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S. J. McKinnon, L. T. Kasmala, A. L. Horman, F. -. L. Silver; Double Knockout of TNF Receptors 1 and 2 Prevents RGC Death in a Mouse Glaucoma Model. Invest. Ophthalmol. Vis. Sci. 2009;50(13):4049.
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© ARVO (1962-2015); The Authors (2016-present)
Differential effects of individual knockout (KO) of TNFR1 and TNFR2 on RGC survival have previously been shown using a short-term laser model of mouse glaucoma. Using the Morrison model of chronic ocular hypertension (COH) in mice, we sought to investigate the role of TNF signaling in adult RGCs exposed to long-term IOP elevation.
We obtained TNFR1/2 double KO mice and age-matched B6129SF2/J mice from Jackson Labs. TNFR1/2 KO mice display decreased inflammatory responses and increased circulating TNF levels. 21 TNFR1/2 KO and 25 B6129SF2/J mice were treated in the right eye to induce COH by the Morrison method of limbal injection of hypertonic (1.5 M) saline. IOP was recorded weekly for 27 weeks by TonoLab rebound tonometry (Colonial Medical Supply). After sedation, treated and control eyes were enucleated, and optic nerve cross-sections stained with toluidine blue. Axon counts were obtained in a masked fashion using the KS400 imaging system (Zeiss), and % axon survival (treated/control axon counts) for each mouse was calculated. % axon survivals for the two groups were tested for significance with Student’s t-test.
13 TNFR1/2 KO and 17 B6129SF2/J mice met inclusion criteria, yielding a conversion rate of 65% (30/46). Mean IOP integrals for the TNFR1/2 KO and B6129SF2/J groups were 461 and 412 mm-days, respectively. 2-tailed Student’s t-test showed no significant difference between the two groups in IOP integral distribution (P=0.97), indicating equivalent levels of IOP exposure between the two groups. The two groups showed average axon counts of: TNFR1/2 KO: 25462 ± 8270 (right eye; mean ± SD) and 27544 ± 7069 (left eye); B6129SF2/J: 17974 ± 9142 (right eye) and 31803 ± 8100 (left eye). The two groups showed average % axon survivals (treated/control axon counts) of: TNFR1/2 KO: 94.4% ± 28.4% (mean ± SD); B6129SF2/J: 56.4% ± 24.7%. 2-tailed Student’s t-test showed a significant difference between the two groups in % axon survival (P=0.0005).
In a mouse model of COH, double knockout of TNF receptors 1 and 2 provided robust neuroprotection when compared to wild-type controls. Similar experiments using individual TNFR1 and R2 mice are ongoing to determine the relative contributions of each of these receptors to RGC death caused by exposure to long-term IOP elevation.
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