstream mTORC1 signaling in THP-1-differentiated macrophages in a p62/sequestosome 1-independent manner. Inhibition of Akt or mTORC1 attenuated the effects of MSCs on the suppression of tumor necrosis factor-α and interleukin-12 production and the promotion of interleukin-10 and tumor growth factor-β1 in macrophages stimulated by lipopolysaccharide/ATP. Conversely, activation of Akt or mTORC1 reproduced and potentiated MSC effects on macrophage cytokine production. MSCs with cyclooxygenase-2 knockdown, however, failed to activate the Akt/mTORC1 signaling in macrophages and were less effective in the modulation of macrophage cytokine production than control MSCs.

CONCLUSIONS

These data demonstrate that MSCs control THP-1-differentiated macrophage activation at least partly through upregulation of the Akt/mTORC1 signaling in a cyclooxygenase-2-dependent manner.

MSC therapy ameliorates experimental gouty arthritis hinting an early COX-2 induction

Objective

The specific effect of Adipose-Derived Mesenchymal Stem Cells (Ad-MSC) on acute joint inflammation, where the response mostly depends on innate immunity activation, remains elusive. The pathogenesis of gouty arthritis, characterized by the deposition of monosodium urate (MSU) crystals in the joints, associated to acute flares, has been associated to NLRP3 inflammasome activation and subsequent amplification of the inflammatory response. Our aim was to study the effect of human Ad-MSC administration in the clinical inflammatory response of rabbits after MSU injection, and the molecular mechanisms involved.

Methods

Ad-MSC were administered by intraarterial route shortly after intraarticular MSU crystal injections. Joint and systemic inflammation was sequentially studied, and the mechanisms involved in NLRP3 inflammasome activation, and the synthesis of inflammatory mediators were assessed in the synovial membranes 72h after insult. Ad-MSC and THP-1-derived macrophages stimulated with MSU were co-cultured in transwell system.

Results

A single systemic dose of Ad-MSC accelerated the resolution of local and systemic inflammatory response. In the synovial membrane, Ad-MSC promoted alternatively M2 macrophage presence, inhibiting NLRP3 inflammasome and inducing the production of anti-inflammatory cytokines, such as IL-10 or TGF-β, and decreasing nuclear factor-κB activity. Ad-MSC induced a net anti-inflammatory balance in MSU-stimulated THP-1 cells, with a higher increase in IL-10 and IDO expression than that observed for IL-1β and TNF.

Conclusion

Our in vivo and in vitro results showed that a single systemic dose of Ad-MSC decrease the intensity and duration of the inflammatory response by an early local COX-2 upregulation and PGE2 release. Ad-MSCs suppressed NF-kB activity, NLRP3 inflammasome, and promoted the presence of M2 alternative macrophages in the synovium. Therefore, this therapeutic approach could be considered as a pharmacological alternative in patients with comorbidities that preclude conventional treatment.

A novel mesenchymal stem cell-based regimen for acute myeloid leukemia differentiation therapy

Currently the main treatment of acute myeloid leukemia (AML) is chemotherapy combining hematopoietic stem cell transplantation. However, the unbearable side effect of chemotherapy and the high risk of life-threatening infections and disease relapse following hematopoietic stem cell transplantation restrict its application in clinical practice. Thus, there is an urgent need to develop alternative therapeutic tactics with significant efficacy and attenuated adverse effects. Here, we revealed that umbilical cord-derived mesenchymal stem cells (UC-MSC) efficiently induced AML cell differentiation by shuttling the neutrophil elastase (NE)-packaged extracellular vesicles (EVs) into AML cells. Interestingly, the generation and release of NE-packaged EVs could be dramatically increased by vitamin D receptor (VDR) activation in UC-MSC. Chemical activation of VDR by using its agonist 1α,25-dihydroxyvitamin D3 efficiently enhanced the pro-differentiation capacity of UC-MSC and then alleviated malignant burden in AML mouse model. Based on these discoveries, to evade the risk of hypercalcemia, we synthetized and identified sw-22, a novel non-steroidal VDR agonist, which exerted a synergistic pro-differentiation function with UC-MSC on mitigating the progress of AML. Collectively, our findings provided a non-gene editing MSC-based therapeutic regimen to overcome the differentiation blockade in AML.

