Biopotency and surrogate assays to validate the immunomodulatory potency of extracellular vesicles derived from mesenchymal stem/stromal cells for the treatment of experimental autoimmune uveitis

Extracellular vesicles (EVs) derived from mesenchymal stem/stromal cells (MSCs) have been recognized as promising cytotherapeutics due to their demonstrated immunomodulatory effects in various preclinical models. The immunomodulatory capabilities of EVs stem from the proteins and genetic materials they carry from parent cells, but the cargo contents of EVs are significantly influenced by MSC tissues and donors, cellular age and culture conditions, resulting in functional variations. However, there are no surrogate assays available to validate the immunomodulatory potency of MSC-EVs before in vivo administration. In previous work, we discovered that microcarrier culture conditions enhance the immunomodulatory function of MSC-EVs, as well as the levels of immunosuppressive molecules such as TGF-β1 and let-7b in MSC-EVs. Building on these findings, we investigated whether TGF-β1 levels in MSC-EVs could serve as a surrogate biomarker for predicting their potency in vivo. Our studies revealed a strong correlation between TGF-β1 and let-7b levels in MSC-EVs, as well as their capacity to suppress IFN-γ secretion in stimulated splenocytes, establishing biopotency and surrogate assays for MSC-EVs. Subsequently, we validated MSC-EVs generated from monolayer cultures (ML-EVs) or microcarrier cultures (MC-EVs) using murine models of experimental autoimmune uveoretinitis (EAU) and additional in vitro assays reflecting the Mode of Action of MSC-EVs in vivo. Our findings demonstrated that MC-EVs carrying high levels of TGF-β1 exhibited greater efficacy than ML-EVs in halting disease progression in mice with EAU as well as inducing apoptosis and inhibiting the chemotaxis of retina-reactive T cells. Additionally, MSC-EVs suppressed the MAPK/ERK pathway in activated T cells, with treatment using TGF-β1 or let-7b showing similar effects on the MAPK/ERK pathway. Collectively, our data suggest that MSC-EVs directly inhibit the infiltration of retina-reactive T cells toward the eyes, thereby halting the disease progression in EAU mice, and their immunomodulatory potency in vivo can be predicted by their TGF-β1 levels.

The Yin and Yang of non-immune and immune responses in meibomian gland dysfunction

Meibomian gland dysfunction (MGD) is a leading cause of dry eye disease and one of the most common ophthalmic conditions encountered in eye clinics worldwide. These holocrine glands are situated in the eyelid, where they produce specialized lipids, or meibum, needed to lubricate the eye surface and slow tear film evaporation - functions which are critical to preserving high-resolution vision. MGD results in tear instability, rapid tear evaporation, changes in local microflora, and dry eye disease, amongst other pathological entities. While studies identifying the mechanisms of MGD have generally focused on gland obstruction, we now know that age is a major risk factor for MGD that is associated with abnormal cell differentiation and renewal. It is also now appreciated that immune-inflammatory disorders, such as certain autoimmune diseases and atopy, may trigger MGD, as demonstrated through a T cell-driven neutrophil response. Here, we independently discuss the underlying roles of gland and immune related factors in MGD, as well as the integration of these two distinct mechanisms into a unified perspective that may aid future studies. From this unique standpoint, we propose a revised model in which glandular dysfunction and immunopathogenic pathways are not primary versus secondary contributors in MGD, but are fluid, interactive, and dynamic, which we likened to the Yin and Yang of MGD.

Involvement of Angiopoietin 2 and vascular endothelial growth factor in uveitis

PURPOSE

Angiopoietin (Ang) 2 is released from vascular endothelial cells by the stimulation of vascular endothelial growth factor (VEGF)A. Ang2 increases the expression of leukocyte adhesion molecules on endothelial cells via nuclear factor κB. The aim of this study was to evaluate the effects of Ang2 and VEGFA on ocular autoimmune inflammation.

