Changes in glomerular epithelial cells induced by FGF2 and FGF2 neutralizing antibody in puromycin aminonucleoside nephropathy

Spinal Canal and Spinal Cord in Rat Continue to Grow Even after Sexual Maturation: Anatomical Study and Molecular Proposition

Although rodents have been widely used for experimental models of spinal cord diseases, the details of the growth curves of their spinal canal and spinal cord, as well as the molecular mechanism of the growth of adult rat spinal cords remain unavailable. They are particularly important when conducting the experiments of cervical spondylotic myelopathy (CSM), since the disease condition depends on the size of the spinal canal and the spinal cord. Thus, the purposes of the present study were to obtain accurate growth curves for the spinal canal and spinal cord in rats; to define the appropriate age in weeks for their use as a CSM model; and to propose a molecular mechanism of the growth of the adult spinal cord in rats. CT myelography was performed on Lewis rats from 4 weeks to 40 weeks of age. The vertical growth of the spinal canal at C5 reached a plateau after 20 and 12 weeks, and at T8 after 20 and 16 weeks, in males and females, respectively. The vertical growth of the C5 and T8 spinal cord reached a plateau after 24 weeks in both sexes. The vertical space available for the cord (SAC) of C5 and T8 did not significantly change after 8 weeks in either sex. Western blot analyses showed that VEGFA, FGF2, and BDNF were highly expressed in the cervical spinal cords of 4-week-old rats, and that the expression of these growth factors declined as rats grew. These findings indicate that the spinal canal and the spinal cord in rats continue to grow even after sexual maturation and that rats need to be at least 8 weeks of age for use in experimental models of CSM. The present study, in conjunction with recent evidence, proposes the hypothetical model that the growth of rat spinal cord after the postnatal period is mediated at least in part by differentiation of neural progenitor cells and that their differentiation potency is maintained by VEGFA, FGF2, and BDNF.

Circulating fibroblast growth factor-2 precipitates HIV nephropathy in mice

People of African ancestry living with the human immunodeficiency virus-1 (HIV-1) are at risk of developing HIV-associated nephropathy (HIVAN). Children with HIVAN frequently show high plasma fibroblast growth factor-2 (FGF-2) levels; however, the role of circulating FGF-2 in the pathogenesis of childhood HIVAN is unclear. Here, we explored how circulating FGF-2 affected the outcome of HIVAN in young HIV-Tg26 mice. Briefly, we demonstrated that FGF-2 was preferentially recruited in the kidneys of mice without pre-existing kidney disease, precipitating HIVAN by activating phosphorylated extracellular signal-regulated kinase (pERK) in renal epithelial cells, without inducing the expression of HIV-1 genes. Wild-type mice injected with recombinant adenoviral FGF-2 (rAd-FGF-2) vectors carrying a secreted form of human FGF-2 developed transient and reversible HIVAN-like lesions, including proteinuria and glomerular enlargement. HIV-Tg26 mice injected with rAd-FGF-2 vectors developed more-significant proliferative and pro-fibrotic inflammatory lesions, similar to those seen in childhood HIVAN. These lesions were partially reversed by treating mice with the FGF/VEGF receptor tyrosine kinase inhibitor PD173074. These findings suggest that high plasma FGF-2 levels may be an independent risk factor for precipitating HIVAN in young children.

Myocardial-Infarction-Responsive Smart Hydrogels Targeting Matrix Metalloproteinase for On-Demand Growth Factor Delivery

Although in situ restoration of blood supply to the infarction region and attenuating pre-existing extracellular matrix degradation remain potential therapeutic approaches for myocardial infarction (MI), local delivery of therapeutics has been limited by low accumulation (inefficacy) and unnecessary diffusion (toxicity). Here, a dual functional MI-responsive hydrogel is fabricated for on-demand drug delivery to promote angiogenesis and inhibit cardiac remodeling by targeting upregulated matrix metalloproteinase-2/9 (MMP-2/9) after MI. A glutathione (GSH)-modified collagen hydrogel (collagen-GSH) is prepared by conjugating collagen amine groups with GSH sulfhydryl groups and the recombinant protein GST-TIMP-bFGF (bFGF: basic fibroblast growth factor) by fusing bFGF with glutathione-S-transferase (GST) and MMP-2/9 cleavable peptide PLGLAG (TIMP). Specific binding between GST and GSH significantly improves the amount of GST-TIMP-bFGF loaded in collagen-GSH hydrogel. The TIMP peptide enclosed between GST and bFGF responds to MMPs for on-demand release during MI. Additionally, the TIMP peptide is a competitive substrate of MMPs that inhibits the excessive degradation of cardiac matrix by MMPs after MI. GST-TIMP-bFGF/collagen-GSH hydrogels promote the recovery of MI rats by enhancing vascularization and ameliorating myocardium remodeling. The results suggest that on-demand growth factor delivery by synchronously controlling binding and responsive release to promote angiogenesis and attenuate cardiac remodeling might be promising for the treatment of ischemic heart disease.