Interferon-γ elicits the ocular surface pathology mimicking dry eye through direct modulation of resident corneal cells

Despite accumulating evidence indicating a key role of interferon-γ (IFN-γ)-producing immune cells in ocular infection and immunity, little is known about the direct effects of IFN-γ on resident corneal cells or on the ocular surface. Here, we report that IFN-γ impacts corneal stromal fibroblasts and epithelial cells to promote inflammation, opacification, and barrier disruption on the ocular surface, leading to dry eye. Our results demonstrated that IFN-γ dose-dependently induced cytotoxicity, pro-inflammatory cytokine/chemokine production, and expression of major histocompatibility complex class II and CD40 in cultures of corneal stromal fibroblasts and epithelial cells while increasing myofibroblast differentiation of corneal stromal fibroblasts. In mice, subconjunctival IFN-γ administration caused corneal epithelial defects and stromal opacity in dose- and time-dependent manners while promoting neutrophil infiltration and inflammatory cytokine expression in the cornea. Moreover, IFN-γ reduced aqueous tear secretion and the number of conjunctival goblet cells responsible for mucinous tear production. Together, our findings suggest that IFN-γ induces the ocular surface changes characteristic of dry eye disease at least in part through its direct effects on resident corneal cells.

Current perspectives on mesenchymal stromal cell therapy for graft versus host disease

Graft versus host disease (GvHD) is the clinical condition in which bone marrow-derived mesenchymal stromal cells (MSCs) have been most frequently studied. In this review, we summarize the experience from clinical trials that have paved the way to translation. While MSC-based therapy has shown an exceptional safety profile, identifying potency assays and disease biomarkers that reliably predict the capacity of a specific MSC batch to alleviate GvHD has been difficult. As GvHD diagnosis and staging are based solely on clinical criteria, individual patients recruited in the same clinical trial may have vastly different underlying biology, obscuring trial outcomes and making it difficult to determine the benefit of MSCs in subgroups of patients. An accumulating body of evidence indicates the importance of considering not only the cell product but also patient-specific biomarkers and/or immune characteristics in determining MSC responsiveness. A mode of action where intravascular MSC destruction is followed by monocyte-efferocytosis-mediated skewing of the immune repertoire in a permissive inflammatory environment would both explain why cell engraftment is irrelevant for MSC efficacy and stress the importance of biologic differences between responding and nonresponding patients. We recommend a combined analysis of clinical outcomes and both biomarkers of disease activity and MSC potency assays to identify patients with GvHD who are likely to benefit from MSC therapy.

The critical role of apoptosis in mesenchymal stromal cell therapeutics and implications in homeostasis and normal tissue repair

Mesenchymal stromal cells (MSCs) have been extensively tested for the treatment of numerous clinical conditions and have demonstrated good safety but mixed efficacy. Although this outcome can be attributed in part to the heterogeneity of cell preparations, the lack of mechanistic understanding and tools to establish cell pharmacokinetics and pharmacodynamics, as well as the poorly defined criteria for patient stratification, have hampered the design of informative clinical trials. We and others have demonstrated that MSCs can rapidly undergo apoptosis after their infusion. Apoptotic MSCs are phagocytosed by monocytes/macrophages that are then reprogrammed to become anti-inflammatory cells. MSC apoptosis occurs when the cells are injected into patients who harbor activated cytotoxic T or NK cells. Therefore, the activation state of cytotoxic T or NK cells can be used as a biomarker to predict clinical responses to MSC treatment. Building on a large body of preexisting data, an alternative view on the mechanism of MSCs is that an inflammation-dependent MSC secretome is largely responsible for their immunomodulatory activity. We will discuss how these different mechanisms can coexist and are instructed by two different types of MSC "licensing": one that is cell-contact dependent and the second that is mediated by inflammatory cytokines. The varied and complex mechanisms by which MSCs can orchestrate inflammatory responses and how this function is specifically driven by inflammation support a physiological role for tissue stroma in tissue homeostasis, and it acts as a sensor of damage and initiator of tissue repair by reprogramming the inflammatory environment.

