Demonstration of collagen type VI and alpha-smooth muscle actin in renal fibrotic injury in man

COL28 promotes proliferation, migration, and EMT of renal tubular epithelial cells

Type XXVIII collagen (COL28) is involved in cancer and lung fibrosis. COL28 polymorphisms and mutations might be involved in kidney fibrosis, but the exact role of COL28 in renal fibrosis is unknown. This study explored the function of COL28 in renal tubular cells by examining the expression of COL28 mRNA and the effects of COL28 overexpression in human tubular cells. COL28 mRNA expression and localization were observed in normal and fibrotic kidney tissues from humans and mice using real-time PCR, western blot, immunofluorescence, and immunohistochemistry. The consequences of COL28 overexpression on cell proliferation, migration, cell polarity, and epithelial-to-mesenchymal transition (EMT) induced by TGF-β1 were examined in human tubular HK-2 cells. COL28 expression was low in human normal renal tissues, mainly observed in the renal tubular epithelial cells and especially in proximal renal tubules. COL28 protein expression in human and mouse obstructive kidney disease was higher than in normal tissues (p < 0.05) and more significant in the UUO2-Week than the UUO1-Week group. The overexpression of COL28 promoted HK-2 cell proliferation and enhanced their migration ability (all p < 0.05). TGF-β1 (10 ng/ml) induced COL28 mRNA expression in HK-2 cells, decreased E-cadherin and increased α-SMA in the COL28-overexpression group compared with controls (p < 0.05). ZO-1 expression decreased while COL6 increased in the COL28-overexpression group compared with controls (p < 0.05). In conclusion, COL28 overexpression promotes the migration and proliferation of renal tubular epithelial cells. The EMT could also be involved. COL28 could be a therapeutic target against renal- fibrotic diseases.

Endotrophin, a collagen type VI-derived matrikine, reflects the degree of renal fibrosis in patients with IgA nephropathy and in patients with ANCA-associated vasculitis

BACKGROUND

Renal fibrosis is the hallmark of chronic kidney disease (CKD) and is characterized by an imbalanced extracellular matrix remodelling. Endotrophin (ETP) is a signalling molecule released from collagen type VI (COL VI). ETP can be measured by the PRO-C6 assay, which quantifies the levels of COL VI formation. ETP levels were previously associated with mortality and disease progression in patients with CKD. We hypothesized that serum and urinary ETP levels correlate with the degree of interstitial fibrosis in kidney biopsies from patients with immunoglobulin A nephropathy (IgAN) and patients with anti-neutrophil cytoplasmic antibody-associated vasculitis (AAV).

METHODS

We examined a cohort of 49 IgAN and 47 AAV patients. A validation cohort of 85 IgAN patients was included. ETP was measured in serum (S-ETP) and urine (U-ETP/Cr) samples, taken on the same day before renal biopsy was performed, using the enzyme-linked immunosorbent assay PRO-C6. The biopsies were evaluated for interstitial fibrosis and tubular atrophy according to the Banff and MEST-C scores.

RESULTS

S-ETP and U-ETP/Cr levels correlated with kidney function, increased CKD severity, correlated with the extent of interstitial fibrosis and gradually increased with increasing degree of interstitial fibrosis and tubular atrophy. ETP outperformed the known fibrosis biomarker Dickkopf-3 for discrimination of patients with high fibrotic burden. The association of S-ETP and U-ETP/Cr with the level of kidney fibrosis was confirmed in the validation cohort.

CONCLUSIONS

We demonstrated that high levels of circulating and excreted ETP are not only indicative of lower kidney function, but also reflect the burden of fibrosis in the kidneys.

Collagen fibrils and cell nuclei are entrapped within Randall's plaques but not in CaOx matrix overgrowth: A microscopic inquiry into Randall's plaque stone pathogenesis

