A systematic review and meta-analysis of murine models of uremic cardiomyopathy

Chronic kidney disease (CKD) triggers the risk of developing uremic cardiomyopathy as characterized by cardiac hypertrophy, fibrosis and functional impairment. Traditionally, animal studies are used to reveal the underlying pathological mechanism, although variable CKD models, mouse strains and readouts may reveal diverse results. Here, we systematically reviewed 88 studies and performed meta-analyses of 52 to support finding suitable animal models for future experimental studies on pathological kidney-heart crosstalk during uremic cardiomyopathy. We compared different mouse strains and the direct effect of CKD on cardiac hypertrophy, fibrosis and cardiac function in "single hit" strategies as well as cardiac effects of kidney injury combined with additional cardiovascular risk factors in "multifactorial hit" strategies. In C57BL/6 mice, CKD was associated with a mild increase in cardiac hypertrophy and fibrosis and marginal systolic dysfunction. Studies revealed high variability in results, especially regarding hypertrophy and systolic function. Cardiac hypertrophy in CKD was more consistently observed in 129/Sv mice, which express two instead of one renin gene and more consistently develop increased blood pressure upon CKD induction. Overall, "multifactorial hit" models more consistently induced cardiac hypertrophy and fibrosis compared to "single hit" kidney injury models. Thus, genetic factors and additional cardiovascular risk factors can "prime" for susceptibility to organ damage, with increased blood pressure, cardiac hypertrophy and early cardiac fibrosis more consistently observed in 129/Sv compared to C57BL/6 strains. Chronic kidney disease (CKD) triggers the risk of developing uremic cardiomyopathy as characterized by cardiac hypertrophy, fibrosis and functional impairment. Traditionally, animal studies are used to reveal the underlying pathological mechanism, although variable CKD models, mouse strains and readouts may reveal diverse results. Here, we systematically reviewed 88 studies and performed meta-analyses of 52 to support finding suitable animal models for future experimental studies on pathological kidney-heart crosstalk during uremic cardiomyopathy. We compared different mouse strains and the direct effect of CKD on cardiac hypertrophy, fibrosis and cardiac function in "single hit" strategies as well as cardiac effects of kidney injury combined with additional cardiovascular risk factors in "multifactorial hit" strategies. In C57BL/6 mice, CKD was associated with a mild increase in cardiac hypertrophy and fibrosis and marginal systolic dysfunction. Studies revealed high variability in results, especially regarding hypertrophy and systolic function. Cardiac hypertrophy in CKD was more consistently observed in 129/Sv mice, which express two instead of one renin gene and more consistently develop increased blood pressure upon CKD induction. Overall, "multifactorial hit" models more consistently induced cardiac hypertrophy and fibrosis compared to "single hit" kidney injury models. Thus, genetic factors and additional cardiovascular risk factors can "prime" for susceptibility to organ damage, with increased blood pressure, cardiac hypertrophy and early cardiac fibrosis more consistently observed in 129/Sv compared to C57BL/6 strains. see commentary on page 214 see commentary on page 214 Translational StatementChronic kidney disease (CKD) highly increases cardiovascular risk. This systematic review with meta-analyses summarizes the effect of CKD on cardiovascular remodeling and function in mice according to CKD model, strain dependency, CKD duration, and "single" versus "multifactorial" hits relevant for patients with CKD. This reveals that genetic and/or multifactorial preconditioning increases susceptibility to organ damage, in line with multiple risk factors known to increase CKD and/or cardiovascular disease risk in patients. Overall, this article will support finding suitable animal models for future experimental studies on pathologic kidney–heart crosstalk, which is highly needed to reveal underlying pathologic mechanisms and, therefore, strategies for the diagnosis and