Cardiotrophin 1 Is Involved in Cardiac, Vascular, and Renal Fibrosis and Dysfunction
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Abstract
Cardiotrophin 1 (CT-1), a cytokine belonging to the interleukin 6 family, is increased in hypertension and in heart failure. We aimed to study the precise role of CT-1 on cardiac, vascular, and renal function; morphology; and remodeling in early stages without hypertension. CT-1 (20 μg/kg per day) or vehicle was administrated to Wistar rats for 6 weeks. Cardiac and vascular functions were analyzed in vivo using M-mode echocardiography, Doppler, and echo tracking device and ex vivo using a scanning acoustic microscopy method. Cardiovascular and renal histomorphology were measured by immunohistochemistry, RT-PCR, and Western blot. Kidney functional properties were assessed by serum creatinine and neutrophile gelatinase-associated lipocalin and microalbuminuria/creatininuria ratio. Without alterations in blood pressure levels, CT-1 treatment increased left ventricular volumes, reduced fractional shortening and ejection fraction, and induced myocardial dilatation and myocardial fibrosis. In the carotid artery of CT-1–treated rats, the circumferential wall stress-incremental elastic modulus curve was shifted leftward, and the acoustic speed of sound in the aorta was augmented, indicating increased arterial stiffness. Vascular media thickness, collagen, and fibronectin content were increased by CT-1 treatment. CT-1–treated rats presented unaltered serum creatinine concentrations but increased urinary and serum neutrophile gelatinase-associated lipocalin and microalbuminuria/creatininuria ratio. This paralleled a glomerular and tubulointerstitial fibrosis accompanied by renal epithelial-mesenchymal transition. CT-1 is a new potent fibrotic agent in heart, vessels, and kidney able to induce cardiovascular-renal dysfunction independent from blood pressure. Thus, CT-1 could be a new target simultaneously integrating alterations of heart, vessels, and kidney in early stages of heart failure.
Introduction
Heart failure (HF) is associated with cardiac hypertrophy, fibrosis, arterial stiffness, and renal impairment, all of which influence cardiovascular outcomes.1–3 Cardiac hypertrophy is attributable to cardiomyocyte hypertrophy, the proliferation of interstitial fibroblasts, and increased depositions of extracellular matrix (ECM) components.4 Arterial stiffening is associated with decreased distensibility and modified wall structure mainly characterized by increased ECM.5,6 Chronic kidney disease progression is generally associated with tubulointerstitial fibrosis.7,8 Therefore, it is of paramount importance to identify common pathways able to trigger cardiovascular and renal fibrosis.
Cardiotrophin 1 (CT-1) is an interleukin 6 superfamily member.9 Elevated CT-1 levels have been reported in HF and in hypertensive patients.10–12 Moreover, CT-1 positively correlates with left ventricular (LV) mass index and the serum concentration of carboxy-terminal propeptide of procollagen type I, a biomarker of collagen synthesis,10 suggesting that CT-1 may contribute to the development of cardiomyocyte hypertrophy and fibrosis. Accordingly, CT-1 administration increases heart weight in mice.13 Our group has characterized CT-1–induced cardiomyocyte survival and hypertrophy,10,14 as well as CT-1–induced proliferation, hypertrophy, and secretion of ECM proteins in vascular smooth muscle cells (VSMCs).15 Furthermore, CT-1 stimulates proliferation and collagen synthesis in ventricular fibroblasts.16 In addition, the expression of CT-1 mRNA has been described in the kidney,17 and mice treated with CT-1 showed increased renal weight.13 Although these observations suggest that CT-1 may directly induce cardiac, vascular, and renal remodeling, no studies have directly investigated an integrative role of CT-1 in mediating fibrosis or cardiac, vascular, and renal dysfunction in vivo. Therefore, we aimed to examine the precise role of CT-1 on cardiac, vascular, and renal functions; morphologies; and remodeling in rats chronically treated with CT-1.
Methods
Please see the online-only Data Supplement.