Calcium oxalate (CaOx) stones can grow attached to the renal papillary calcification known as Randall's plaque. Although stone growth on Randall's plaque is a common phenomenon, this mechanism of stone formation is still poorly understood. The objective of this study was to investigate the microenvironment of mature Randall's plaque, explore its molecular composition and differentiate plaque from CaOx overgrowth using multimodal imaging on demineralized stone sections. Fluorescence imaging showed consistent differences in autofluorescence patterns between Randall's plaque and calcium oxalate overgrowth regions. Second harmonic generation imaging established the presence of collagen only in regions of decalcified Randall's plaque but not in regions of CaOx overgrowth matrix. Surprisingly, in these stone sections we observed cell nuclei with preserved morphology within regions of mature Randall's plaque. These conserved cells had variable expression of vimentin and CD45. The presence of nuclei in mature plaque indicates that mineralization is not necessarily associated with cell death. The markers identified suggest that some of the entrapped cells may be undergoing dedifferentiation or could emanate from a mesenchymal or immune origin. We propose that entrapped cells may play an important role in the growth and maintenance of Randall's plaque. Further characterization of these cells and thorough analyses of the mineralized stone forming renal papilla will be fundamental in understanding the pathogenesis of Randall's plaque and CaOx stone formation.

Collagen VI as a driver and disease biomarker in human fibrosis

Fibrosis of visceral organs such as the lungs, heart, kidneys and liver remains a major cause of morbidity and mortality and is also associated with many other disorders, including cancer and metabolic disease. In this review, we focus upon the microfibrillar collagen VI, which is present in the extracellular matrix (ECM) of most tissues. However, expression is elevated in numerous fibrotic conditions, such as idiopathic pulmonary disease (IPF), and chronic liver and kidney diseases. Collagen VI is composed of three subunits α1, α2 and α3, which can be replaced with alternate chains of α4, α5 or α6. The C-terminal globular domain (C5) of collagen VI α3 can be proteolytically cleaved to form a biologically active fragment termed endotrophin, which has been shown to actively drive fibrosis, inflammation and insulin resistance. Tissue biopsies have long been considered the gold standard for diagnosis and monitoring of progression of fibrotic disease. The identification of neoantigens from enzymatically processed collagen chains have revolutionised the biomarker field, allowing rapid diagnosis and evaluation of prognosis of numerous fibrotic conditions, as well as providing valuable clinical trial endpoint determinants. Collagen VI chain fragments such as endotrophin (PRO-C6), C6M and C6Mα3 are emerging as important biomarkers for fibrotic conditions.

Biopsy-Controlled Non-Invasive Quantification of Collagen Type VI in Kidney Transplant Recipients: A Post-Hoc Analysis of the MECANO Trial

The PRO-C6 assay, a reflection of collagen type VI synthesis, has been proposed as a non-invasive early biomarker of kidney fibrosis. We aimed to investigate cross-sectional and longitudinal associations between plasma and urine PRO-C6 and proven histological changes after kidney transplantation. The current study is a post-hoc analysis of 94 participants of the MECANO trial, a 24-month prospective, multicenter, open-label, randomized, controlled trial aimed at comparing everolimus-based vs. cyclosporine-based immunosuppression. PRO-C6 was measured in plasma and urine samples collected 6 and 24 months post-transplantation. Fibrosis was evaluated in biopsies collected at the same time points by Banff interstitial fibrosis/tubular atrophy (IF/TA) scoring and collagen staining (Picro Sirius Red; PSR); inflammation was evaluated by the tubulo-interstitial inflammation score (ti-score). Linear regression analyses were performed. Six-month plasma PRO-C6 was cross-sectionally associated with IF/TA score (Std. β = 0.34), and prospectively with 24-month IF/TA score and ti-score (Std. β = 0.24 and 0.23, respectively) (p < 0.05 for all). No significant associations were found between urine PRO-C6 and any of the biopsy findings. Fibrotic changes and urine PRO-C6 behaved differentially over time according to immunosuppressive therapy. These results are a first step towards non-invasive fibrosis detection after kidney transplantation by means of collagen VI synthesis measurement, and further research is required.

Collagen turnover profiles in chronic kidney disease

Renal fibrosis is a hallmark of chronic kidney disease (CKD) caused by an imbalance between formation and degradation of extracellular matrix proteins. We investigated the collagen turnover profile of 81 non-dialysis CKD stage 2-5 patients by measuring peptides reflecting formation and degradation of collagen type (COL) I, III, IV, and VI. Based on the collagen turnover profile, we identified four clusters of patients. Cluster 1 contained one patient with prostate cancer, who had a distinct collagen turnover. The other clusters generally had severe (Cluster 2), moderate (Cluster 4), or mild CKD (Cluster 3). Cluster 4 patients were characterized by higher levels of COL III, COL IV, and COL VI (all p < 0.001) degradation fragments in plasma, while patients in Clusters 2 and 4 had higher levels of COL VI formation (p < 0.05). COL IV fragments in plasma were lower in Cluster 2 (p < 0.01). Urinary COL III fragments decreased from Cluster 3 to 4, and from Cluster 4 to 2 (both p < 0.001). We show that patients with similar kidney function have a different collagen remodeling profile, suggesting that different phenotypes exist with different disease activity and potentially disease progression. Biomarkers of collagen remodeling could provide additional information to traditional markers of renal function.

