Aging is associated with progressive structural and functional deterioration of the kidney. Among... more Aging is associated with progressive structural and functional deterioration of the kidney. Among the morphological changes associated with renal aging is an accumulation of extracellular matrix (ECM) in the glomeruli and tubuloinsterstitium, which may ultimately lead to the development of renal fibrosis. The mechanisms governing the regulation of ECM metabolism during renal aging are only incompletely defined. We present data from a genome-wide mRNA expression study on renal tissue from 90 wk old male Wistar rats and 10 wk old controls using Illumina BeadArray cDNA microarray. Regulation of candidate gene products was verified by real-time PCR. Morphological changes were evaluated by routine histological methods. Activated fibroblasts were identified by their expression of alpha-smooth muscle actin and collagen I. Morphological analysis demonstrated an expansion of the tubulointerstitial compartment with increased amounts of fibrous collagen but no overt glomerular or tubular damag...
<b><i>Background:</i></b> Tubular atrophy and interstitial fibrosis mark ... more <b><i>Background:</i></b> Tubular atrophy and interstitial fibrosis mark the final stage in most forms of progressive kidney diseases. Little is known regarding changes in the tubular proteome. In this study, we investigated changes in the tubular proteome of normal or minimally damaged tubular tissue in the non-clipped kidney from rats with two-kidney one-clip (2K1C) hypertension. <b><i>Methods:</i></b> Formalin-fixed paraffin-embedded kidney sections from four 2K1C rats with hypertensive kidney damage and 6 sham rats were used. Tubulointerstitial tissue without discernable interstitial expansion or pronounced tubular alterations was microdissected and this was assumed to represent an early stage of chronic tubular damage in 2K1C. Samples were analyzed by mass spectrometry and relative protein abundances were compared between 2K1C and sham. <b><i>Results:</i></b> A total of 1,160 proteins were identified with at least 2 unique peptides, allowing for relative quantitation between samples. Among these, 151 proteins were more abundant, and 192 proteins were less abundant in 2K1C compared with sham. Transgelin, vimentin and creatine kinase B-type were among the proteins that were most increased in 2K1C. Ingenuity Pathway Analysis showed increased abundance of proteins related to Rho signaling and protein turnover (eIF2 signaling and protein ubiquitination), and decreased abundance of proteins related to fatty acid β-oxidation. <b><i>Conclusion:</i></b> Tubular tissue from normal or minimally damaged hypertensive kidney damage demonstrate extensive proteomic changes with upregulation of pathways associated with progressive kidney damage, such as Rho signaling and protein turnover. Thus, proteomics presents itself to be a promising tool for the discovery of early damage markers from not yet morphologically visible tubular damage.
Male wistar rats were randomly divided into four groups: control and three hyperoxaluric groups i... more Male wistar rats were randomly divided into four groups: control and three hyperoxaluric groups i.e. ethylene glycol alone, ethylene glycol with ammonium chloride and hydroxy-l-proline, respectively. After the induction of hyperoxaluria, 24 hour urine was collected from the rats and THP was isolated from it. To elucidate any changes in the isolated THP conformation its surface hydrophobicity, FTIR spectra were observed and sialic acid content of the protein was estimated. Further, rats were then sacrificed and kidneys were removed and expression of THP and ST-8 in renal tissue was analysed. RESULTS: A concentrated expression of THP near calcium oxalate crystal deposits in the renal tissue of all the hyperoxaluric groups was observed, however no significant altered levels of THP were found at gene level as revealed by the study. Further, hyperoxaluric treatment resulted in the absence of peak at 1462 cm-1 as demonstrated by the FTIR spectrum of THP accompanied by a significant alteration in the extent of hydrophobicity. In addition, sialic acid content of renal tissues and isolated THP was observed to be significantly lowered in the animals exposed to hyperoxaluric insult. CONCLUSIONS: Above mentioned revelations advocate the possibility that hyperoxaluric environment can adversely affect the functional integrity THP by regulating its structural, conformational and functional aspects, thus jeopardising its role in renal stone formation. These findings plausibly could pave a path directed towards the development of novel therapeutic approaches with an aim for remediating urinary glycoproteins.
