Exosomes derived from mesenchymal stem cells

The functional mechanisms of mesenchymal stem cells (MSCs) have become a research focus in recent years. Accumulating evidence supports the notion that MSCs act in a paracrine manner. Therefore, the biological factors in conditioned medium, including exosomes and soluble factors, derived from MSC cultures are being explored extensively. The results from most investigations show that MSC-conditioned medium or its components mediate some biological functions of MSCs. Several studies have reported that MSC-derived exosomes have functions similar to those of MSCs, such as repairing tissue damage, suppressing inflammatory responses, and modulating the immune system. However, the mechanisms are still not fully understood and the results remain controversial. Compared with cells, exosomes are more stable and reservable, have no risk of aneuploidy, a lower possibility of immune rejection following in vivo allogeneic administration, and may provide an alternative therapy for various diseases. In this review, we summarize the properties and biological functions of MSC-derived exosomes and discuss the related mechanisms.

Effects of Mesenchymal Stem Cell-Derived Exosomes on Experimental Autoimmune Uveitis

We previously demonstrated that mesenchymal stem cells (MSCs) ameliorated experimental autoimmune uveoretinitis (EAU) in rats. Recently, MSC-derived exosomes (MSC-Exo) were thought to carry functions of MSCs. In this study, we tested the effect of local administration of human MSC-Exo on established EAU in the same species. Rats with EAU induced by immunization with interphotoreceptor retinol-binding protein 1177-1191 peptide were treated by periocular injections of increasing doses of MSC-Exo starting at the disease onset for 7 consecutive days. The in vitro effects of MSC-Exo on immune cell migration and responder T cell proliferation were examined by chemotactic assays and lymphocyte proliferation assays, respectively. We found that MSC-Exo greatly reduced the intensity of ongoing EAU as their parent cells by reducing the infiltration of T cell subsets, and other inflammatory cells, in the eyes. Furthermore, the chemoattractive effects of CCL2 and CCL21 on inflammatory cells were inhibited by MSC-Exo. However, no inhibitory effect of MSC-Exo on IRBP-specific T cell proliferation was observed. These results suggest that MSC-Exo effectively ameliorate EAU by inhibiting the migration of inflammatory cells, indicating a potential novel therapy of MSC-Exo for uveitis.

Exosomes derived from MSCs ameliorate retinal laser injury partially by inhibition of MCP-1

Although accumulated evidence supports the notion that mesenchymal stem cells (MSCs) act in a paracrine manner, the mechanisms are still not fully understood. Recently, MSC-derived exosomes (MSC-Exos), a type of microvesicle released from MSCs, were thought to carry functional proteins and RNAs to recipient cells and play therapeutic roles. In the present study, we intravitreally injected MSCs derived from either mouse adipose tissue or human umbilical cord, and their exosomes to observe and compare their functions in a mouse model of laser-induced retinal injury. We found that both MSCs and their exosomes reduced damage, inhibited apoptosis, and suppressed inflammatory responses to obtain better visual function to nearly the same extent in vivo. Obvious down-regulation of monocyte chemotactic protein (MCP)-1 in the retina was found after MSC-Exos injection. In vitro, MSC-Exos also down-regulated MCP-1 mRNA expression in primarily cultured retinal cells after thermal injury. It was further demonstrated that intravitreal injection of an MCP-1-neutralizing antibody promoted the recovery of retinal laser injury, whereas the therapeutic effect of exosomes was abolished when MSC-Exos and MCP-1 were administrated simultaneously. Collectively, these results suggest that MSC-Exos ameliorate laser-induced retinal injury partially through down-regulation of MCP-1.

Development and Evaluation of Diagnostic Criteria for Vogt-Koyanagi-Harada Disease

Importance

To our knowledge, a set of well-defined diagnostic criteria is not yet developed for the diagnosis of Vogt-Koyanagi-Harada (VKH) disease.

Objective

To develop and evaluate a set of diagnostic criteria for VKH disease using data from Chinese patients.

Design, Setting, and Participants

This case-control study reviewed medical records of patients from a tertiary referral center between October 2011 and October 2016. Data from 634 patients with VKH disease and 623 patients with non-VKH uveitis from southern China were used to develop the Diagnostic Criteria for VKH Disease (DCV). Data from an additional group of 537 patients with a definite VKH disease diagnosis and 525 patients with non-VKH uveitis from northern China were used to evaluate the diagnostic criteria.

Main Outcomes and Measures

Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and receiver operating characteristic.