Animals
The investigation was performed in accordance with the Guide for Care and Use of Laboratory Animals published by the National Institutes of Health (publication No. 82-23, revised in 1996). Male Wistar rats (15 weeks old) were obtained from Harlan and treated with rat recombinant CT-1 (20 μg/kg per day, IP; n=30) or vehicle (PBS, IP; n=30) for 6 weeks and euthanized by decapitation under anesthesia (3% isofluorane/O2).
Blood Pressure Monitoring
The surgical procedure for transmitter implantation was performed as described previously.18
Assessment of Ventricular Size and Heart Function
2D echocardiography, M-mode measurements, and Doppler ultrasound recordings were performed as described previously.19
In Vivo Carotid Mechanical Properties
We recorded intra-arterial diameter of the carotid artery and blood pressure (BP) as, described previously.20
Ex Vivo Aorta Mechanical Properties
Scanning acoustic microscopy (SAM), conducted at 761 MHz, was used to generate speed of sound maps for aorta sections using a novel method21 but using the same sample preparation method, as described previously.22 Any differential contribution to stiffness within the aortic wall was investigated by determining the speed of sound for both the elastic lamellae and interlamellar regions.23
Aortic Composition
Insoluble elastin, total collagen, and cell protein contents were measured on descending thoracic aortas without homogenization, as described previously.24
Histological Evaluation
Histological determinations in cardiac, vascular, and renal tissue were performed as described previously.18
Reverse Transcription and Real-Time PCR
Total RNA extraction and real-time PCR were performed as described previously.18
Western Blot
Western Blot analysis in left ventricles, aortas, and kidneys were performed as described previously.18
Zymography
Gelatin zymography for matrix metalloproteinase (MMP) activity assay was performed as described previously.15
ELISA
Quantikine ELISA kits were used to measure albumin and creatinine (Abnova), neutrophile gelatinase-associated lipocalin (Interchim), and CT-1 (Cusabio) according to the manufacturer's protocols.
Statistical Analysis
Results are presented as mean±SEM, and P values <0.05 were considered significant. Comparisons between treatments or groups of animals were made by the unpaired Student t test, the Mann-Whitney U test, or the repeated-measures ANOVA, as appropriate.
Results
CT-1 Levels in CT-1–Treated Rats
CT-1 plasma levels were measured at baseline and at 1, 3, and 6 weeks of treatment. As shown in Figure 1A, CT-1 levels were increased at 3 (2.8-fold; P<0.01) and 6 weeks of injection (3.8-fold; P<0.01).
Figure 1. Cardiotrophin 1 (CT-1) levels in control and CT-1–treated rats. A, CT-1 treatment induced a time-dependent increase in CT-1 plasma levels. B through D, CT-1 expression, at the protein and the mRNA level, was enhanced in myocardium, the aorta, and the kidney from CT-1–treated rats. 18s gene expression or β-actin levels were used as loading controls in RT-PCR and Western blot, respectively. Values are mean±SEM; **P<0.01 vs control.
CT-1 was spontaneously expressed in cardiac tissue, both in cardiomyocytes and fibroblasts. Moreover, CT-1–treated rats presented higher (70%; P<0.01) CT-1 immunostaining as compared with controls. This increase was confirmed at the mRNA (4.1-fold; P<0.01) and the protein (2.8-fold; P<0.01) levels (Figure 1B). CT-1 was also expressed in aortic VSMCs. The expression was higher (80%; P<0.01) in CT-1-treated animals. The cytokine was also enhanced at the mRNA (3.7-fold; P<0.01) and the protein (2.3-fold; P<0.01) levels in aorta from CT-1–treated rats (Figure 1C). In kidney, CT-1 was spontaneously localized in the distal tubular cells of the cortex but not in glomeruli. CT-1 expression was higher (48%; P<0.01) in renal cortex from CT-1–treated animals. Moreover, CT-1 expression was increased at the protein level (2.3-fold; P<0.01) but not significantly at the mRNA level in kidney from CT-1–infused rats relative to controls (Figure 1D). The expression of CT-1 receptors gp130 and Leukemia inhibitory factor receptor was also evaluated in heart, aorta, and kidney (please see Figure S1).
