Recent immunomodulatory strategies in transplantation

Exosomes in the pathogenesis and treatment of ocular diseases

Exosomes have diverse functions and rich content and are involved in intercellular communication, immune regulation, viral infection, tissue regeneration, and the occurrence, development and metastasis of tumours. Notably, various stem cell-derived exosomes are expected to become new therapeutic approaches for inflammatory diseases and tumours and have good clinical application prospects. However, few studies have examined exosomes in ophthalmic diseases. Therefore, based on the functions of exosomes, this paper summarizes progress in the possible use of exosomes as treatment for specific ophthalmic diseases, aiming to determine the pathogenesis of exosomes to achieve more effective clinical diagnosis and treatment of these diseases.

Effect of Pomegranate Extract in Mesenchymal Stem Cells by Modulation of microRNA-155, microRNA-21, microRNA-23b, microRNA-126a, and PI3K\AKT1\NF-[Formula: see text]B Expression

Today, mesenchymal stem cells (MSCs) are candidates for various autoimmune disease treatments due to immunomodulatory activity in these cells. Much research has recently been done to improve the immunomodulatory activity of MSCs. Genetic variation is one of these methods. microRNAs (miRNAs) are small noncoding RNAs that control most of the cell's biological activities. Recent studies have shown that miRNAs play a significant role in the regulation of MSC immunomodulatory activity. Pomegranate is a fruit that has antioxidant, anti-inflammatory, and anticancer properties and has been used for many years for therapeutic purposes. The objective of this research is to evaluate the immunoregulatory-related miRNAs level of adipose-derived MSCs (Ad-MSCs) obtained from adipose tissue in the presence or lack of pomegranate (Punica granatum) extract (PGE). Our results showed that miRNA-23 and miRNA-126 were upregulated by PGE treatment in MSCs, and in contrast, miRNA-21 and miRNA-155 were downregulated by PGE treatment in MSCs. In addition this research shows that PGE can downregulate the expression of PI3K\AKT1\NF-[Formula: see text]B in Ad-MSCs. Our bioinformatics data have shown that the target of these four miRNAs and the signaling pathways, in which these targets are involved, can play an important role in regulating the immunomodulation function of stem cells. In conclusion, PGE can inhibit the expression of PI3K\AKT1\NF-[Formula: see text]B genes involved in inflammatory pathways via miRNA-23 and miRNA-126 overexpression or miRNA-21 and miRNA-155 downregulation that plays a role in the pathways of immune modulation in Ad-MSCs. These results may provide insight into the mechanism underlying the regulation of the immunomodulatory activity of Ad-MSCs by PGE.

A Novel Immunosuppressant, Luteolin, Modulates Alloimmunity and Suppresses Murine Allograft Rejection

An allograft is rejected in the absence of any immunosuppressive treatment because of vigorous alloimmunity and thus requires extensive immunosuppression for its survival. Although there are many conventional immunosuppressants for clinical use, it is necessary to seek alternatives to existing drugs, especially in case of transplant patients with complicated conditions. Luteolin, a natural ingredient, exists in many plants. It exhibits multiple biological and pharmacological effects, including anti-inflammatory properties. In particular, luteolin has been shown to upregulate CD4⁺CD25⁺ regulatory T cells (Tregs) in the context of airway inflammation. However, it remains unknown whether luteolin regulates alloimmune responses. In this study, we demonstrated that luteolin significantly prolonged murine skin allograft survival, ameliorated cellular infiltration, and downregulated proinflammatory cytokine gene expression in skin allografts. Furthermore, luteolin increased the percentage of CD4⁺Foxp3⁺ Tregs while reducing frequency of mature dendritic cells and CD44^highCD62L^low effector CD4⁺/CD8⁺ T cells posttransplantation. It also suppressed the proliferation of T cells and their production of cytokines IFN-γ and IL-17A in vitro while increasing IL-10 level in the supernatant. Moreover, luteolin promoted CD4⁺Foxp3⁺ Treg generation from CD4⁺CD25^- T cells in vitro. Depleting Tregs largely, although not totally, reversed luteolin-mediated extension of allograft survival. More importantly, luteolin inhibited AKT/mTOR signaling in T cells. Thus, for the first time, to our knowledge, we found that luteolin is an emerging immunosuppressant as an mTOR inhibitor in allotransplantation. This finding could be important for the suppression of human allograft rejection, although it remains to be determined whether luteolin has an advantage over other conventional immunosuppressants in suppression of allograft rejection.