METHODS

We measured the concentrations of Ang2 and VEGFA in vitreous samples among patients with uveitis. Vitreous samples were collected from 16 patients with idiopathic uveitis (uveitis group) and 16 patients with non-inflammatory eye disease (control group). Experimental autoimmune uveoretinitis (EAU) was induced in B10.BR mice with a human interphotoreceptor retinoid-binding protein-derived peptide. The retinochoroidal tissues of the EAU mice were removed, and the mRNA levels of Ang2 and VEGFA were examined. EAU mice treated with anti-Ang2, anti-VEGFA, a combination of anti-Ang2 and anti-VEGFA, anti-Ang2/VEGFA bispecific, or IgG control antibodies were clinically and histopathologically evaluated.

RESULTS

The protein levels of Ang2 and VEGFA were significantly higher in the vitreous samples of patients with uveitis than in controls (P<0.05). The retinochoroidal mRNA levels of Ang2 and VEGFA were significantly upregulated in EAU mice compared to controls (n = 6, P<0.05). Although there was no significant difference, treatment with anti-VEGFA antibody reduced the clinical and histopathological scores. However, treatment with anti-Ang2 antibody reduced the clinical and histopathological scores (n = 18-20, P<0.05). Furthermore, these scores were further decreased when treated by inhibiting both Ang2 and VEGFA.

CONCLUSIONS

Based on these results, VEGFA and Ang2 were shown to be upregulated locally in the eye of both uveitis patients and models of uveitis. Dual inhibition of Ang2 and VEGFA is suggested to be a new therapeutic strategy for uveitis.

The Role of Adenosine in γδ T-Cell Regulation of Th17 Responses in Experimental Autoimmune Uveitis

Autoimmune diseases caused by T cells can arise from either T-helper 1 (Th1) or T-helper 17 (Th17)-type pathogenic T cells. However, it is unclear whether these two T-cell subsets are influenced by distinct pathogenic factors and whether treatments that are effective for Th1 responses also work for Th17 responses. To compare these two pathogenic responses, we conducted a systematic analysis in a mouse model of experimental autoimmune uveitis (EAU) to identify the factors that promote or inhibit each response and to determine their responses to various treatments. Our study found that the two types of pathogenic responses differ significantly in their pathological progressions and susceptibility to treatments. Specifically, we observed that extracellular adenosine is a crucial pathogenic molecule involved in the pathogenicity of inflammation and T-cell reactivity and that reciprocal interaction between adenosine and gamma delta (γδ) T cells plays a significant role in amplifying Th17 responses in the development of autoimmune diseases. The potential effect of targeting adenosine or adenosine receptors is analyzed regarding whether such targeting constitutes an effective approach to modulating both γδ T-cell responses and the pathogenic Th17 responses in autoimmune diseases.

The role of C5a receptors in autoimmunity

The complement system is an essential component of the innate immune response and plays a vital role in host defense and inflammation. Dysregulation of the complement system, particularly involving the anaphylatoxin C5a and its receptors (C5aR1 and C5aR2), has been linked to several autoimmune diseases, indicating the potential for targeted therapies. C5aR1 and C5aR2 are seven-transmembrane receptors with distinct signaling mechanisms that play both partially overlapping and opposing roles in immunity. Both receptors are expressed on a broad spectrum of immune and non-immune cells and are involved in cellular functions and physiological processes during homeostasis and inflammation. Dysregulated C5a-mediated inflammation contributes to autoimmune diseases such as rheumatoid arthritis, systemic lupus erythematosus, multiple sclerosis, epidermolysis bullosa acquisita, antiphospholipid syndrome, and others. Therefore, targeting C5a or its receptors may yield therapeutic innovations in these autoimmune diseases by reducing the recruitment and activation of immune cells that lead to tissue inflammation and injury, thereby exacerbating the autoimmune response. Clinical trials focused on the inhibition of C5 cleavage or the C5a/C5aR1-axis using small molecules or monoclonal antibodies hold promise for bringing novel treatments for autoimmune diseases into practice. However, given the heterogeneous nature of (systemic) autoimmune diseases, there are still several challenges, such as patient selection, optimal dosing, and treatment duration, that require further investigation and development to realize the full therapeutic potential of C5a receptor inhibition, ideally in the context of a personalized medicine approach. Here, we aim to provide a brief overview of the current knowledge on the function of C5a receptors, the involvement of C5a receptors in autoimmune disorders, the molecular mechanisms underlying C5a receptor-mediated autoimmunity, and the potential for targeted therapies to modulate their activity.

