Renal vascular changes in renal disease independent of hypertension
Willem Jan W. Bos1,3,,
Mustafa M. Demircan1,
Jan J. Weening2,
Raymond T. Krediet1 and
Allard C. van der Wal2
1 Departments of Nephrology and
2 Pathology, Academic Medical Center, Amsterdam,
3 Department of Internal Medicine, St Antonius Hospital, Nieuwegein, The Netherlands
 |
Abstract
|
---|
Introduction. Cardiovascular disease is common in patients with renal disease, but little is known about the effect of renal disease and loss of renal function on vascular morphology. Intima proliferation of small renal arteries, which correlates with atherosclerosis in the aorta, is sometimes present in renal disease and has been shown to increase with age and hypertension. We studied the effect of chronic renal disease and renal function, independent of hypertension, on intima proliferation.
Methods. We retrospectively selected renal biopsies of subjects in whom a glomerular filtration rate (GFR) measurement with [125I] iothalamate had been performed. To separate the effects of renal disease and renal function, we selected biopsies from (A) normotensive controls undergoing nephrectomy because of renal carcinomas; (B) normotensive patients with renal disease and GFR>90 ml/min; (C) normotensive patients with GFR 3090 ml/min, and (D) hypertensive patients with a GFR<90 ml/min. The area of the arteriolar lumen, intima, and media were measured.
Results. No significant changes from control subjects were observed in group B. Intima proliferation was observed when renal function declined (intima/total vessel surface ratio was 0.262±0.071 in group C, 0.192±0.032 in group A, and 0.205±0.035 in group B, P<0.05). The intima proliferation was aggravated in patients with renal insufficiency and hypertension (0.333±0.121, P<0.05). Media surface area was not different between groups.
Conclusion. Renal disease with preserved GFR does not cause significant intima proliferation of small renal arteries. Loss of renal function is accompanied by intima proliferation, even in the absence of systemic hypertension.
Keywords: arteries; blood pressure; cardiovascular system; hypertension; kidney failure (chronic); pathology
 |
Introduction
|
---|
Cardiovascular disease is very common in patients with end stage renal disease. Accelerated arterial stiffening and a high prevalence of atherosclerotic lesions contribute to high cardiovascular mortality rates in this population [15]. Although relatively little is known about the nature of the vascular changes in earlier stages of renal disease, there appears to be an association with several distinct pathological conditions. Intima proliferation of small renal arteries increases with age [6], and correlates with the extent of atherosclerosis in the aorta and coronary arteries [7]. Intima proliferation of small intrarenal arteries occurs at an accelerated rate in subjects with hypertension and in smokers [6,8]. It has also been observed in patients with renal disease, particularly in patients with IgA nephropathy, with or without hypertension [911]. Hypertension is generally considered to play an important role in the pathogenesis of intrarenal vascular changes in patients with renal disease.
The aim of the present study was to separate the effects of renal disease, renal function, and hypertension on vascular pathology of small renal arteries. We therefore compared the renal microvasculature in renal biopsies taken from selected patient groups. Selection was based on the presence of chronic renal disease, on glomerular filtration rate, and on the presence or absence of hypertension.
 |
Subjects and methods
|
---|
Subjects
We retrospectively analysed renal tissue of patients in whom both a renal biopsy and a [125I] iothalamate glomerular filtration rate (GFR) measurement had been performed between 1985 and 1999. Subjects with acute renal failure or any type of vasculitis were excluded. Age, diagnosis, GFR, blood pressure level, antihypertensive medication, smoking habits and, if available, total cholesterol levels at the time of the renal biopsy were collected from the patient files.
Four groups were selected:
- (A) Normotensive patients in whom nephrectomy was performed, in most cases because of a renal cell carcinoma. In those subjects, no GFR measurement was available.
- (B) Patients with chronic renal disease, having a GFR >90 ml/min, without hypertension, (blood pressure <160/90 mmHg, without the use of antihypertensive medication).
- (C) Patients with chronic renal disease, without hypertension and a GFR between 30 and 90 ml/min.
- (D) Patients with chronic renal disease, and a GFR <90 ml/min, in the presence of hypertension (blood pressure
160/90 mmHg, and/or the use of one or more antihypertensive medications).
Processing of biopsies and morphometry
Paraffin-embedded renal biopsies of all patients included in the study (two tissue samples per patient, groups B, C, D) and tissue blocks containing normal renal parenchyma (group A) were retrieved from the files of the Department of Pathology, Academic Medical Center (AMC). Three-micrometre sections were cut and stained with elastic van Gieson (EvG) and haematoxylin and eosin (H&E) respectively.