Results

Of the 1257 patients used to construct the DCV, 665 (52.9%) were male, and the mean (SD) age at disease onset was 38.6 (13.6) years. The 3-class model and 21 clinical findings were selected by latent class analysis. Variables with a high positive rate in the early-phase or late-phase VKH group or high specificity constituted essential parameters. Constellations of these essential parameters constructed the DCV. The sensitivity and NPV of the DCV were higher than those of the Revised Diagnostic Criteria for VKH Disease (RDC) (sensitivity: 94.6% vs 71.9%; difference, 22.7%; 95% CI, 18.5-27.0; NPV: 94.3% vs 76.6%; difference, 17.7%; 95% CI, 13.9-21.5). The specificity and PPV of the DCV were not different from that of the RDC (specificity: 92.2% vs 93.9%; difference, 1.7%; 95% CI, -1.4 to 4.8; PPV: 89.3% vs 92.3%; difference, 3.0%; 95% CI, -1.4 to 4.8). The area under the receiver operating characteristic curve of the DCV and the RDC were 0.934 (95% CI, 0.917-0.951) and 0.829 (95% CI, 0.803-0.855), respectively.

Conclusions and Relevance

The DCV were developed and evaluated using data from Chinese patients with VKH disease and showed a high sensitivity, NPV, and area under the receiver operating characteristic curve in comparison with the RDC. However, they were developed using a retrospective analysis and should be evaluated in prospective studies in other racial/ethnic populations.

Effects of mesenchymal stem cells and their exosomes on the healing of large and refractory macular holes

PURPOSE

To assess the efficacy of mesenchymal stem cells (MSCs) and MSC-derived exosomes (MSC-Exos) to promote the healing of large and refractory macular holes (MHs).

METHODS

Seven patients (age 51-75 years old) with large and long-standing idiopathic MHs underwent vitrectomy, internal limiting membrane peeling, MSC (two patients) or MSC-Exo (five patients) intravitreal injection, and heavy silicon oil, air, 20% SF6, or 14% C3F8 tamponade. The MSCs were isolated from human umbilical cord tissue, and MSC-Exos were isolated from the supernatants of cultured MSCs using sequential ultracentrifugation.

RESULTS

Five eyes underwent pars plana vitrectomy (PPV) only, while two underwent PPV combined with cataract surgery. Six MHs were closed, while one remained in a flat-open state. The best-corrected visual acuity (BCVA) was improved in five patients with MH closure and remained unchanged in one patient with MH closure who had a 4-year history of MH. A fibrotic membrane was observed on the surface of the retina in one patient who underwent MSC therapy. One patient who received a higher dose of MSC-Exos exhibited an inflammatory reaction.

CONCLUSIONS

MSC and MSC-Exo therapy may promote functional and anatomic recovery from MH. MSC-Exo therapy may be a useful and safe method for improving the visual outcomes after surgery for refractory MHs.

Immunomodulatory effects of mesenchymal stem cells in a rat corneal allograft rejection model

Mesenchymal stem cells (MSCs) are promising candidates for immunomodulatory therapy that are currently being tested in several organ transplant rejection models. In this study, we tested the immunomodulatory effects of MSC injection in a rat model of corneal allograft rejection. MSCs were isolated and cultured from bone marrow of Wistar rats. A rat corneal allograft rejection model was established using Wistar rats as donors and Lewis rats as recipients. Lewis rats were randomly separated into 12 groups and treated with MSCs alone or MSCs combined with Cyclosporin A (CsA) at different doses. In MSC-treated rats, the T cell response to ConA was evaluated, Th1/Th2 cytokines produced by T lymphocytes were measured, and the number of CD4+CD25+Foxp3+ regulatory T cells (Treg) was assessed. Results demonstrated that postoperative injection of MSCs prolonged graft survival time. MSCs significantly inhibited proliferation of pathogenic T cells in vitro and prevented T cell response in vivo (p < 0.05). Postoperative injection also reduced Th1 pro-inflammatory cytokines and elevated IL-4 cytokine secretion from T lymphocytes derived from cornea-transplanted rats. In addition, Tregs were upregulated by MSC treatment. Unexpectedly, the application of MSCs combined with low dose CsA therapy (1 mg/kg) accelerated graft rejection compared with postoperative MSC therapy alone. However, when 2 mg/kg CsA was given together with MSCs, graft survival was significantly prolonged. These results suggested that MSCs could exert therapeutic effect against corneal allograft rejection, and further investigation of combined MSC and CsA treatment be required as opposite effects were observed depending on CsA dose.

INTRAVITREAL CONBERCEPT (KH902) FOR SURGICAL TREATMENT OF SEVERE PROLIFERATIVE DIABETIC RETINOPATHY

PURPOSE

To evaluate the role, safety, and effectiveness of intravitreal conbercept (KH902) injections as an adjunct to vitrectomy in the management of severe proliferative diabetic retinopathy.

METHODS

A randomized controlled trial was performed on 36 eyes of 36 patients affected by vitreous hemorrhage and tractional retinal detachment, which occurred as a consequence of active proliferative diabetic retinopathy. The patients were randomly assigned to two groups. The patients in one of the groups received an intravitreal injection of conbercept in the inferior temporal sector 4 mm from the sclerocorneal limbus with a sterile technique 1 week before vitrectomy.