CD83+ B cells alleviate uveitis through inhibiting DCs by sCD83

Soluble CD83 (sCD83) exerts immunosuppressive functions in many autoimmune diseases, including experimental autoimmune uveitis (EAU), but the cells and mechanisms involved are unclear. This study showed that CD83+ B cells were the main sources of sCD83. They alleviated the symptoms of EAU and decreased the percentage of T cells and DCs in the eyes and lymph nodes. These CD83+ B cells decreased IL-1β, IL-18 and IFN-γ secretion by DCs through sCD83. sCD83 interacted with GTPase Ras-related protein (Rab1a) in DCs to promote Rab1a accumulation in autolysosomes and inhibit mTORC1 phosphorylation and NLRP3 expression. Hence, CD83+ B cells play a regulatory role in EAU by secreting sCD83. The lack of regulation of CD83+ B cells might be an important factor leading to hyperimmune activation in patients with autoimmune uveitis. CD83+ B cells suppress activated DCs in uveitis, indicating the potential therapeutic role of CD83+ B cells in uveitis.

Combined Therapy of Experimental Autoimmune Uveitis by a Dual-Drug Nanocomposite Formulation with Berberine and Dexamethasone

Purpose

Autoimmune uveitis is a kind of sight-threatening ocular and systemic disorders. Recent treatments on autoimmune uveitis still remain many limitations due to extreme complexity and undetermined pathogenesis. In this study, a novel dual-drug nanocomposite formulation is developed to treat experimental autoimmune uveitis by a combined and sustained therapy method.

Methods

The dual-drug nanocomposite formulation is constructed by integrating berberine (BBR)-loaded mesoporous silica nanoparticles (MSNs) into dexamethasone (DEX)-loaded thermogel (BBR@MSN-DEX@Gel). The BBR@MSN-DEX@Gel is characterized by transmission electron microscopy, dynamic light scattering, Fourier transform infrared spectrometer and rheometer. The in vitro drug release profile, cytotoxicity and anti-inflammation effectiveness of BBR@MSN-DEX@Gel on lipopolysaccharide-stimulated human conjunctival epithelial cells are investigated. After the in vivo drug release profile and biosafety of the dual-drug nanocomposite formulation are confirmed, its treatment effectiveness is fully assessed based on the induced experimental autoimmune uveitis (EAU) Lewis rat's model.

Results

The dual-drug nanocomposite formulation has good injectability and thermosensitivity, suitable for administration by an intravitreal injection. The BBR@MSN-DEX@Gel has been found to sustainably release both drugs for up to 4 weeks. The carrier materials have minimal in vitro cytotoxicity and high in vivo biosafety. BBR@MSN-DEX@Gel presents obviously anti-inflammatory effectiveness in vitro. After administration of BBR@MSN-DEX@Gel into Lewis rat's eye with EAU by an intravitreal injection, the nanocomposite formulation significantly suppresses inflammatory reaction of autoimmune uveitis via a dual-drug combined and sustained therapy method, compared with the equivalent dose of single-component formulations.

Conclusion

BBR@MSN-DEX@Gel serves as a promising dual-drug nanocomposite formulation for future treatment of autoimmune uveitis.