In glomerular cells of puromycin aminonucleoside nephrosis rats both phosphorylated and total STAT3 levels increased during proteinuria

Recent studies showed that JAK/STAT pathway plays role in glomerular damages. The fact that STAT3 could be activated also by oxidative stress make Puromycin Aminonucleoside (PAN) Nephrosis model very appropriate for examination of STAT3 expression changes in glomerular pathology. Along with a control group, three PAN groups sacrificed on different days were formed by the i.p. injection of PAN for 5 consecutive days. Throughout the experiment, 24-hour-urines were collected on specific days and proteinuria levels were monitored. At the end of the experiments, tissue specimens were stained immunohistochemically for both total and phosphorylated STAT3 and evaluated subjectively. They were also examined ultrastructurally in transmission electron microscope. The proteinuria levels did not increase significantly on 5th day but showed a dramatic increase on 10th and 15th days. On 20th and 25th days, urinary protein levels gradually decreased. Ultrastructural examinations showed glomerular damages such as significant decrease in slit pore number, a significant gradual increase in glomerular basement membrane thickness and podocyte hypertrophy on 5th and 15th days; besides significant increase in mesangial matrix. The first significant increases in phosphorylated and total STAT3 levels occurred in 5th day and 15th day groups respectively. These increases diminished in 25th day group. Regarding all the findings, it was deduced that STAT3 is one of the active factors in glomerular pathologies.

Expression of Cathepsin L and Its Intrinsic Inhibitors in Glomeruli of Rats With Puromycin Aminonucleoside Nephrosis

Cathepsin L, a lysosomal cysteine proteinase, may have a key role in various biological and disease processes by intracellular and extracellular degradation of proteins. We examined the levels of cathepsin L and its intrinsic inhibitors in glomeruli of rats with puromycin aminonucleoside (PAN) nephrosis. In contrast to the weak levels of cathepsin L in normal glomeruli, on days 4 and 8, strong immunostaining was detected in almost all podocytes when proteinuria and pathological changes of the podocytes developed. Cathepsin L was reduced after day 28, but remained in a focal and segmental manner. Cystatin β, an intracellular inhibitor, was not detected in podocytes. However, cystatin C, an extracellular inhibitor, was detected in podocytes after day 4, coincident with cathepsin L. Cystatin C levels were gradually reduced but sustained in many podocytes on day 28, while cystatin C was not detected in podocytes sustained cathepsin L. These results demonstrated that cathepsin L levels are not always accompanied by the levels of its inhibitors in podocytes of PAN nephrosis, suggesting a potential role of cathepsin L in podocyte injury, which is a critical process for the development and progression of tuft adhesion and sclerosis.

Intramyocardial delivery of bFGF with a biodegradable and thermosensitive hydrogel improves angiogenesis and cardio-protection in infarcted myocardium

Basic fibroblast growth factor (bFGF), a known angiogenic factor, may provide a potential strategy for the treatment of myocardial infarction (MI), but it is limited by a relatively short half-life. Dex-PCL-HEMA/PNIPAAm hydrogel provides a reservoir for the controlled release of growth factors. The aim of the current study was to evaluate the effects of bFGF incorporated into a Dex-PCL-HEMA/PNIPAAm hydrogel on angiogenesis and cardiac health in a rat model of acute MI, induced by coronary artery ligation. Phosphate-buffered solution (PBS group), Dex-PCL-HEMA/PNIPAAm hydrogel (Gel group), bFGF in phosphate-buffered solution (bFGF group) or bFGF in hydrogel (Gel + bFGF group) was injected into a peri-infarcted area of cardiac tissue immediately following MI. On day 30 post-surgery, cardiac function was assessed by echocardiography, apoptosis index by terminal deoxynucleotidyl transferase dUTP nick-end labeling assessment and vascular development by immunohistochemical staining. The findings demonstrated that injection of bFGF along with hydrogel induced angiogenesis, reduced collagen content, MI area and cell apoptosis and improved cardiac function compared with the injection of either bFGF or hydrogel alone. bFGF incorporated with Dex-PCL-HEMA/PNIPAAm hydrogel injection induces angiogenesis, attenuates cardiac remodeling and improves cardiac function following MI.

Advances in growth factor delivery for therapeutic angiogenesis

Therapeutic angiogenesis is a new revascularization strategy involving the administration of growth factors to induce new vessel formation. The biology and delivery of angiogenic growth factors involved in vessel formation have been extensively studied but success in translating the angiogenic capacity of growth factors into benefits for vascular disease patients is still limited. This could be attributed to issues related to patient selection, growth factor delivery methods or lack of vessel maturation. Comprehensive understanding of the cellular and molecular cross-talk during the different stages of vascular development is needed for the design of efficient therapeutic strategies. The presentation of angiogenic factors either in series or in parallel using a strategy that mimics physiological events, such as concentration and spatio-temporal profiles, is an immediate requirement for functional blood vessel formation. This review provides an overview of the recent delivery strategies of angiogenic factors and discusses targeting neovascular maturation as a promising approach to induce stable and functional vessels for therapeutic angiogenesis.