Cardiac, Vascular, and Renal Functions in CT-1–Treated Rats
Chronic CT-1 administration had no effect on BP parameters throughout the experimental period. The heart weight/body weight ratio was not significantly different in the 2 groups, indicating a similar LV mass index (Table).
| Parameter | Control | CT-1 |
|---|---|---|
| N | 10 | 10 |
| BW, g | 265±6 | 278±5 |
| HW, g | 0.593±0.01 | 0.677±0.01* |
| HW/BW, mg · g−1 | 2.25±0.07 | 2.45±0.08 |
| KW, g | 1.95±0.05 | 2.15±0.08* |
| KW/BW, mg · g−1 | 7.39±0.23 | 7.76±0.32 |
| SBP, mm Hg | 135±7 | 133±6 |
| DBP, mm Hg | 90±6 | 84±6 |
| MBP, mm Hg | 105±6 | 100±6 |
| PP, mm Hg | 45±2 | 49±3 |
| HR, bpm | 426±11 | 404±10 |
| Echocardiographic parameters | ||
| LVMI, mg · g−1 | 1.136±0.04 | 1.145±0.03 |
| LVDd, mm | 5.3±0.2 | 5.8±0.2* |
| LVSd, mm | 3.0±0.3 | 3.8±0.2* |
| LVDv, mL | 0.37±0.02 | 0.47±0.05* |
| LVSv, mL | 0.09±0.02 | 0.15±0.03* |
| FS, % | 44.0±3.3 | 34.0±3.0* |
| EF, % | 79.5±3.1 | 69.3±3.9* |
| E/A | 1.42±0.04 | 1.60±0.04* |
| Vascular parameters, at MBP | ||
| Carotid diameter, mm | 1.20±0.05 | 1.03±0.03* |
| Carotid compliance | 8.1±0.7 | 6.5±0.6 |
| Distensibility, 10−3mm Hg−1 | 7.5±0.9 | 7.9±0.7 |
| Incremental elastic modulus, kPa | 749±166 | 362±36* |
| Wall stress, kPa | 298±37 | 154±14* |
| Renal parameters | ||
| SCr, pg/mL | 0.174±0.002 | 0.176±0.003 |
| SAlb, pg/mL | 241±10 | 405±109 |
| SNGAL, ng/mL | 43±7 | 83±16* |
| UCr, pg/mL | 1.94±0.06 | 2.01±0.06 |
| UAlb, pg/mL | 2359±370 | 3349±355* |
| ACR, μg/μg creatinine | 1.21±0.20 | 1.75±0.17* |
| UNGAL, ng/mL | 176±2 | 362±51* |
Echocardiographic analysis confirmed that LV mass index was similar in the 2 groups. CT-1 administration increased (P<0.01) systolic and diastolic LV diameters and volumes. CT-1–treated rats exhibited LV chamber dilatation (representative images are shown in Figure 3A). CT-1–treated rats presented decreased (P<0.01) fractional shortening and ejection fraction as compared with controls and increased E/A ratio (P<0.01), suggesting a trend toward restrictive filling (Table). The ratio between end-systolic volume and stroke volume was increased by CT-1 treatment (36%; P<0.01), suggesting that CT-1 impaired LV-arterial coupling.
Ultrasonic echo tracking assessment revealed that the carotid diameter was smaller in CT-1–treated rats than in the controls (Table). There were no significant differences in compliance and distensibility calculated at the mean BP. Incremental elastic modulus and wall stress were lower in CT-1–treated rats compared with controls. Within the common range of arterial pressure, the diameter-arterial pressure curve in the CT-1–treated group was significantly shifted downwards from that of the control group (Figure 2A). The distensibility-arterial pressure curve was similar in the 2 groups (Figure 2B). By contrast, the incremental elastic modulus-WS curve of CT-1–treated rats was shifted leftward significantly (Figure 2C). Accordingly, in CT-1–treated rats the mean WS within the 350- to 2000-kPa range of incremental elastic modulus was decreased (P<0.01), indicating an increase in stiffness (Figure 2D). Typical SAM speed of sound maps for the aorta samples are shown in Figure 2E and 2F. Mean speed of sound in the CT-1–treated rats was found to increase significantly (P<0.01), confirming increased arterial stiffness.
