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.

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.

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.

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.

Characteristics of syphilitic uveitis in northern China

Background

To describe the characteristics of patients with syphilitic uveitis in northern China.

Methods

A case series of 21 patients (33 eyes) diagnosed with syphilitic uveitis from 2011 to 2016 at a tertiary center in northern China was retrospectively analyzed.

Results

Twenty-one patients (33 eyes) were diagnosed as syphilitic uveitis. Posterior segment involvement was found in 32 eyes (97.0%). Vitreous haze, neuroretinitis, and posterior placoid chorioretinitis were mainly found in patients with a relatively short duration of the disease, while diffuse chorioretinitis, pseudoretinitis pigmentosa, cystoid macular edema, and epiretinal membrane were found in patients with relatively long duration of ocular involvement. A low best-corrected visual acuity (P = 0.022) and a delay of syphilis treatment (P < 0.001) were associated with a significantly worse visual outcome.

Conclusions

Syphilitic uveitis should be included in the differential diagnosis of any form of posterior ocular inflammation. The pattern of ocular involvement may change with the disease progression.

Therapeutic effects of mesenchymal stem cells administered at later phase of recurrent experimental autoimmune uveitis

AIM

To test the therapeutic effects of delayed treatment of mesenchymal stem cells (MSCs) in recurrent experimental autoimmune uveitis (rEAU).

METHODS

The efficacy of different regimens of MSC administration in rEAU were tested by evaluation of clinical and pathological intraocular inflammation, as well as retinal structural and functional integrity using optical coherence tomography (OCT) and electroretinogram (ERG). The retinal sections were also immunostained with antibodies to glial fibrillary acidic protein (GFAP) and rhodopsin (RHO).

RESULTS

Delayed treatment of MSCs effectively alleviated the severity of intraocular inflammation with relative intact of outer retinal structure and function. Moreover, double therapies with longer interval led to an even better clinical evaluation, as well as a trend of decrease in relapse and amelioration of retinal function. MSC therapies also effectively reduced GFAP expression and increased RHO expression in the retina.

CONCLUSION

MSC administration can effectively treat developed diseases of rEAU, and multiple therapies can provide additional therapeutic benefits.

Rapamycin ameliorates experimental autoimmune uveoretinitis by inhibiting Th1/Th2/Th17 cells and upregulating CD4+CD25+ Foxp3 regulatory T cells

AIM

To determine the effects of rapamycin on experimental autoimmune uveoretinitis (EAU) and investigate of role of rapamycin on T cell subsets in the disease.

METHODS

EAU was induced in rats using peptides 1169 to 1191 of the interphotoreceptor binding protein (IRBP). Rapamycin (0.2 mg/kg/d) was administrated by intraperitoneal injection for a consecutive 7d after immunization. Th1/Th2/Th17 cytokines, TGF-β1, and IL-6 produced by lymphocyteswere measured by ELISA, while Th17 cells and CD4+CD25+ regulatory T cells (Tregs) from rat spleen were detected by flow cytometry.

RESULTS

Intraperitoneal treatment immediately after immunization dramatically ameliorated the clinical course of EAU. Clinical responses were associated with reduced retinal inflammatory cell infiltration and tissue destruction. Rapamycin induced suppression of Th1/Th2/Th17 cytokines, including IFN-γ, IL-2, IL-17, IL-4, and IL-10 release from T lymphocytes of EAU rats, in vitro. Rapamycin also significantly increased TGF-β1 production but had no effect on IL-6 productionof T lymphocytes from EAU rats in vitro. Furthermore, rapamycin decreased the ratio of Th17 cells/CD4+T cells and upregulated Tregs in EAU, as detected by flow cytometry.

CONCLUSION

Rapamycin effectively interferes with T cell mediated autoimmune uveitis by inhibiting antigen-specific T cell functions and enhancing Tregs in EAU. Rapamycin is a promising new alternative as an adjunct corticosteroid-sparing agent for treating uveitis.

Neuroprotection of retinal cells by Caffeic Acid Phenylethyl Ester（CAPE) is mediated by mitochondrial uncoupling protein UCP2

Oxidative stress due to mitochondrial produced reactive oxygen species is a major cause of damage seen in many retinal degenerative diseases. Caffeic acid phenylethyl ester （CAPE） is protective agent in multiple tissues and is reported to have anti-oxidant properties. Systemically applied CAPE protected retinal ganglion cells from ischemic injury induced by increased intraocular pressure. CAPE provided complete protection for ARPE19 retinal pigment epithelial cells against tert-butyl hydrogen peroxide and reduced both basal and LPS-stimulated ROS production. The major effect of CAPE was mediated by the mitochondrial uncoupling protein UCP2 since both pharmacological inhibition of UCP2 and siRNA-induced knockdown removed the ability of CAPE to block ROS production. Based on common structural features, CAPE may be acting as a mimetic of the natural UCP2 homeostatic regulator 4-hydroxy-2-nonenal. CAPE may provide a valuable tool to treat oxidative stress-related damage in retinal and other degenerative diseases.

[Experimental research on mesenchymal stem cells (MSCs) therapy for autoimmune uveitis]

Autoimmune uveitis is a major cause of visual disability. Treatment of chronic and recurrent uveitis can be extremely difficult, as various complications of it could impede the long-term usage of corticosteroids and immunosuppressants. Mesenchymal stem cells are of both immunosuppressive and neurotrophic effect, and can enhance the antimicrobial ability of the body, thereby hold great promise in clinical application for treating uveitis. (Chin J Ophthalmol, 2018, 54: 712-715).