Biomedical subjects

Kelly L Hudkins

Publications and source records attributed to Kelly L Hudkins.

At least 19 recordsLinked to original sources

PubMed2026

Urinary clusterin as a biomarker of human kidney disease progression and response to the endothelin receptor antagonist atrasentan: An exploratory analysis from the SONAR trial.

The endothelin receptor antagonist atrasentan improved kidney outcomes in the SONAR trial for type 2 diabetes and chronic kidney disease (NCT01858532), though individual responses varied. To identify molecular biomarkers of atrasentan response and outcome, we conducted a nested case-control proteomics study (N = 180) within the SONAR trial population and identified urinary clusterin (uCLU) as the top candidate. Transcriptomic analyses of human kidney biopsies at tissue and single cell level from independent cohorts revealed higher CLU mRNA levels associated with worse kidney function and outcomes. An endothelin signaling activation score derived from pathway genes was reduced by atrasentan in mice with diabetic kidney disease. In the SONAR trial (N = 3,060) population, higher uCLU predicted worse outcomes, while atrasentan reduced uCLU by 42.6% over six weeks. Early uCLU changes independently predict improved kidney outcomes. In summary, uCLU is associated with kidney disease progression and response to atrasentan treatment, supporting its potential as a pharmacodynamic biomarker to target therapy.

Humans↗

PubMed2006

Lung cancer induced in mice by the envelope protein of jaagsiekte sheep retrovirus (JSRV) closely resembles lung cancer in sheep infected with JSRV.

BACKGROUND: Jaagsiekte sheep retrovirus (JSRV) causes a lethal lung cancer in sheep and goats. Expression of the JSRV envelope (Env) protein in mouse lung, by using a replication-defective adeno-associated virus type 6 (AAV6) vector, induces tumors resembling those seen in sheep. However, the mouse and sheep tumors have not been carefully compared to determine if Env expression alone in mice can account for the disease features observed in sheep, or whether additional aspects of virus replication in sheep are important, such as oncogene activation following retrovirus integration into the host cell genome. RESULTS: We have generated mouse monoclonal antibodies (Mab) against JSRV Env and have used these to study mouse and sheep lung tumor histology. These Mab detect Env expression in tumors in sheep infected with JSRV from around the world with high sensitivity and specificity. Mouse and sheep tumors consisted mainly of well-differentiated adenomatous foci with little histological evidence of anaplasia, but at long times after vector exposure some mouse tumors did have a more malignant appearance typical of adenocarcinoma. In addition to epithelial cell tumors, lungs of three of 29 sheep examined contained fibroblastic cell masses that expressed Env and appeared to be separate neoplasms. The Mab also stained nasal adenocarcinoma tissue from one United States sheep, which we show was due to expression of Env from ovine enzootic nasal tumor virus (ENTV), a virus closely related to JSRV. Systemic administration of the AAV6 vector encoding JSRV Env to mice produced numerous hepatocellular tumors, and some hemangiomas and hemangiosarcomas, showing that the Env protein can induce tumors in multiple cell types. CONCLUSION: Lung cancers induced by JSRV infection in sheep and by JSRV Env expression in mice have similar histologic features and are primarily characterized by adenomatous proliferation of peripheral lung epithelial cells. Thus it is unnecessary to invoke a role for insertional mutagenesis, gene activation, viral replication, or expression of other viral gene products in sheep lung tumorigenesis, although these processes may play a role in other clinically less important sequelae of JSRV infection such as metastasis observed with variable frequency in sheep.

Adenocarcinoma↗

PubMed2006

Localization of TGF-beta signaling intermediates Smad2, 3, 4, and 7 in developing and mature human and mouse kidney.