therapy of CKD-induced cardiovascular disease. Chronic kidney disease (CKD) highly increases cardiovascular risk. This systematic review with meta-analyses summarizes the effect of CKD on cardiovascular remodeling and function in mice according to CKD model, strain dependency, CKD duration, and "single" versus "multifactorial" hits relevant for patients with CKD. This reveals that genetic and/or multifactorial preconditioning increases susceptibility to organ damage, in line with multiple risk factors known to increase CKD and/or cardiovascular disease risk in patients. Overall, this article will support finding suitable animal models for future experimental studies on pathologic kidney–heart crosstalk, which is highly needed to reveal underlying pathologic mechanisms and, therefore, strategies for the diagnosis and therapy of CKD-induced cardiovascular disease. Chronic kidney disease (CKD) is an independent risk factor for cardiovascular disease, and almost half of the patients in CKD stage 4 and 5 die of cardiovascular events.1Webster A.C. Nagler E.V. Morton R.L. Masson P. Chronic kidney disease.Lancet. 2017; 389: 1238-1252Abstract Full Text Full Text PDF PubMed Scopus (1259) Google Scholar,2Thompson S. James M. Wiebe N. et al.Cause of death in patients with reduced kidney function.J Am Soc Nephrol. 2015; 26: 2504-2511Crossref PubMed Scopus (219) Google Scholar In addition to a high risk of atherosclerosis-related cardiovascular disease,2Thompson S. James M. Wiebe N. et al.Cause of death in patients with reduced kidney function.J Am Soc Nephrol. 2015; 26: 2504-2511Crossref PubMed Scopus (219) Google Scholar in particular patients with advanced CKD suffer from uremic cardiomyopathy,3Cox E.J. Marsh S.A. A systematic review of fetal genes as biomarkers of cardiac hypertrophy in rodent models of diabetes.PLoS One. 2014; 9: e92903Crossref PubMed Scopus (0) Google Scholar encompassing cardiac hypertrophy, fibrosis, and inflammation.4Marx N. Noels H. Jankowski J. et al.Mechanisms of cardiovascular complications in chronic kidney disease: research focus of the Transregional Research Consortium SFB TRR219 of the University Hospital Aachen (RWTH) and the Saarland University.Clin Res Cardiol. 2018; 107: 120-126Crossref PubMed Scopus (0) Google Scholar This triggers, for example, reduced left ventricular function, cardiac arrhythmias, and sudden cardiac death.5Shamseddin M.K. Parfrey P.S. Sudden cardiac death in chronic kidney disease: epidemiology and prevention.Nat Rev Nephrol. 2011; 7: 145-154Crossref PubMed Scopus (100) Google Scholar To support patient therapy, appropriate animal models are required to clarify the mechanisms underlying pathological kidney–heart crosstalk. Over the past years, an increasing number of animal studies have reported myocardial changes as a consequence of reduced kidney function,6Kaesler N. Babler A. Floege J. Kramann R. Cardiac remodeling in chronic kidney disease.Toxins (Basel). 2020; 12: 161Crossref Scopus (17) Google Scholar though using different CKD models, mouse strains, and readouts. The effect of the kidney on the heart has not only been studied in pure kidney injury models ("single hit strategies"). Patients with CKD often display additional cardiovascular risk factors such as hypertension, obesity, diabetes, and dyslipidemia.4Marx N. Noels H. Jankowski J. et al.Mechanisms of cardiovascular complications in chronic kidney disease: research focus of the Transregional Research Consortium SFB TRR219 of the University Hospital Aachen (RWTH) and the Saarland University.Clin Res Cardiol. 2018; 107: 120-126Crossref PubMed Scopus (0) Google Scholar,7Muntner P. Anderson A. Charleston J. et al.Hypertension awareness, treatment, and control in adults with CKD: results from the Chronic Renal Insufficiency Cohort (CRIC) Study.Am J Kidney Dis. 2010; 55: 441-451Abstract Full Text Full Text PDF PubMed Scopus (236) Google Scholar Also, especially in advanced CKD stages, patients suffer from hyperphosphatemia, a main challenge in CKD-mineral bone disorder.8Hruska K.A. Mathew S. Lund R. et al.Hyperphosphatemia of chronic kidney disease.Kidney Int. 2008; 74: 148-157Abstract Full Text Full Text PDF PubMed Scopus (278) Google Scholar,9Viegas C. Araujo N. Marreiros C. et al.The interplay between mineral metabolism, vascular calcification and inflammation in chronic kidney disease (CKD): challenging old concepts with new facts.Aging (Albany NY). 