MitoEVs: A new player in multiple disease pathology and treatment

Mitochondrial damage plays vital roles in the pathology of many diseases, such as cancers, neurodegenerative diseases, aging, metabolic diseases and many types of organ injury. However, the regulatory mechanism of mitochondrial functions among different cells or organs in vivo is still unclear, and efficient therapies for attenuating mitochondrial damage are urgently needed. Extracellular vesicles (EVs) are cell-derived nanovesicles that can deliver bioactive cargoes among cells or organs. Interestingly, recent evidence shows that diverse mitochondrial contents are enriched in certain EV subpopulations, and such mitoEVs can deliver mitochondrial components to affect the functions of recipient cells under different conditions, which has emerged as a hot topic in this field. However, the overview and many essential questions with respect to this event remain elusive. In this review, we provide a global view of mitoEVs biology and mainly focus on the detailed sorting mechanisms, functional mitochondrial contents, and diverse biological effects of mitoEVs. We also discuss the pathogenic or therapeutic roles of mitoEVs in different diseases and highlight their potential as disease biomarkers or therapies in clinical translation. This review will provide insights into the pathology and drug development for various mitochondrial injury-related diseases.

Mesenchymal Stem/Stromal Cells Derived from Cervical Cancer Promote M2 Macrophage Polarization

Macrophages with the M2 phenotype promote tumor development through the immunosuppression of antitumor immunity. We previously demonstrated the presence of mesenchymal stem/stromal cells (MSCs) in cervical cancer (CeCa-MSCs), suggesting an immune protective capacity in tumors, but to date, their effect in modulating macrophage polarization remains unknown. In this study, we compared the capacities of MSCs from normal cervix (NCx) and CeCa to promote M2 macrophage polarization in a coculture system. Our results demonstrated that CeCa-MSCs, in contrast to NCx-MSCs, significantly decreased M1 macrophage cell surface marker expression (HLA-DR, CD80, CD86) and increased M2 macrophage expression (CD14, CD163, CD206, Arg1) in cytokine-induced CD14+ monocytes toward M1- or M2-polarized macrophages. Interestingly, compared with NCx-MSCs, in M2 macrophages generated from CeCa-MSC cocultures, we observed an increase in the percentage of phagocytic cells, in the intracellular production of IL-10 and IDO, the capacity to decrease T cell proliferation and for the generation of CD4+CD25+FoxP3+ Tregs. Importantly, this capacity to promote M2 macrophage polarization was correlated with the intracellular expression of macrophage colony-stimulating factor (M-CSF) and upregulation of IL-10 in CeCa-MSCs. Furthermore, the presence of M2 macrophages was correlated with the increased production of IL-10 and IL-1RA anti-inflammatory molecules. Our in vitro results indicate that CeCa-MSCs, in contrast to NCx-MSCs, display an increased M2-macrophage polarization potential and suggest a role of CeCa-MSCs in antitumor immunity.

GPR174 knockdown enhances blood flow recovery in hindlimb ischemia mice model by upregulating AREG expression

Regulatory T cells (Tregs) are critically involved in neovascularization, an important compensatory mechanism in peripheral artery disease. The contribution of G protein coupled receptor 174 (GPR174), which is a regulator of Treg function and development, in neovascularization remains elusive. Here, we show that genetic deletion of GPR174 in Tregs potentiated blood flow recovery in mice after hindlimb ischemia. GPR174 deficiency upregulates amphiregulin (AREG) expression in Tregs, thereby enhancing endothelial cell functions and reducing pro-inflammatory macrophage polarization and endothelial cell apoptosis. Mechanically, GPR174 regulates AREG expression by inhibiting the nuclear accumulation of early growth response protein 1 (EGR1) via Gαs/cAMP/PKA signal pathway activation. Collectively, these findings demonstrate that GPR174 negatively regulates angiogenesis and vascular remodeling in response to ischemic injury and that GPR174 may be a potential molecular target for therapeutic interventions of ischemic vascular diseases.