Smad proteins are signaling intermediates of the TGF-beta superfamily and are involved in a range of biological activities including development and immune responses. We studied the expression of TGF-beta-receptor activated Smads (Smad2 and Smad3), the common partner Smad (Smad4), an inhibitory Smad (Smad7), and the activated (phosphorylated) Smad2 (pSmad2) in developing and adult kidneys of humans and mice. These studies demonstrate associated expression of these Smads in multiple renal cell types in all developmental stages and in mature non-diseased kidneys. Smad expression is in general most widespread at the earliest stages of nephron development and diminishes as components of the nephrons become more differentiated. Paucity of Smad expression in mesangial cells in contrast to widespread expression of these Smads in glomerular visceral epithelial cells in both developing and mature kidneys was remarkable. Divergent and less extensive expression of Smad4, compared with other Smad proteins, was also demonstrated in tubules of human kidneys. Based on the observed expression patterns, these findings demonstrate, for the first time, expression of the TGF-beta-receptor-activated Smad2 and Smad3, the common mediator Smad4, and the inhibitory Smad7 in the developing human fetal kidney, extending observations previously made in rodent systems to humans.

Adult↗

PubMed2006

Bone morphogenetic protein 4: potential regulator of shear stress-induced graft neointimal atrophy.

OBJECTIVE: Placement in baboons of a distal femoral arteriovenous fistula increases shear stress through aortoiliac polytetrafluoroethylene (PTFE) grafts and induces regression of a preformed neointima. Atrophy of the neointima might be controlled by shear stress-induced genes, including the bone morphogenetic proteins (BMPs). We have investigated the expression and function of BMPs 2, 4, and 5 in the graft neointima and in cultured baboon smooth muscle cells (SMCs). METHODS: Baboons received bilateral aortoiliac PTFE grafts and 8 weeks later, a unilateral femoral arteriovenous fistula. RESULTS: Quantitative polymerase chain reaction showed that high shear stress increased BMP2, 4, and 5 messenger RNA (mRNA) in graft intima between 1 and 7 days, while noggin (a BMP inhibitor) mRNA was decreased. BMP4 most potently (60% inhibition) inhibited platelet-derived growth factor-stimulated SMC proliferation compared with BMP2 and BMP5 (31% and 26%, respectively). BMP4 also increased SMC death by 190% +/- 10%. Noggin reversed the antiproliferative and proapoptotic effects of BMP4. Finally, Western blotting confirmed BMP4 protein upregulation by high shear stress at 4 days. BMP4 expression demonstrated by in situ hybridization was confined to endothelial cells. CONCLUSIONS: Increased BMPs (particularly BMP4) coupled with decreased noggin may promote high shear stress-mediated graft neointimal atrophy by inhibiting SMC proliferation and increasing SMC death.

Animals↗

PubMed2006

Membranous glomerulopathy with spherules: an uncommon variant with obscure pathogenesis.

BACKGROUND: Occasional case reports of membranous glomerulopathy described unique subepithelial accumulations of an unusual type of immune deposit composed of spherular structures. The identity of such structures as nuclear pores has been suggested, but not established. METHODS: We identified a cohort of patients (n = 14, including 1 patient with disease recurrence in an allograft) who presented with nephrotic syndrome and had renal biopsy specimens with light and immunofluorescence microscopic findings characteristic of membranous glomerulopathy. These patients were distinguished by ultrastructural studies that showed glomerular capillary wall accumulations of subepithelial immune deposits composed of uniform spherular structures, while lacking the typical granular electron-dense deposits seen in membranous glomerulopathy. The molecular identity of these spherular structures as nuclear pores was tested by using immunofluorescence microscopy and immunohistochemistry with mouse monoclonal antinuclear pore antibodies (Covance, Princeton, NJ) and anti-Nuclear Pore-O-Linked Glycoprotein (Affinity BioReagents Inc, Golden, CO) antibodies. RESULTS: Measurement of spherular structures by using high-magnification electron microscopy showed an average diameter of 84.5 nm, which correlated well with accepted diameters of nuclear pores (80 to 120 nm). Immunofluorescence microscopy and immunoperoxidase staining with both antibodies showed characteristic beaded staining of nuclear membranes of multiple cell types within normal control kidney, but no staining of immune-type deposits within glomerular basement membranes. CONCLUSION: These cases form a rare, but distinctive, morphological subclass of membranous glomerulopathy. The antigenic specificity of immune deposits in these cases remains elusive.

