Ritter Group

Investigating the therapeutic effects of mesenchymal stromal cells and their secreted vesicles for local immunomodulation to prevent corneal graft rejection and ocular injury 

Researchers involved: Aoife Canning, Ellen Donohoe 

Corneal transplantation is the last option for patients suffering from serious ocular disease or injury (1). Topical corticosteroids with or without adjuvant immunosuppressant therapy remains the gold standard treatment for preventing corneal allograft rejection, however, patients are still highly susceptible to immune-mediated rejection. Therefore, novel therapies are urgently needed to improve the prognosis of corneal transplantation. 

Mesenchymal stromal cells’ (MSCs) therapeutic potential is associated with their ability to effectively modulate host repair responses and inflammation and their safety profile following administration to patients. We have recently shown that systemic administration of MSCs prolongs corneal allograft survival and promotes ocular surface regeneration (2, 3). Most pre-clinical and clinical studies administer MSCs systemically, however, this often requires high doses of cell numbers to achieve a therapeutic effect, which may lead to adverse side effects. In contrast, local application of MSCs may have the potential to exert local immunomodulatory effects, which may allow for the application of reduced cell numbers.  

Current research investigates if local (subconjunctival) administration of MSCs is able to promote corneal allograft survival and modulate ocular injury and inflammation. We also investigate if extracellular vesicles secreted from MSCs have therapeutic efficacy in these diseases and the mechanism of action.

Pre-activation or “licensing” of mesenchymal stromal cells for enhanced immunomodulation 

Researchers involved: Aoife Canning, Ellen Donohoe, Jiemin Wang 

Mesenchymal stromal cells (MSCs) are being extensively investigated in the context of immune modulation and suppression for the treatment of inflammatory disorders and for prolongation of allograft survival/tolerance induction in the setting of transplantation (2). It is now well accepted that in order to fully harness MSC suppressive activity, the cells must be activated or licensed. This may occur in vivo due to inflammation or be pre-induced in vitro prior to downstream use. Multiple factors have been tested in an attempt to increase MSC efficacy in this regard. We have investigated licensing of MSCs using pro-inflammatory cytokines TNF‐α, IFN‐γ and IL‐1β either singly or in the combinations IL‐1β + TNF‐α (4). Moreover, we have also investigated the effects of anti-inflammatory cytokine licensing using TGF- on MSC therapeutic efficacy, particularly in the context of MSC immunosuppressive capacity (5). We show that licensing of MSC with either pro- or anti-inflammatory cytokines significantly enhances their immunomodulatory capacity both in vitro and in vivo.  

Current research further investigates the mechanism of action, migration, survival and therapeutic efficacy of licensed MSC in other models of ocular inflammation and injury. 

Investigating the potential of extracellular vesicles secreted from mesenchymal stromal cells for intraocular inflammation (Uveitis) 

Researchers involved: Aoife Canning, Ellen Donohoe, Jiemin Wang  

Uveitis is a common ocular inflammatory disease and a leading cause of blindness both in the western world and in the Asia-Pacific region, accounting for 10% of the population with vision loss (6, 7). Current treatment options include corticosteroids and surgery; however, corticosteroid use in patients causes immunosuppression, leading to serious systemic and ocular side effects. Therefore, development of novel therapeutics is urgently required. 

Mesenchymal stromal cells (MSCs) are immunomodulatory cells with therapeutic effects in various immune-mediated diseases and have demonstrated improved wound healing when applied topically. In recent years, MSCs showed potential in treating uveitis. Evidence suggests T-lymphocytes, particularly Th1/Th17 subsets, are key mediators of tissue damage associated with Uveitis. Intraperitoneal injection of MSCs reduced incidence and severity of Endotoxin-induced uveitis (EIU) in mice by suppressing Th1/Th17 cell responses. Treatment with MSCs highlights less infiltration of immune cells and decreased production of Th1-secreted IFN-γ, resulting in reduced retinal damage in mice. Furthermore, data from the Ritter lab has shown that ‘licensed’ MSCs are highly suppressive to T cell proliferation and modulate corneal allograft rejection (5, 8). 

Although MSC-based cell therapy is being evaluated in various studies, the potential risks of cell-based therapies should not be under-estimated. Therapies derived from cells but devoid of cellular components would be a major breakthrough. Several studies have suggested that extracellular vesicles (EVs) mediate at least some of MSCs beneficial effects (for review see  (9, 10)). Preliminary data from the Ritter lab demonstrated that human MSC-derived EVs significantly enhanced the healing of alkali burn injury to the eye thereby indicating their therapeutic efficacy, however, their role in the treatment of Endotoxin-induced anterior Uveitis is unknown.  

Current research investigates the intraocular and subconjunctival administration of “licensed” MSC-EVs for therapeutic efficacy in pre-clinical models of uveitis.

Schematic MSC immunomodulation. (modified from Lynch et al., 2016) 

Development of a novel artificial cornea (Keratoprosthesis) for serious ocular injury 

Researchers involved: Dr. Elizabeth Moloney, Aoife Canning, Jack Schofield 

Data recorded from early 2000 suggests that approximately 50 million people worldwide are blind. The global data identified corneal diseases as the second most important cause of blindness today, behind cataract. Although corneal transplantation can often be performed successfully, some patients have a poor prognosis (e.g. patients with chemical burns or recurrent graft failure). Additionally, the demand for corneas greatly exceeds the supply in many parts of the world. Only 1% of affected patients receive donor corneal tissue. Nevertheless, its clinical utility is limited due to a severe shortage of high-quality donors. As an alternative to donor corneas, artificial corneas (also known as keratoprosthesis) have been developed. Keratoprosthetic devices consisting of a central optic and a biointegrating anchoring skirt have been developed to improve the limitations of prosthetic corneal transplantation. 

The AlphaCor keratoprosthesis is a biocompatible, flexible, one-piece synthetic cornea based on poly(2-hydroxyethyl methacrylate) (PHE MA) that has a peripheral region with interconnecting pores allowing biointegration with the surrounding corneal tissue (11-13). However, the persistence of inflammatory cells compared to the absence of successful biointegration suggests that the healing process is somewhat protracted. Therefore, new research needs to be undertaken to improve the success rate of the AlphaCor device. 

For this project, a novel, improved version of the AlphaCor keratoprosthesis, consisting of a central optic and a biointegrating anchoring skirt, has been developed to improve the limitations of prosthetic corneal transplantation. Current research involves the in vitro and pre-clinical testing of the novel AlphaCor keratoprosthesis for enhanced cell survival and biointegration. 

Artificial cornea. Courtesy of Dr. Elizabeth Moloney 

TGF-β MSCs prolong corneal allograft survival 

(A) Timeline of events and injection strategy used to assess the ability of MSCs with or without TGF-β pre-activation to prolong corneal allograft survival. (B) Kaplan-Meier survival curve analysis of allogeneic transplant controls (black line) (n=12), corneal allograft + MSCs (dashed green line) (n=14) and corneal allograft + TGF-βMSCs (dashed blue line) (n=13). (C) Opacity and (D) neovascularization scores up to POD 40 (n=12-14 with numbers per treatment group the same as in part B). (E) Opacity and neovascularization scores were compared between the three groups at POD 19 (corresponding to the average timepoint of rejection in allogeneic transplant controls) (n=12-14 with numbers per treatment group the same as in part B). (F) Representative light microscope images of corneal transplants taken at multiple time-points over the period of observation. Error bars: mean ± SD. *p<0.05, **p<0.01, ***p<0.001. One-way ANOVA, Tukey’s Post Hoc test (n=12-14). Modified from Lynch et al., 2020.

Please see here for research publications.