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L G Fine

Publications and source records attributed to L G Fine.

At least 37 records · Page 2Linked to original sources
PubMed1995

An endothelin-1 mediated autocrine growth loop involved in human renal tubular regeneration.

Renal tubules have the capacity to regenerate following injury. We have investigated the possibility that tubular-derived endothelins, acting as autocrine growth factors, may be involved in this response in human kidney. ET-1 immunoreactivity was demonstrated by immunohistochemical staining in proximal tubules, distal cortical tubules and medullary collecting ducts of human kidney. In cultured human renal proximal tubular cells, RNAase protection assays demonstrated the expression of ET-1 and ET-2 mRNA's, and radioimmunoassay, following separation of conditioned medium by reverse phase HPLC, showed immunoreactive material which co-eluted with ET-1 and ET-2. Competition binding studies revealed the presence of at least two types of endothelin receptor: one with high and one with low affinity for ET-3 relative to ET-1. Analysis of cellular RNA by RT-PCR demonstrated expression of mRNA's for both ETA and ETB receptor subtypes. Combined blockade of ETA and ETB receptors (by PD-145065) but not that of ETA receptors alone (by BQ-123) blocked the mitogenic effect of exogenous or endogenous ET-1 and also profoundly suppressed endogenous ET-1 synthesis. By contrast, incubation with the ETB receptor agonist, BQ-3020, stimulated endogenous ET-1 synthesis. Exposure of the cells to hypoxia (1% O2 for 16 to 24 hr) resulted in specific up-regulation of ET-1 but not ET-2 gene expression. These findings reveal the existence of a hypoxia-inducible, autocrine growth system in human proximal tubular cells, which is mediated by ET-1 through the ETB receptor, and which could function in vivo as an autoregenerative system for restoring tubular integrity after injury. The widespread distribution of ET-1 peptide in different tubular segment suggests that ET-1 mediated tubular regeneration may also occur in other nephron segments.

Binding, Competitive↗
PubMed1995

Transfer of a mutated gene encoding active transforming growth factor-beta 1 suppresses mitogenesis and IL-1 response in the glomerulus.

Using in vivo gene transfer, we examined the anti-inflammatory potential of transforming growth factor-beta 1 (TGF-beta 1) in the renal glomerulus. TGF-beta 1 cDNA, modified to allow for secretion of the active form of TGF-beta 1, was introduced into cultured rat mesangial cells. The responses of the established transfectants were examined in culture. In vitro, the transduced mesangial cells showed a reduced mitogenic response to fetal calf serum and were insensitive to induction of matrix metalloproteinase-9 (MMP-9) by the proinflammatory cytokine IL-1 beta. To examine whether glomeruli which express active TGF-beta 1 in vivo are insensitive to these same stimuli, TGF-beta transfectants were transferred into normal rat glomeruli via renal artery injection. After 24 hours, isolated glomeruli containing transfectants exhibited TGF-beta bioactivity, a reduced mitogenic response, and repressed expression of MMP-9 in response to IL-1 beta. We further examined the responses of these chimeric glomeruli to an in vivo mitogenic stimulus by transferring TGF-beta transfectants into glomeruli of kidneys one day after the induction of anti-Thy-1 nephritis. The mitogenic activity of isolated glomeruli was examined four days after the cell injection. Compared to unmodified or mock cell-containing glomeruli, the in vivo mitogenic activity of glomeruli containing TGF-beta transfectants was significantly repressed. Furthermore, cellular outgrowth from nephritic glomeruli expressing active TGF-beta 1 was also suppressed ex vivo compared to controls. These data indicate that TGF-beta 1 inhibits mitogenesis and IL-1 response of the glomerulus and may, in part, act as a potential early suppressor of glomerular inflammation.

Animals↗
PubMed1995

Roles of hepatocyte growth factor/scatter factor and the met receptor in the early development of the metanephros.