Hypertensive nephrosclerosis is one of the most frequent causes of chronic kidney failure. Proteo... more Hypertensive nephrosclerosis is one of the most frequent causes of chronic kidney failure. Proteome analysis potentially improves the pathophysiological understanding and diagnostic precision of this disorder. In the present exploratory study, we investigated experimental nephrosclerosis in the two-kidney, one-clip (2K1C) hypertensive rat model. The renal cortex proteome from juxtamedullary cortex and outer cortex of 2K1C male Wistar-Hannover rats (n = 4) was compared with the sham-operated controls (n = 6), using mass spectrometry-based quantitative proteomics. We combined a high abundant plasma protein depletion strategy with an extended liquid chromatographic gradient to improve peptide and protein identification. Immunohistology was used for independent confirmation of abundance. We identified 1724 proteins, of which 1434 were quantified with at least two unique peptides. Comparative proteomics revealed 608 proteins, including the platelet-derived growth factor receptor-β signal...
Two-kidney, one-clip (2K1C) is a model of renovascular hypertension where we previously found an ... more Two-kidney, one-clip (2K1C) is a model of renovascular hypertension where we previously found an exaggerated intracellular calcium (Ca[Formula: see text]) response to ANG II in isolated afferent arterioles (AAs) from the clipped kidney (Helle F, Vagnes OB, Iversen BM. Am J Physiol Renal Physiol 291: F140–F147, 2006). To test whether nitric oxide (NO) ameliorates the exaggerated ANG II response in 2K1C, we studied ANG II (10−7 mol/l)-induced calcium signaling and contractility with or without the NO synthase (NOS) inhibitor NG-nitro-l-arginine methyl ester (l-NAME). In AAs from the nonclipped kidney, l-NAME increased the ANG II-induced Ca[Formula: see text] response from 0.28 ± 0.05 to 0.55 ± 0.09 (fura 2, 340 nm/380 nm ratio) and increased contraction from 80 ± 6 to 60 ± 6% of baseline ( P < 0.05). In vessels from sham and clipped kidneys, l-NAME had no effect. In diaminofluorescein-FM diacetate-loaded AAs from the nonclipped kidney, ANG II increased NO-derived fluorescence to 14...
Uninephrectomy (UNX) causes hyperperfusion of the contralateral remaining kidney via increased ni... more Uninephrectomy (UNX) causes hyperperfusion of the contralateral remaining kidney via increased nitric oxide (NO) synthesis. Although the exact mechanism remains largely unknown, we hypothesize that this would be localized to the afferent arteriole and that it depends on cellular uptake of l-arginine. The experiments were performed in rats 2 days (early) or 6 wk (late) after UNX and compared with controls (Sham) to study acute and chronic effects on NO metabolism. Renal blood flow was increased after UNX (21 ± 2 ml·min−1·kg−1 in sham, 30 ± 3 in early, and 26 ± 1 in late, P < 0.05). NO inhibition with Nω-nitro-l-arginine methyl ester hydrochloride (l-NAME) caused a greater increase in renal vascular resistance in early UNX compared with Sham and late UNX (138 ± 24 vs. 88 ± 10, and 84 ± 7%, P < 0.01). The lower limit of autoregulation was increased both in early and late UNX compared with Sham ( P < 0.05). l-NAME did not affect the ANG II-induced contraction of isolated affere...