Figure 2. In vivo and ex vivo vascular mechanical properties in control and cardiotrophin 1 (CT-1)–treated rats. A, The diameter-arterial pressure curve of the CT-1–treated group (n=9) was significantly shifted downward versus controls (n=9). B, No difference in arterial distensibility was observed between the 2 groups. C, The wall stress (WS)- incremental elastic modulus (Einc) curve of CT-1–treated rats was significantly shifted to the left versus controls. D, Mean WS (MWS) within the 350- to 2000-KPa range of Einc (MWS 350-2000) was decreased in CT-1–treated rats. E and F, 200×200-μm speed of sound maps for a typical control and CT-1–treated rat aorta determined with scanning acoustic microscopy (SAM). N=1000 speed of sound measurements per group. Values are mean±SEM. *P<0.05 vs control; **P<0.01 vs control. A through C, ○, control; ●, CT-1. F, Black line, control; dashed line, CT-1.
The kidney weight/body weight ratio was not significantly different in both groups (Table). At the end of the treatment, CT-1–treated rats presented enhanced (44%; P<0.05) albumin-creatinine ratio as compared with controls. Furthermore, neutrophile gelatinase-associated lipocalin, a tubular injury biomarker, was increased in serum from CT-1–treated rats (93%; P<0.05), as well as in urine (234%, P<0.05), as compared with controls.
Myocardial, Vascular, and Renal Fibrosis in CT-1–Treated Rats
Myocardial Fibrosis
CT-1 treatment increased cardiomyocyte length (14%; P<0.01), without modifying cardiomyocyte width. Moreover, CT-1 treatment induced the expression of the contractile proteins α-major histocompatibility complex, β-major histocompatibility complex, α-sarcomeric actin, and myosin light chain 1 without modifying α-skeletal actin or myosin light chain 2v levels (please see Figure S2).
CT-1–infused rats presented a 2-fold increase (P<0.01) in cardiac interstitial collagen and a 2.5-fold increase (P<0.01) in perivascular collagen (Figure 3A) as compared with controls. CT-1–treated rats showed higher cardiac expression of α-1-procollagen mRNA (80%; P<0.01), collagen type I (80%; P<0.01), and type III (2-fold; P<0.01; Figure 3B). Moreover, CT-1–treated rats exhibited higher levels of osteopontin (75%; P<0.01) and periostin (65%; P<0.05; Figure 3C). CT-1–treated rats presented enhanced MMP-2 activity (80%; P<0.05), as well as MMP-13/tissue inhibitor of metalloproteinase 1 ratio (2.4-fold; P<0.01), without significant changes in MMP-9 activity (Figure 3D).
Figure 3. Cardiac morphology and composition in controls and cardiotrophin 1 (CT-1)–treated rats. A, CT-1–treated rats presented left ventricular (LV) chamber dilatation and interstitial and perivascular fibrosis. B and C, The expression of the extracellular matrix (ECM) components was quantified by RT-PCR and Western blot in the myocardium from controls (n=10) and CT-1–treated rats (n=10). 18s gene expression or β-actin levels were used as loading controls in RT-PCR and Western blot, respectively. CT-1–treated rats presented increased cardiac α-1-procollagen, collagen type I, collagen type III, osteopontin, and periostin. D, CT-1–treated rats exhibited cardiac activation of MMP-2 and -13. Representative images are shown, and the histogram bars represent the mean±SEM obtained in the 2 groups of animals. *P<0.05 vs control; **P<0.01 vs control.
Vascular Fibrosis
Media thickness and media cross-sectional area of the carotid artery were higher (41% and 43%, respectively; P<0.01), whereas carotid diameter was reduced by 15% (P<0.01) in CT-1–treated animals as compared with controls (Figure S3, and representative images are shown in Figure 4A).