Urinary endotrophin predicts disease progression in patients with chronic kidney disease

Renal fibrosis is the central pathogenic process in progression of chronic kidney disease (CKD). Collagen type VI (COL VI) is upregulated in renal fibrosis. Endotrophin is released from COL VI and promotes pleiotropic pro-fibrotic effects. Kidney disease severity varies considerably and accurate information regarding CKD progression may improve clinical decisions. We tested the hypothesis that urinary endotrophin derived during COL VI deposition in fibrotic human kidneys is a marker for progression of CKD in the Renal Impairment in Secondary Care (RIISC) cohort, a prospective observational study of 499 CKD patients. Endotrophin localised to areas of increased COL VI deposition in fibrotic kidneys but was not present in histologically normal kidneys. The third and fourth quartiles of urinary endotrophin:creatinine ratio (ECR) were independently associated with one-year disease progression after adjustment for traditional risk factors (OR (95%CI) 3.68 (1.06–12.83) and 8.65 (2.46–30.49), respectively). Addition of ECR quartiles to the model for disease progression increased prediction as seen by an increase in category-free net reclassification improvement (0.45, 95% CI 0.16–0.74, p = 0.002) and integrated discrimination improvement (0.04, 95% CI 0.02–0.06, p < 0.001). ECR was associated with development of end-stage renal disease (ESRD). It is concluded that ECR predicts disease progression of CKD patients.

The effect of calorie restriction on mouse skeletal muscle is sex, strain and time-dependent

Loss of skeletal muscle mass and function occurs with increasing age. Calorie restriction (CR) increases the lifespan of C57Bl/6 mice, but not in the shorter-lived DBA/2 strain. There is some evidence that calorie restriction reduces or delays many of the age-related defects that occur in rodent skeletal muscle. We therefore investigated the effect of short (2.5 month) and longer term (8.5 and 18.5 months) CR on skeletal muscle in male and female C57Bl/6 and DBA/2 mice. We found that short-term CR increased the satellite cell number and collagen VI content of muscle, but resulted in a delayed regenerative response to injury.Consistent with this, the in vitro proliferation of satellite cells derived from these muscles was reduced by CR. The percentage of stromal cells, macrophages, hematopoietic stem cells and fibroadipogenic cells in the mononucleated cell population derived from skeletal muscle was reduced by CR at various stages. But overall, these changes are neither consistent over time, nor between strain and sex. The fact that changes induced by CR do not persist with time and the dissimilarities between the two mouse strains, combined with sex differences, urge caution in applying CR to improve skeletal muscle function across the lifespan in humans.

Non-invasive quantification of collagen turnover in renal transplant recipients

Kidney allograft failure due to chronic injury/rejection remains the main cause of graft loss in renal transplant recipients (RTR). Here, we investigated whether specific biomarkers of extracellular matrix (ECM) turnover are associated with allograft function and chronic kidney disease (CKD) stage in RTR. Seventy-eight patients who attended the University Medical Center Groningen for a routine check-up after kidney transplantation were enrolled in the study. Plasma and/or 24h-urine samples were collected and specific matrix-metalloproteinase-generated neo-epitope fragments of collagens were measured by enzyme-linked immunosorbent assay. Our results demonstrated that urinary levels of C3M, a marker for collagen type III degradation, correlated with estimated glomerular filtration rate (eGFR; r = 0.58, p<0.0001), with lower levels detected in the urine of patients with advanced CKD. In addition, plasma levels of Pro-C6, a marker for collagen type VI formation, significantly increased with disease progression and correlated with eGFR (r = -0.72, p<0.0001). Conversely, plasma C3M and urinary Pro-C6 levels showed no correlation with renal function. We identified two neo-epitope biomarkers of tissue turnover associated with ECM remodeling and fibrosis that can stratify patients by CKD stage. This is as promising first step towards non-invasive monitoring of ECM turnover in the kidneys.