Extracorporeal photopheresis for the treatment of graft rejection in 33 adult kidney transplant recipients

Background - Extracorporeal photopheresis (ECP) has shown encouraging results in the prevention of allograft rejection in heart transplantation. However, the role of ECP in kidney transplant (KT) rejection needs to be determined. Methods - This multicentre retrospective study included 33 KT recipients who were treated with ECP for allograft rejection (23 acute antibody-mediated rejections (AMRs), 2 chronic AMRs and 8 acute cellular rejections (ACRs)). The ECP indications were KT rejection in patients who were resistant to standard therapies (n = 18) or in patients for whom standard therapies were contraindicated because of concomitant infections or cancers (n = 15). Results - At 12 months (M12) post-ECP, 11 patients (33%) had a stabilization of kidney function with a graft survival rate of 61%. The Banff AMR score (g + ptc + v) was a risk factor for graft loss at M12 (HR 1.44 [1.01-2.05], p < 0.05). The factorial mixed data analysis identified 2 clusters. Patients with a functional graft at M12 tended to have cellular and/or chronic rejections. Patients with graft loss at M12 tended to have acute rejections and/or AMR; higher serum creatinine levels; DSA levels and histologic scores of AMR; and a longer delay between the rejection and ECP start than those of patients with functional grafts. Conclusions - ECP may be helpful to control ACR or moderate AMR in KT recipients presenting concomitant opportunistic infections or malignancies when it is initiated early.

A potential role of TLR2 in xenograft rejection of porcine iliac endothelial cells: An in vitro study

BACKGROUND

Porcine vascular endothelial cells are a major participant in xenograft rejection. The Toll-like receptor 2 (TLR2) pathway plays an important role in both innate and adaptive immunity. The specific role of TLR2 in the response to a xenograft has not been reported. Whether the TLR2 pathway in pig vascular endothelial cells is involved in acute rejection needs to be investigated, and the mechanism is explored.

METHODS

We used a modified antibody-dependent complement-mediated cytotoxicity (ADCC) assay to conduct in vitro experiments. In porcine iliac artery endothelial cells (PIECs), siRNA was used to knock down the expression of TLR2, CXCL8, and CCL2. The effect of human serum or inactivated human serum on the expression of TLR2 was analyzed by real-time PCR and Western blotting, and transwell assays were used to assess the chemotactic efficiency of PIECs on human monocyte-macrophages (THP-1 cells) and human neutrophils. The downstream signaling pathways activated by human serum were detected by Western blotting, and the regulation of proinflammatory chemokines and cytokines by TLR2 signaling was assessed by real-time PCR and ELISA.

RESULTS

TLR2 was significantly upregulated in PIECs after exposure to human serum, and porcine proinflammatory chemokines, CXCL8 and CCL2, were induced, at least partially, in a TLR2-dependent pattern; the upregulated chemokines participated in the chemotaxis of human neutrophils and THP-1 cells across the species barrier.

CONCLUSIONS

(i) TLR2 is significantly upregulated in PIECs by human serum, (ii) the elevated TLR2 participates in the chemotaxis of inflammatory cells through the secretion of chemokine CCL2 and CXCL8, and (iii) blockade of TLR2 would be beneficial for xenograft survival.

A Comparison of Iron Oxide Particles and Silica Particles for Tracking Organ Recellularization

Reseeding of decellularized organ scaffolds with a patient’s own cells has promise for eliminating graft versus host disease. This study investigated whether ultrasound imaging or magnetic resonance imaging (MRI) can track the reseeding of murine liver scaffolds with silica-labeled or iron-labeled liver hepatocytes. Mesoporous silica particles were created using the Stöber method, loaded with Alexa Flour 647 fluorophore, and conjugated with protamine sulfate, glutamine, and glycine. Fluorescent iron oxide particles were obtained from a commercial source. Liver cells from donor mice were loaded with the silica particles or iron oxide particles. Donor livers were decellularized and reperfused with silica-labeled or iron-labeled cells. The reseeded livers were longitudinally analyzed with ultrasound imaging and MRI. Liver biopsies were imaged with confocal microscopy and scanning electron microscopy. Ultrasound imaging had a detection limit of 0.28 mg/mL, while MRI had a lower detection limit of 0.08 mg/mL based on particle weight. The silica-loaded cells proliferated at a slower rate compared to iron-loaded cells. Ultrasound imaging, MRI, and confocal microscopy underestimated cell numbers relative to scanning electron microscopy. Ultrasound imaging had the greatest underestimation due to coarse resolution compared to the other imaging modalities. Despite this underestimation, both ultrasound imaging and MRI successfully tracked the longitudinal recellularization of liver scaffolds.

Sports Injuries: Diagnosis, Prevention, Stem Cell Therapy, and Medical Sport Strategy

Sports injuries diagnosis, prevention, and treatment are the most important issues of sports medicine. Fortunately, sports injuries are often treated effectively, and people with damage recover and return to the sport in a satisfactory condition. Meanwhile, many sports injuries and complications can be prevented. In general, sports injuries include acute or chronic injuries. Given increasing in popularity, sports medicine doctors use stem cells to treat a wide variety of sports injuries, including damage to tendons, ligaments, muscles, and cartilage. Stem cell therapy to an injured area could be done through direct surgical application, stem-cell-bearing sutures, and injection. Stem cell therapy holds potential for repair and functional plasticity following sports injuries compared to traditional methods; however, the mechanism of stem cell therapy for sports injuries remains largely unknown. Medical imaging technologies provide the hope to ample the knowledge concerning basic stem cell biology in real time when transplanted into sport-induced damaged organs. Using stem cell treatment might restore continuity and regeneration and promote growth back the organ targets. Besides, using a noninvasive medical imaging method would have the long-time monitoring advantage to the stem cells transplanting individual. The multimodality imaging technique allows for studying acute pathological events following sports injuries; therefore, the use of imaging techniques in medicine permits the straight examination of dynamic regenerative events of specific stem cells following a sports injury in people.