Several lines of evidence suggest that hepatocyte growth factor/scatter factor (HGF/SF), a soluble protein secreted by embryo fibroblasts and several fibroblast lines, may elicit morphogenesis in adjacent epithelial cells. We investigated the role of HGF/SF and its membrane receptor, the product of the c-met protooncogene, in the early development of the metanephric kidney. At the inception of the mouse metanephros at embryonic day 11, HGF/SF was expressed in the mesenchyme, while met was expressed in both the ureteric bud and the mesenchyme, as assessed by reverse transcription PCR, in situ hybridization, and immunohistochemistry. To further investigate the expression of met in renal mesenchyme, we isolated 13 conditionally immortal clonal cell lines from transgenic mice expressing a temperature-sensitive mutant of the SV-40 large T antigen. Five had the HGF/SF+/met+ phenotype and eight had the HGF/SF-/met+ phenotype. None had the HGF/SF+/met- nor the HGF/SF-/met- phenotypes. Thus the renal mesenchyme contains cells that express HGF/SF and met or met alone. When metanephric rudiments were grown in serum-free organ culture, anti-HGF/SF antibodies (a) inhibited the differentiation of metanephric mesenchymal cells into the epithelial precursors of the nephron; (b) increased cell death within the renal mesenchyme; and (c) perturbed branching morphogenesis of the ureteric bud. These data provide the first demonstration for coexpression of the HGF/SF and met genes in mesenchymal cells during embryonic development and also imply an autocrine and/or paracrine role for HGF/SF and met in the survival of the renal mesenchyme and in the mesenchymal-epithelial transition that occurs during nephrogenesis. They also confirm the postulated paracrine role of HGF/SF in the branching of the ureteric bud.

Animals↗
PubMed1994

Tubular-derived growth factors and cytokines in the pathogenesis of tubulointerstitial fibrosis: implications for human renal disease progression.

Detailed histomorphometric analysis of human biopsy tissue over the last 30 years has convincingly demonstrated that preservation of the tubulointerstitial compartment of the kidney is the major determinant of renal outcome in a variety of human renal diseases. Nevertheless, the pathophysiology of tubulointerstitial disease remains obscure. In particular, the primary role of tubular injury has not been explored adequately. There is now accumulating evidence that apart from their many transport functions, tubular cells also secrete an array of cytokines, including chemotactic cytokines, polypeptide growth factors, and vasoactive peptides. Three paracrine growth systems acting at different levels in the kidney are described as examples of potential interactions between tubular and interstitial cells in health and disease. We hypothesize that while glomerular injury may precede tubular injury, it is tubular injury that sets into motion the irreversible process of tubulointerstitial fibrosis characteristic of progressive human renal disease, leading to secondary loss of glomerular function.

Animals↗
PubMed1994

John Blackall (1771-1860): failure to see the obvious in dropsical patients with coagulable urine?

Despite his success in publishing a book which was widely read and which drew attention to the fact that some cases of dropsy are associated with coagulable urine, John Blackall failed to make the link between this phenomenon and disease of the kidneys. Thus, to Richard Bright must go the credit for providing the critical understanding of the phenomenon. The single most probable reason for Bright's success and Blackall's failure was that Bright carried out post mortem examinations of almost all of his patients. In addition, Bright was ruthlessly systematic in documenting his autopsy findings, and not least was the fact that he possessed the rare talent of being objective in looking at his data, without being influenced by the preconceptions of the times.

Edema↗
PubMed1994

Gene transfer into the rat renal glomerulus via a mesangial cell vector: site-specific delivery, in situ amplification, and sustained expression of an exogenous gene in vivo.

To evaluate the pathophysiological function of specific molecules in the renal glomerulus, selective, sustained, and modifiable expression of such molecules will be required. Towards achieving this end, we devised a gene transfer system using the glomerular mesangial cell as a vector for gene delivery. A reporter gene which encodes bacterial beta-galactosidase was introduced into cultured rat mesangial cells, and the stable transfectants were transferred into the rat kidney via the renal artery, leading to selective entrapment within the glomeruli. In the normal kidney, the reporter cells populated into 57 +/- 13% of glomeruli site specifically, and the expression of beta-galactosidase was sustained for 4 wk and declined thereafter. Within the glomerulus, some of the reporter cells remained in the glomerular capillaries, while others repopulated the mesangial area and, in part, extended their cytoplasmic processes toward the surrounding capillaries. When the cells were transferred into glomeruli subjected to transient mesangiolysis induced by monoclonal antibody 1-22-3, in situ expression of beta-galactosidase was amplified 7-12-fold, and the enhanced level of expression continued for up to 8 wk. The mesangial cell vector system thus achieves site-specific delivery of an exogenous gene into the glomerulus and is amenable to in situ amplification and sustained expression by preconditioning of the target site.

Animals↗
PubMed1993

Genetically engineered kidneys.

We review the available methods of creating genetically engineered kidneys. These include transgenic technology to introduce novel genes or delete existing genes and methods of gene transfer into the post-natal or adult kidney. The use of such technology has provided insights into renal development and growth and created new animal models of human diseases. Although some of these techniques are of potential use for introducing therapeutically useful gene products into the diseased kidney, many problems remain to be solved before this aim is attained.