Serum endotrophin, a type VI collagen cleavage product, is associated with increased mortality in chronic kidney disease

Background

Patients with chronic kidney disease (CKD) are at increased risk of end-stage renal disease (ESRD) and early mortality. The underlying pathophysiological processes are not entirely understood but may include dysregulation of extracellular matrix formation with accelerated systemic and renal fibrosis. We assessed the relationship between endotrophin (ETP), a marker of collagen type VI formation, and adverse outcomes in a cohort of patients with CKD.

Methods

We measured serum ETP levels in 500 patients from the Renal Impairment in Secondary Care (RIISC) study, a prospective observational study of patients with high-risk CKD. Patients were followed up until death or progression to ESRD. Cox regression analysis was used to assess the relationship between ETP and risk of adverse outcomes.

Results

During a median follow-up time of 37 months, 104 participants progressed to ESRD and 66 died. ETP level was significantly associated with progression to ESRD (HR 1.79 [95% CI 1.59–2.02] per 10 ng/mL increase; HR 11.05 [4.98–24.52] for highest vs lowest quartile; both P<0.0001). ETP level was also significantly associated with mortality (HR 1.60 [1.35–1.89] per 10 ng/mL increase; HR 12.14 [4.26–34.54] for highest vs lowest quartile; both P<0.0001). After adjustment for confounding variables, ETP was no longer significantly associated with progression to ESRD but remained independently associated with mortality (HR 1.51 [1.07–2.12] per 10 ng/mL increase, P = 0.019).

Conclusions

Serum ETP level is independently associated with mortality in CKD. This study provides the basis for further exploratory work to establish whether collagen type VI formation is mechanistically involved in the increased mortality risk associated with CKD.

Urinary monocyte chemoattractant protein-1 levels and interstitial changes in the renal cortex and their relationship with loss of renal function in renal transplant patients with delayed graft function

Background

Inflammatory cell infiltration and residual areas of fibrosis in kidneys after renal transplantation can lead to functional abnormalities with long-term implications.

Objectives

The aim of this study was to determine urinary monocyte chemoattractant protein-1 (uMCP-1) levels, relative cortical interstitial area (RCIA), and cortical tubulointerstitial macrophage infiltration in renal transplant patients with delayed graft function (DGF) and their possible correlation with graft outcome.

Design

Patients were followed after biopsies for one year, and their renal function and structure were evaluated, as well as parameters of inflammatory process.

Setting

Clinical Hospital of the School of Medicine of Ribeirão Preto.

Patients

Twenty-two cadaveric kidney transplant recipients with DGF were followed for one year.

Measurements

Renal function, RCIA, macrophages infiltration and uMCP-1 levels were evaluated.

Methods

Renal function was evaluated by plasma creatinine levels. RCIA was determined by morphometry. Immunohistochemical staining of macrophages was performed using an anti-CD68 monoclonal antibody. uMCP-1 levels were determined using a human MCP-1/CCL2 immunoassay kit.

Results

There was a significant increase in uMCP-1 levels in transplant patients compared with controls (p < 0.001). RCIA was 7.1% (6.4 to 9.2; median and 25th to 75th percentiles) in controls and 37.1% (28.1 to 43.7) in patients with kidney transplants (p < 0.001). The patients who presented with a higher RCIA in the first biopsy showed higher levels of plasma creatinine one year after transplantation (r = 0.44; p < 0.05). The number of tubulointerstitial macrophages per 0.10 mm² grid field was higher in the renal cortex of transplant patients compared with the controls (19.4 (9.0 to 47.1) vs. 2.5 (1.8 to 3.4), p < 0.001). There was also a positive correlation between the RCIA and the number of tubulointerstitial macrophages in the renal cortex of these patients (r = 0.49; p < 0.001).

Limitations

The number of patients studied was relatively small and may not be reflecting outcomes over a larger spectrum of kidney cadaveric transplants.

Conclusions

Our results demonstrate increased levels of uMCP-1 in transplant patients with DGF, in addition to increased tubulointerstitial macrophage infiltration and RCIA, which could predict the outcome of renal function in these patients.