Macrophage immunotherapy: overcoming impediments to realize promise

As an essential component of immunity, macrophages have key roles in mammalian host defense, tissue homeostasis, and repair, as well as in disease pathogenesis and pathophysiology. A source of fascination and extensive research, in this Opinion we challenge the utility of the M1-M2 paradigm, and discuss the importance of accurate characterization of human macrophages. We comment on the application of single cell analytics to define macrophage subpopulations and how this could advance therapeutic options. We argue that human macrophage cell therapy can be used to alleviate many diseases, and offer a viewpoint on the knowledge gaps that must be filled to render such a therapeutic approach a reality and, ideally, a common future practice in precision medicine.

Inflammation in myocardial infarction: roles of mesenchymal stem cells and their secretome

Inflammation plays crucial roles in the regulation of pathophysiological processes involved in injury, repair and remodeling of the infarcted heart; hence, it has become a promising target to improve the prognosis of myocardial infarction (MI). Mesenchymal stem cells (MSCs) serve as an effective and innovative treatment option for cardiac repair owing to their paracrine effects and immunomodulatory functions. In fact, transplanted MSCs have been shown to accumulate at injury sites of heart, exerting multiple effects including immunomodulation, regulating macrophages polarization, modulating the activation of T cells, NK cells and dendritic cells and alleviating pyroptosis of non-immune cells. Many studies also proved that preconditioning of MSCs can enhance their inflammation-regulatory effects. In this review, we provide an overview on the current understanding of the mechanisms on MSCs and their secretome regulating inflammation and immune cells after myocardial infarction and shed light on the applications of MSCs in the treatment of cardiac infarction.

Mesenchymal stromal/stem cells spheroid culture effect on the therapeutic efficacy of these cells and their exosomes: A new strategy to overcome cell therapy limitations

Cell therapy is one of the new treatment methods in which mesenchymal stem/stromal cell (MSCs) transplantation is one of the cells widely used in this field. The results of MSCs application in the clinic prove their therapeutic efficacy. For this reason, many clinical trials have been designed based on the application of MSCs for various diseases, especially inflammatory disease and regenerative medicine. These cells perform their therapeutic functions through multiple mechanisms, including the differentiative potential, immunomodulatory properties, production of therapeutic exosomes, production of growth factors and cytokines, and anti-apoptotic effects. Exosomes are nanosized extracellular vesicles (EVs) that change target cell functions by transferring different cargos. The therapeutic ability of MSCs-derived exosomes has been demonstrated in many studies. However, some limitations, such as the low production of exosomes by cells and the need for large amounts of them and also their limited therapeutic ability, have encouraged researchers to find methods that increase exosomes' therapeutic potential. One of these methods is the spheroid culture of MSCs. Studies show that the three-dimensional culture (3DCC) of MSCs in the form of multicellular spheroids increases the therapeutic efficacy of these cells in laboratory and animal applications. In addition, the spheroid culture of MSCs leads to enhanced therapeutic properties of their exosomes and production rate. Due to the novelty of the field of using 3DCC MSCs-derived exosomes, examination of their properties and the results of their therapeutic application can increase our view of this field. This review discussed MSCs and their exosomes enhanced properties in spheroid culture.

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.