Animals↗
PubMed1993

Mechanisms of tubulo-interstitial injury in progressive renal diseases.

A vast amount of evidence, based upon human renal biopsy material, indicates that the presence of tubular atrophy and interstitial fibrosis is a better indicator of outcome of renal function than is the extent of glomerular sclerosis. The pathophysiological basis for this surprising fact has not been adequately addressed. In this review we point out that the systemic hypertension which accompanies most forms of chronic renal disease could impact adversely upon the vasodilated interstitial vascular compartment which, together with a component of primary capillary injury related to the disease process, could cause progressive obliteration of particular capillaries. This would initiate a process of chronic tubular ischaemia ultimately leading to tubular atrophy. Since tubular cells have been shown to produce an array of cytokines and growth factors which modulate fibroblast proliferation, extracellular matrix production and chemo-attracts for infiltrating cells, it is further proposed that it is the tubular injury which initiates the deleterious cascade of events. Tubular injury may be aggravated by the filtration of potentially 'noxious' molecules through the diseased glomerulus and by infiltrating cells. As the vascular bed into which glomerular blood flow empties is progressively obliterated, glomerular function declines and renal failure advances in relation to the degree of tubulo-interstitial fibrosis.

Atrophy↗
PubMed1993

Gene transfer into the mammalian kidney: first steps towards renal gene therapy.

In this review we discuss two strategies for successful retrovirally-mediated transfer (transduction) of a reporter gene (bacterial beta-galactosidase) into the mammalian kidney. Retroviruses only integrate into dividing cells, but the adult kidney has a very low cell turnover. One approach used is the rapidly-dividing metanephros, or precursor of the adult kidney, as a target for proviral integration. After infection and microtransplantation of fragments of this tissue into the renal cortex of neonatal mice, the implants grew and developed within the host kidney and reporter gene expression was located in glomerular and interstitial cells. A similar approach has been used by other investigators to grow genetically-engineered metanephros in a subcapsular location in the kidney. However, access of the gene product to the parenchyma of the kidney may be limited using this approach. A second strategy was to induce renal tubular cell replication by causing nephrotoxic damage with a folic acid injection. This created a 'biological window' in which a specific cell population, that is, tubular cells, was targeted for retroviral infection. One to four weeks later foci of tubular cells were found to express the reporter gene product. In both models, 50 to 90% of the experiments showed evidence of proviral integration as judged by the presence of a 559 base-pair DNA fragment amplified by the polymerase chain reaction. This persisted for four to seven weeks, the limit of the period of observation.

Animals↗
PubMed1992

Growth factors in the pathogenesis of renovascular complications of diabetes mellitus.

PURPOSE: We reviewed the evidence that links altered levels of circulating and intrarenal growth factors with the genesis of renal glomerular hypertrophy, microvascular disease and interstitial fibrosis as seen in diabetes mellitus. ANIMAL DATA: Insulin-like growth factor 1 (IGF-1) appears to be a hypertrophic factor in experimental renal disease, and is also known to be mitogenic for mesangial and vascular smooth muscle cells. However, an alteration in the balance of other factors, such as platelet-derived growth factor and angiotensin (Ang) II, could contribute to the growth disorder. Data from healthy animals suggest that the paracrine stimulation of interstitial fibroblasts by adjoining renal epithelial cells may contribute to the progressive interstitial fibrosis and microvascular occlusion found in diabetic nephropathy and other chronic renal diseases. HUMAN DATA: The progressive fall in the glomerular filtration rate in patients with diabetic nephropathy may be partly explained by structural damage in the glomerulus subsequent to hyperfiltration and hypertrophy. However, interstitial disease is independently correlated with serum creatinine. There is no evidence to show whether growth factors contribute to the genesis of human diabetic nephropathy, and circulatory levels of IGF-1 and Ang II are not clearly correlated with renal disease. It is possible, but not proven, that intrarenal levels of growth factors may be particularly relevant to the pathogenesis of glomerular microvascular and interstitial disease.

Angiotensin II↗
PubMed1992

Renal growth responses to acute and chronic injury: routes to therapeutic intervention.