Mature adult dystrophic mouse muscle environment does not impede efficient engrafted satellite cell regeneration and self-renewal

Changes that occur in the skeletal muscle environment with the progress of muscular dystrophies may affect stem cell function and result in impaired muscle regeneration. It has previously been suggested that the success of stem cell transplantation could therefore be dependent both on the properties of the cell itself and on the host muscle environment. Here we engrafted young and mature adult mdx-nude mice, which are the genetic homolog of Duchenne muscular dystrophy, with a small number of satellite cells freshly isolated from young, normal donor mice. We found that the donor satellite cells contributed to muscle regeneration and self-renewal as efficiently within mature adult, as in young, dystrophic host muscle. Donor-derived satellite cells also contributed to robust regeneration after further injury, showing that they were functional despite the more advanced dystrophic muscle environment. These findings provide evidence that muscle tissue in a later stage of dystrophy may be effectively treated by stem cells.

An in vitro investigation of herbs traditionally used for kidney and urinary system disorders: potential therapeutic and toxic effects

AIM

Renal fibrosis is central to progression of most chronic renal pathologies. Antioxidants that protect the tubular epithelium and anti-fibrotics that induce apoptosis of pro-fibrotic myofibroblasts without adversely affecting tubular epithelium may slow progression of renal fibrosis, while toxic substances may exacerbate renal scarring. We investigated 47 herbs for their in vitro toxic or antioxidant effects on normal renal mammalian fibroblasts (NRK49F) and tubular epithelial cells (NRK52E) to determine their potential value as therapeutic agents in renal fibrosis involving oxidative stress.

METHODS

Herbs were chosen because of their traditional use in kidney or urinary system disorders, or because of recent published interest in their therapeutic or toxic potential in kidney disease. Extracts of herbs were made using a sequential multi-solvent extraction process. Each extract was analysed separately. Extraction solvents were ethyl acetate, methanol and 50% aqueous methanol. Cells were treated with extracts with/without oxidative stress (1.0 mM hydrogen peroxide). Cellular changes (apoptosis, necrosis, mitosis, transdifferentiation) were identified and quantified using defined criteria.

RESULTS

All extracts of Dioscorea villosa showed significant toxicity to both cell lines. At low concentrations (5-50 microg/mL) they induced epithelial to mesenchymal transdifferentiation, as demonstrated by increased immunohistochemistry staining for alpha-smooth muscle actin and transforming growth factor-beta1 in treated versus control cells. Angelica sinensis, Centella asiatica, Glycyrrhiza glabra, Scutellaria lateriflora, and Olea europaea demonstrated strong antioxidant effects in epithelial cells and/or apoptotic effects on fibroblasts.

CONCLUSION

This investigation has revealed renotoxicity of D. villosa and anti-fibrotic, oxidant potential of several herbal extracts, all of which require further study.

Endothelin-1 mediated regulation of extracellular matrix collagens in cells of human lamina cribrosa

Endothelin-1 (ET-1), a potent vaso-active peptide, mediates extracellular matrix regulation resulting in an increase in collagen deposition in various cell types and tissues and has been proposed to play a key role in glaucoma pathology. The role of ET-1 in the regulation of extracellular matrix collagens at the level of optic nerve head is not known. In this study we have examined the role of ET-1 in extracellular matrix collagen regulation in primary cultures of human lamina cribrosa cells. Our hypothesis is that ET-1 increases remodeling of the ECM of cells of the lamina cribrosa. Such actions could contribute to the development of optic neuropathy. QPCR analysis revealed that ET-1 mediated an increase in mRNA levels of collagen type I alpha1 and collagen type VI alpha1 chains at all doses of ET-1 with a significant increase at 1nM and 10nM concentration in LC cells. A dose-dependent increase in collagen type I and type VI protein deposition and secretion was also observed by Western blot in response to ET-1 and was significant at 10nM and 100nM concentrations of ET-1. ET-1 increased the [3H] proline uptake in LC cells suggesting that ET-1 contributed to an increase in total collagen synthesis in LC cells. ET-1-mediated increase in collagen type I, type VI and total collagen synthesis was significantly blocked by the ET(A) receptor antagonist, BQ610, as well as with the ET(B) receptor antagonist, BQ788, suggesting the involvement of both receptor subtypes in ET-1 mediated collagen synthesis in LC cells. These results suggest that ET-1 regulates extracellular matrix collagen synthesis in LC cells and may contribute to ECM remodeling at the level of LC of POAG subjects who have elevated plasma and aqueous humor levels of endothelin-1.