For morphometrical analysis, cross-sectional areas of the entire artery (total surface), lumen, intima and media were planometrically quantified in EvG-stained sections using TIM image analysis software on a PC provided with a VS-100-AT frame grabber (Data Measuring Systems, Breda, the Netherlands). Sections were projected on a video screen and the inner border of the intima, the internal elastic lamina (IEL), and the outer border of the vessel (media) were outlined manually. The cross-sectional area of the intima was represented by the surface area enclosed within the inner border of the intima and the IEL. The cross-sectional area of the media was defined as the area enclosed within the IEL and the outer border of the media. All areas were measured automatically, expressed in µm2, and stored on disk. All arterioles and small arteries in the range from 5000 to 20 000 µm2 were included in the study. Of these vessels the wall/lumen, lumen/total surface, wall/total surface, intima/total surface, and media/total surface ratios were calculated.
Statistical analysis
Results are expressed as means±SD. Paired t-tests were used to compare results of the different groups, if a one-way ANOVA had shown significant differences to be present. P values <0.05 were considered significant. Linear regression analysis was performed to calculate correlation coefficients.
 |
Results
|
---|
Basic characteristics for all four groups are given in Table 1
. All subjects of group A underwent unilateral nephrectomy because of renal cell carcinoma. In group B, five subjects suffered from IgA nephropathy, three from membranous glomerulopathy, one from minimal-change glomerulopathy, and one from focal glomerulosclerosis. In group C, chronic interstitial nephritis was diagnosed in nine patients, and IgA nephropathy and minimal-change glomerulopathy in one patient each. In group D, hypertensive nephropathy was diagnosed in three subjects, IgA nephropathy in two, and mesangioproliferative glomerulopathy and membranous glomerulopathy in one patient each. In group A, no GFR measurements were available. However all subjects in this group had normal serum creatinine values.
Serum cholesterol levels were available in 17 subjects. Serum cholesterol ranged from 5.7 to 10.3 mmol/l (n=8) in group B, from 3.9 to 8.7 mmol/l in group C (n=5), and from 4.7 to 7.9 mmol/l in group D (n=4), with no significant differences between groups.
Histologically the intima thickening consisted of an accumulation of extracellular matrix, including thickening and multiplication of elastin lamellae, in which sparse spindle shaped cells (smooth-muscle cells) were present. There were no obvious structural differences in composition among the four groups, although the formation of concentric lamellae of elastin was most pronounced in the patients with hypertension. Representative examples are shown in Figure 1
.

View larger version (45K):
[in this window]
[in a new window]
|
Fig. 1. Histological samples. Representative examples of the light microscopy of small renal arteries in biopsies of patients enrolled in group A (A), group C (B) and group D (C). Elastic van Gieson stain, 175x.
|
|
The total surface of the vessels studied tended to be largest in group A; the intima surface was largest in group D (Table 2
). The wall-to-lumen ratio did not differ between groups A and B. The wall-to-lumen ratio was elevated both in normotensive and hypertensive patients with renal function loss (groups C and D, Table 2
). The contribution of the wall area to the total surface area was clearly increased in group C and D.
This increase could be attributed to an increase of intima surface at the expense of luminal surface (Figures 2
, 3
). The relative media surface was not different among the four groups (Table 2
).

View larger version (8K):
[in this window]
[in a new window]
|
Fig. 2. Luminal surface. Individual luminal surface area normalized for the total surface area (lumen area/total surface area) in percentage. Group A, normotensive controls (n=12); group B, normotensive renal patients with GFR >90 ml/min (n=10); group C, normotensive renal patients with GFR 3090 ml/min (n=11); group D, hypertensive renal patients with GFR 3090 ml/min (n=7).
|
|

View larger version (8K):
[in this window]
[in a new window]
|
Fig. 3. Intima surface. Individual intima surface area normalized for the total surface area (intima area/total surface area) in percentage. Group A, normotensive controls (n=12); group B, normotensive renal patients with GFR >90 ml/min (n=10); group C, normotensive renal patients with GFR 3090 ml/min (n=11); group D, hypertensive renal patients with GFR 3090 ml/min (n=7).
|
|
We found no significant correlations between age, blood pressure level, serum cholesterol levels, or smoking behaviour, and intima proliferation.
 |
Discussion
|
---|
In this study we show that renal function loss is accompanied by intima proliferation of renal arterioles, even in the absence of hypertension. This intima proliferation is accelerated in the presence of hypertension. We further show that the mere presence of a renal disease does not cause intima proliferation.