Background. It is well known that hypertension may cause glomerular damage, but the molecular mec... more Background. It is well known that hypertension may cause glomerular damage, but the molecular mechanisms involved are still incompletely understood. Methods. In the present study, we used formalin-fixed paraffinembedded (FFPE) tissue to investigate changes in the glomerular proteome in the non-clipped kidney of two-kidney one-clip (2K1C) hypertensive rats, with special emphasis on the glomerular filtration barrier. 2K1C hypertension was induced in 6-week-old Wistar Hannover rats (n = 6) that were sacrificed 23 weeks later and compared with age-matched sham-operated controls (n = 6). Tissue was stored in FFPE tissue blocks and later prepared on tissue slides for laser microdissection. Glomeruli without severe morphological damage were isolated, and the proteomes were analysed using liquid chromatographytandem mass spectrometry. Results. 2K1C glomeruli showed reduced abundance of proteins important for slit diaphragm complex, such as nephrin, podocin and neph1. The podocyte foot process had a pattern of reduced abundance of transmembrane proteins but unchanged abundances of the podocyte cytoskeletal proteins synaptopodin and α-actinin-4. Lower abundance of important glomerular basement membrane proteins was seen. Possible glomerular markers of damage with increased abundance in 2K1C were transgelin, desmin and acyl-coenzyme A thioesterase 1. Conclusions. Microdissection and tandem mass spectrometry could be used to investigate the proteome of isolated glomeruli from FFPE tissue. Glomerular filtration barrier proteins had reduced abundance in the non-clipped kidney of 2K1C hypertensive rats.
Hypertensive renal damage starts in the juxtamedullary cortex (JMC) and gradually extends towards... more Hypertensive renal damage starts in the juxtamedullary cortex (JMC) and gradually extends towards the outer cortex (OC). The intention of the study was to examine if the increase of fibrous tissue in the JMC of the spontaneously hypertensive rat (SHR) is dependent on an increase of collagen synthesis or a decreased collagen breakdown compared to the normotensive control (WKY). The renal damage was evaluated by light microscopy, and the amount of fibrosis was quantified using Sirius red staining. Real-time RT-PCR was used to quantify mRNA for: collagen-type-1-alpha-1 (col1a1), procollagen-n- and -c-proteinase, matrix metalloproteases, MMP-2 and MMP-9, tissue inhibitor of metalloproteases, TIMP-1 and TIMP-2. Western blot was used to quantify the proteins of MMP-2, MMP-9, TIMP-1 and TIMP-2. The relative activities of MMP-2 and MMP-9 were assayed by zymography. The JMC in SHR had an increased amount of collagen as measured by Sirius red, and a 15-fold increase in the mRNA for col1a1. The gene expression of procollagen-c-proteinase was unchanged while procollagen-n-proteinase was increased in SHR and had the highest expression in the JMC. The mRNA for MMP-2 and MMP-9 showed increased expression in SHR, but not specifically in the JMC. Protein analysis showed increased expression for MMP-2 in SHR and in the JMC. MMP-9 protein was lower in SHR. TIMP-1 was increased in SHR at both mRNA and protein level and more so in the JMC. The mRNA and protein analysis of TIMP-2 showed small differences between SHR and WKY. An imbalance of collagen metabolism featuring increased synthesis and inhibition of breakdown favours renal interstitial fibrosis in SHR.
The progression of damage in the renal cortex has not been investigated in the nonclipped kidney ... more The progression of damage in the renal cortex has not been investigated in the nonclipped kidney of the two-kidney, one-clip model of renal hypertension. In other hypertensive models, damage has been found to progress from the juxtamedullary cortex (JMC) and outward, which has been attributed to early vascular effects. The present study investigated the relation between perivascular deposition of collagen and structural damage after 16 and 24 weeks of hypertension in the nonclipped kidney in rats. Periarterial collagen density in the kidney was significantly increased already 16 weeks after clipping, at that time tubulointerstitial damage was not evident. After 24 weeks of clipping, periarterial collagen was further increased, and tubulointerstitial damage had developed in the JMC, whereas the outer cortex was protected. Interstitial collagen was not significantly increased in any cortex part during the course of the experiment. Collagen type I a1 mRNA was increased in the JMC after 24 weeks, and α smooth muscle actin histochemistry and collagen type I a2 in-situ hybridization identified myofibroblasts around the arteries after 16 and 24 weeks as the major source of this increase. Fibrosis in the nonclipped kidney of renal hypertensive rats starts around the juxtamedullary resistance vessels and then progresses in the JMC, whereas the outer cortex is protected. This suggests that pressure-induced injury to the vasculature attracts or activates fibroblasts in the perivascular area, which may allow damage to progress by impairing vessel function.