The enigmatic parietal epithelial cell is finally getting noticed: a review

Although the normal glomerulus comprises four resident cell types, least is known about the parietal epithelial cells (PECs). This comprehensive review addresses the cellular origin of PECs, discusses the normal structure and protein makeup of PECs, describes PEC function, and defines the responses to injury in disease and how these events lead to clinical events. The data show that PECs have unique properties and that new functions are being recognized such as their role in differentiating into podocytes during disease.

A urinary biomarker profile for children with HIV-associated renal diseases

Human immunodeficiency virus (HIV)-infected children are at risk of developing several types of renal diseases, including HIV-associated nephropathy (HIVAN), which is usually seen during late stages of infection in children with a high viral load. This disease is defined by the presence of proteinuria associated with mesangial hyperplasia and/or global-focal segmental glomerulosclerosis combined with microcystic transformation of the renal tubules. Because HIVAN can have an insidious clinical onset, renal biopsy is the only definitive way of establishing a diagnosis. Given the risk of performing this procedure in HIV-infected children with other AIDS-defining illness, we sought to identify informative biomarkers such as growth factors in the urine of 55 HIV-infected children that might be predictive of the extent and activity of the renal lesions characteristic of HIVAN. We found that the levels of epidermal growth factor were lower in the urine of children with renal disease, whereas levels of fibroblast growth factor-2 and metalloproteinase-2 were higher as compared with those levels in infected children without renal disease. Similar changes were observed in HIV-Tg26 mice correlating with the progression of renal disease in this model of HIVAN. Our findings suggest that this urinary growth factor profile may be useful in facilitating the diagnosis of HIV-infected children at risk of developing HIVAN when interpreted in the appropriate clinical setting.

Advances in the biology and genetics of the podocytopathies: implications for diagnosis and therapy

CONTEXT

Etiologic factors and pathways leading to altered podocyte phenotype are clearly numerous and involve the activity of different cellular function.

OBJECTIVE

To focus on recent discoveries in podocyte biology and genetics and their relevance to these human glomerular diseases, named podocytopathies.

DATA SOURCES

Genetic mutations in genes encoding for proteins in the nucleus, slit diaphragm, podocyte cytoplasm, and cell membrane are responsible for podocyte phenotype and functional abnormalities. Podocyte injury may also derive from secondary stimuli, such as mechanical stress, infections, or use of certain medications. Podocytes can respond to injury in a limited number of ways, which include (1) effacement, (2) apoptosis, (3) arrest of development, and (4) dedifferentiation. Each of these pathways results in a specific glomerular morphology: minimal change nephropathy, focal segmental glomerulosclerosis, diffuse mesangial sclerosis, and collapsing glomerulopathy.

CONCLUSIONS

Based on current knowledge of podocyte biology, we organized etiologic factors and morphologic features in a taxonomy of podocytopathies, which provides a novel approach to the classification of these diseases. Current and experimental therapeutic approaches are also discussed.

Advances in the biology and genetics of the podocytopathies: implications for diagnosis and therapy

CONTEXT

Etiologic factors and pathways leading to altered podocyte phenotype are clearly numerous and involve the activity of different cellular function.

OBJECTIVE

To focus on recent discoveries in podocyte biology and genetics and their relevance to these human glomerular diseases, named podocytopathies.

DATA SOURCES

Genetic mutations in genes encoding for proteins in the nucleus, slit diaphragm, podocyte cytoplasm, and cell membrane are responsible for podocyte phenotype and functional abnormalities. Podocyte injury may also derive from secondary stimuli, such as mechanical stress, infections, or use of certain medications. Podocytes can respond to injury in a limited number of ways, which include (1) effacement, (2) apoptosis, (3) arrest of development, and (4) dedifferentiation. Each of these pathways results in a specific glomerular morphology: minimal change nephropathy, focal segmental glomerulosclerosis, diffuse mesangial sclerosis, and collapsing glomerulopathy.

CONCLUSIONS

Based on current knowledge of podocyte biology, we organized etiologic factors and morphologic features in a taxonomy of podocytopathies, which provides a novel approach to the classification of these diseases. Current and experimental therapeutic approaches are also discussed.

Intramyocardial injection of low-dose basic fibroblast growth factor or vascular endothelial growth factor induces angiogenesis in the infarcted rabbit myocardium

BACKGROUND

Myocardial angiogenesis after the systemic administration of basic fibroblast growth factor or vascular endothelial growth factor at high therapeutic doses has been implicated in the occurrence of side effects that may undermine their safety. The aim of this study was to investigate the angiogenic effects of the intramyocardial administration of recombinant human basic fibroblast growth factor or vascular endothelial growth factor protein, at low doses, in the infarcted rabbit myocardium.