RESULTS

In the group without conbercept, intraoperative bleeding occurred in 14 patients (77.8%), and in five of these cases, bleeding was significant. The use of endodiathermy was necessary in 8 patients (44.4%). In 3 patients (16.6%), iatrogenic retinal breaks occurred, and in 1 patient (5.5%), a relaxing retinotomy was performed. Endotamponade with silicone oil was performed in 12 patients (66.6%). In the group treated with conbercept, intraoperative bleeding occurred in 2 cases (11.1%). The use of endodiathermy was necessary in 1 patient (5.5%). No patients experienced iatrogenic breaks or relaxing retinotomy during the surgery. Endotamponade with silicone oil was performed in 2 patients (11.1%).

CONCLUSION

Preoperative intravitreal injection of conbercept could reduce the chances of intraoperative bleeding, which are beneficial in the management of proliferative diabetic retinopathy.

Mesenchymal stem cells ameliorate experimental autoimmune uveoretinitis by comprehensive modulation of systemic autoimmunity

PURPOSE

The authors studied the therapeutic effect of rat mesenchymal stem cells (MSCs) on experimental autoimmune uveoretinitis (EAU) induced in rats by peptide 1169-1191 of the interphotoreceptor retinoid-binding protein (IRBP).

METHODS

The authors intravenously injected syngeneic (isolated from Lewis rats) or allogeneic (isolated from Wistar rats) MSCs into IRBP-induced EAU Lewis rats, either before disease onset (simultaneous with immunization, preventive protocol) or at different time points after disease onset (therapeutic protocol). T-cell response to IRBP 1169-1191 from MSC-treated rats was evaluated, Th1/Th2/Th17 cytokines produced by lymphocytes were measured, and CD4(+)CD25(+) regulatory T cells (Treg) were detected.

RESULTS

MSC administration before disease onset not only strikingly reduced the severity of EAU, it also delayed the onset of the disease. MSC administration was also effective after disease onset and at the peak of disease, but not after disease stabilization. Clinical efficacy for all treatments was consistent with reduced cellular infiltrates and milder uveal and retinal impairment. T-cell response to IRBP 1169-1191 from MSC-treated rats was inhibited. MSCs significantly decreased the production of IFN-γ and IL-17 and increased the production of IL-10 of T lymphocytes from EAU rats either in vivo or in vitro. Allogeneic and syngeneic MSCs showed a similar immunosuppression potential with regard to clinical effect, T cell proliferation, and cytokine secretion, and MSC therapy upregulated Treg cells.

CONCLUSIONS

These data suggest that the immunoregulatory properties of MSCs effectively interfere with the autoimmune attack in the course of EAU through the comprehensive modulation of systemic autoimmunity.

ASK1-Mediated Phosphorylation Blocks HDAC6 Ubiquitination and Degradation to Drive the Disassembly of Photoreceptor Connecting Cilia

Retinopathy of prematurity (ROP) is a leading cause of childhood blindness. However, the pathogenesis and molecular mechanisms underlying ROP remain elusive. Herein, using the oxygen-induced retinopathy (OIR) mouse model of ROP, we demonstrate that disassembly of photoreceptor connecting cilia is an early event in response to oxygen changes. Histone deacetylase 6 (HDAC6) is upregulated in the retina of OIR mice and accumulates in the transition zone of connecting cilia. We also show that in response to oxygen changes, apoptosis signal-regulating kinase 1 (ASK1) is activated and phosphorylates HDAC6, blocking its ubiquitination by von Hippel-Lindau and subsequent degradation by the proteasome. Moreover, depletion of HDAC6 or inhibition of the ASK1/HDAC6 axis protects mice from oxygen-change-induced pathological changes of photoreceptors. These findings reveal a critical role for ASK1/HDAC6-mediated connecting cilium disassembly in the OIR mouse model of ROP and suggest a potential value of ASK1/HDAC6-targeted agents for prevention of this disease.

α-Melanocyte-stimulating hormone protects retinal vascular endothelial cells from oxidative stress and apoptosis in a rat model of diabetes

AIMS

Oxidative stress and apoptosis are among the earliest lesions of diabetic retinopathy. This study sought to examine the anti-oxidative and anti-apoptotic effects of α-melanocyte-stimulating hormone (α-MSH) in early diabetic retinas and to explore the underlying mechanisms in retinal vascular endothelial cells.