Formation and function of the myofibroblast during tissue repair

It is generally accepted that fibroblast-to-myofibroblast differentiation represents a key event during wound healing and tissue repair. The high contractile force generated by myofibroblasts is beneficial for physiological tissue remodeling but detrimental for tissue function when it becomes excessive such as in hypertrophic scars, in virtually all fibrotic diseases and during stroma reaction to tumors. Specific molecular features as well as factors that control myofibroblast differentiation are potential targets to counteract its development, function, and survival. Such targets include alpha-smooth muscle actin and more recently discovered markers of the myofibroblast cytoskeleton, membrane surface proteins, and the extracellular matrix. Moreover, intervening with myofibroblast stress perception and transmission offers novel strategies to reduce tissue contracture; stress release leads to the instant loss of contraction and promotes apoptosis.

Organ-specific collagen expression: implications for renal disease

Chronic kidney disease is characterized by progressive accumulation of extracellular matrix and scarring, leading to the loss of kidney function. Excess deposition of the collagen family of proteins is the hallmark of kidney fibrosis. In this review, we survey the collagens that are associated with renal disease and we highlight the use of a transgenic approach to identify cis-acting sequences in the collagen type I promoter which are capable of directing collagen type I expression specifically in the kidney. Ultimately it may be possible to use this approach to halt the accumulation of collagen selectively in this organ.

Type VI collagen induces cardiac myofibroblast differentiation: implications for postinfarction remodeling

Cardiac fibroblast (CF) proliferation and differentiation into hypersecretory myofibroblasts can lead to excessive extracellular matrix (ECM) production and cardiac fibrosis. In turn, the ECM produced can potentially activate CFs via distinct feedback mechanisms. To assess how specific ECM components influence CF activation, isolated CFs were plated on specific collagen substrates (type I, III, and VI collagens) before functional assays were carried out. The type VI collagen substrate potently induced myofibroblast differentiation but had little effect on CF proliferation. Conversely, the type I and III collagen substrates did not affect differentiation but caused significant induction of proliferation (type I, 240.7 +/- 10.3%, and type III, 271.7 +/- 21.8% of basal). Type I collagen activated ERK1/2, whereas type III collagen did not. Treatment of CFs with angiotensin II, a potent mitogen of CFs, enhanced the growth observed on types I and III collagen but not on the type VI collagen substrate. Using an in vivo model of myocardial infarction (MI), we measured changes in type VI collagen expression and myofibroblast differentiation after post-MI remodeling. Concurrent elevations in type VI collagen and myofibroblast content were evident in the infarcted myocardium 20-wk post-MI. Overall, types I and III collagen stimulate CF proliferation, whereas type VI collagen plays a potentially novel role in cardiac remodeling through facilitation of myofibroblast differentiation.

Immunolocalization of collagen types in the subsynovial connective tissue within the carpal tunnel in humans

The tenosynovium within the carpal tunnel consists of a single layer of synovial cells, which lines the bursae within the carpal tunnel, and the subsynovial connective tissue (SSCT), which contains the tendon vasculature and other structural elements. In this study, we used immunogold labeling to localize collagen types within the SSCT in three cadaver specimens and three patients with carpal tunnel syndrome. Positive labeling for collagen types I, III and VI was found with immunoelectron microscopy. Collagen types I and III were codistributed within the SSCT. Type VI was primarily located in microfibrillar structures between collagen bundles, between elastin and collagen bundles and between collagen bundles and cells. There was no difference in the distribution of collagen types when comparing cadaver specimens and carpal tunnel patients.

Interstitial alterations in renal cortex in acute tubular necrosis (ATN) post-renal transplantation and in patients with ATN not related to renal transplant

BACKGROUND

Abnormalities of renal function with long-term implications can persist after acute tubular necrosis (ATN), probably because of permanent loss of nephrons. Residual areas of fibrosis are also observed in the renal cortex post-ATN. In this study, we investigate the interstitial alterations post-ATN using histological and immunohistochemical methods.

METHODS

We studied 11 patients with ATN of different etiologies and 19 patients with ATN post-renal transplantation. Eleven patients with ATN post-renal transplantation and one with ATN not related to renal transplantation were submitted to more than one biopsy because of delayed renal function recovery. The immunohistochemical studies were performed using alpha-smooth muscle-actin (alpha-SM-actin), endothelin, nuclear factor-kappaB (NF-kappaB), Jun-N-terminal kinase (p-JNK) and fibronectin antibodies. We also analyzed the urinary content of transforming growth factor-beta (TGF-beta) during the acute phase of ATN.