Adult↗

PubMed2004

Exogenous PDGF-D is a potent mesangial cell mitogen and causes a severe mesangial proliferative glomerulopathy.

The PDGF family consists of at least four members, PDGF-A, -B, -C, and -D. All of the PDGF isoforms bind and signal through two known receptors, PDGF receptor-alpha and PDGF receptor-beta, which are constitutively expressed in the kidney and are upregulated in specific diseases. It is well established that PDGF-B plays a pivotal role in the mediation of glomerular mesangial cell proliferation. However, little is known of the roles of the recently discovered PDGF-C and -D in mediating renal injury. In this study, adenovirus constructs encoding PDGF-B, -C, and -D were injected into mice. Mice with high circulating levels of PDGF-D developed a severe mesangial proliferative glomerulopathy, characterized by enlarged glomeruli and a striking increase in glomerular cellularity. The PDGF-B-overexpressing mice had a milder proliferative glomerulopathy, whereas the mice overexpressing PDGF-C and those that received adenovirus alone showed no measurable response. Mitogenicity of PDGF-D and -B for mesangial cells was confirmed in vitro. These findings emphasize the importance of engagement of PDGF receptor-beta in transducing mesangial cell proliferation and demonstrate that PDGF-D is a major mediator of mesangial cell proliferation. Finally, this approach has resulted in a unique and potentially valuable model of mesangial proliferative glomerulopathy and its resolution.

Animals↗

PubMed2004

Chemokine receptor CCR1 but not CCR5 mediates leukocyte recruitment and subsequent renal fibrosis after unilateral ureteral obstruction.

As chemokine receptor CCR1 and CCR5 expression on circulating leukocytes is thought to contribute to leukocyte recruitment during renal fibrosis, the authors examined the effects of unilateral ureteral obstruction (UUO) in mice deficient for CCR1 or CCR5. Analysis of UUO kidneys from CCR1-deficient mice revealed a reduction of interstitial macrophages and lymphocytes (35% and 55%, respectively) compared with wild-type controls. CCR1-deficient mice had reduced CCR5 mRNA levels in UUO kidneys, which correlated with a reduction of CCR5+ T cell infiltrate as determined by flow cytometry. Interstitial fibroblasts, renal TGF-beta1 mRNA expression, interstitial volume, and collagen I deposits were all significantly reduced in CCR1-deficient mice. In contrast, renal leukocytes and fibrosis were unaffected in CCR5-deficient mice with UUO. However, if treated with the CCR1 antagonist BX471, CCR5-deficient mice showed a similar reduction of renal leukocytes and fibrosis as CCR1-deficient mice. To determine the underlying mechanism labeled macrophages and T cells isolated from either wild-type, CCR1-deficient, or CCR5-deficient mice were injected into wild-type mice with UUO. Three hours later, renal cell recruitment was reduced for CCR1-deficient cells or cells pretreated with BX471 compared with CCR5-deficient or wild-type cells. Thus, CCR1 but not CCR5 is required for leukocyte recruitment and fibrosis after UUO in mice. Therefore, CCR1 is a promising target for therapeutic intervention in leukocyte-mediated fibrotic tissue injury, e.g. progressive renal fibrosis.

Animals↗

PubMed2004

Late onset of treatment with a chemokine receptor CCR1 antagonist prevents progression of lupus nephritis in MRL-Fas(lpr) mice.