METHODS AND RESULTS

Twenty-five New Zealand White rabbits were divided into five groups (n=5) and subjected to coronary artery ligation after lateral thoracotomy, inducing acute myocardial infarction. Five minutes later, the following substances were injected intramyocardially into the infarcted area: (a) normal saline (controls); (b) 6.25 or 12.5 mug of recombinant human basic fibroblast growth factor protein (basic fibroblast growth factor-1 group or basic fibroblast growth factor-2 group); or (c) 5 or 10 microg of recombinant human vascular endothelial growth factor 165 protein (vascular endothelial growth factor-1 group or vascular endothelial growth factor-2 group). On the 21st postoperative day, the animals were euthanized, and their hearts were subjected to histopathological examination and immunohistochemical assessment of vascular density in the infarcted area. The alkaline phosphatase anti-alkaline phosphatase procedure and the primary monoclonal antibody JC70 were used. Histopathological examination confirmed the induction of myocardial infarction. Vascular density was significantly increased (P<.004) in all treatment groups (in mean+/-S.E. vessels/x 200 optical field: basic fibroblast growth factor-1: 85.8+/-10.9; basic fibroblast growth factor-2: 76.6+/-3.7; vascular endothelial growth factor-1: 73.4+/-3.2; vascular endothelial growth factor-2: 89.5+/-5.2) compared to that in controls (58.9+/-4.9 vessels/x 200 optical field). Vascular density in the vascular endothelial growth factor-2 group was significantly higher than that in the vascular endothelial growth factor-1 group (P<.001).

CONCLUSIONS

Low doses of recombinant human basic fibroblast growth factor or vascular endothelial growth factor protein, when administered intramyocardially, stimulate angiogenesis in the infarcted myocardium.

Vasopeptidase inhibition attenuates proteinuria and podocyte injury in Zucker diabetic fatty rats

Inhibition of the renin angiotensin aldosterone system (RAAS) produces protective effects on cardio-renal injury in type 2 diabetes. Vasopeptidase inhibitors (VPI) represent a new pharmacological tool, acting by simultaneous inhibition of the RAAS and neutral endopeptidase. We examined the effects of chronic VPI on renal function and morphology in experimental type 2 diabetes as compared to angiotensin converting enzyme inhibition (ACE-I). Zucker diabetic fatty rats aged 13 weeks were treated with either VPI (AVE7688, ZDF-VPI, n = 8) or ACE-I (Ramipril, ZDF-ACE-I, n = 7) or placebo (ZDF, n = 8). Heterozygous rats served as non-diabetic controls (Ctr, n = 8). Both treatments led to a similar decrease in blood pressure. After 10 weeks of treatment, ZDF developed marked albuminuria. The latter was significantly attenuated in ZDF-VPI as compared to ZDF and ZDF-ACE-I. Renal histology revealed a significant expansion in the glomerular tuft area in all ZDF groups. However, expression of glomerular desmin, which has been recognized as a sensitive marker of early podocyte damage, was significantly increased in ZDF as compared to Ctr. Desmin was reduced in ZDF-VPI but not in animals treated with ACE-I. There was a correlation between albumin excretion and desmin-positive glomerular area. In experimental type 2 diabetes, albuminuria correlates to podocyte damage. These hallmarks of diabetic nephropathy are attenuated by VPI to a greater extent than by ACE-I alone. These findings suggest that podocyte damage is an early critical step in the progression of diabetic nephropathy, and that VPI is a promising pharmacological tool in the treatment of diabetic renal disease.

Cardiovascular gene delivery: The good road is awaiting

Atherosclerotic cardiovascular disease is a leading cause of death worldwide. Despite recent improvements in medical, operative, and endovascular treatments, the number of interventions performed annually continues to increase. Unfortunately, the durability of these interventions is limited acutely by thrombotic complications and later by myointimal hyperplasia followed by progression of atherosclerotic disease over time. Despite improving medical management of patients with atherosclerotic disease, these complications appear to be persisting. Cardiovascular gene therapy has the potential to make significant clinical inroads to limit these complications. This article will review the technical aspects of cardiovascular gene therapy; its application for promoting a functional endothelium, smooth muscle cell growth inhibition, therapeutic angiogenesis, tissue engineered vascular conduits, and discuss the current status of various applicable clinical trials.

Protein-, gene-, and cell-based therapeutic angiogenesis for the treatment of myocardial ischemia

Therapeutic angiogenesis aims at restoring perfusion to chronically ischemic myocardial territories by using growth factors or cells, without intervening on the epicardial coronary arteries. Despite angiogenesis having received considerable scientific attention over the last decade, it has not yet been shown to provide clinical benefit and is still reserved for patients who have failed conventional therapies. Nevertheless, angiogenesis is a very potent physiologic process involved in the growth and development of every animal and human, and it is likely that its use for therapeutic purposes, once its underlying mechanistic basis is better understood, will one day become an important modality for patients with CAD and other types of organ ischemia. This review summarizes current knowledge in therapeutic angiogenesis research.