RESULTS

The immunohistochemical studies showed increased alpha-SM-actin, fibronectin, endothelin, p-JNK and NF-kappaB staining in the tubulointerstitium area from the renal cortex of all patients when compared with controls (p < 0.001), and these increase persisted in the patients submitted to sequential biopsies. One of the patients with ATN without renal transplant and six patients with ATN post-renal transplant developed chronic renal failure. There was a significant increase of TGF-beta excretion in the urine of patients with acute renal failure (p < 0.01) compared with control.

CONCLUSIONS

Our data show that the enhancement of renal TGF-beta production and the persistent increase of myofibroblasts, fibronectin, endothelin, p-JNK and NF-kappaB in renal cortex tubulointerstitium post-ATN may explain the impaired recovery of renal function observed in patients post-ATN frequently observed in patients with ATN post-renal transplant.

Total RNA yield and microarray gene expression profiles from fine-needle aspiration biopsy and core-needle biopsy samples of breast carcinoma

BACKGROUND

Gene expression profiling should be applicable to needle biopsy samples if microarray technology is to become practically useful for clinical research or management of breast carcinoma. This study compared gene expression profiles derived from fine-needle aspiration biopsy (FNAB) and from core needle biopsy (CBX).

METHODS

Total RNA was extracted from single FNAB and CBX samples. Corresponding pairs of FNAB and CBX were analyzed for similarity of gene expression profiles using cDNA microarrays that contain 30721 human sequences. A subset of genes that distinguished CBX samples from FNAB samples was evaluated in a larger group of needle biopsy samples and in a published genomic database derived from 78 sporadic breast carcinomas with known clinical outcome.

RESULTS

Sixty-eight patients with newly diagnosed breast carcinoma were included in the current study. Sixty-five patients underwent FNAB (17 had both FNAB and CBX) and 3 underwent CBX only. Extracted RNA was of suitable quality for hybridization in 46 (71%) FNABs and 15 (75%) CBXs. Total RNA yield in those samples was similar for single-pass FNAB (mean = 3.6 microg and median = 2.2 microg; n = 46) and CBX (mean = 2.8 microg and median = 2.0 microg; n = 15), with 1 microg or more of total RNA in all cases. Transcriptional profiling was performed successfully in all cases when it was attempted, in a total of 50 samples (38 FNABs and 12 CBXs), including matched FNAB and CBX samples from 10 patients. There were differences in gene expression profiles in 10 matched FNAB and CBX sample pairs. Genes that were expressed differently in CBX samples, compared with FNAB samples, were recognized as being predominantly from the endothelium, fibroblasts, myofibroblasts or smooth muscle, and histiocytes. Corresponding microscopic cell counts from FNABs demonstrated means of 80% tumor cells, 15% lymphocytes, and 5% stromal cells, whereas CBXs contained 50% tumor cells, 20% lymphocytes, and 30% stromal cells. Considering that CBXs are approximately six-fold richer in nonlymphoid stromal cells than FNABs and that CBXs differentially express a set of recognized stromal genes, the authors used these biopsies to define a transcriptional profile of breast carcinoma stroma. A set of 120 genes differentially expressed in CBXs was assessed independently in a published breast carcinoma genomic database to classify breast carcinomas based on stromal gene expression. Subgroups of tumors with low or high stromal signal were identified, but there was no correlation with the development of systemic metastases within 5 years.

CONCLUSIONS

Both FNAB and CBX yield a similar quality and quantity of total RNA and are suitable for cDNA microarray analyses in approximately 70-75% of single-pass samples. Transcriptional profiles from FNAB and CBX of the same tumor generally are similar and are driven by the tumor cell population. The authors concluded that each technique has relative advantages. The FNABs provide transcriptional profiles that are a purer representation of the tumor cell population, whereas transcriptional profiles from CBXs include more representation from nonlymphoid stromal elements. Selection of the preferred needle biopsy sampling technique for genomic studies of breast carcinomas should depend on whether variable stromal gene expression is desirable in the samples.

