Abstract
Purpose:
Mouse aqueous humor dynamics (AHD) have been studied by several laboratories, but there is no clear consensus. We hypothesize that strain/age differences may play a role. This study evaluated differences in AHD among younger and older age groups of several strains.
Methods:
A/J, BALB/cJ, C3H/HeJ, & C57-BL/6J mice (all ♀) were studied. Animals in each strain were divided into 2 cohorts (young, 2½-4½ mo; aged, 10-12 mo) (N=5-7/cohort). Baseline (BL) intraocular pressure (IOP) was measured (TonoLab). AHD parameters (outflow facility (C), episcleral venous pressure (Pe), aqueous humor formation (Fin), uveoscleral outflow (Fu)) were established (constant flow infusion).
Results:
BL IOP did not exhibit age-dependence, except in C57-BL/6J animals, which showed an age-related increase (13.90±0.25 vs 15.43±0.21 mmHg, P=0.00048). In other strains, BL IOP (young vs aged) was: 12.42±0.08 mmHg vs 12.56±0.10 mmHg (A/J), 11.35±0.11 mmHg vs 11.68±0.20 mmHg (BALB/cJ), 13.27±0.17 mmHg vs 13.65±0.09 mmHg (C3H/HeJ). Fu decreased with age in the BALB/cJ strain (0.066±0.022 μL/min vs. 0.011±0.007 μL/min, P=0.0055, ↓83%), the C3H/HeJ strain (0.109±0.028 μL/min vs 0.024±0.009 μL/min, P=0.015, ↓78%), the C57-BL/6J strain (0.080±0.022 μL/min vs 0.012±0.008 μL/min, P=0.013, ↓85%), and the A/J strain (0.12±0.048 μL/min vs. 0.036±0.031 μL/min, NS, ↓70%). Fin decreased with age in the A/J strain (0.202±0.035 vs 0.116±0.029 μL/min, P=0.047) and the C3H/HeJ strain (0.140±0.027 vs 0.065±0.006, P=0.021). Fu as % of Fin decreased with age in the BALB/cJ strain (37.41±10.24% vs 7.91±4.93%, P=0.038), the C3H/HeJ strain (71.17±8.59% vs 34.44±8.59%, P=0.029), the C57-BL/6J strain (52.66±13.66% vs 14.23±8.24%, P=0.033) and the A/J strain (53.93±14.51% vs 24.77±11.91%, NS). C in the BALB/cJ strain increased with age (0.039±0.005 vs 0.024±0.002 μL/min/mmHg, P=0.02). In C3H/HeJ and C57-BL/6J strains C trended towards an increase with age. Pe was (young vs aged): 6.56±0.12 mmHg vs 6.49±0.08 mmHg (A/J), 5.96±0.11 mmHg vs 5.99±0.03 mmHg (BALB/cJ), 8.52±0.09 mmHg vs 8.60±0.06 mmHg (C3H/HeJ), 8.73±0.16 mmHg vs. 8.88±0.08 mmHg (C57-BL/6J). Pe was not age dependent but was higher in pigmented animals.
Conclusions:
In mice, with age, Fu diminishes (70-85%), and Fin tends to diminish, as in humans and NHPs. C tends to increase with age as animals progress to early middle-life. There are also strain differences in Fu, IOP, and Pe in young and aged animals, and C and Fin in aged animals.