METHODS

Sprague-Dawley rats were injected intravenously with streptozocin to induce diabetes. The diabetic rats were injected intravitreally with α-MSH or saline. At week 5 after diabetes, the retinas were analyzed for reactive oxygen species (ROS) and gene expression. One week later, the retinas were processed for terminal deoxynucleotidyl transferase dUTP nick-end labeling staining and transmission electron microscopy. Retinal vascular endothelial cells were stimulated by high glucose (HG) with or without α-MSH. The expression of Forkhead box O genes (Foxos) was examined through real-time PCR. The Foxo4 gene was overexpressed in endothelial cells by transient transfection prior to α-MSH or HG treatment, and oxidative stress and apoptosis were analyzed through CM-H2DCFDA and annexin-V assays, respectively.

RESULTS

In diabetic retinas, the levels of H2O2 and ROS and the total anti-oxidant capacity were normalized, the apoptotic cell number was reduced, and the ultrastructural injuries were ameliorated by α-MSH. Treatment with α-MSH also corrected the aberrant changes in eNOS, iNOS, ICAM-1, and TNF-α expression levels in diabetic retinas. Furthermore, α-MSH inhibited Foxo4 up-regulation in diabetic retinas and in endothelial cells exposed to HG, whereas Foxo4 overexpression abrogated the anti-oxidative and anti-apoptotic effects of α-MSH in HG-stimulated retinal vascular endothelial cells.

CONCLUSIONS

α-MSH normalized oxidative stress, reduced apoptosis and ultrastructural injuries, and corrected gene expression levels in early diabetic retinas. The protective effects of α-MSH in retinal vascular endothelial cells may be mediated through the inhibition of Foxo4 up-regulation induced by HG. This study suggests an α-MSH-mediated potential intervention approach to early diabetic retinopathy and a novel regulatory mechanism involving Foxo4.

The effect of mesenchymal stem cells on dynamic changes of T cell subsets in experimental autoimmune uveoretinitis

Mesenchymal stem cells (MSCs) are being explored extensively as a promising treatment for autoimmune diseases. We have recently reported that MSCs could ameliorate experimental autoimmune uveoretinitis (EAU) in rats. In this study, we examined further the effects of MSCs on the dynamics of T cell subsets in both eye and spleen and their cytokine production during the course of EAU. We focused on when and where the MSCs had inhibitory effects on T helper type 1 (Th1) and Th17 cells and how long the inhibitory effect lasted, in order to provide more mechanistic evidence for MSCs on the treatment of uveitis. Compared to the control group, administration of MSCs decreased the production of Th1 and Th17 cytokines significantly, while the production of Th2 and regulatory T cell (T(reg)) cytokines [interleukin (IL)-10 and transforming growth factor (TGF)-β] was elevated during the entire course of EAU. Correspondingly, the dynamic levels of IL-17 in the aqueous humour (AqH) were reduced in MSC-treated rats. Moreover, the ratio of Th17/T(reg) cells in both spleen and eye was decreased. These results provide powerful evidence that MSCs can regulate negatively both Th1 and Th17 responses and restore the balance of Th17/T(regs) in the whole course of EAU, which is important for the regression of the disease.

Therapeutic effects of mesenchymal stem cell-derived exosomes on retinal detachment

Retinal detachment (RD) induces ischemia and oxygen deficiency in the retina and results in multiple pathological events; photoreceptor cell degeneration and death is the eventual cause of vision decline. In this study, we investigated the therapeutic effects of mesenchymal stem cell-derived exosomes (MSC-Exos) in a rat retinal detachment (RD) model. The model was developed using a subretinal injection of 1% hyaluronic acid in male Sprague-Dawley rats. MSC-Exos were sub-retinally injected at the time of retinal separation to study their therapeutic function. The retinal expression levels of inflammatory cytokines TNF-α, IL-1β, and MCP-1 were detected by RT-PCR, the autophagy-related protein 5 (Atg5) and microtubule-associated protein 1 light chain 3 beta (LC3) were detected by Western blot, and apoptosis was examined using TUNEL assays at 3 days following RD. Retinal structure was observed at 7 days post-RD. Proteomic analysis was also performed to detect proteins carried by MSC-Exos using iTRAQ-based technology combined with one-dimensional nano LC-nano-ESI- MS/MS. We found that expression of TNF-α and IL-1β were significantly reduced, the LC3-II to LC3-I ratio was enhanced and cleavage of Atg5 was decreased after MSC-Exo treatment. Treatment with MSC-Exos also suppressed photoreceptor cell apoptosis and maintained normal retinal structure when compared to control groups. Proteomic analysis revealed that MSC-Exos contained proteins with anti-inflammatory, neuroprotective and anti-apoptotic effects. These results suggest that MSC-Exos have therapeutic effects on RD-induced retinal injury and can be used to reduce effects of retinal detachment on photoreceptor cell degeneration in patients.