Slowly progressive renal injury is the major cause for ESRD. The model of progressive immune complex glomerulonephritis in autoimmune MRL(lpr/lpr) mice was used to evaluate whether chemokine receptor CCR1 blockade late in the disease course can affect progression to renal failure. Mice were treated with subcutaneous injections of either vehicle or BX471, a nonpeptide CCR1 antagonist, three times a day from week 20 to 24 of age [corrected]. BX471 improved blood urea nitrogen levels (BX471, 35.1 +/- 5.3; vehicle, 73.1 +/- 39.6 mg/dl; P < 0.05) and reduced the amount of ERHR-3 macrophages, CD3 lymphocytes, Ki-67 positive proliferating cells, and ssDNA positive apoptotic cells in the interstitium but not in glomeruli. Cell transfer studies with fluorescence-labeled T cells that were pretreated with either vehicle or BX471 showed that BX471 blocks macrophage and T cell recruitment to the renal interstitium of MRL(lpr/lpr) mice. This was associated with reduced renal expression of CC chemokines CCL2, CCL3, CCL4, and CCL5 and the chemokine receptors CCR1, CCR2, and CCR5. Furthermore, BX471 reduced the extent of interstitial fibrosis as evaluated by interstitial smooth muscle actin expression and collagen I deposits, as well as mRNA expression for collagen I and TGF-beta. BX471 did not affect serum DNA autoantibodies, proteinuria, or markers of glomerular injury in MRL(lpr/lpr) mice. This is the first evidence that, in advanced chronic renal injury, blockade of CCR1 can halt disease progression and improve renal function by selective inhibition of interstitial leukocyte recruitment and fibrosis.

Animals↗

PubMed2004

Differential expression of chemokines and chemokine receptors in murine islet allografts: the role of CCR2 and CCR5 signaling pathways.

Chemokines and their receptors play a pivotal role in the initiation and amplification of the immune response. Investigated was their differential expression after syngeneic and allogeneic islet transplantation. During the 7 d after transplantation, the chemokines MCP-1, MCP-2, RANTES, MIG, IP-10, I-TAC, and two CC chemokine receptors CCR2 and CCR5 were highly expressed in allografts when compared with isografts. Disrupting the CCR2 and CCR5 pathways individually resulted in prolongation of the survival time 16.1 +/- 0.4 and 15.8 +/- 0.9 d, respectively, of fully major histocompatibility complex-mismatched islet grafts compared with wild-type controls (11.2 +/- 1.0 d). Blockade of both receptors had no synergistic effect. Rapamycin-treated wild-type recipients rejected their grafts at 17.4 +/- 2.2 d, in contrast to rapamycin-treated CCR2-/- recipients at 38 +/- 8.6 d (P = 0.025). The disruption of the CCR2 and CCR5 signaling, alone or in combination, moderately prolong islet allograft survival. However, the combination of low-dose immunosuppression and targeting of CCR2 greatly augmented islet graft survival.

Animals↗

PubMed2004

Hyperlipidemia aggravates renal disease in B6.ROP Os/+ mice.

INTRODUCTION: Reduction of renal mass is frequently associated with progressive loss of kidney function. We examined the effects of hyperlipidemia on renal pathology and mediators of tissue damage in B6.ROP Os/+ mice, a model of reduced renal mass. METHODS: C57BL/6 control mice and B6.ROP Os/+ mice were fed normal rodent chow or a high fat, high cholesterol (HFHC) diet for 12 weeks. Kidney function and renal pathology were assessed. RESULTS: Hyperlipidemia led to a decline in kidney function in C57BL/6 mice. Renal pathology was characterized by an increase in glomerular matrix and cellularity, glomerular and tubulointerstitial macrophage influx, and increased tubular epithelial cell turnover. Chow-fed B6.ROP Os/+ animals demonstrated glomerular hypertrophy with an increase in mesangial matrix and cellularity that was characterized by macrophage influx and increased proliferation. The tubulointerstitium showed increased macrophages as well as tubular atrophy and dilation. Renal pathology was accompanied by an increase in blood urea nitrogen (BUN) and proteinuria. Hyperlipidemia in B6.ROP Os/+ mice resulted in increased plasma BUN compared to chow-fed B6.ROP Os/+ animals and aggravated renal pathology by further increasing glomerular matrix and glomerular hypercellularity. Glomerular hypercellularity was associated with increased expression of platelet-derived growth factor-B (PDGF B) and its receptor beta. Glomerular transforming growth factor-beta (TGF-beta) mRNA expression was increased in B6.ROP Os/+ mice, hyperlipidemic C57BL/6 mice and hyperlipidemic B6.ROP Os/+ animals compared to controls and correlated with the amount of mesangial matrix. CONCLUSION: This study demonstrates that hyperlipidemia worsens renal pathology in B6.ROP Os/+ mice with a decline in renal function mediated at least in part through increased renal expression of the cytokines PDGF B and TGF-beta.