Systemic Expression of Rat Soluble Retinal Antigen Induces Resistance to Experimental Autoimmune Uveoretinitis

To assess the role of sequestration in the maintenance of the immune privilege of the retina, retrovirally mediated gene transfer was used to express a defined, specific retinal autoantigen, rat soluble retinal Ag (S-Ag), in a systemic, nonsequestered manner. In this study we report the stable, long term transduction of rat retinal S-Ag into PBMC. Tolerance to S-Ag was assayed by challenging the S-Ag chimeric animals with S-Ag peptides in CFA and monitoring the time course and severity of experimental autoimmune uveoretinitis (EAU). The resulting data showed a correlation between the incidence of S-Ag chimerism and the loss of susceptibility to EAU. The development of resistance to EAU induction supports the hypothesis that Ag sequestration contributes to retinal immune privilege.

Pregnancy Ameliorates Induction and Expression of Experimental Autoimmune Uveitis

Female patients suffering from autoimmune uveitis are reported to experience a temporary remission during pregnancy. Experimental autoimmune uveitis (EAU) is a model for human uveitis. Here we examine the effect of pregnancy on the development of EAU and its associated immunological responses. Susceptible C57BL/6 mice were immunized with interphotoreceptor retinoid-binding protein (IRBP). EAU scores and Ag-specific responses were evaluated 21 days later. Mice immunized during pregnancy developed significantly less EAU than nonpregnant controls. Their lymph node cells and splenocytes produced a distinct pattern of cytokines in response to IRBP: reduced IFN-γ and IL-12 p40, but unchanged levels of TNF-α, IL-4, IL-5, and IL-10. Anti-IRBP Ab isotypes revealed an up-regulation of IgG1, indicating a possible Th2 bias at the humoral level. Ag-specific proliferation and delayed hypersensitivity, as well as mitogen-induced IFN-γ production, remained undiminished, arguing against an overall immune deficit. Interestingly, pregnant mice that received an infusion of IRBP-primed lymphoid cells from nonpregnant donors also developed reduced EAU, suggesting that pregnancy suppresses not only the generation, but also the function of mature uveitogenic effector T cells. Pregnant mice at the time of immunization exhibited elevated levels of TGF-β, but not of IL-10, in the serum. We suggest that protection from EAU during pregnancy is due primarily to a selective reduction of Ag-specific Th1 responses with only marginal enhancement of Th2 function, and that these effects may in part be secondary to elevated systemic levels of TGF-β.

Endogenous IL-12 Is Required for Induction and Expression of Experimental Autoimmune Uveitis

Experimental autoimmune uveitis (EAU) has been associated with a Th1 response. However, in IFN-γ-deficient mice, EAU develops in the context of an effector response having Th2-like elements, and administration of IL-12 to mice immunized for EAU induction can be protective. We, therefore, investigated whether endogenous IL-12 is required for development of EAU. IL-12 p40-deficient mice (12KO) were resistant to EAU induced with the uveitogenic retinal Ag interphotoreceptor retinoid binding protein (IRBP). Delayed hypersensitivity to IRBP was marginally reduced, whereas Ag-specific proliferation was enhanced. Primed lymphocytes of wild-type (wt) mice, cultured with IRBP, produced a Th1-like cytokine profile and transferred EAU to syngeneic wt recipients. Interestingly, the same cells were inefficient in transferring EAU to 12KO recipients, unless IL-12 was included in the culture. Primed cells of the 12KO mice produced a Th2-like cytokine profile and failed to transfer EAU. However, when IL-12 was added to the culture, 12KO cells produced large amounts of IFN-γ and transferred EAU to naive 12KO recipients. We conclude that resistance to EAU of 12KO mice is not due to an inherent inability of these mice to develop ocular disease. Despite an apparent similarity in Ag-specific cytokine responses to IFN-γ-deficient mice, 12KO mice have inhibited generation of uveitogenic effector cells, a situation that can be reversed even after priming, by adding exogenous IL-12 ex vivo. Lastly, the diminished ability of primed wt lymphocytes to induce EAU in 12KO mice indicates a role for endogenous IL-12 in the efferent phase of disease expression that is distinct from its role during Ag priming.