CD73 Pathway Contributes to the Immunosuppressive Ability of Mesenchymal Stem Cells in Intraocular Autoimmune Responses

Mesenchymal stem cells (MSCs) exhibit a potent immunomodulatory capacity and have been applied to treat diseases such as graft versus host disease and severe autoimmune diseases. However, the mechanism underlying their immunosuppressive effect is not yet completely understood. Here, we investigated the role of the CD73/adenosine pathway in immune modulation by MSCs using a mouse model of experimental autoimmune uveitis (EAU). Moreover, we examined the in vitro modulatory effect of MSCs mediated through the CD73/adenosine pathway in human and mouse T cells. We found that the severity of EAU was significantly attenuated by MSCs; however, most therapeutic effects of MSCs were lost by pretreatment with a CD73 inhibitor. The inhibitory mechanism of MSCs might be contributed by CD73 on MSCs that cooperated with CD39 and CD73 on activated T cells to produce adenosine, resulting in inhibition of T-cell proliferation. Furthermore, MSCs increased the expression of CD73 on CD4(+) T cells, and transforming growth factor-β1 (TGF-β1) was the only tested cytokine that contributed to upregulation of CD73. Hence, our study demonstrates that the CD73/adenosine pathway involves the immunomodulatory function of MSCs in autoimmune responses.

Identification of an intraocular microbiota

The current dogma in ophthalmology and vision research presumes the intraocular environment to be sterile. However, recent evidence of intestinal bacterial translocation into the bloodstream and many other internal organs including the eyes, found in healthy and diseased animal models, suggests that the intraocular cavity may also be inhabited by a microbial community. Here, we tested intraocular samples from over 1000 human eyes. Using quantitative PCR, negative staining transmission electron microscopy, direct culture, and high-throughput sequencing technologies, we demonstrated the presence of intraocular bacteria. The possibility that the microbiome from these low-biomass communities could be a contamination from other tissues and reagents was carefully evaluated and excluded. We also provide preliminary evidence that a disease-specific microbial signature characterized the intraocular environment of patients with age-related macular degeneration and glaucoma, suggesting that either spontaneous or pathogenic bacterial translocation may be associated with these common sight-threatening conditions. Furthermore, we revealed the presence of an intraocular microbiome in normal eyes from non-human mammals and demonstrated that this varied across species (rat, rabbit, pig, and macaque) and was established after birth. These findings represent the first-ever evidence of intraocular microbiota in humans.

Mesenchymal stem cell-derived extracellular vesicles as a new therapeutic strategy for ocular diseases

Mesenchymal stem cells (MSCs) have attracted considerable attention for their activity in the treatment of refractory visual disorders. Since MSCs were found to possess the beneficial effects by secreting paracrine factors rather than direct differentiation, MSC-derived extracellular vesicles (EVs) were widely studied in various disease models. MSCs generate abundant EVs, which act as important mediators by exchanging protein and genetic information between MSCs and target cells. It has been confirmed that MSC-derived EVs possess unique anti-inflammatory, anti-apoptotic, tissue repairing, neuroprotective, and immunomodulatory properties, similar to their parent cells. Upon intravitreal injection, MSC-derived EVs rapidly diffuse through the retina to alleviate retinal injury or inflammation. Due to possible risks associated with MSC transplantation, such as vitreous opacity and pathological proliferation, EVs appear to be a better choice for intravitreal injection. Small size EVs can pass through biological barriers easily and their contents can be modified genetically for optimal therapeutic effect. Hence, currently, they are also explored for the possibility of serving as drug delivery vehicles. In the current review, we describe the characteristics of MSC-derived EVs briefly, comprehensively summarize their biological functions in ocular diseases, and discuss their potential applications in clinical settings.

Prevalence of diabetic retinopathy, proliferative diabetic retinopathy and non-proliferative diabetic retinopathy in Asian T2DM patients: a systematic review and Meta-analysis

AIM

To investigate the pooled prevalence of diabetic retinopathy (DR), proliferative DR (PDR) and nonproliferative DR (NPDR) in Asian type 2 diabetes mellitus (T2DM) patients.

METHODS

We performed a systematic search online search using PubMed, EMBASE, Web of Science, the Cochrane Library, and China WeiPu Library to identify eligible studies that reported the prevalence of DR, PDR and NPDR in Asian T2DM patients. Effect size (ES) with 95% confidence interval (CI) was used to evaluate the prevalence of DR, PDR and NPDR in Asian T2DM patients, respectively.