Aging is associated with progressive structural and functional deterioration of the kidney. Among... more Aging is associated with progressive structural and functional deterioration of the kidney. Among the morphological changes associated with renal aging is an accumulation of extracellular matrix (ECM) in the glomeruli and tubuloinsterstitium, which may ultimately lead to the development of renal fibrosis. The mechanisms governing the regulation of ECM metabolism during renal aging are only incompletely defined. We present data from a genome-wide mRNA expression study on renal tissue from 90 wk old male Wistar rats and 10 wk old controls using Illumina BeadArray cDNA microarray. Regulation of candidate gene products was verified by real-time PCR. Morphological changes were evaluated by routine histological methods. Activated fibroblasts were identified by their expression of alpha-smooth muscle actin and collagen I. Morphological analysis demonstrated an expansion of the tubulointerstitial compartment with increased amounts of fibrous collagen but no overt glomerular or tubular damage in the aged rats. Activated fibroblasts were readily detectable in the adventitial layer of large renal vessels in controls and were not found in the old animals. In agreement with this finding, gene expression analysis revealed significant downregulation of collagen I mRNA along with numerous other ECM components. Concomitantly, collagen-stabilizing proteins were induced, whereas matrix metalloproteinase 9, an enzyme involved in collagen breakdown, was reduced. In conclusion, our results suggest that ECM expansion during renal aging results from an augmented stabilization in conjunction with a reduced breakdown of collagen fibers. Collagen stabilizing proteins may be essential for the control of renal ECM turnover and the pathogenesis of kidney fibrosis.
Aging is associated with progressive structural and functional deterioration of the kidney. Among... more Aging is associated with progressive structural and functional deterioration of the kidney. Among the morphological changes associated with renal aging is an accumulation of extracellular matrix (ECM) in the glomeruli and tubuloinsterstitium, which may ultimately lead to the development of renal fibrosis. The mechanisms governing the regulation of ECM metabolism during renal aging are only incompletely defined. We present data from a genome-wide mRNA expression study on renal tissue from 90 wk old male Wistar rats and 10 wk old controls using Illumina BeadArray cDNA microarray. Regulation of candidate gene products was verified by real-time PCR. Morphological changes were evaluated by routine histological methods. Activated fibroblasts were identified by their expression of alpha-smooth muscle actin and collagen I. Morphological analysis demonstrated an expansion of the tubulointerstitial compartment with increased amounts of fibrous collagen but no overt glomerular or tubular damag...
<b><i>Background:</i></b> Tubular atrophy and interstitial fibrosis mark ... more <b><i>Background:</i></b> Tubular atrophy and interstitial fibrosis mark the final stage in most forms of progressive kidney diseases. Little is known regarding changes in the tubular proteome. In this study, we investigated changes in the tubular proteome of normal or minimally damaged tubular tissue in the non-clipped kidney from rats with two-kidney one-clip (2K1C) hypertension. <b><i>Methods:</i></b> Formalin-fixed paraffin-embedded kidney sections from four 2K1C rats with hypertensive kidney damage and 6 sham rats were used. Tubulointerstitial tissue without discernable interstitial expansion or pronounced tubular alterations was microdissected and this was assumed to represent an early stage of chronic tubular damage in 2K1C. Samples were analyzed by mass spectrometry and relative protein abundances were compared between 2K1C and sham. <b><i>Results:</i></b> A total of 1,160 proteins were identified with at least 2 unique peptides, allowing for relative quantitation between samples. Among these, 151 proteins were more abundant, and 192 proteins were less abundant in 2K1C compared with sham. Transgelin, vimentin and creatine kinase B-type were among the proteins that were most increased in 2K1C. Ingenuity Pathway Analysis showed increased abundance of proteins related to Rho signaling and protein turnover (eIF2 signaling and protein ubiquitination), and decreased abundance of proteins related to fatty acid β-oxidation. <b><i>Conclusion:</i></b> Tubular tissue from normal or minimally damaged hypertensive kidney damage demonstrate extensive proteomic changes with upregulation of pathways associated with progressive kidney damage, such as Rho signaling and protein turnover. Thus, proteomics presents itself to be a promising tool for the discovery of early damage markers from not yet morphologically visible tubular damage.