2019; 11: 4274-4299Crossref PubMed Scopus (37) Google Scholar Furthermore, patients with CKD display reduced survival after myocardial injury.10Nauta S.T. van Domburg R.T. Nuis R.J. et al.Decline in 20-year mortality after myocardial infarction in patients with chronic kidney disease: evolution from the prethrombolysis to the percutaneous coronary intervention era.Kidney Int. 2013; 84: 353-358Abstract Full Text Full Text PDF PubMed Scopus (24) Google Scholar Therefore, animal studies investigating CKD-mediated effects on the heart include "multifactorial hit models" that combine models of kidney injury with models mimicking traditional cardiovascular risk factors (hypertension, hyperlipidemia, and diabetes), CKD-specific cardiovascular risk factors (hyperphosphatemia), as well as myocardial infarction models. We performed a systematic review and meta-analysis to analyze the effect of experimental animal models of CKD on the heart. Because mice are superior to rat models in terms of the availability of genetic modifications to study molecular mechanisms, we focused on mouse models. This systematic review with meta-analysis was registered in the International Prospective Register of Systematic Reviews (PROSPERO) database (CRD42020218123) and performed according to the PRISMA guidelines.11Raun S.H. Henriquez-Olguín C. Karavaeva I. et al.Housing temperature influences exercise training adaptations in mice.Nat Commun. 2020; 11: 1560Crossref PubMed Scopus (0) Google Scholar PubMed and the Web of Science Core Collection were searched for studies investigating parameters of cardiac function, structure, and/or pathophysiology after inducing CKD in mouse models until February 14, 2021 (Figure 1). Meta-analyses were performed to analyze CKD-induced effects on cardiac hypertrophy, fibrosis, and systolic function (Supplementary Methods). For studies included in these meta-analyses, effects on kidney function (plasma/serum creatinine, urea, or blood urea nitrogen) and blood pressure were also summarized in meta-analyses and correlation analyses were performed in relation to effects on cardiac hypertrophy, fibrosis, and/or systolic function, if possible. Details about the search strategy (Supplementary Table S1), exclusion criteria (Figure 1), data extraction (parameter list: Supplementary Table S2; tables summarizing effects on cardiac outcome parameters: Supplementary Tables S3–S6), as well as quality assessment (risk of bias: Supplementary Figure S1; funnel plots: Supplementary Figures S2 and S3) and meta-analyses are described in Supplementary Methods. Literature screening identified 88 studies for inclusion in the systematic review (Figure 1). Most studies were performed in C57BL/6 mice (Supplementary Tables S3 and S5), the mouse strain with the highest availability of genetic modifications for mechanistic analysis. 129/Sv variants were also frequently studied, whereas other strains were only scarcely analyzed (Supplementary Tables S4 and S6). As depicted in Figure 2, all studies were categorized as (i) analyzing the direct effect of CKD on heart parameters ("single hit approach"; Supplementary Tables S3 and S4) or (ii) analyzing the cardiac effect of kidney injury combined with additional cardiovascular risk factors ("multifactorial hit approach") to clarify the effect of comorbidities on the heart (Supplementary Tables S5 and S6). Studies were classified according to the method of CKD induction as well as the duration of CKD, defined as short (0–4 weeks), intermediate (5–12 weeks), or long (≥13 weeks). Readouts for blood pressure, pathophysiological cardiac changes, left ventricular morphology, and cardiac function were extracted into data tables (Figure 1; Supplementary Tables S3–S6). Study results were described in detail for C57BL/6 mice and 129/Sv variants, with results from other strains available in Supplementary Material. Findings in the most commonly used models in C57BL/6 and 129/Sv mice are also summarized in Figure 3 ("single hit approach") and Figure 4 ("multifactorial hit approach"). Overall, 