RESULTS

There were 41 references and 48 995 T2DM patients involved in this study. The prevalence of DR, PDR, and NPDR was 28%, 6%, and 27% in T2DM patients, respectively; while the prevalence of PDR and NPDR in DR patients was 17% and 83%, respectively. Subgroup analysis showed that prevalence of DR in T2DM patients from Singaporean, Indian, South Korean, Malaysian, Asian, and Chinese was 33%, 42%, 16%, 35%, 21% and 25%, respectively. In T2DM patients with NPDR from Indian, South Korean, Malaysian, Asian, Chinese, higher prevalence was found than that in PDR patients (45% vs 17%, 13% vs 3%, 30% vs 5%, 23% vs 2% and 22% vs 3%), as well as in DR patients (74% vs 26%, 81% vs 19%, 86% vs 14%, 92% vs 8% and 85% vs 15%). The prevalence of PDR in T2DM from India was higher than patients from other locations of Asia, and the same results were also observed in NPDR patients.

CONCLUSION

In either T2DM Asian patients or DR patients, NPDR is more common than PDR. Based on our results, we should pay more attention to NPDR screening and management in T2DM patients, and we also recommend suitable interventions to prevent its progression.

KLF6 Induces Apoptosis in Human Lens Epithelial Cells Through the ATF4-ATF3-CHOP Axis

Background

Many studies have confirmed that high myopia is related to the high prevalence of cataracts, which results from apoptosis of lens epithelial cells (LECs) due to endoplasmic reticulum stress. Krüppel-like factor 6 (KLF6) is a tumor suppressor that is involved in the regulation of cell proliferation and apoptosis.

Purpose

In this study, our purpose was to find the relationship between KLF6-induced apoptosis in LECs and ATF4 (activating transcription factor 4)-ATF3 (activating transcription factor 3)-CHOP (C/EBP homologous protein) signaling pathway.

Methods

KLF6, ATF4, ATF3, and CHOP were ectopically expressed using cDNAs subcloned into the pCDNA3.1+ vector. ATF4, ATF3, and CHOP knockdown were performed by small interfering RNA (siRNA). Expression of relative gene was tested using QT-PCR and western-blot. Then, accompanied by UVB stimulation, cell viability was measured by CCK-8 assay; The cell damage was examined by live & dead staining; The apoptotic markers Bax and Bcl-2 were detected by immunoblotting; Quantitative apoptotic levels were measured with the Apoptosis Detection Kit; The expression level of reactive oxygen-free radical (ROS) was analyzed by DCFH-DA` probe.

Results

Ectopically expressed ATF4, ATF3, and CHOP-induced apoptosis in cells, whereas ATF4, ATF3, and CHOP knockdown by small interfering RNA (siRNA) blocked KLF6-induced apoptosis. In addition, we determined that ATF4 regulates ATF3 and CHOP expression and that ATF3 silencing reduces CHOP upregulation without changing ATF4 levels; however, ATF4 and ATF3 expression was unaffected by blockade of CHOP, suggesting that KLF6 triggers endoplasmic reticulum stress in LECs by mediating the ATF4-ATF3/CHOP axis. Besides, KLF6 overexpression significantly induced LEC apoptosis under UV radiation, as demonstrated by the elevated Bax/Bcl-2 ratio.

Conclusion

The ATF4-ATF3-CHOP pathway plays an important role in KLF6-induced apoptosis in HLECs. Our results increase our understanding of the mechanisms that regulate LEC apoptosis and contribute to the development of a new preventative strategy for cataract.

Cytokines that Modulate the Differentiation of Th17 Cells in Autoimmune Uveitis

Increasing evidence has suggested that T helper 17 (Th17) cells play a central role in the pathogenesis of ocular immune disease. The association between pathogenic Th17 cells and the development of uveitis has been confirmed in experimental and clinical studies. Several cytokines affect the initiation and stabilization of the differentiation of Th17 cells. Therefore, understanding the mechanism of related cytokines in the differentiation of Th17 cells is important for exploring the pathogenesis and the potential therapeutic targets of uveitis. This article briefly describes the structures, mechanisms, and targeted drugs of cytokines-including interleukin (IL)-6, transforming growth factor-β1 (TGF-β1), IL-1β, IL-23, IL-27, IL-35, IL-2, IL-4, IL-21, and interferon (IFN)-γ-which have an important influence on the differentiation of Th17 cells and discusses their potential as therapeutic targets for treating autoimmune uveitis.

Multi-omics analysis of human mesenchymal stem cells shows cell aging that alters immunomodulatory activity through the downregulation of PD-L1

Mesenchymal stem cells (MSCs) possess potent immunomodulatory activity and have been extensively investigated for their therapeutic potential in treating inflammatory disorders. However, the mechanisms underlying the immunosuppressive function of MSCs are not fully understood, hindering the development of standardized MSC-based therapies for clinical use. In this study, we profile the single-cell transcriptomes of MSCs isolated from adipose tissue (AD), bone marrow (BM), placental chorionic membrane (PM), and umbilical cord (UC). Our results demonstrate that MSCs undergo a progressive aging process and that the cellular senescence state influences their immunosuppressive activity by downregulating PD-L1 expression. Through integrated analysis of single-cell transcriptomic and proteomic data, we identify GATA2 as a regulator of MSC senescence and PD-L1 expression. Overall, our findings highlight the roles of cell aging and PD-L1 expression in modulating the immunosuppressive efficacy of MSCs and implicating perinatal MSC therapy for clinical applications in inflammatory disorders.