A 20-year history of childhood HIV-associated nephropathy

In 1984, physicians in New York and Miami reported HIV-infected adult patients with heavy proteinuria and rapid progression to end-stage renal disease. These patients showed large edematous kidneys with a combination of focal segmental glomerulosclerosis (FSGS) and tubulointerstitial lesions. This renal syndrome, named HIV-associated nephropathy (HIVAN), was found predominantly in African Americans. Subsequent studies confirmed the presence of HIVAN in children, who frequently develop nephrotic syndrome in association with FSGS and/or mesangial hyperplasia with microcystic tubular dilatation. Since then, substantial progress has been made in our understanding of the etiology and pathogenesis of HIVAN. This article reviews 20 years of research into the pathogenesis of HIVAN and discusses how these concepts could be applied to the treatment of children with HIVAN. HIV-1 infection plays a direct role in the pathogenesis of childhood HIVAN, at least partially by affecting the growth and differentiation of glomerular and tubular epithelial cells and enhancing the renal recruitment of infiltrating mononuclear cells and cytokines. An up-regulation of renal heparan sulfate proteoglycans seems to play a relevant role in this process, by increasing the recruitment of heparin-binding growth factors (i.e., FGF-2), chemokines, HIV-infected cells, and viral proteins (i.e., gp120, Tat). These changes enhance the infectivity of HIV-1 in the kidney and induce injury and proliferation of intrinsic renal cells. Highly active anti-retroviral therapy (HAART) appears to be the most promising treatment to prevent the progression of childhood HIVAN. Hopefully, in the near future, better education, prevention, and treatment programs will lead to the eradication of this fatal childhood disease.

Connective tissue growth factor participates in scar formation of crescentic glomerulonephritis

Glomerular crescents are a major determinant of progression in various renal diseases. Some types of growth factors are known to be involved in the evolution of crescents and the subsequent scar formation. Although glomerular parietal epithelial cells (PECs) are the major component of cellular crescents, the influence of growth factors on PECs is unknown. We performed immunohistochemical studies and in situ hybridization to examine alterations in connective tissue growth factor (CTGF) expression and to identify CTGF-synthesizing cells in crescents in the crescentic glomerulonephritis model of Wistar Kyoto rats. In addition, we examined the roles of fibroblast growth factor (FGF)-2, platelet-derived growth factor (PDGF)-BB, transforming growth factor (TGF)-beta, and CTGF in cell proliferation and matrix synthesis in an established rat PEC cell line (PEC line). In an acute phase of rat crescentic glomerulonephritis, a major component of the crescents were macrophages, which did not express CTGF mRNA. However, in the advanced phase, crescents strongly expressed CTGF mRNA and the epithelial marker pan-cadherin but did not express the macrophage marker ED1, suggesting that PECs synthesized the CTGF. In the PEC line, FGF-2 predominantly promoted [(3)H]thymidine incorporation compared with PDGF-BB. Both TGF-beta and PDGF-BB strongly stimulated extracellular matrix synthesis in association with up-regulation of endogenous CTGF, but TGF-beta showed a predominant role. FGF-2 had a minor effect on it. In addition, blockade of endogenous CTGF using an antisense oligodeoxynucleotide significantly attenuated both TGF-beta- and PDGF-BB-induced extracellular matrix synthesis. These results suggest that several growth factors promote cell proliferation and matrix production in PECs. CTGF-mediated matrix production via the TGF-beta or PDGF-BB pathway in PECs may, in part, play a role in the progression of scar formation in crescents.

Angiogenic protein therapy

Therapeutic angiogenesis, in the form of growth factor protein administration or gene therapy, has emerged as a new method of treatment for patients with severe, inoperable coronary artery disease. Improved myocardial perfusion and function after the administration of angiogenic growth factors has been demonstrated in animal models of chronic myocardial ischemia. A recent clinical study reported beneficial long-term effects of therapeutic angiogenesis using FGF-2 protein in terms of freedom from angina and myocardial perfusion on nuclear imaging and suggested that protein angiogenic therapy has the potential to extend treatment options to patients who are not optimal candidates for conventional methods of myocardial revascularization. The ultimate role that angiogenesis will play in the treatment of ischemic heart disease will, however, be determined from adequately powered, randomized, double-blind, placebo-controlled trials. It is likely that endogenous antiangiogenic influences, intrinsic lack of response of patients with severe endothelial dysfunction, and other limitations will have to be overcome before angiogenesis becomes standard therapy for the treatment of coronary artery disease.

Hypertension superimposed on type II diabetes in Goto Kakizaki rats induces progressive nephropathy

BACKGROUND

Type II diabetes in the Goto Kakizaki (GK) rats (derived from Wistar rats) is not associated with the development of obesity, hyperlipidemia, hypertension, or pronounced renal functional changes. The aim of this study was to investigate the effect of superimposed hypertension on renal function and morphology under conditions of hyper- and normoglycemia.