Knowledge of the control of cell growth and extracellular matrix deposition has assumed center stage in the understanding of how the diseased kidney responds to injury. After acute tubular injury, there may be reversible, partial depolarization of renal cells or cell necrosis. The latter requires a regenerative response, which could be under the control of growth factors such as epidermal growth factor (EGF). Up-regulation of EGF receptors on viable cells provides the cell with an enhanced growth response despite a reduction in EGF production by the kidney. Acute glomerular injury involves a highly complex network of cytokines and growth inhibitors, the most important of which appear to be platelet-derived growth factor as a mitogen and transforming growth factor beta as an activator of extracellular matrix deposition. The long-term growth responses of the kidney to injury, reflected by chronic renal diseases, include tubular hypertrophy in those nephrons which are less affected by the primary disease. Tubular cell enlargement appears to proceed along a pathway that is different from the growth in cell size which precedes cell division, at least as indicated by a fundamentally different pattern of early gene expression. This pattern is not suggestive of a classical growth factor-initiated process. Other chronic changes that seem to correlate well with the progression of human disease are tubular atrophy and interstitial fibrosis. Growth factors produced by tubular cells may cause proliferation and matrix deposition by adjacent interstitial fibroblasts. A scheme is proposed in which low-grade ischemic injury to tubular cells, secondary to microvascular injury, leads to tubular atrophy, the release of growth factors, interstitial fibrosis, and the obliteration of peritubular capillaries. This would aggravate primary glomerular injury by compromising the vascular outflow from the glomerulus and would account for the long-recognized association between tubulo-interstitial injury and the progression of a variety of renal diseases. The use of growth factors to stimulate specific growth responses, antibodies, or inhibitory molecules to inhibit scarring generated by cytokines and the potential for genetic manipulation of the kidney provide future avenues for manipulating the growth response of the diseased kidney.

Animals↗
PubMed1992

Evolving role of growth factors in the renal response to acute and chronic disease.

The roles of growth factors in the pathogenesis of various forms of acute and chronic renal disease are largely putative. Nevertheless, there is a growing body of information that links specific growth factors to particular forms of renal injury. In all instances, it is supposed that such associations are not necessarily unique and that multiple cytokines probably interact to determine the pattern of injury or the regenerative response to such injury. Regeneration of tubular epithelium after acute tubular necrosis involves upregulation of the epidermal growth factor (EGF) receptor. Early studies of exogenously administered EGF indicate that the severity and duration of renal failure may be attenuated by this growth factor. Thus far, the observed responses have been limited and the role of EGF as a therapeutic agent requires more study. The mechanism of generation of tubulointerstitial injury in most forms of renal disease is difficult to understand. Early in vitro studies of growth factor production by tubular cells (in the absence of any infiltrating cells) indicate that platelet-derived growth factor produced by the medullary collecting duct is mitogenic for renal medullary fibroblasts, suggesting a paracrine growth system in this region of the kidney. Insulin-like growth factor I has also been shown to be produced by collecting duct cells. Its production is increased by EGF, and its association with certain forms of renal hypertrophy, i.e., diabetes and hypersomatotrophic states, implies its participation in the hypertrophic growth response. Platelet-derived growth factor is a potent mitogen for glomerular mesangial cells, and its production is regulated by a variety of cytokines.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Stimulation of Na+/H+ exchange is not required for induction of hypertrophy of renal cells in vitro.

Hypertrophy of renal proximal tubular cells is associated with an early increase in Na+/H+ antiport activity both in vivo and in vitro. The purpose of the study presented here was to determine whether functioning Na+/H+ antiport activity is required for hypertrophy to occur. LLC-PK1 cells deficient in Na+/H+ antiport activity were prepared by the "proton-suicide" method. Mutant cells had 28 to 40% of the normal Na+/H+ antiport activity. The addition of 50 nM methylisobutylamiloride to these cells decreased the antiport activity to less than 5% of the control value. In the mutant cells, steady-state intracellular pH was normal as was the protein content. After exposure of the wild-type cells for 72 h to 10(-6) M insulin and 10(-9) M insulin-like growth factor 1, cell protein content increased significantly. The increase in protein content induced by these growth factors in the mutant cells did not differ significantly from the response of the wild-type cells. Lowering the Na+/H+ exchange further by the addition of methylisobutylamiloride (50 nM) to less than 5% of the control value did not blunt the hypertrophic response in the mutant cells. These studies indicate that hypertrophy can be induced in LLC-PK1 cells by growth factors when basal Na+/H+ antiport activity is reduced to low levels by selective mutation or by competitive inhibition. The results suggest that stimulation of the Na+/H+ antiporter is not an essential prerequisite for the induction of hypertrophy in renal cells.

Amiloride↗