Long-term therapeutic effects of mesenchymal stem cells compared to dexamethasone on recurrent experimental autoimmune uveitis of rats

PURPOSE

We tested the long-term effects of different regimens of mesenchymal stem cell (MSC) administration in a recurrent experimental autoimmune uveitis (rEAU) model in rats, and compared the efficacy of MSC to that of dexamethasone (DEX).

METHODS

One or two courses of MSC treatments were applied to R16-specific T cell-induced rEAU rats before or after disease onsets. The DEX injections were given for 7 or 50 days continuously after disease onsets. Clinical appearances were observed until the 50th day after transfer. On the 10th day, T cells from control and MSC groups were analyzed by flow cytometry. Supernatants from the proliferation assay and aqueous humor were collected for cytokine detection. Functions of T cells and APCs in spleens also were studied by lymphocyte proliferation assays.

RESULTS

One course of MSC therapy, administered after disease onset, led to a lasting therapeutic effect, with a decreased incidence, reduced mean clinical score, and reduced retinal impairment after 50 days of observation, while multiple courses of treatment did not improve the therapeutic benefit. Although DEX and MSCs equally reduced the severity of the first episode of rEAU, the effect of DEX was shorter lasting, and DEX therapy failed to control the disease even with long periods of treatment. The MSCs significantly decreased T helper 1 (Th1) and Th17 responses, suppressed the function of antigen-presenting cells, and upregulated T regulatory cells.

CONCLUSIONS

These results suggested that MSCs might be new corticosteroid spring agents, while providing fewer side effects and longer lasting suppressive effects for recurrent uveitis.

Comparison of cell-suspension and explant culture of rabbit limbal epithelial cells

Currently, most investigators directly use limbal explants to culture corneal epithelial cells. However, it has not been identified that limbal stem cells do readily migrate from the limbal explants onto culture plate or amniotic membrane carrier. In this study a cell-suspension culture system for rabbit limbal stem cells was developed and compared with the direct explant method in the aspect of stem cells content in the culture system. Rabbit limbal epithelial cells were dissociated from rabbit eyes by dispase and single cell suspension was made for cell-suspension culture. DeltaNp63 expression of cultured rabbit limbal epithelial cells by cell-suspension technique and explant technique was detected. In cell-suspension culture, isolated cell-suspension was evaluated by flow cytometric analysis for vimentin expression and residual limbal tissue after dispase treatment was examined by scanning electron microscopy. In limbal epithelial cells suspension less than 5% cells were vimentin positive. Examination of residual limbal tissue confirmed that all the limbal epithelial cells had been removed. Histological examination revealed that with cell-suspension culture the cultured epithelial cells could differentiate better than with explant technique. In cells cultured with cell-suspension, there were much more cells expressing DeltaNp63 than in explant cultured cells. In cells cultured with explants, most of DeltaNp63 labelling cells mustered around the explants, and peripheral cells on the slides were DeltaNp63 negative. These results suggested that with pure limbal epithelial cells suspension including basal cells, which could directly enter into culture system, cell-suspension culture technique was significantly superior to explant culture technique in terms of stem cells content.

Therapeutic effect of bone marrow mesenchymal stem cells on laser-induced retinal injury in mice

Stem cell therapy has shown encouraging results for neurodegenerative diseases. The retina provides a convenient locus to investigate stem cell functions and distribution in the nervous system. In the current study, we investigated the therapeutic potential of bone marrow mesenchymal stem cells (MSCs) by systemic transplantation in a laser-induced retinal injury model. MSCs from C57BL/6 mice labeled with green fluorescent protein (GFP) were injected via the tail vein into mice after laser photocoagulation. We found that the average diameters of laser spots and retinal cell apoptosis were decreased in the MSC-treated group. Interestingly, GFP-MSCs did not migrate to the injured retina. Further examination revealed that the mRNA expression levels of glial fibrillary acidic protein and matrix metalloproteinase-2 were lower in the injured eyes after MSC transplantation. Our results suggest that intravenously injected MSCs have the ability to inhibit retinal cell apoptosis, reduce the inflammatory response and limit the spreading of damage in the laser-injured retina of mice. Systemic MSC therapy might play a role in neuroprotection, mainly by regulation of the intraocular microenvironment.