Although we had data of a limited number of patients only, we were able to separate the effects of renal disease, renal function loss, and hypertension. Using [125I] iothalamate GFR measurements, which are more precise in estimating renal function than creatinine clearance, we separated subjects with preserved renal function from those with chronic renal function loss. Since many patients with chronic renal function loss are hypertensive, it has been difficult to separate the effects of renal function loss and hypertension on intima proliferation. Selection of normotensive and hypertensive patients groups allowed us to make this distinction.
We did not observe a significant difference in intima proliferation of small renal arteries between normotensive controls (group A) and normotensive subjects with a renal disease and preserved renal function (group B). However, the age of the control group tended to be higher and the average size of the studied arteries tended to be larger in the control group. Both age [6] and artery size [12] were found to correlate positively with the extent of intima proliferation. Therefore, a small effect of the mere presence of renal disease cannot be completely excluded.
The results in group C show that chronic renal function loss is accompanied by intima proliferation of small renal arteries, even in the absence of systemic hypertension. This increased intima proliferation could not be explained by differences in age, smoking pattern, or cholesterol level. However, other factors have been shown to be involved in the pathogenesis of cardiovascular disease in renal failure. Lipid profiles become more atherogenic and oxidative stress increases, as do cytokine levels and levels of various growth-promoting substances such as angiotensin 2, endothelin, platelet-derived growth factor, and vascular endothelial growth factor [1316]. The latter substances especially may be involved in smooth-muscle proliferation, which is often present in the expanding intima of renal arteries [11]. The increased arteriolar wall thickening in the absence of hypertension is also in agreement with studies in uraemic animals. In several studies progression, as well as treatment-induced regression, of hypertrophy of cardiac arterioles was shown to be, at least in part, independent of blood pressure [1618].
Although the increase in intima surface between groups C and D did not reach statistical significance, there seems to be a trend towards increased intima proliferation in hypertensive patients with chronic renal function loss. The use of antihypertensive medication might have affected the intima proliferation in group D. We did not observe an age-dependent increase of the intima surface within the control group, possibly because normotensive subjects were selected. Blood pressure, which increases with age, is more strongly related to intima proliferation than to age [19]. The relatively small sample size of the control group might be another reason why no age-dependent intima proliferation was found.
Media hypertrophy was not found, even in hypertensive subjects. This is in agreement with previous findings in hypertensive rats. Whereas hypertension causes media hypertrophy in other organs, this is not necessarily the case in small renal arteries [20]. Furthermore, arterial remodelling has mainly been shown in arteries that were slightly larger (100200 µm diameter) [21], than most of the small arteries investigated in the present study. In the hypertensive subjects (group D), the lack of media hypertrophy might be partly explained by the use of antihypertensive agents.
 |
Limitations
|
---|
The number of normotensive patients in whom both a renal biopsy and a GFR measurement had been performed was limited. Therefore we could not make a distinction between subjects with mild, moderate, and severe renal function loss. However, the main finding of this study, the fact that renal disease with preserved GFR does not cause intima proliferation of small renal arteries, was based on the comparison of the two largest groups, the normotensive controls (group A, n=12) vs group B normotensive renal patients with GFR >90 ml/min (n=10). Testing the significance of the 1.3% difference in intima surface between these groups with a power of 0.8 at a significance level of 0.05 requires a study in which 128 subjects would have to be included in both groups! Although based on relatively small groups, we think our data provide a strong indication that intima proliferation is not accelerated in normotensive renal patients with a preserved GFR.
The study population is too small to study the effect of individual renal diseases. Furthermore, it cannot be concluded that the increase in intima proliferation observed in group C, the normotensive subjects with decreased GFR, in comparison with group B, the normotensive renal patients with preserved GFR is solely due to the difference in renal function. The fact that group B consisted completely of patients with glomerulopathies, whereas the majority of group C suffered from interstitial nephritis, might have affected our results as well.
We do not think that the use of different sampling techniques (tissue samples obtained after nephrectomy in group A vs two transcutaneous renal biopsies in the other groups) introduced a further bias. As detailed in Table 2
, the average number of vessels was only marginally larger in group A. We were aware of the risk of studying larger vessels in the groups in which larger tissue specimens were available (group A). By limiting our study to vessels with a total surface area less than 20 000 µm2, such differences could be prevented.