Animals↗

PubMed2003

Hyperglycemia and hyperlipidemia act synergistically to induce renal disease in LDL receptor-deficient BALB mice.

Diabetic nephropathy is the leading cause of end-stage renal disease in Western countries, but only a portion of diabetic patients develop diabetic nephropathy. Dyslipidemia represents an important aspect of the metabolic imbalance in diabetic patients. In this study, we addressed the impact of combined hyperlipidemia and hyperglycemia on renal pathology. Kidneys from wild-type (WT) or LDL receptor-deficient BALB/cBy mice (BALB.LDLR-/-) were examined at 22 weeks of age. Diabetes was induced by administration of streptozotocin and mice were randomly assigned to either standard chow or Western diet. Chow fed BALB.LDLR-/- mice did not demonstrate renal abnormalities, whereas BALB. LDLR-/- mice fed a Western diet showed occasional glomerular and tubulointerstitial foam cells. Diabetic WT mice had modestly increased glomerular cellularity and extracellular matrix. Hyperlipidemic and diabetic BALB.LDLR-/- mice exhibited an increase in glomerular cellularity and extracellular matrix, accumulation of glomerular and tubulointerstitial foam cells and mesangial lipid deposits. The tubular epithelium demonstrated pronounced lipid induced tubular degeneration with increased tubular epithelial cell turnover. Hyperlipidemia and hyperglycemia seem to act synergistically in inducing renal injury in the BALB.LDLR-/- mouse. This model of diabetic nephropathy is unique in its development of tubular lesions and may represent a good model for hyperlipidemia-exacerbated diabetic nephropathy.

Animals↗

PubMed2003

Growth factor expression in a murine model of cryoglobulinemia.

BACKGROUND: Increased expression of growth factors including platelet-derived growth factor (PDGF) and transforming growth factor-beta (TGF-beta) are thought to play pivotal roles during mesangial expansion and glomerulosclerosis. Thymic stromal lymphopoietin (TSLP) transgenic mice develop mixed cryoglobulinemia and a membranoproliferative glomerulonephritis (MPGN). Here we describe the renal expression of isoforms of PDGF and TGF-beta in relation to changes in extracellular matrix (ECM) components and markers of cell proliferation and activation in this model. METHODS: A total of 123 mice, including 61 TSLP transgenic mice and 62 wild-type controls, were sacrificed at defined intervals. PDGF-A chain, -B chain, PDGF alpha- and beta-receptor (beta-R) and TGF-beta1 mRNA were analyzed by in situ hybridization. Expression of alpha smooth muscle actin (alphaSMA), collagen type I, collagen type IV, laminin, and a marker of proliferating cells (PCNA) were assessed by immunohistochemistry. Slides also were studied by combined immunohistochemistry and in situ hybridization with an antibody that recognizes monocytes/macrophage and with riboprobes that detect PDGF B-chain, PDGF beta-R or TGF-beta1 mRNA. RESULTS: Increased numbers of proliferating glomerular cells appeared early in the disease course, associated with de novo expression of alphaSMA. Expression of PDGF B-chain and beta-R mRNA was increased in the mesangium and in parietal epithelial cells of TSLP transgenic mice and correlated with the number of PCNA positive cells. Increased TGF-beta1 mRNA expression paralleled the deposition of type IV collagen. A significant proportion of Mac-2 positive macrophages expressed TGF-beta1 mRNA, while only a small percentage of glomerular macrophages expressed PDGF B-chain mRNA. No PDGF beta-R mRNA expression by macrophages was detected. CONCLUSION: TSLP transgenic mice develop a membranoproliferative glomerulonephritis in which glomerular cell proliferation and matrix deposition are associated with an increased expression of PDGF B-chain, PDGF beta-R and TGF-beta1. These findings extend the paradigms covering these growth factors established in the rat Thy 1 model of mesangiolysis and repairs to a murine model of progressive glomerulonephritis closely resembling human MPGN.