Figure 4. Vascular morphology and composition in controls and cardiotrophin 1 (CT-1)–treated rats. A, Carotid artery from CT-1–treated rats exhibited increased media cross-sectional area of the carotid artery (MCSA), collagen, and fibronectin contents, whereas elastin levels were not modified. B, CT-1–treated rats presented increased aortic α-1-procollagen mRNA, collagen type I, collagen type III, and fibronectin, whereas elastin levels were similar. C, left, 2D analysis of scanning acoustic microscopy (SAM) images; the lamellar and interlamellar regions of the aorta are demarcated, after which the speed of sounds (stiffness) values are extracted for each of these regions. Right, There is a significant increase in both the lamellar (L) and interlamellar (IL) regions of the aorta, with the most prominent changes being in the interlamellar region (n=33, L and IL per group). D, In aorta from CT-1–treated rats there was an activation of MMP-2, -9, and -13. Representative images are shown, and the histogram bars represent the mean±SEM obtained in the 2 groups of animals. *P<0.05 vs control. **P<0.01 vs control.
Thoracic aortic medial dry weight per centimeter of length and cell protein content were increased significantly by the CT-1 treatment compared with control rats (Figure S3), indicating that hypertrophy of the media had occurred. There were no changes in elastin with CT-1 treatment. However, CT-1–treated rats presented enhanced aortic collagen content (30% to 50%; P<0.01) as compared with controls.
To determine whether CT-1 could modify ECM attachments, integrins expression was studied. CT-1 treatment increased the expression of the integrins α-1, α-5, α-v, and β-3. To analyze whether CT-1 also modified the cytoskeletal proteins involved in linkage to integrin adhesion molecules to the actin cytoskeleton, we quantified the phosphorylation of focal adhesion kinase and the expression of 2 focal adhesions proteins, vinculin and talin. Aortas from CT-1–treated rats exhibited enhanced expression of vinculin and talin, as well as greater focal adhesion kinase activity (Figure S3).
CT-1–treated rats had higher carotid collagen (80%; P<0.01) and enhanced fibronectin (80%; P<0.01) but similar elastin densities compared with controls (Figure 4A). Moreover, in aorta from CT-1–treated rats, the expression of α-1-procollagen mRNA was higher (2.1-fold; P<0.01), as well as the expression of collagen type I (2.4-fold; P<0.01) and type III (3.6-fold; P<0.01; Figure 4B). In addition, CT-1–administrated rats presented enhanced aortic fibronectin content at the mRNA (2.4-fold; P<0.01) and the protein (80%; P<0.01) levels but similar content of elastin compared with controls (Figure 4B).
The SAM images were also analyzed to determine whether there was any localized stiffening by examining the speed of sound in the lamellar and interlamellar regions of the aorta. There was a significant increase in stiffness in both lamellar and interlamellar regions; however, the interlamellar regions exhibited the most significant change in the CT-1–treated rats (Figure 4C). This is consistent with the increase in collagen content (Figure 4A and 4B), which would be expected to accumulate more in the interlamellar regions. Aortas from CT-1–treated rats showed enhanced MMP-2 (40%; P<0.05), MMP-9 (20%; P<0.05), and MMP-13 (30%; P<0.05) activities as compared with controls (Figure 4D).
Renal Fibrosis
CT-1–infused rats presented increased (49%; P<0.01) renal interstitial collagen as compared with controls. Moreover, glomerular collagen volume fraction in CT-1–treated rats was markedly increased (72%; P<0.01). Tubulointerstitial collagen type I and type IV were higher (240% and 260%; P<0.01, respectively) in CT-1–treated animals (Figure 5A). This was confirmed by molecular analysis (Figure 5B). In addition, CT-1–administrated rats presented enhanced expression of transforming growth factor-β1 (84% to 55%; P<0.05) and connective tissue growth factor (87% to 21%; P<0.05) at the mRNA and protein levels, respectively (Figure 5C). MMP-9 and MMP-2 activities and MMP-3/tissue inhibitor of metalloproteinase 3 ratio were similar in the kidneys from the 2 groups of rats, whereas the MMP-13/tissue inhibitor of metalloproteinase 1 ratio was decreased in CT-1–treated animals (64%; P<0.01; Figure 5D).