We conclude that renal disease with preserved GFR does not cause significant intima proliferation of small renal arteries. However, once associated with a loss of renal function, renal disease appears to be accompanied by intimal proliferations, even in the absence of systemic hypertension.
 |
Acknowledgments
|
---|
W. J. W. Bos is the recipient of grant 90218307 of the Netherlands Foundation for Scientific Research (NWO).
 |
Notes
|
---|
Correspondence and offprint requests to: W. J. W. Bos MD PhD, Department of Internal Medicine, St Antonius Hospital, PO Box 2500, 3430 EM Nieuwegein, The Netherlands. 
 |
References
|
---|
-
Sarnak MJ, Levey AS. Epidemiology of cardiac disease in dialysis patients. Semin Dial1999; 12: 6976[ISI]
-
Foley RN, Parfrey PS, Sarnak M. The clinical epidemiology of cardiovascular disease in chronic renal disease. Am J Kidney Dis1998; 32 [Suppl.]: S112115[ISI][Medline]
-
Parfrey PS, Foley RN, Harnett JD. Organ and metabolic complications: cardiac. In: Jacobs C, Kjellstrand CM, Koch KM, Winchester JF, eds. Replacement of Renal Function by Dialysis. Kluwer, Dordrecht, 1996, 9901002
-
London GM, Guerrin AP, Marchais SJ et al. Cardiac and arterial interactions in end-stage renal disease. Kidney Int1996; 50: 600608[ISI][Medline]
-
London GM, Guerin AP, Marchais SJ. Hemodynamic overload in end-stage renal disease patients. Semin Dial1999; 12: 7783[ISI]
-
Tracey RE, Berenson G, Wattigney W, Barrett TJ. The evolution of benign arterionephrosclerosis from age 6 to 70. Am J Pathol1990; 136: 429439[Abstract]
-
Tracey RE, Strong JP, Newman WP, Malcolm GT, Oalmann MC, Guzman MA. Renovasculopathies of nephrosclerosis in relation to atherosclerosis at ages 25 to 54 years. Kidney Int1996; 49: 564570[ISI][Medline]
-
Black HR, Zeevi GR, Silten RM, Smith GJW. Effect of heavy cigarette smoking on renal and myocardial arterioles. Nephron1983; 34: 173179[ISI][Medline]
-
Clarkson AR, Seymour AE, Thompson AJ, Haynes WDG, Chan YL, Jackson B. IgA nephropathy: a syndrome of uniform morphology, diverse clinical features and uncertain prognosis. Clin Nephrol1977; 8: 459471[ISI][Medline]
-
Feiner HD, Cabili S, Baldwin DS, Schacht RG, Gallo GR. Intrarenal vascular sclerosis in IgA nephropathy. Clin Nephrol1982; 18: 183192[ISI][Medline]
-
Helmchen U. Effects of hypertension on renal vasculature and structure. In: Cameron S, Davison AM, Gruenfeld JP, Kerr D, Ritz E, eds. Oxford Textbook of Clinical Nephrology, Oxford University Press, Oxford, 1992, 20752083
-
Tracey RE, Mercante DE, Moncada A, Berenson G. Quantitation of hypertensive nephrosclerosis on an objective rational scale of measure in adults and children. Am J Clin Pathol1986; 85: 312318[ISI][Medline]
-
Prichard S. Dyslipidemia as a risk factor for cardiac disease in dialysis patients. Semin Dial1999; 12: 8790[ISI]
-
Rigatto C, Singal PK. Oxidative stress in uremia: impact on cardiac disease in dialysis patients. Semin Dial1999; 12: 9196[ISI]
-
Amann K, Ritz E. Cardiovascular abnormalities in ageing and in uraemiaonly analogy or shared pathomechanisms? Nephrol Dial Transplant1998; 13 [Suppl. 7]: 611[Free Full Text]
-
Amann K, Kronenberg G, Gehlen F et al. Cardiac remodelling in experimental renal failurean immunohistochemical study. Nephrol Dial Transplant1998; 13: 19581966[Abstract]
-
Tornig J, Gross ML, Simonaviciene A, Mall G, Ritz E, Amann K. Hypertrophy of intramyocardial arteriolar smooth muscle cells in experimental renal failure. Am Soc Nephrol1999; 10: 7783[Abstract/Free Full Text]
-
Nabokov AV, Amann K, Wessels S, Munter K, Wagner J, Ritz E. Endothelin receptor antagonists influence cardiovascular morphology in uremic rats. Kidney Int1999; 55: 512519[ISI][Medline]
-
Tracey RE, Velez-Duran M, Heigle T, Oalmann MC. Two variants of nephrosclerosis separately related to age and blood pressure. Am J Pathol1988; 131: 270282[Abstract]
-
Skov K, Fenger-Gron J, Mulvany MJ. Effects of an angiotensin-converting enzyme inhibitor, a calcium antagonist and an endothelin receptor antagonist on renal afferent arteriolar structure. Hypertension1996; 28: 464471[Abstract/Free Full Text]
-
Mulvany MJ. Resistance vessel structure and the pathogenesis of hypertension. J Hypertens1993; 11 [Suppl 5]: S712[ISI]
Received for publication: 14. 3.00
Revision received 10.10.00.