Actins↗

PubMed2003

Adenovirus transduction induces expression of multiple chemokines and chemokine receptors in murine beta cells and pancreatic islets.

Adenoviral vectors are highly efficient for transferring genes to islets. However, the inflammatory and immune responses stimulated by adenovirus may be detrimental to islet survival. Given the role of chemokines and their receptors in inflammation, we analyzed their expression in isolated murine islets, in a murine beta cell line and in syngeneic islet grafts after adenovirus transduction (AdRSVLacZ). AdRSVLacZ transduction enhanced and induced the expression of a variety of chemokines. Transduced syngeneic transplanted islets showed significantly enhanced expression of multiple chemokines and receptors, including monocyte chemoattractant protein-1 (MCP-1), CC chemokine receptor 2 (CCR2) and regulated upon activation, normal T cell expressed and secreted (RANTES), compared with untransduced islet grafts. AdRSVLacZ-transduced islet grafts had significant mononuclear infiltrates, and in situ hybridization demonstrated intragraft expression of MCP-1, CCR2 and RANTES. Although adenovirus transduction did not impair in vitro insulin secretion, diabetes was reversed in only one of six recipients of a marginal mass of AdRSVLacZ-transduced islets, compared with six of six control recipients. In conclusion, multiple chemokines and chemokine receptors are expressed by murine islets constitutively and in response to adenovirus transduction. Adenovirus transduction impairs engraftment of marginal mass of transplanted islets. This is not because of direct vector toxicity of islet secretory capacity, but may be related to host innate immunity in response to adenovirus vector.

Adenoviridae↗

PubMed2003

Amelioration of diabetic nephropathy in SPARC-null mice.

SPARC (Secreted Protein, Acidic and Rich in Cysteine) is a matricellular protein that inhibits mesangial cell proliferation and also affects production of extracellular matrix (ECM) by regulating transforming growth factor-beta1 (TGF-beta1) and type I collagen in mesangial cells. This study is an investigation of the role of SPARC in streptozotocin (STZ)-induced diabetic nephropathy (DN) of 6-mo duration in wild type (WT) and SPARC-null mice. SPARC expression was evaluated by immunohistochemistry (IHC) and by in situ hybridization (ISH). Deposition of type I and IV collagen and laminin was evaluated by IHC, and TGF-beta 1 mRNA was assessed by ISH. Renal function studies revealed no significant difference in BUN between diabetic SPARC-null mice and diabetic WT mice, whereas a significant increase in albumin excretion was detected in diabetic WT relative to diabetic SPARC-null mice. Diabetic WT animals exhibited increased levels of SPARC mRNA and protein in glomerular epithelial cells and in interstitial cells, in comparison with nondiabetic WT mice. Neither SPARC mRNA nor protein was detected in SPARC-null mice. Morphometry revealed a significant increase in the percentage of the glomerular tufts occupied by ECM in diabetic WT compared with nondiabetic WT mice, although there was no difference in the mean glomerular tuft area among groups. In contrast, diabetic SPARC-null mice did not show a significant difference in the percentage of the glomerular tufts occupied by ECM relative to nondiabetic null mice. Tubulointerstitial fibrosis was ameliorated in diabetic SPARC-null mice compared with diabetic WT animals. Further characterization of diabetic SPARC-null mice revealed diminished glomerular deposition of type IV collagen and laminin, and diminished interstitial deposition of type I and type IV collagen correlated with decreases in TGF-beta 1 mRNA compared with WT diabetic mice. These observations suggest that SPARC contributes to glomerulosclerosis and tubulointerstitial damage in response to hyperglycemia through increasing TGF-beta 1 expression in this model of chronic DN.

Animals↗

PubMed2003

Obstructive uropathy in mice and humans: potential role for PDGF-D in the progression of tubulointerstitial injury.