Mesenchymal stem cells can induce regulatory T cells via modulating miR-126a but not miR-10a

Among the different immunosuppressive properties attributed to mesenchymal stem cells (MSCs), one relies on their ability to induce regulatory T cells (iTregs) from conventional T cells under particular inflammatory context. Stable Foxp3 expression plays a major role in the phenotypic and functional stability of iTregs. However, the mechanism behind Foxp3 induction in iTregs by MSCs remains unknown. Here, we assessed the possible effect of MSCs on miR-126a and miR-10a expression in iTregs and, consequently on Foxp3 stability, a regulatory pathway that has not yet been explored. We first demonstrated that in vitro MSC-iTreg generation was directly associated with strong modifications of miR-126a. We next infused high doses of MSCs in a murine model of allogeneic skin transplantation (C57BL/6 into Balb/c). This treatment significantly prolonged skin allograft survival compared to PBS treated mice. When splenocytes from grafted mice were collected, we observed that the expression of Foxp3 gene was elevated at day 5 and 10 post-graft merely in MSCs treated mice. Moreover, Foxp3 expression was not associated with modified miR-10a expression comparable to in vitro experiments. Thus, our data identify a solid mechanism where MSCs induce conversion of conventional T cells to iTregs through strong modifications of miR-126a. Although miR-10a expression level remains unchanged in vitro and in vivo, we observed expression of this miR in MSC-DC condition.

Mesenchymal Stem Cells Upregulate the Expression of PD-L1 But Not VDR in Dendritic Cells

OBJECTIVE

Mesenchymal stem cells (MSCs) show immunomodulatory functions. But the exact mechanism underlying these activities of MSCs is still not completely understood. There have been a few studies which have assessed the effects of these cells on dendritic cells (DCs) function. Given the importance of programmed cell death receptor-1 (PD-L1) and vitamin D receptor (VDR) expression in induction of tolerance in DCs, we were encouraged to investigate if one of the immunomodulatory functions of MSCs could be inducing upregulation of PD-L1 and VDR on DCs or not.

METHODS

DCs were co-cultured with MSCs or treated with them in transwell plates in the presence or absence of Lipopolysaccharide (LPS). Expression of PD-L1 and VDR mRNA and proteins in treated DCs were assessed by Real-time PCR and Western blot techniques. Furthermore, treated DCs were co-cultured with allogeneic T-cells, and T-cell proliferation and cytokine secretions in co-culture supernatants were assessed.

RESULTS

The results showed that PD-L1 but not VDR expression is significantly upregulated in the DCs co-cultured with MSCs. Furthermore, cell-to-cell contact and also presence of maturation inducers like LPS is necessary for this function. Moreover, our results indicated that MSCs could induce tolerogenic DCs (TolDCs) which could decrease the secretion of IL-2 by T-cells and inhibit T-cell proliferation as well as increase secretion of IL-10.

CONCLUSIONS

Overall, our results show that MSCs may have several suppressive effects on immune responses by induction of TolDCs expressing more PD-L1 immunomodulatory molecule and change the cytokines profile of DCs and T-cells.

Genetically modified murine adipose-derived mesenchymal stem cells producing interleukin-2 favor B16F10 melanoma cell proliferation

Adipose-derived mesenchymal stem cells (ADSCs) are attractive tools for cancer gene therapy due to their intrinsic tropism to the tumor environment. Interleukin-2 (IL2) is recognized as a key regulatory molecule, which enhances the activity and growth of the immune effector cell function. High-Dose IL2 Therapy is an option for treatment of malignant melanoma but has frequent, often serious and sometimes life-threatening side effects. Here we investigated the effect of genetically modified ADSCs (GM-ADSCs) expressing IL2 in immunocompetent mouse models of subcutaneous and lung metastatic melanoma. Prior to in vivo studies, we demonstrated that IL2 produced by GM-ADSCs may act as a growth factor for melanoma cells due to the increased viability and reduced apoptosis of melanoma cells after in vitro treatment. Subcutaneous co-injection of IL2-expressing ADSCs with melanoma cells significantly enhanced the melanoma tumor growth. Furthermore, histological analysis of subcutaneous tumors for IL2 and Melan-A (a melanocytic differentiation marker) confirmed that most of cells in melanoma/IL2-ADSC co-injected tumors are melanoma cells, not IL2-ADSCs. In pulmonary metastases model, melanoma cells were injected intravenously and 10 days later mice were treated by systematical injection of GM-ADSCs. Intravenously injected IL2-ADSCs engrafted into melanoma lung tumors but were unable to reduce melanoma lung metastases. Besides, administered IL2-ADSCs significantly reduced systemic CD4+ cells and did not impact the total survival of lung metastases melanoma bearing mice. In conclusion, this study showed that IL2-producing ADSCs can favor B16F10 melanoma cell proliferation. Therefore, therapies utilizing IL2 have to be taken into careful consideration.