HEART-SPECIFIC CSRP3 DELETION INDUCES CHRONIC CARDIORENAL SYNDROME: ESTABLISHMENT OF A NOVEL MOUSE MODEL

Chronic cardiorenal syndrome (cardiorenal syndrome type 2: CRS2) refers to a condition in which chronic kidney disease is caused by chronic heart failure. Reportedly, 20-60% of heart failure patients have some form of renal dysfunction, which leads to further cardiovascular disease and worsening prognosis. Although several animal models have been used for the investigation of the pathophysiology of CRS2, technical difficulty and poor reproducibility of kidney damage have been pointed out. Cysteine and glycine-rich protein 3 (CSRP3) is known to be a key factor in the development and regeneration of cardiomyocytes. We generated a tamoxifen-inducible, heart-specific CSRP3 knockout (iCSRP3KO) mouse and evaluated its potential utility as an experimental CRS2 model.

CSRP3 flox/flox mice were bred to mice expressing tamoxifen-dependent Cre recombinase in cells that expressed the heart-specific alpha-myosin heavy chain (αMHC; Myh6) promoter (Myh6cre/Esr1*). Experimental mice (CSRP3fl/fl/Myh6cre/Esr1*+, iCSRP3KO) were intraperitoneally injected with tamoxifen to induce heart-specific CSRP3 deletion. Tamoxifen-treated cre-negative littermates were used as controls. Mice were sacrificed following 24h urine collection at 9 weeks after tamoxifen treatment. Cardiac findings were assessed by echocardiography at 2 weeks after tamoxifen treatment. Cardiac fibrosis was assessed by Masson’s trichrome staining, and body weight-corrected cardiac weight was measured at 9 weeks after tamoxifen treatment. Renal findings were assessed by transdermal GFR measurement, blood urea nitrogen (BUN), 24h urine volume, and urine albumin mass at 9 weeks after tamoxifen treatment. Blood pressure was also measured at 9 weeks after tamoxifen treatment as a major confounder in the relationship between heart failure and renal failure.

After tamoxifen treatment, iCSRP3KO mice did not express CSRP3 in the myocardium. Systolic, diastolic, and mean blood pressure were comparable between the groups. Echocardiography revealed reduced ejection fraction and cardiac output in iCSRP3KO mice (EF: 50.0±2.7 vs 62±1.7 %, p=0.01. Cardiac output: 13±0.7 vs. 15.9±0.4 mL/min, p=0.03. n=4-6/group). Left ventricular end-systolic volume was greater in iCSRP3KO mice (27.9±5.9 µL vs 20.3±1.9 µL, p=0.04). iCSRP3KO mice demonstrated progressive cardiomegaly and increased cardiac weight (male: 0.73±0.07 vs 0.61±0.07 % of body weight (%BW), p=0.04, n=4-5/group. female: 0.80±0.09 vs 0.64±0.06 %BW, p=0.01, n=5/group), as well as fibrosis surrounding coronary arteries compared with controls. Additionally, iCSRP3KO mice demonstrated impaired renal function in both male and female evaluated by transdermal GFR measurement (male: 909.7±116.3 vs 1078.4±57.1 µL/min/100gBW, p=0.034, n=4-5/group. female: 974.3±102.5 vs 1221.5±57.6 µL/min/100gBW, p=0.002, n=5/group) and BUN (male: 31.1±5.0 vs 24.4±1.9 mg/dL, p=0.04, n=4-5/group. female: 28.0±6.4 vs 21.6±2.0 mg/dL, p=0.06, n=5/group). Urinary albumin mass and urine volume were comparable among groups in both male and female.

Heart-specific CSRP3 deletion resulted in a stable heart failure phenotype and reduced renal function. This approach provides a potentially useful novel CRS2 mouse model.