Role of Ras isoforms in the stimulated proliferation of human renal fibroblasts in primary culture

The proliferation of renal fibroblasts is implicated in the pathophysiologic processes of renal fibrosis. Many of the growth factors involved in proliferation are known to activate intracellular signaling pathways that converge on Ras monomeric GTPases. Although three ras family genes exist, their functional specificity is not yet known. Using antisense oligonucleotides, a role for Kirsten (Ki)-Ras in the stimulated proliferation of a primate renal fibroblast cell line was previously demonstrated. This study examines Ras in primary cultures of adult human renal fibroblasts. Using reverse transcription-PCR, mRNA for Harvey (Ha)-ras, Ki(4B)-ras, and neural (N)-ras, but not Ki(4A)-ras, were detected. Antisense oligonucleotides targeting Ha-, Ki-, and N-ras mRNA, which were used for liposomal transfection at 100 to 200 nM, were demonstrated to be active and isoform-specific in quantitative reverse transcription-PCR assays. Cellular Ras protein levels, as estimated using isoform-specific monoclonal antibodies, indicated that Ki-Ras was the predominantly expressed isoform (>95% of total Ras protein) under both serum-containing and serum-free conditions, with N- and Ha-Ras being detected in small amounts. Consistent with this finding, the antisense oligonucleotide directed against Ki-Ras reduced total cellular Ras levels by >70%, whereas Ha-Ras, N-Ras, and control oligonucleotides had no significant effect. Proliferation of oligonucleotide-transfected cells was measured using epidermal growth factor (EGF) and serum stimulation. The Ki-Ras oligonucleotide at 100 nM reduced serum-stimulated proliferation by >50% and EGF-stimulated proliferation by 25%, compared with data obtained with the control oligonucleotide (P: < 0. 01). The N-Ras oligonucleotide was not active, compared with the control oligonucleotide. The Ha-Ras oligonucleotide was not significantly active at 100 nM but reduced serum-stimulated proliferation by 13% and EGF-stimulated growth by 40% at 200 nM (P: < 0.01). These results demonstrate that Ki-Ras(4B) is the predominantly expressed Ras isoform in human renal fibroblasts in primary culture and is important for both serum- and EGF-stimulated proliferation. Ha-Ras appears to be expressed at low levels but may also play a distinct role in stimulated proliferation.

The tubulointerstitium in progressive diabetic kidney disease: more than an aftermath of glomerular injury?

Although the glomerulus, particularly the mesangium, has been the focus of intense investigation in diabetes, tubulointerstitial injury is also a major feature of diabetic nephropathy and an important predictor of renal dysfunction. The renal tubule in diabetes is subject to both direct and indirect pathogenetic influences as a consequence of its position in the nephron and its resorptive function. On exposure to glucose, proximal tubular cells elaborate vasoactive hormones, including angiotensin II and injurious cytokines such as transforming growth factor-beta (TGF-beta), as well as extracellular matrix proteins. In turn, angiotensin II may further increase TGF-beta expression in both proximal tubular and interstitial cells, thus amplifying the stimulus to fibrogenesis in the renal tubulointerstitium. In addition to these mostly direct influences, the renal tubule, particularly its proximal segment, is exposed to glomerular effluent. In the diabetic state, this includes large quantities of advanced glycation end products and glucose and, at later stages in the evolution of diabetic nephropathy, protein, all of which are factors that may induce TGF-beta expression and fibrosis. Diabetic nephropathy should therefore be viewed as a disease affecting the entire nephron. Continued exploration into tubulointerstitial disease in addition to glomerular injury in diabetes may help provide further insights into the pathogenesis of diabetic nephropathy and additional targets for therapeutic intervention.

Type VI collagen immunoreactivity in skeinoid fibers in small intestinal stromal tumors

By immunoperoxidase analysis for types I to VI collagen, elastin, cytoskeletal components and some glycoproteins, we found type VI collagen immunoreactivity in amorphous eosinophilic deposits (skeinoid fibers) in three small intestinal stromal tumors. Negative results were obtained for types I, II, III, IV and V collagen, elastin, laminin, ubiquitin, intracellular filaments such as actin, desmin, vimentin, calponin and caldesmon, and glycoprotein such as lysozyme, factor XIIIa, beta2-microglobulin, alpha1-antitrypsin and alpha1-antichymotrypsin. In two lesions, the periodic acid-Schiff-positive skeinoid fibers were also focally labeled for amyloid P component.