METHODS

The evolution of biochemical and morphologic renal changes was examined in GK and Wistar rats treated with deoxycorticosterone acetate (DOCA) salt over 24 weeks.

RESULTS

Blood pressure was increased from 6 weeks on in GK and Wistar rats with no difference in blood pressure levels between both groups (week 24, 183 +/- 14 mm Hg vs. 191 +/- 13 mm Hg, P = NS, vs. 144 +/- 6 mm Hg in normal controls, P < 0.01). A progressive increase in proteinuria was observed in hypertensive GK rats from 12 weeks on (week 24, 168 +/- 62 mg/day vs. 41 +/- 30 mg/day in hypertensive Wistar rats, P = 0.002). Histologic analysis at weeks 15 and 24 showed progressive glomerulosclerosis in hypertensive GK and Wistar rats (week 24, 13 +/- 4% vs. 8 +/- 1%, P = NS) but not in nonhypertensive GK controls. This was associated with evidence of podocyte damage (de novo desmin expression) in hypertensive as compared to nonhypertensive GK rats (week 24, score 1.4 +/- 0.1 vs. 0.8 +/- 0.1, P < 0.001) while no significant increase was observed in hypertensive vs. nonhypertensive Wistar rats. Tubulointerstitial damage was increased in hypertensive GK as compared to hypertensive Wistar rats (week 24, score 1.5 +/- 0.6 vs. 0.6 +/- 0.3, P = 0.01). By immunohistochemistry, this was associated with an up-regulation of tubulointerstitial type IV collagen as well as alpha-smooth muscle actin (alpha-SMA) expression, macrophage infiltration and cell proliferation in hypertensive GK rats.

CONCLUSION

Our data demonstrate that long-standing type II diabetes alone is not sufficient to induce progressive nephropathy unless secondary injurious mechanisms such as hypertension are present. The hypertensive GK rat provides a novel model to investigate the mechanisms involved in diabetic nephropathy.

Vascular growth factors and angiogenesis in cardiac surgery

Therapeutic angiogenesis, in the form of growth factor protein administration or gene therapy, has emerged as a new method of treatment for patients with severe, inoperable coronary artery disease. Improved myocardial perfusion and function after administration of angiogenic growth factors has been demonstrated in animal models of chronic myocardial ischemia. Recently, preliminary clinical trials using growth factor proteins or genes encoding these angiogenic factors have demonstrated clinical and other objective evidence of relevant angiogenesis. A recent study reported beneficial long-term effects of therapeutic angiogenesis using fibroblast growth factor (FGF)-2 protein in terms of freedom from angina and perfusion on single-photon emission computed tomographic imaging. Thus, therapeutic angiogenesis has the potential to extend treatment options to patients who are not optimal candidates for conventional methods of myocardial revascularization. However, endogenous antiangiogenic influences, intrinsic lack of response of patients with severe endothelial dysfunction, and other limitations will need to be overcome before angiogenesis becomes a standard therapy for the treatment of patients with severe coronary disease.

Cell biology of the glomerular podocyte

Glomerular podocytes are highly specialized cells with a complex cytoarchitecture. Their most prominent features are interdigitated foot processes with filtration slits in between. These are bridged by the slit diaphragm, which plays a major role in establishing the selective permeability of the glomerular filtration barrier. Injury to podocytes leads to proteinuria, a hallmark of most glomerular diseases. New technical approaches have led to a considerable increase in our understanding of podocyte biology including protein inventory, composition and arrangement of the cytoskeleton, receptor equipment, and signaling pathways involved in the control of ultrafiltration. Moreover, disturbances of podocyte architecture resulting in the retraction of foot processes and proteinuria appear to be a common theme in the progression of acquired glomerular disease. In hereditary nephrotic syndromes identified over the last 2 years, all mutated gene products were localized in podocytes. This review integrates our recent physiological and molecular understanding of the role of podocytes during the maintenance and failure of the glomerular filtration barrier.

Selective modulation of the secretion of proteinases and their inhibitors by growth factors in cultured differentiated podocytes

Selective modulation of the secretion of proteinases and their inhibitors by growth factors in cultured differentiated podocytes.

BACKGROUND

Podocyte damage is considered to be an important factor in the development of glomerulosclerosis. Morphological studies on experimental models of progressive glomerular disease have identified the detachment of podocytes from the glomerular basement membrane (GBM) as a critical step in the development and progression of glomerulosclerosis. Degradation of the GBM by proteinases also might be a potential mechanism of the detachment because the process impairs the connection between podocytes and the GBM. The present study examined the effects of basic fibroblast growth factor (bFGF), transforming growth factor-beta1 (TGF-beta1) and platelet-derived growth factor (PDGF) on the secretion of proteinases [cathepsin L and matrix metalloproteinases (MMPs)] and their inhibitors [cystatin C and tissue inhibitor of metalloproteinase-2 (TIMP-2)] from differentiated podocytes in culture.