Tubulointerstitial fibrosis is a major characteristic of progressive renal diseases. Platelet-derived growth factor (PDGF) is a family of growth regulatory molecules consisting of PDGF-A and -B, along with the newly discovered PDGF-C and -D. They signal through cell membrane receptors, PDGF receptor alpha (PDGF-Ralpha) and receptor beta (PDGF-Rbeta). Involvement of PDGF-B and PDGF-Rbeta in the initiation and progression of renal fibrosis has been well documented. The authors studied the localization of PDGF ligands and receptors by immunohistochemistry, with emphasis on the role of PDGF-D in murine renal fibrosis induced by unilateral ureteral obstruction (UUO). In mice with UUO, de novo expression of PDGF-D was detected in interstitial cells at day 4, which increased to maximal expression at day 14. Increased expression of PDGF-B by interstitial cells and in some tubules was observed after day 4. The diseased mice did not show augmentation of PDGF-A or PDGF-C proteins in the areas of fibrosis. PDGF-Ralpha and -Rbeta protein expression was increased in interstitial cells after day 4 and reached maximal expression at day 14. Human renal nephrectomies (n = 10) of chronic obstructive nephropathy demonstrated similar de novo expression of PDGF-D in interstitial cells, correlating with expression of PDGF-Rbeta and PDGF-B, as it did in the murine model. These observations suggest that PDGF-D plays an important role in the pathogenesis of tubulointerstitial injury through binding of PDGF-Rbeta in both human obstructive nephropathy and the corresponding murine model of UUO.

Actins↗

PubMed2002

Expression of the fractalkine receptor (CX3CR1) in human kidney diseases.

BACKGROUND: CX3CL1 (fractalkine) is a membrane bound chemokine that can function as an adhesion molecule for cells expressing the receptor CX3CR1. This receptor is involved in the recruitment of inflammatory cells in a rat model of crescentic glomerulonephritis, where blockade of CX3CR1 has been shown to be of benefit. Here we describe the distribution of CX3CR1 positive cells in a variety of kidney diseases and renal development. METHODS: A total of 84 formalin-fixed, paraffin-embedded specimens including fetal kidneys (N = 12), normal areas of kidneys uninvolved by neoplasia from tumor nephrectomies (N = 4), renal transplant nephrectomies (N = 5), renal transplant biopsies (N = 19), and kidney biopsies from patients with crescentic glomerulonephritis (N = 7), membranous nephropathy (N = 7), membranoproliferative glomerulonephritis (N = 8), focal and segmental glomerulosclerosis (N = 10), collapsing glomerulopathy (N = 6), and minimal change disease (N = 6) were studied. Immunohistochemistry was performed on consecutive tissue sections for CD3 positive T cells, CD68 positive monocyte/macrophages, CCR5 positive cells and CX3CR1 positive cells. RESULTS: The majority of inflammatory leukocytes infiltrating the kidney expressed CX3CR1. The distribution pattern was consistent with expression by both T cells and monocytes/macrophages. In contrast to the distribution of CCR5, which was expressed on a subset of infiltrating cells predominantly localized in the interstitium, CX3CR1 was present on both interstitial and glomerular infiltrating leukocytes. In developing kidneys CX3CR1 positive cells formed a small, scattered population of cells, consistent with the distribution of infiltrating leukocytes. CONCLUSIONS: The high number of CX3CR1-positive inflammatory cells in various disease entities is consistent with its having a role in the accumulation of intrarenal inflammatory cells, but does not provide evidence of specificity of leukocytes bearing this receptor for specific types of injury. Other chemokine gradients, like those created by the ligands for the chemokine receptor CCR5, might subsequently guide leukocyte subsets to specific microenvironments.

CX3C Chemokine Receptor 1↗

PubMed2002

Platelet-derived growth factor-D expression in developing and mature human kidneys.