52 studies were included in a meta-analysis for CKD-induced effects on cardiac hypertrophy, fibrosis, and/or systolic function. For models applying unilateral kidney surgery as a "single hit" or with a "second multifactorial hit," kidney parameters as readouts of confirmed kidney injury are summarized in Supplementary Table S7. For "single hit" studies applying bilateral kidney surgery, a meta-analysis was performed for kidney function (serum/plasma creatinine and urea/blood urea nitrogen).Figure 4Effect of chronic kidney disease (CKD) in combination with typical cardiovascular risk factors in CKD on blood pressure, pathophysiological cardiac changes, left ventricular (LV) dimension, and LV function in C57BL/6 versus 129/Sv strains. Significant effects are color-graded according to the percentage of studies reporting on the respective parameters (see legend). Refer to Supplementary Tables S3–S6 for detailed information about which study measured which cardiac parameters. When a study reported on multiple readouts for a specific parameter, the study was included as "changed" when at least 1 relevant readout was "changed." For LV function, "decreased" refers to cardiac dysfunction. Systolic dysfunction (other than altered systolic LV volume) may include decreased ejection fraction, fractional shortening, cardiac output, stroke volume, and/or dP/dt max. Diastolic dysfunction (other than altered diastolic LV volume) may include decreased E/A ratio, E/e′ ratio, E/A′ ratio, and/or dP/dt min as well as altered isovolumetric relaxation time and/or isovolumic relaxation time constant (τ). Studies examining the same mouse model at different time points were counted only once and were included as "differential effects" if these were observed at least on 1 time point. If different models were examined in 1 publication, each of these models was separately counted. A, LV filling velocity, late or atrial filling (A-wave) measured by pulsed wave Doppler; A', LV filling velocity, late or atrial filling (A-wave) measured by tissue Doppler; Aldo, aldosterone; AngII, angiotensin II; DOCA, deoxycorticosterone acetate; dP/dT max, maximum rate of LV pressure change; dP/dt min, minimum rate of LV pressure change; E, LV filling velocity, early filling (E-wave) measured by pulsed wave Doppler; e', LV filling velocity, early filling (E-wave) measured by tissue Doppler; HFD, high-fat diet; MI, myocardial infarction; MI/RI, myocardial ischemia/reperfusion injury; RAC, renal artery clipping; SNX, 5/6 nephrectomy; UNX, uninephrectomy; WT, wild type.View Large Image Figure ViewerDownload Hi-res image Download (PPT) Only 4 studies were identified that examined cardiac effects in mice displaying signs of kidney damage in response to unilateral kidney surgery (Supplementary Tables S3, S4, and S7).12Gaikwad A.B. Sayyed S.G. 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Wang M. et al.Klotho alleviates indoxyl sulfate-induced heart failure and kidney damage by promoting M2 macrophage polarization.Aging (Albany NY). 2020; 12: 9139-9150Crossref PubMed Scopus (11) Google Scholar In contrast, most studies analyzed cardiac effects after applying bilateral kidney damage through surgery, specific food supplementation, or genetic modification (Figure 3; Supplementary Tables S3 and S4). Four weeks after subtotal (5/6) nephrectomy (SNX), a hypertrophic, fibrotic, and inflammatory response was observed in the myocardium in ≥75% of studies (Figure 3; Supplementary Table S3). Furthermore, mild diastolic cardiac dysfunction was detected whereas systolic function or left ventricular dimensions were only rarely affected.16Guo J. Zhu J. Ma L. et al.Chronic kidney disease exacerbates myocardial ischemia reperfusion injury: role of endoplasmic reticulum stress-mediated apoptosis.Shock. 2018; 49: 712-720Crossref PubMed Scopus (0) Google Scholar, 17Leelahavanichkul A. 