Reprograming the immune niche for skin tissue regeneration - From cellular mechanisms to biomaterials applications

Despite the rapid development of therapeutic approaches for skin repair, chronic wounds such as diabetic foot ulcers remain an unaddressed problem that affects millions of people worldwide. Increasing evidence has revealed the crucial and diverse roles of the immune cells in the development and repair of the skin tissue, prompting new research to focus on further understanding and modulating the local immune niche for comprehensive, 'perfect' regeneration. In this review, we first introduce how different immunocytes and certain stromal cells involved in innate and adaptive immunity coordinate to maintain the immune niche and tissue homeostasis, with emphasis on their specific roles in normal and pathological wound healing. We then discuss novel engineering approaches - particularly biomaterials systems and cellular therapies - to target different players of the immune niche, with three major aims to i) overcome 'under-healing', ii) avoid 'over-healing', and iii) promote functional restoration, including appendage development. Finally, we highlight how these strategies strive to manage chronic wounds and achieve full structural and functional skin recovery by creating desirable 'soil' through modulating the immune microenvironment.

The Amphiregulin/EGFR axis protects from lupus nephritis via downregulation of pathogenic CD4+ T helper cell responses

Systemic lupus erythematosus (SLE) is a common autoimmune disorder with a complex and poorly understood immuno-pathogenesis. Lupus nephritis (LN) is a frequent and difficult to treat complication, which causes high morbidity and mortality. The multifunctional cytokine amphiregulin (AREG) has been implicated in SLE pathogenesis, but its function in LN currently remains unknown. We thus studied the model of pristane-induced LN and found increasing renal and systemic AREG expression during the course of disease. Importantly, renal injury was significantly aggravated in the absence of AREG, revealing a net anti-inflammatory role. Analyses of immune responses showed dual effects. On the one hand, AREG enhanced activation of pro-inflammatory myeloid cells, which however did not play a major role for the course of LN. More importantly, on the other hand, AREG strongly suppressed pathogenic cytokine production by T helper effector cells. This effect was more general in nature and could be reproduced in response to antigen immunization. Since AREG has been postulated to downregulate T cell responses via enhancing Treg suppressive capacity, we followed up on this aspect. Interestingly, however, in vitro studies revealed potential direct and Treg independent effects of AREG on T helper effector cells. In favor of this notion, we found significantly enhanced T cell responses and consecutive aggravation of LN, only if epidermal growth factor receptor (EGFR) signaling was abrogated in total T cells, but not if the EGFR was absent on Tregs alone. Finally, we also found enhanced AREG expression in plasma and renal biopsies of patients with LN, supporting the relevance of our findings for human disease. In summary, our data identify AREG as an anti-inflammatory mediator of LN via broad downregulation of pathogenic T cell immunity. These findings further highlight the AREG/EGFR axis as a potential therapeutic target.

HLA-A2 Promotes the Therapeutic Effect of Umbilical Cord Blood-Derived Mesenchymal Stem Cells in Hyperoxic Lung Injury

Mesenchymal stem cells (MSCs) are one of the most extensively studied stem cell types owing to their capacity for differentiation into multiple lineages as well as their ability to secrete regenerative factors and modulate immune functions. However, issues remain regarding their further application for cell therapy. Here, to demonstrate the superiority of the improvement of MSCs, we divided umbilical cord blood-derived MSCs (UCB-MSCs) from 15 donors into two groups based on efficacy and revealed donor-dependent variations in the anti-inflammatory effect of MSCs on macrophages as well as their immunoregulatory effect on T cells. Through surface marker analyses (242 antibodies), we found that HLA-A2 was positively related to the anti-inflammatory and immunoregulatory function of MSCs. Additionally, HLA-A2 mRNA silencing in MSCs attenuated their therapeutic effects in vitro; namely, the suppression of LPS-stimulated macrophages and phytohemagglutinin-stimulated T cells. Moreover, HLA-A2 silencing in MSCs significantly decreased their therapeutic effects in a rat model of hyperoxic lung damage. The present study provides novel insights into the quality control of donor-derived MSCs for the treatment of inflammatory conditions and diseases.