Figure 5. Renal fibrosis in control and cardiotrophin 1 (CT-1)–treated rats. A, Total tubulointerstitial and glomerular collagen content, tubulointerstitial collagen type I, and collagen type IV were increased in kidney from CT-1–treated rats, as compared with controls. B, Collagen type I expression was augmented, whereas the expression of α-1 procollagen and collagen type IV mRNA was unchanged in kidney from CT-1–treated rats as compared with controls. C, Transforming growth factor (TGF)-β1 and connective tissue growth factor (CTGF) mRNA and protein expression were enhanced in whole kidney tissue from rats treated with CT-1 as compared with controls. D, In kidney from CT-1–treated rats there was a decrease in matrix metalloproteinase (MMP) 13 activity. GAPDH expression or β-actin levels are used as loading controls in RT-PCR and Western blot, respectively. Bars represent the mean±SEM obtained in the 2 groups of animals. *P<0.05 vs control; **P<0.01 vs control.
Discussion
The purpose of this study was to investigate the influence of an excess of circulating CT-1 in cardiac, vascular, and renal remodeling and function in rats. Indeed, in the absence of BP modifications, chronic CT-1 treatment induced cardiac, vascular, and renal fibrosis, resulting in further structural and functional damage in heart, aorta, and kidney. Moreover, increased CT-1 mRNA expression observed in the cardiovascular system from CT-1–treated rats suggests a positive feedback inducing a vicious circle.
Hypertension, HF, and chronic kidney disease have been shown to be associated with increased CT-1 plasma levels,10,11,14,25,26 with these being increases similar to those found in the present study. Furthermore, CT-1 treatment weakens cardiomyocyte contractility in reconstituted heart tissue,27 suggesting a role for CT-1 in the impairment of cardiac function. However, the precise contribution of CT-1 to the pathogenesis of cardiac remodeling and dysfunction is unclear, because, to our knowledge, the in vivo CT-1 effects have not yet been investigated. CT-1 induced cardiomyocyte hypertrophy in vitro, with a special morphometric pattern of lengthening without modifying cell width and without changing α-skeletal actin or myosin light chain 2v expression.14 CT-1 also increased collagen synthesis in fibroblasts.16 Our study showed that CT-1–treated rats developed LV dilatation accompanied by cardiomyocyte elongation, produced by an increase in contractile proteins except for α-skeletal actin and myosin light chain 2v, as well as enhanced myocardial fibrosis characterized by ECM protein deposition. In addition, CT-1 treatment decreased LV mechanical efficiency by modulating the heart-vessel coupling, independent of BP. Thus, direct structural changes produced by CT-1, cardiomyocyte lengthening, and myocardial fibrosis could contribute overall to cardiac dysfunction and LV-arterial uncoupling.
In addition to cardiac fibrosis and dysfunction, CT-1 induced significant vascular remodeling characterized by ECM proteins accumulation and arterial stiffness. We have shown recently that CT-1 increases proliferation, ECM synthesis, and hypertrophy in VSMCs.15 The molecular mechanisms underlying the development of vascular stiffness are generally attributed to modifications in ECM molecules, VSMC changes, and vascular tone.28,29 Interestingly, chronic CT-1 treatment reduced arterial diameter and increased media cross-sectional area of the carotid artery in vessels, with a marked deposition of ECM proteins, integrins, and focal adhesion molecules. These modifications may represent quantitative or topographical changes in interactions between VSMCs and matrix proteins, resulting in a restructured vascular wall, as described previously in other models.28,29 With the novel SAM technique, we found an increase in speed of sound of 29 ms−1 in the CT-1–treated rat aorta. This is much higher than the age-related increase reported with a SAM method for ovine aorta,23 thereby highlighting the profound effect of CT-1 on vascular stiffening. The increased stiffness determined with SAM ex vivo on thin sections of tissue follows the trends observed with more conventional techniques in vivo, providing high spatial resolution measurements of stiffness, which are related to tissue structure. Consequently, these findings provide additional evidence suggesting that CT-1 may contribute to increase the arterial stiffness, ultimately leading to vascular dysfunction.