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Furthermore, these studies consistently reported on increased left ventricular diameter and diastolic as well as systolic dysfunction. Only 3 studies performed a cardiac analysis in long experimental setups beyond 12 weeks.17Leelahavanichkul A. Yan Q. Hu X. et al.Angiotensin II overcomes strain-dependent resistance of rapid CKD progression in a new remnant kidney mouse model.Kidney Int. 2010; 78: 1136-1153Abstract Full Text Full Text PDF PubMed Scopus (107) Google Scholar,25Maizel J. Six I. Dupont S. et al.Effects of sevelamer treatment on cardiovascular abnormalities in mice with chronic renal failure.Kidney Int. 2013; 84: 491-500Abstract Full Text Full Text PDF PubMed Scopus (0) Google Scholar,45Ke H.Y. Chin L.H. Tsai C.S. et al.Cardiac calcium dysregulation in mice with chronic kidney disease.J Cell Mol Med. 2020; 24: 3669-3677Crossref PubMed Scopus (0) Google Scholar Cardiac hypertrophy and diastolic dysfunction were reported 14 weeks after SNX,25Maizel J. Six I. Dupont S. et al.Effects of sevelamer treatment on cardiovascular abnormalities in mice with chronic renal failure.Kidney Int. 2013; 84: 491-500Abstract Full Text Full Text PDF PubMed Scopus (0) Google Scholar although cardiac fibrosis could not be detected 16 weeks postsurgery.17Leelahavanichkul A. Yan Q. Hu X. et al.Angiotensin II overcomes strain-dependent resistance of rapid CKD progression in a new remnant kidney mouse model.Kidney Int. 2010; 78: 1136-1153Abstract Full Text Full Text PDF PubMed Scopus (107) Google Scholar At 24 weeks postsurgery, systolic dysfunction was reported, though without altered left ventricular dimensions or induction of cardiac hypertrophy.45Ke H.Y. Chin L.H. Tsai C.S. et al.Cardiac calcium dysregulation in mice with chronic kidney disease.J Cell Mol Med. 2020; 24: 3669-3677Crossref PubMed Scopus (0) Google Scholar Bilateral ischemia/reperfusion injury induced cardiac hypertrophy and fibrosis after 4 to 8 weeks, though without effect on systolic function.46Pang P. Abbott M. Abdi M. et al.Pre-clinical model of severe glutathione peroxidase-3 deficiency and chronic kidney disease results in coronary artery thrombosis and depressed left ventricular function.Nephrol Dial Transplant. 2018; 33: 923-934Crossref PubMed Scopus (0) Google Scholar When using heart weight as an outcome parameter for cardiac hypertrophy, a meta-analysis for bilateral surgery–induced "single hit" approaches in C57BL/6 mice revealed a mild increase in hypertrophy (Figure 5a; standardized mean difference [SMD] 1.34; 95% confidence interval [CI] 0.50–2.18; n = 24 studies; P = 0.0031). However, study heterogeneity was very high (I2 = 82%): almost half of the studies could not detect a significant induction of cardiac hypertrophy after 6 to 11 weeks or beyond 14 weeks of study. Subgroup analysis based on study duration did not reveal a time-dependent increase in cardiac hypertrophy (1–4 weeks: 95% CI, −1.03 to 9.23; 5–8 weeks: 95% CI, −0.01 to 1.67; 9–13 weeks: 95% CI, −0.02 to 2.09; ≥14 weeks: 95% CI, −7.89 to 8.70). No significant overall effect was observed on cardiomyocyte size among 6- to 12-week studies (Supplementary Figure S4A; SMD, 2.85; 95% CI, −2.07 to 7.77; P = 0.1963), with low study number and high heterogeneity (n = 6 studies; I2 = 91%) impeding conclusions on time-dependent effects.Figure 5Meta-analysis for cardiac hypertrophy (a) in C57BL/6 mice with surgery-induced chronic kideny disease (CKD), (b) in 129/Sv variants with surgery-induced CKD, and (c) in C57BL/6 mice with CKD and hypertension-inducing strategies. Aldo, aldosterone; AngII, angiotensin II; BW, body weight; CI, confidence interval; Ctrl, control; HW, heart weight; IRI, ischemia/reperfusion injury; LV, left ventricular; SMD, standardized mean difference; SNX, 5/6 nephrectomy; TL, tibia length; UNX, uninephrectomy.View Large Image Figure ViewerDownload Hi-res image Download (PPT) Cardiac fibrosis was significantly induced (Figure 6a; SMD, 5.43; 95% CI, 3.27–7.59; n = 16; P < 0.0001; I2 = 83%). Time-dependent subgroup analysis revealed fibrosis mainly in intermediate study setups (8 weeks: 95% CI, 1.88–5.51; n = 3; 11–13 weeks: 95% CI, 3.47–10.95; n = 9).Figure 6Meta-analysis for cardiac fibrosis (a) in C57BL/6 mice with surgery-induced chronic kideny disease (CKD), (b) in 129/Sv variants with surgery-induced CKD, and (c) in C57BL/6 mice with CKD and hypertension-inducing strategies. Aldo, aldosterone; AngII, angiotensin II; CI, confidence interval; Ctrl, control; IHC, immunohistochemistry; SMD, standardized mean difference; SNX, 5/6 nephrectom