Are cytokine patterns in aqueous humour useful in distinguishing corneal graft rejection from opacification due to herpetic stromal keratitis?

Role of Human Corneal Stroma-Derived Mesenchymal-Like Stem Cells in Corneal Immunity and Wound Healing

Corneal tissue regeneration is of crucial importance for maintaining normal vision. We aimed to isolate and cultivate human corneal stroma-derived mesenchymal stem-like cells (CSMSCs) from the central part of cadaver corneas and study their phenotype, multipotency, role in immunity and wound healing. The isolated cells grew as monolayers in vitro, expressed mesenchymal- and stemness-related surface markers (CD73, CD90, CD105, CD140b), and were negative for hematopoietic markers as determined by flow cytometry. CSMSCs were able to differentiate in vitro into fat, bone and cartilage. Their gene expression profile was closer to bone marrow-derived MSCs (BMMSCs) than to limbal epithelial stem cells (LESC) as determined by high-throughput screening. The immunosuppressive properties of CSMSCs were confirmed by a mixed lymphocyte reaction (MLR), while they could inhibit proliferation of activated immune cells. Treatment of CSMSCs by pro-inflammatory cytokines and toll-like receptor ligands significantly increased the secreted interleukin-6 (IL-6), interleukin-8 (IL-8) and C-X-C motif chemokine 10 (CXCL-10) levels, as well as the cell surface adhesion molecules. CSMSCs were capable of closing a wound in vitro under different stimuli. These cells thus contribute to corneal tissue homeostasis and play an immunomodulatory and regenerative role with possible implications in future cell therapies for treating sight-threatening corneal diseases.

Total protein concentration and T-cell suppression activity of aqueous humour before and after penetrating keratoplasty

PURPOSE

We wished to determine whether immune privilege parameters assayed in aqueous humour (AqH) are relevant to the fate of penetrating keratoplasty (PK) in humans.

METHODS

AqH was collected in 28 patients before PK (prospective cohort), in 6 patients with no history of graft rejection undergoing cataract surgery after PK (acceptors), in another 6 patients undergoing treatment of an acute endothelial immune reaction (rejectors), and in 65 controls undergoing uncomplicated cataract extraction. AqH was tested for total protein concentration and the ability to suppress T-cell activation.

RESULTS

AqH protein concentrations of acceptors and rejectors post-PK were elevated (2.7 ± 0.8 and 2.7 ± 0.7 mg/ml, respectively) compared with pre-PK AqH level and cataract controls (1.0 ± 0.1 mg/ml, P = 0.01). All AqH samples suppressed T-cell activation, irrespective of source and timing of AqH removal.

CONCLUSION

Assays of immune privilege markers in AqH suggest that PK surgery may result in a sustained loss of integrity of the blood-aqueous barrier. Although trends were evident, values of immune privilege markers determined pre- and post-PK were not statistically significantly different between the study groups. However, further prospective studies determining additional immune privilege markers have to be conducted in order to find out whether these markers might serve as predictive parameters for immune reactions following PK.

Simultaneous quantification of 17 immune mediators in aqueous humour from patients with corneal rejection

PURPOSE

To simultaneously quantitate and compare the concentrations of 17 immune mediators: (1) the cytokines interleukin-1beta, IL-2, IL-4, IL-5, IL-6, IL-7, IL-10, IL-12p70, IL-13, IL-17, tumour necrosis factor-alpha, interferon-gamma; (2) the growth factors granulocyte-monocyte colony-stimulating factor (GM-CSF) and granulocyte colony-stimulating factor (G-CSF), and (3) the chemokines CXCL-8, monocyte chemoattractant protein-1, and macrophage inflammatory protein-1beta in aqueous humour from patients with corneal rejection and patients with a non-inflammatory condition in the anterior chamber.

METHODS

Aqueous humour was obtained by paracentesis of the anterior chamber in 14 patients with corneal rejection, three patients with cataract and six patients with Fuchs' endothelial dystrophy. Simultaneous quantitation of 17 mediators in 25 micro l aqueous humour from each patient was performed by employing a highly sensitive Luminex 100 multiplex array assay.

RESULTS

All 17 immune mediators were detected in aqueous humour from rejection patients. The ranges of the immune mediators were determined. The immune mediators were significantly increased in aqueous humour from rejection patients compared with that from other patients.

CONCLUSIONS

The Luminex 100 multiplex array assay is very efficient in simultaneous quantitation of multiple immune mediators in small volumes of aqueous humour. A total of 17 immune mediators were increased in aqueous humour from rejection patients. This underlines the complex immunological interactions of the rejection process.