Cytokine Profile and Anti-Inflammatory Activity of a Standardized Conditioned Medium Obtained by Coculture of Monocytes and Mesenchymal Stromal Cells (PRS CK STORM)

Intercellular communication between monocytes/macrophages and cells involved in tissue regeneration, such as mesenchymal stromal cells (MSCs) and primary tissue cells, is essential for tissue regeneration and recovery of homeostasis. Typically, in the final phase of the inflammation-resolving process, this intercellular communication drives an anti-inflammatory immunomodulatory response. To obtain a safe and effective treatment to counteract the cytokine storm associated with a disproportionate immune response to severe infections, including that associated with COVID-19, by means of naturally balanced immunomodulation, our group has standardized the production under GMP-like conditions of a secretome by coculture of macrophages and MSCs. To characterize this proteome, we determined the expression of molecules related to cellular immune response and tissue regeneration, as well as its possible toxicity and anti-inflammatory potency. The results show a specific molecular pattern of interaction between the two cell types studied, with an anti-inflammatory and regenerative profile. In addition, the secretome is not toxic by itself on human PBMC or on THP-1 monocytes and prevents lipopolysaccharide (LPS)-induced growth effects on those cell types. Finally, PRS CK STORM prevents LPS-induced TNF-A and IL-1Β secretion from PBMC and from THP-1 cells at the same level as hydrocortisone, demonstrating its anti-inflammatory potency.

Systemic and local innate immune responses to surgical co-transplantation of mesenchymal stromal cells and biphasic calcium phosphate for bone regeneration

Bone regeneration from mesenchymal stromal cells (MSC) is attributed to comprehensive immune modulation mediated by the MSC. However, the temporal and spatial regulation of these immune responses has not yet been described. The aim of the present study was to assess the local and systemic innate immune responses to implantation of biphasic calcium phosphate biomaterial (BCP) alone, or with bone marrow derived MSC (BCP+MSC), in critical-sized calvarial bone defects of Lewis rats. Four weeks after implantation, flow cytometry analysis of innate immune cells revealed increased numbers of circulating classical monocyte-macrophages (MM) and decreased non-classical MM in the BCP+MSC group. At week 8, this differential systemic MM response was associated with an increased presence of local tissue anti-inflammatory macrophages expressing CD68 and CD163 markers (M2-like). In the BCP group without MSC, NK cells increased at weeks 1 and 4, and neutrophils increased in circulation at weeks 2 and 8. At week 8, the increase in number of neutrophils in circulation was associated with decreased local tissue neutrophils, in the BCP+MSC group. Gene expression analysis of tissue biopsies from defects implanted with BCP+MSC, in comparison to BCP alone, revealed upregulated expression of early osteogenesis genes along with macrophage differentiation-related genes at weeks 1 and 8 and neutrophil chemotaxis-related genes at week 1. This study is the first to demonstrate that surgical implantation of BCP or BCP+MSC grafts differentially regulate both systemic and local tissue innate immune responses which enhance bone formation. The results provide new insights into immune mechanisms underlying MSC-mediated bone regeneration. STATEMENT OF SIGNIFICANCE: The suitability of biphasic calcium phosphate and mesenchymal stromal cell construct (BCP+MSC) transplantation is evident from their progress in clinical trials for treating challenging maxillofacial bone defects. But less is known about the overall immune response generated by this surgical process and how it later impacts the bone formation. To this end, it is crucial to understand for both clinicians and researchers, the systemic immune response to transplanting MSC in patients for ensuring both the safety and efficacy of cell therapies. In this study, we used rat calvarial bone defect model and showed that both systemic and local innate immunes responses (monocyte-macrophages and neutrophils) are favorably directed towards enhanced bone formation in BCP+MSC implanted defects, as compared to BCP alone.