Male wistar rats were randomly divided into four groups: control and three hyperoxaluric groups i... more Male wistar rats were randomly divided into four groups: control and three hyperoxaluric groups i.e. ethylene glycol alone, ethylene glycol with ammonium chloride and hydroxy-l-proline, respectively. After the induction of hyperoxaluria, 24 hour urine was collected from the rats and THP was isolated from it. To elucidate any changes in the isolated THP conformation its surface hydrophobicity, FTIR spectra were observed and sialic acid content of the protein was estimated. Further, rats were then sacrificed and kidneys were removed and expression of THP and ST-8 in renal tissue was analysed. RESULTS: A concentrated expression of THP near calcium oxalate crystal deposits in the renal tissue of all the hyperoxaluric groups was observed, however no significant altered levels of THP were found at gene level as revealed by the study. Further, hyperoxaluric treatment resulted in the absence of peak at 1462 cm-1 as demonstrated by the FTIR spectrum of THP accompanied by a significant alteration in the extent of hydrophobicity. In addition, sialic acid content of renal tissues and isolated THP was observed to be significantly lowered in the animals exposed to hyperoxaluric insult. CONCLUSIONS: Above mentioned revelations advocate the possibility that hyperoxaluric environment can adversely affect the functional integrity THP by regulating its structural, conformational and functional aspects, thus jeopardising its role in renal stone formation. These findings plausibly could pave a path directed towards the development of novel therapeutic approaches with an aim for remediating urinary glycoproteins.
Hypertensive nephrosclerosis is one of the most frequent causes of chronic kidney failure. Proteo... more Hypertensive nephrosclerosis is one of the most frequent causes of chronic kidney failure. Proteome analysis potentially improves the pathophysiological understanding and diagnostic precision of this disorder. In the present exploratory study, we investigated experimental nephrosclerosis in the two-kidney, one-clip (2K1C) hypertensive rat model. The renal cortex proteome from juxtamedullary cortex and outer cortex of 2K1C male Wistar-Hannover rats (n = 4) was compared with the sham-operated controls (n = 6), using mass spectrometry-based quantitative proteomics. We combined a high abundant plasma protein depletion strategy with an extended liquid chromatographic gradient to improve peptide and protein identification. Immunohistology was used for independent confirmation of abundance. We identified 1724 proteins, of which 1434 were quantified with at least two unique peptides. Comparative proteomics revealed 608 proteins, including the platelet-derived growth factor receptor-β signal...
Two-kidney, one-clip (2K1C) is a model of renovascular hypertension where we previously found an ... more Two-kidney, one-clip (2K1C) is a model of renovascular hypertension where we previously found an exaggerated intracellular calcium (Ca[Formula: see text]) response to ANG II in isolated afferent arterioles (AAs) from the clipped kidney (Helle F, Vagnes OB, Iversen BM. Am J Physiol Renal Physiol 291: F140–F147, 2006). To test whether nitric oxide (NO) ameliorates the exaggerated ANG II response in 2K1C, we studied ANG II (10−7 mol/l)-induced calcium signaling and contractility with or without the NO synthase (NOS) inhibitor NG-nitro-l-arginine methyl ester (l-NAME). In AAs from the nonclipped kidney, l-NAME increased the ANG II-induced Ca[Formula: see text] response from 0.28 ± 0.05 to 0.55 ± 0.09 (fura 2, 340 nm/380 nm ratio) and increased contraction from 80 ± 6 to 60 ± 6% of baseline ( P < 0.05). In vessels from sham and clipped kidneys, l-NAME had no effect. In diaminofluorescein-FM diacetate-loaded AAs from the nonclipped kidney, ANG II increased NO-derived fluorescence to 14...