METHODS

Expression of mRNAs for receptors of growth factors (bFGF, PDGF, TGF-beta1), the proteinases and their inhibitors in differentiated podocytes were shown by RT-PCR. The secretion of cathepsin L, cystatin C and TIMP-2 from differentiated podocytes were shown by immunoblot analysis. The activities of MMPs-2 and -9 from differentiated podocytes were shown by gelatin zymography.

RESULTS

Expression of mRNAs for receptors of the growth factors, the proteinases and their inhibitors were confirmed. bFGF increased the secretion of cathepsin L (5.04-fold at 20 ng/mL), but did not alter the secretion of its extracellular inhibitor, cystatin C. In contrast, TGF-beta1 increased the activities of MMPs-2 and -9 (3.23-fold at 10 ng/mL and 25.3-fold at 10 ng/mL, respectively) from differentiated podocytes, but did not enhance the secretion of its inhibitor, TIMP-2. In addition, bFGF enhanced the secretion of TIMP-2 (2.75-fold at 20 ng/mL) and TGF-beta1 enhanced the secretion of cystatin C (2.32-fold at 20 ng/mL). These results demonstrate the imbalance of the secretion of proteinases and their inhibitors after incubation of such growth factors. Of particular interest was the observation of differences in regulation of proteinases and their extracellular inhibitors in response to bFGF and TGF-beta1. PDGF only slightly increased the secretion of cathepsin L (2.54-fold at 20 ng/mL) but exerted no effect on the secretion of cystatin C, MMPs, and TIMP-2 from differentiated podocytes.

CONCLUSION

These results indicate, to our knowledge for the first time, that in differentiated podocytes, both cathepsin L and its inhibitor are independently regulated by different growth factors. It appears that increases in proteolytic activities may induce degradation of the glomerular basement membrane (GBM), which plays an important role in the progression of glomerulosclerosis.

Vascular endothelial growth factor enhances glomerular capillary repair and accelerates resolution of experimentally induced glomerulonephritis

Vascular endothelial growth factor (VEGF) regulates angiogenesis through endothelial cell proliferation and plays an important role in capillary repair in damaged glomeruli. We tested the hypothesis that VEGF might be beneficial in rats with severe glomerular injury in glomerulonephritis (GN) based on its angiogenic and vascular remodeling properties. Acute GN with severe glomerular destruction was induced in rats by injection of anti-Thy-1.1 antibody (day 0) and Habu-snake venom (day 1). Rats were intraperitoneally injected with recombinant human VEGF(165) (10 microg/100 g body wt/day) or vehicle from day 2 to day 9, and monitored changes in glomerular capillaries, development of glomerular inflammation, and progression to glomerular sclerosis after acute glomerular destruction in both groups. Rats that received anti-Thy-1.1 antibody and Habu-snake venom showed severe mesangiolysis and marked destruction of capillary network on day 2. VEGF was expressed on glomerular epithelial cells, proliferating mesangial cells, and some infiltrating leukocytes, and VEGF(165) protein levels increased in damaged glomeruli during day 5 to day 7. Normal, damaged, and regenerating glomerular endothelial cells expressed VEGF receptor flk-1. However, endothelial cell proliferation and capillary repair was rare in vehicle-treated rats with severe glomerular damage, which progressed to global sclerosis and chronic renal failure by week 8. In contrast, in the VEGF-treated group, VEGF(165) significantly enhanced endothelial cell proliferation and capillary repair in glomeruli by day 9 (proliferating endothelial cells: VEGF(165), 4.3 +/- 1.1; control, 2.2 +/- 0.9 cells on day 7, P < 0.001; and glomerular capillaries: VEGF(165), 24.6 +/- 4.8; control, 16.9 +/- 3.4 capillaries on day 7, P < 0.01). Thereafter, damaged glomeruli gradually recovered after development of capillary network by week 8, and significant improvement of renal function was evident in the VEGF-treated group during week 8 (creatinine: VEGF(165), 0.3 +/- 0.1; control, 2.6 +/- 0.9 mg/dl, P < 0.001; proteinuria: VEGF(165), 54 +/- 15; control, 318 +/- 60 mg/day, P < 0.001). We conclude that the beneficial effect of VEGF(165) in severe glomerular injury in GN emphasizes the importance of capillary repair in the resolution of GN, and may allow the design of new therapeutic strategies against severe GN.