Rapid 3D bioprinting of a multicellular model recapitulating pterygium microenvironment

Pterygium is an ocular surface disorder with high prevalence that can lead to vision impairment. As a pathological outgrowth of conjunctiva, pterygium involves neovascularization and chronic inflammation. Here, we developed a 3D multicellular in vitro pterygium model using a digital light processing (DLP)-based 3D bioprinting platform with human conjunctival stem cells (hCjSCs). A novel feeder-free culture system was adopted and efficiently expanded the primary hCjSCs with homogeneity, stemness and differentiation potency. The DLP-based 3D bioprinting method was able to fabricate hydrogel scaffolds that support the viability and biological integrity of the encapsulated hCjSCs. The bioprinted 3D pterygium model consisted of hCjSCs, immune cells, and vascular cells to recapitulate the disease microenvironment. Transcriptomic analysis using RNA sequencing (RNA-seq) identified a distinct profile correlated to inflammation response, angiogenesis, and epithelial mesenchymal transition in the bioprinted 3D pterygium model. In addition, the pterygium signatures and disease relevance of the bioprinted model were validated with the public RNA-seq data from patient-derived pterygium tissues. By integrating the stem cell technology with 3D bioprinting, this is the first reported 3D in vitro disease model for pterygium that can be utilized for future studies towards personalized medicine and drug screening.

Aging-related olfactory loss is associated with olfactory stem cell transcriptional alterations in humans

BACKGROUNDPresbyosmia, or aging-related olfactory loss, occurs in a majority of humans over age 65 years, yet remains poorly understood, with no specific treatment options. The olfactory epithelium (OE) is the peripheral organ for olfaction and is subject to acquired damage, suggesting a likely site of pathology in aging. Adult stem cells reconstitute the neuroepithelium in response to cell loss under normal conditions. In aged OE, patches of respiratory-like metaplasia have been observed histologically, consistent with a failure in normal neuroepithelial homeostasis.MethodsAccordingly, we have focused on identifying cellular and molecular changes in presbyosmic OE. The study combined psychophysical testing with olfactory mucosa biopsy analysis, single-cell RNA-Sequencing (scRNA-Seq), and culture studies.ResultsWe identified evidence for inflammation-associated changes in the OE stem cells of presbyosmic patients. The presbyosmic basal stem cells exhibited increased expression of genes involved in response to cytokines or stress or the regulation of proliferation and differentiation. Using a culture model, we found that cytokine exposure drove increased TP63, a transcription factor acting to prevent OE stem cell differentiation.ConclusionsOur data suggest aging-related inflammatory changes in OE stem cells may contribute to presbyosmia via the disruption of normal epithelial homeostasis. OE stem cells may represent a therapeutic target for restoration of olfaction.FundingNIH grants DC018371, NS121067, DC016224; Office of Physician-Scientist Development, Burroughs-Wellcome Fund Research Fellowship for Medical Students Award, Duke University School of Medicine.

Intraperitoneal microbial contamination drives post-surgical peritoneal adhesions by mesothelial EGFR-signaling

Abdominal surgeries are lifesaving procedures but can be complicated by the formation of peritoneal adhesions, intra-abdominal scars that cause intestinal obstruction, pain, infertility, and significant health costs. Despite this burden, the mechanisms underlying adhesion formation remain unclear and no cure exists. Here, we show that contamination of gut microbes increases post-surgical adhesion formation. Using genetic lineage tracing we show that adhesion myofibroblasts arise from the mesothelium. This transformation is driven by epidermal growth factor receptor (EGFR) signaling. The EGFR ligands amphiregulin and heparin-binding epidermal growth factor, are sufficient to induce these changes. Correspondingly, EGFR inhibition leads to a significant reduction of adhesion formation in mice. Adhesions isolated from human patients are enriched in EGFR positive cells of mesothelial origin and human mesothelium shows an increase of mesothelial EGFR expression during bacterial peritonitis. In conclusion, bacterial contamination drives adhesion formation through mesothelial EGFR signaling. This mechanism may represent a therapeutic target for the prevention of adhesions after intra-abdominal surgery.