Uninephrectomy (UNX) causes hyperperfusion of the contralateral remaining kidney via increased ni... more Uninephrectomy (UNX) causes hyperperfusion of the contralateral remaining kidney via increased nitric oxide (NO) synthesis. Although the exact mechanism remains largely unknown, we hypothesize that this would be localized to the afferent arteriole and that it depends on cellular uptake of l-arginine. The experiments were performed in rats 2 days (early) or 6 wk (late) after UNX and compared with controls (Sham) to study acute and chronic effects on NO metabolism. Renal blood flow was increased after UNX (21 ± 2 ml·min−1·kg−1 in sham, 30 ± 3 in early, and 26 ± 1 in late, P < 0.05). NO inhibition with Nω-nitro-l-arginine methyl ester hydrochloride (l-NAME) caused a greater increase in renal vascular resistance in early UNX compared with Sham and late UNX (138 ± 24 vs. 88 ± 10, and 84 ± 7%, P < 0.01). The lower limit of autoregulation was increased both in early and late UNX compared with Sham ( P < 0.05). l-NAME did not affect the ANG II-induced contraction of isolated affere...
Background. It is well known that hypertension may cause glomerular damage, but the molecular mec... more Background. It is well known that hypertension may cause glomerular damage, but the molecular mechanisms involved are still incompletely understood. Methods. In the present study, we used formalin-fixed paraffinembedded (FFPE) tissue to investigate changes in the glomerular proteome in the non-clipped kidney of two-kidney one-clip (2K1C) hypertensive rats, with special emphasis on the glomerular filtration barrier. 2K1C hypertension was induced in 6-week-old Wistar Hannover rats (n = 6) that were sacrificed 23 weeks later and compared with age-matched sham-operated controls (n = 6). Tissue was stored in FFPE tissue blocks and later prepared on tissue slides for laser microdissection. Glomeruli without severe morphological damage were isolated, and the proteomes were analysed using liquid chromatographytandem mass spectrometry. Results. 2K1C glomeruli showed reduced abundance of proteins important for slit diaphragm complex, such as nephrin, podocin and neph1. The podocyte foot process had a pattern of reduced abundance of transmembrane proteins but unchanged abundances of the podocyte cytoskeletal proteins synaptopodin and α-actinin-4. Lower abundance of important glomerular basement membrane proteins was seen. Possible glomerular markers of damage with increased abundance in 2K1C were transgelin, desmin and acyl-coenzyme A thioesterase 1. Conclusions. Microdissection and tandem mass spectrometry could be used to investigate the proteome of isolated glomeruli from FFPE tissue. Glomerular filtration barrier proteins had reduced abundance in the non-clipped kidney of 2K1C hypertensive rats.