BACKGROUND: Platelet-derived growth factor (PDGF) is a family of growth regulatory molecules composed of sulfide-bonded dimeric structures. Two well-studied PDGF peptides (PDGF-A and PDGF-B) have been shown to mediate a wide range of biological effects. PDGF-D is a newly recognized member of the PDGF family. Initial studies of the PDGF-D gene found its expression in cells of the vascular wall, suggesting that it could participate in vascular development and pathology. However, its localization in human kidney tissues has never been studied. METHODS: PDGF-D expression in fetal (N = 30) and adult (N = 25) human kidney tissues was examined by immunohistochemistry using an affinity-purified antibody raised to human PDGF-D. Antibody absorption with the immunizing peptide was employed to confirm the specificity of this antibody. PDGF-D protein and gene expression in human kidneys also were demonstrated by Western blotting and reverse transcription-polymerase chain reaction (RT-PCR). RESULTS: In the developing kidney, PDGF-D was first expressed by epithelial cells of comma- and S-shaped structures of the developing nephron, and most consistently in the visceral epithelial cells in the later stages of glomerular differentiation. In addition, PDGF-D could be found in mesenchymal, presumptively fibroblast cells in the interstitium of developing renal pelvis and in fetal smooth muscle cells in arterial vessels. In the adult normal kidney, PDGF-D was expressed by the visceral epithelial cells. There was persistent expression in arterial smooth muscle cells as well as in some neointimal smooth muscle cells of arteriosclerotic vessels, and expression in smooth muscle cells of vasa rectae in the medulla. PDGF-D could be identified at the basolateral membrane of some injured tubules in areas of chronic tubulointerstitial injury routinely encountered in aging kidneys. Western blotting of homogenates of adult kidneys demonstrated monospecific bands at 50 kD corresponding to previously established size parameter for this protein. RT-PCR of human kidney RNA resulted in a 918 basepair band, the sequence of which corresponded to human PDGF-D (Genbank number AF336376). CONCLUSIONS: To our knowledge, these are the first studies to localize PDGF-D in human kidneys and suggest that PDGF-D may have a role in kidney development. PDGF-D was shown to bind to PDGF beta receptor, which localizes to mesangial cells, parietal epithelial cells, and interstitial fibroblasts, suggesting potential paracrine interactions between those cells and the visceral epithelium.

Adult↗

PubMed2002

Localization of SPARC in developing, mature, and chronically injured human allograft kidneys.

BACKGROUND: The matricellular protein SPARC (secreted protein acidic and rich in cysteine) is expressed during development, tissue remodeling and repair. It functions as an endogenous inhibitor of cell proliferation, regulates angiogenesis, regulates cell adhesion to extracellular matrix, binds cytokines such as platelet derived growth factor and stimulates transforming growth factor-beta (TGF-beta) production. This study describes the expression of SPARC during human renal development, in normal kidneys and during renal allograft rejection. METHODS: A total of 60 renal specimens, including normal areas from tumor nephrectomies (N = 24), fetal kidneys (N = 27) and explanted renal allografts (N = 9), were included in the study. SPARC protein was localized by immunohistochemistry using two different antibodies. On consecutive sections SPARC mRNA was detected by in situ hybridization. RESULTS: In the normal adult kidney SPARC protein was expressed by visceral and parietal epithelial cells, collecting duct epithelium (CD), urothelium, smooth muscle cells of muscular arteries and focally in interstitial cells. During renal development immature glomeruli demonstrated a polarized SPARC expression in visceral epithelial cells at their surface abutting the capillary basement membranes. In the fully differentiated glomeruli the expression pattern mirrored that of the adult kidney. Furthermore, SPARC was abundantly expressed by derivatives of the ureteric bud, and smooth muscle cells of arterial walls. During chronic allograft rejection SPARC is expressed in neointimal arterial smooth muscle cells, infiltrating inflammatory cells as well as by interstitial myofibroblasts in areas of interstitial fibrosis. SPARC mRNA synthesis detected by in situ hybridization mirrored these protein expression patterns. CONCLUSION: These studies co-localize SPARC to several sites of renal injury previously shown to be sites of PDGF B-chain expression and/or activity. We speculate that SPARC could function as an accessory molecule in chronic PDGF-mediated sclerosing interstitial and vascular injury. SPARC localization to glomerular epithelial cells corresponds to similar findings in rodents, and may reflect its role in cell adhesion and /or regulation of cell shape.

Adult↗