In kidney, only the expression of CT-1 mRNA has been described to date.17 Moreover, mice treated with CT-1 showed increased renal weight.13 Consistent with observations in myocardium and vessels, CT-1–treated rats presented increased tubulointerstitial and glomerular fibrosis, accompanied by enhanced transforming growth factor-β and connective tissue growth factor expressions, 2 molecules that act synergistically to promote kidney fibrosis.30 Moreover, CT-1 has the ability to alter the differentiation state of tubular epithelial cells toward an EMT phenotype, which ultimately generates fibrosis and dysfunction. CT-1 also altered kidney functional properties, inducing albuminuria and increasing urinary and serum neutrophile gelatinase-associated lipocalin, an immediate early gene, which is associated with chronic kidney disease progression.31 Taken together, these data indicate that chronic CT-1 exposure plays a role in renal fibrosis and tubular damage in vivo.
Conclusion and Perspectives
This experimental model of chronic CT-1 exposure presents integrated early changes of heart, artery, and kidney functions, which may ultimately lead to HF development. Of interest, our study identifies new important direct effects of CT-1 in the absence of BP modifications. Previous studies demonstrated that CT-1 may be stimulated by hypertension and by aldosterone even in the absence of BP elevation.18 In the present study, CT-1 levels were similar to those observed in human HF,10–12 and, moreover, CT-1 infusion was associated with increased CT-1 transcription in heart and vessels, thereby suggesting a positive feedback loop able to promote further CT-1 effects. Therefore, CT-1, per se, could be an additional therapeutic target downstream to many ischemia-derived neurohumoral influences involved in HF pathophysiology. There is currently no way to inhibit CT-1 in vivo. Finally, we suggest that CT-1 emerges as a target candidate to interfere with the development of cardiac-vascular-renal fibrosis and dysfunction that characterizes cardiovascular-renal diseases evolving with HF.
Acknowledgments
We especially thank Prof Simon Thornton for editing this article, and Ginny Simon, Natacha Sloboda, and Patrick Costello for technical assistance. Prof Brian Derby must be thanked for leading the development of the SAM technique under the Wellcome Trust grant WT085981AIA, along with Drs Michael Sherratt and Rachel Watson. We thank Dr Sebastian Brand (Fraunhofer Institute of Material Mechanics, Germany) and Prof Kay Raum (Julius Wolff Institut and Berlin-Brandenburg School for Regenerative Therapies, Germany), who developed the MATSAM software. We also thank Drs Maria Antonia Fortuno, Pascal Challande, Mary Osborne, and Jean-Paul Duong Van Huyen for helpful discussion.
Sources of Funding
This work was supported by a grant from the
Disclosures
None.
Footnotes
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Novelty and Significance
What Is New?
We report the whole picture of CT-1 in vivo effects, with major insights into the profibrotic properties and the key role of CT-1 throughout the cardiovascular and renal continuum, ultimately leading to heart failure and kidney insufficiency.
What Is Relevant?
First, we have characterized cardiac function, hypertrophy, and fibrosis induced by a chronic treatment with CT-1 in rats. Then, we provided data showing an increased arterial stiffness using classic methods, as well as a novel ultra-high frequency SAM phase contrast method that enables the determination of tissue elastic data within the aortic wall. Moreover, we present mechanistic insights regarding integrin expression and focal adhesion proteins in the aorta. Finally, we have explored CT-1 effects throughout the cardiovascular system, in renal tissue, presenting exciting data that suggest a key role for this molecule in the cardiovascular-renal syndrome. Our results are particularly original, because therapies that target the heart, the large arteries, and the kidney to directly reduce left ventricular dysfunction, arterial stiffness, and renal insufficiency are an important unmet clinical need.
Summary
CT-1 could be a new biotarget to reduce fibrosis, arterial stiffness, and cardiorenal dysfunction.
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