Role of mesenchymal stem cells in immunological rejection of organ transplantation

The discovery that Mesenchymal Stem Cells (MSCs) can strongly inhibit T cell proliferation in vitro and in vivo and exert similar inhibitory effects on B cells, dendritic cells, and natural killer cells has highlighted the potential for clinical translation of these cells as a new class of stem cell therapy for autoimmune disease, organ transplantation and treatment of graft-versus-host disease (GVHD). Even though the mechanism underlying these immunosuppressive effects of MSCs has not been clearly defined, their immunosuppressive properties are already being exploited in the clinical setting. Most of these early clinical studies are investigating the effect of MSCs in suppressing GVHD after allogenenic hematopoietic stem cell transplantation (HSCT). Additional studies, mostly in animal models, are being conducted in solid organ transplantation, such as: heart, renal, liver and skin. While the early results of these studies are conflicting, the potential for clinical benefit remains high and further studies are warranted in order to discover the best methods and settings for consistent clinical results. MSCs have opened a series of opportunities for researchers in the areas of transplantation and autoimmune disease. While it is important not to overestimate the potential therapeutic effects of MSCs, and well-designed preclinical trials should be done before clinical use.

Effect of small extracellular vesicles derived from IL-10-overexpressing mesenchymal stem cells on experimental autoimmune uveitis

BACKGROUND

Autoimmune uveitis is a sight-threatening intraocular inflammation mainly caused by immune dysregulation. The development of safe and effective therapeutic approaches is urgently needed. Small extracellular vesicles (sEVs) derived from mesenchymal stem cells (MSCs) have been demonstrated to inhibit autoimmune responses; however, the immunosuppressive effect of MSC-sEVs is too weak for clinical transfer. In the current study, we investigated the therapeutic effect of IL-10-overexpressing MSC-sEVs (sEV-IL10) on experimental autoimmune uveitis (EAU) and studied the underlying mechanism.

METHODS

Mice were randomly grouped and received a single tail vein injection of different sEVs (50 μg) or PBS on day 11 post-immunization. The clinical and histological scores were graded, and the percentage of T helper cell was measured. To investigate the effect of sEVs on the proliferation of T-cells and the differentiation of Th1, Th17 and Treg cells, T-cells were cocultured with sEVs under the corresponding culture conditions. After labeled with PKH-26, sEVs were traced both in vivo and in vitro.

RESULTS

Compared with normal or vector sEV-treated groups, mice in the sEV-IL10-treated group had lower clinical and histological scores with lower percentages of Th1 and Th17 cells in the eyes and higher percentages of Treg cells in the spleen and draining lymph nodes (LN). Furthermore, sEV-IL10 enhanced the suppressive effect of MSC-sEVs on the proliferation of T-cells and differentiation of Th1 and Th17 cells, whereas upregulated the differentiation of Treg cells. Both in vivo and in vitro experiments demonstrated that MSC-sEVs were rapidly enriched in target tissues and internalized by T-cells.

CONCLUSION

These results suggested that sEV-IL10 effectively ameliorates EAU by regulating the proliferation and differentiation of T-cells, indicating sEVs as a potential novel therapy for autoimmune uveitis or other autoimmune diseases.

Proteomic analysis of aqueous humor in patients with pathologic myopia

Complications from pathologic myopia (PM) are a major cause of visual impairment and blindness. However, an efficient clinical therapeutic strategy for PM is still lacking. The aim of this study was to quantitatively compare the proteomic profiles of aqueous humor between PM and non-PM cataract patients. Twenty aqueous humor samples from each group were analyzed with label-free quantitative proteomic analysis to identify the differentially expressed proteins for function enrichment analyses and protein-protein interaction network construction. Hub protein was validated with ELISA using an independent cohort consisting of 20 samples from each group and its receiver operating characteristic (ROC) curve analysis was conducted. A total of 583 proteins were identified and 101 proteins were found to be differentially expressed, including 63 up-regulated proteins and 38 down-regulated proteins. The bioinformatics analysis suggested that PM is closely associated with immunity and inflammation interactions, and remodeling of extracellular matrix. Apolipoprotein A-I (ApoA1) was enriched as the hub protein of the network with the highest score, degree and centrality. ROC analysis showed that ApoA1 could distinguish PM from controls with an area under the curve of 0.963 (p < 0.001). The findings could provide potential clues for further study on the molecular mechanisms and developing new treatments for PM, especially related to immunity and inflammation interactions. ApoA1 may be a potential key protein and therapeutic target in human PM. SIGNIFICANCE: It is important and urgent to discover the mechanisms of pathologic myopia (PM) to inhibit its progression. This study applied the quantitative proteomic analysis to study aqueous humor from patients with or without PM, aiming to discover dysregulated proteins related to PM. Our results suggested that those dysregulated proteins are closely associated with immunity and inflammation interactions, and remodeling of extracellular matrix. The findings from this study could provide potential clues for further research on the molecular mechanisms and developing new treatments for PM, especially related to immunity and inflammation. ApoA1 may be a potential key protein and therapeutic target in human PM.