Hypertensive renal damage starts in the juxtamedullary cortex (JMC) and gradually extends towards... more Hypertensive renal damage starts in the juxtamedullary cortex (JMC) and gradually extends towards the outer cortex (OC). The intention of the study was to examine if the increase of fibrous tissue in the JMC of the spontaneously hypertensive rat (SHR) is dependent on an increase of collagen synthesis or a decreased collagen breakdown compared to the normotensive control (WKY). The renal damage was evaluated by light microscopy, and the amount of fibrosis was quantified using Sirius red staining. Real-time RT-PCR was used to quantify mRNA for: collagen-type-1-alpha-1 (col1a1), procollagen-n- and -c-proteinase, matrix metalloproteases, MMP-2 and MMP-9, tissue inhibitor of metalloproteases, TIMP-1 and TIMP-2. Western blot was used to quantify the proteins of MMP-2, MMP-9, TIMP-1 and TIMP-2. The relative activities of MMP-2 and MMP-9 were assayed by zymography. The JMC in SHR had an increased amount of collagen as measured by Sirius red, and a 15-fold increase in the mRNA for col1a1. The gene expression of procollagen-c-proteinase was unchanged while procollagen-n-proteinase was increased in SHR and had the highest expression in the JMC. The mRNA for MMP-2 and MMP-9 showed increased expression in SHR, but not specifically in the JMC. Protein analysis showed increased expression for MMP-2 in SHR and in the JMC. MMP-9 protein was lower in SHR. TIMP-1 was increased in SHR at both mRNA and protein level and more so in the JMC. The mRNA and protein analysis of TIMP-2 showed small differences between SHR and WKY. An imbalance of collagen metabolism featuring increased synthesis and inhibition of breakdown favours renal interstitial fibrosis in SHR.
The progression of damage in the renal cortex has not been investigated in the nonclipped kidney ... more The progression of damage in the renal cortex has not been investigated in the nonclipped kidney of the two-kidney, one-clip model of renal hypertension. In other hypertensive models, damage has been found to progress from the juxtamedullary cortex (JMC) and outward, which has been attributed to early vascular effects. The present study investigated the relation between perivascular deposition of collagen and structural damage after 16 and 24 weeks of hypertension in the nonclipped kidney in rats. Periarterial collagen density in the kidney was significantly increased already 16 weeks after clipping, at that time tubulointerstitial damage was not evident. After 24 weeks of clipping, periarterial collagen was further increased, and tubulointerstitial damage had developed in the JMC, whereas the outer cortex was protected. Interstitial collagen was not significantly increased in any cortex part during the course of the experiment. Collagen type I a1 mRNA was increased in the JMC after 24 weeks, and α smooth muscle actin histochemistry and collagen type I a2 in-situ hybridization identified myofibroblasts around the arteries after 16 and 24 weeks as the major source of this increase. Fibrosis in the nonclipped kidney of renal hypertensive rats starts around the juxtamedullary resistance vessels and then progresses in the JMC, whereas the outer cortex is protected. This suggests that pressure-induced injury to the vasculature attracts or activates fibroblasts in the perivascular area, which may allow damage to progress by impairing vessel function.
Aging is associated with progressive structural and functional deterioration of the kidney. Among... more Aging is associated with progressive structural and functional deterioration of the kidney. Among the morphological changes associated with renal aging is an accumulation of extracellular matrix (ECM) in the glomeruli and tubuloinsterstitium, which may ultimately lead to the development of renal fibrosis. The mechanisms governing the regulation of ECM metabolism during renal aging are only incompletely defined. We present data from a genome-wide mRNA expression study on renal tissue from 90 wk old male Wistar rats and 10 wk old controls using Illumina BeadArray cDNA microarray. Regulation of candidate gene products was verified by real-time PCR. Morphological changes were evaluated by routine histological methods. Activated fibroblasts were identified by their expression of alpha-smooth muscle actin and collagen I. Morphological analysis demonstrated an expansion of the tubulointerstitial compartment with increased amounts of fibrous collagen but no overt glomerular or tubular damage in the aged rats. Activated fibroblasts were readily detectable in the adventitial layer of large renal vessels in controls and were not found in the old animals. In agreement with this finding, gene expression analysis revealed significant downregulation of collagen I mRNA along with numerous other ECM components. Concomitantly, collagen-stabilizing proteins were induced, whereas matrix metalloproteinase 9, an enzyme involved in collagen breakdown, was reduced. In conclusion, our results suggest that ECM expansion during renal aging results from an augmented stabilization in conjunction with a reduced breakdown of collagen fibers. Collagen stabilizing proteins may be essential for the control of renal ECM turnover and the pathogenesis of kidney fibrosis.
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Papers by T. Skogstrand