Intrauterine food restriction as a determinant of nephrosclerosis

We previously showed that 3-month-old rats subjected to a 50% intrauterine food restriction had a decreased number of nephrons with increased glomerular diameter, which suggests compensatory hypertrophy. Hypertrophy could be the early event of glomerular damage. In this study, we extended our investigation and performed functional, morphological, and immunohistochemical evaluations in 3- and 18-month-old rats that underwent a 50% intrauterine food restriction (RT3 and RT18, respectively) and age-matched control rats (C3 and C18, respectively). Our findings showed that glomerular filtration rate was significant decreased in RT18 rats (2.42 +/- 0.15 mL/min/kg; n = 28; P: < 0.05) compared with C18 control rats (4.19 +/- 0.10 mL/min/kg; P: < 0.05) and the percentage of glomeruli with sclerosis was greater in RT18 rats (13.01% +/- 2.95%; n = 9; P: < 0.01) than in C18 rats (2.71% +/- 0.35%; n = 6). RT18 rats also showed more intense tubulointerstitial lesions and immunohistochemical alterations in the renal cortex. Immunohistochemical studies showed increased fibronectin and desmin expression in glomeruli and tubulointerstitium and increased vimentin and alpha-smooth muscle actin in the tubulointerstitial area from the renal cortex of RT18 rats (P: < 0.05). Desmin was also increased at the edge of glomeruli from RT18 rats, suggesting podocyte injury. Our data show that when food restriction is imposed during pregnancy, permanent damage occurs in the kidney of the offspring. Glomerular lesions were more severe than the tubulointerstitial damage in these animals.

Early events leading to renal injury in obese Zucker (fatty) rats with type II diabetes

Early events leading to renal injury in obese Zucker (fatty) rats with type II diabetes.

BACKGROUND

More than half of the new patients admitted to dialysis therapy in some centers are diagnosed with type IIb diabetes, that is, diabetes associated with obesity. This study searched for a common final pathway of renal damage in this progressive renal disease.

METHODS

The evolution of biochemical and morphological renal changes was examined in 6- to 60-week-old Zucker rats (fa/fa-rats), a model of obesity associated with type II diabetes.

RESULTS

fa/fa-rats exhibited pronounced hyperinsulinemia and hyperlipidemia at 6 weeks and became diabetic after 14 weeks of age. Significant focal segmental glomerulosclerosis was first noted in 18-week-old fa/fa-rats and tubulointerstitial damage and proteinuria in 40-week-old fa/fa-rats. A comparison of kidneys of six-week-old fa/fa-and lean control (Fa/?) rats by immunohistology revealed a 1.8-fold increase in glomerular monocyte/macrophage counts in fa/fa-rats and a significant increase in de novo desmin expression in podocytes. Electron microscopy demonstrated an increase in the number of podocyte mitochondria and intracytoplasmic protein and fat droplets. Podocyte desmin scores markedly increased until week 18 in fa/fa-rats, whereas glomerular monocyte/macrophage counts peaked at 3.2-fold at week 14. Podocyte desmin expression, but not glomerular macrophage infiltration, correlated with damage in adjacent tubular cells, as evidenced by their de novo expression of vimentin. Progressive glomerular hypertrophy was detected in fa/fa-rats after 10 weeks. GBM width was significantly increased in 14-week-old fa/fa-rats as compared with lean controls. Mesangial cell activation (de novo expression of alpha-smooth muscle actin) and proliferation was low to absent throughout the observation period in fa/fa-rats. Renal cell death counts (TUNEL) remained unchanged in 6- to 40-week-old fa/fa-rats. Tubulointerstitial myofibroblast formation and matrix accumulation occurred late during the study duration in fa/fa-rats.

CONCLUSION

These data suggest that early progressive podocyte damage and macrophage infiltration is associated with hyperlipidemia and type IIb diabetes mellitus, and antedates both the development of glomerulosclerosis and tubulointerstitial damage.

The role of the podocyte in glomerulosclerosis

Focal segmental glomerulosclerosis is a pathological hallmark of many forms of progressive renal disease. The 'classic' lesion, based on the adhesion of the capillary tuft to Bowman's capsule, results from the loss of podocytes from the capillary basement membrane. The recently described 'collapsing' variant, in contrast, has an apparent excess of extracapillary cells, which may represent dedifferentiated, 'dysregulated' podocytes.

Progression of glomerular diseases: is the podocyte the culprit?

The stereotyped development of the glomerular lesions in many animal models and human forms of progressive renal disease suggests that there are common mechanisms of disease progression. We propose the outline of such a mechanism based on following aspects: (1) The glomerulus is a complex structure, the stability of which depends on the cooperative function of the basement membrane, mesangial cells and podocytes, counteracting the distending forces originating from the high glomerular hydrostatic pressures. Failure of this system leads to quite uniform architectural lesions. (2) There is strong evidence that the podocyte is incapable of regenerative replication post-natally; when podocytes are lost for any reason they cannot be replaced by new cells. Loss of podocytes may therefore lead to areas of "bare" GBM. which represent potential starting points for irreversible glomerular injury. (3) Attachment of parietal epithelial cells to bare GBM invariably occurs when bare GBM coexists with architectural lesions, leading to the formation of a tuft adhesion to Bowman's capsule, the first "committed" lesion progressing to segmental sclerosis. (4) Within an adhesion the tuft merges with the interstitium, allowing filtration from perfused capillaries inside the adhesion towards the interstitium. The relevance of such filtration is as yet unclear but may play a considerable role in progression to global sclerosis and interstitial fibrosis.