Alpha-1--antitrypsin in aqueous humour from patients with corneal allograft rejection

PURPOSE

To investigate the presence and concentration of alpha1-antitrypsin in aqueous humour at the time of corneal rejection and to compare results obtained from patients with reversible and irreversible rejection.

METHODS

Samples of aqueous humour were obtained from 17 patients with acute corneal endothelial allograft rejection. The presence of alpha1-antitrypsin in aqueous humour was confirmed by immunoblotting and measured employing a sandwich ELISA. Total protein concentrations in aqueous humour were measured using Bradford's method. The outcome of corneal rejection episodes was determined 1 month after diagnosing corneal rejection and described as reversible or irreversible rejection.

RESULTS

alpha1-antitrypsin was detected in aqueous humour. Patients with reversible rejection had significantly higher alpha1-antitrypsin concentration than patients with irreversible rejection (p = 0.044). There was no significant difference in total protein concentrations (p = 0.745), and no correlation was found between alpha1-antitrypsin and total protein concentrations (p = 0.368).

CONCLUSIONS

alpha1-antitrypsin in aqueous humour seems to signal a favourable outcome of corneal rejection. The possible mechanism is discussed.

Soluble CD163 and interleukin-6 are increased in aqueous humour from patients with endothelial rejection of corneal grafts

PURPOSE

To evaluate soluble CD163 (sCD163) as a new marker of macrophage activity in aqueous humour from patients with corneal rejection and to investigate correlations between sCD163, the CD163 inducing interleukin-6 (IL-6), and albumin; to investigate whether increases in sCD163 and IL-6 levels in aqueous humour were results of intra- or extraocular production, and to investigate the impact of sCD163 and IL-6 levels on graft outcome.

METHODS

Aqueous humour was obtained from 19 patients with endothelial rejection of corneal grafts, seven cataract patients and five cataract patients with uncomplicated corneal grafts. The presence of sCD163 was investigated by immunoprecipitation and immunoblotting. The concentrations of sCD163, IL-6 and albumin were measured by ELISA.

RESULTS

Soluble CD163 was detected in aqueous humour from patients with corneal rejection. Soluble CD163, IL-6 and albumin were significantly increased in aqueous humour from patients with corneal rejection when compared with control patients. When normalizing sCD163 and IL-6 with albumin, the differences between rejection patients and control groups became insignificant for sCD163 but remained significant for IL-6. Neither IL-6 nor sCD163 were related to the outcome of the corneal rejection.

CONCLUSIONS

Both sCD163 and IL-6 are present in high levels in aqueous humour from patients with rejection of corneal grafts. Our data suggest that IL-6 is produced locally, whereas sCD163 is at least partly derived from influx from plasma.

Proteomic analysis of aqueous humour from patients with acute corneal rejection

PURPOSE

To compare the basic proteomic composition of aqueous humour (AH) from patients with corneal rejection (patients) with AH from patients with cataract (controls).

METHODS

Aqueous humour was analysed for total protein concentration using Bradford's method and for protein composition using two-dimensional (2D) gel electrophoresis. Image analysis was used to detect protein spots in 2D gels that were increased by more than factor 2 in patients as compared with controls. Increased spots were identified by immunoblotting and mass spectrometry.

RESULTS

Aqueous humour from patients contained significantly higher total protein concentration than did AH from controls. A total of 31 spots were significantly increased in 2D gels from patients. The spots were derived from albumin, alpha1-antitrypsin, apolipoprotein J, cytokeratin type II, serin proteinase inhibitor and transthyretin. After correction of spot volumes by total protein concentrations, 10 spots derived from albumin, cytokeratin type II and alpha1-antitrypsin remained significantly increased.

CONCLUSION

The proteomic composition of AH differed significantly between patients and controls. The identified proteins suggest that the changes in AH are due to at least three different mechanisms: breakdown of the aqueous-blood barrier, enzymatic degradation, and liberation of locally synthesized proteins.

[Immunomodulation in penetrating keratoplasty. Current status and perspectives]

The immune privileged nature of the cornea contributes to the favourable outcome in corneal grafts. However, preventive measures are necessary to reduce allograft rejection particular in "high-risk" cases. Although corticosteroids are still a major component of our immunopharmacological armentarium, they might be supplemented by other more specific immunomodulating agents. The spectrum includes agents such as azathioprin, methotrexate or more specific calcineurin inhibitors affecting T-cells (cyclosporin A, FK506) and highly selective monoclonal antibodies directed against T-cell subpopulations and other targets. In order to better evaluate the risks and benefit of these agents, the properties of established and forthcoming agents are presented. In addition, this review attempts to address some new concepts of tolerance induction following penetrating keratoplasty.