Kidney biopsy in patients with diabetes mellitus.

BACKGROUND: The clinical consequences of the results obtained by kidney biopsy in patients with diabetes mellitus Type 1 or Type 2 have been controversial. Our study was conducted to assess clinical symptoms and histological diagnoses in patients with diabetes mellitus Type 1 and Type 2 undergoing kidney biopsy. DESIGN, SETTING AND PATIENTS: Observational study. The study included data from 567 consecutive renal biopsies of patients with diabetes mellitus Type 1 or 2 and chronic kidney disease (CKD) examined by standard histopathological procedures. The main outcome measures were incidence of diabetic nephropathy (DN) and glomerulonephritis (GN), predictors for the presence of both DN or GN. RESULTS: Approximately 70% of patients with diabetes mellitus Type 1 or 2 and evidence for CKD had DN. Glomerular diseases present in approximately 30% of patients with diabetes were predominantly immune complex GN and secondary focal glomerulosclerosis, followed by IgA-GN, which was associated with microhematuria (p = 0.01) and hypertension (p = 0.04). Only a minority had membranous GN, which was associated with nephrotic syndrome (p = 0.004). Progressive CKD predicted the presence of GN in diabetes mellitus Type 2 (r = -0.98; p = 0.02). CONCLUSION: GN is not uncommon in patients with diabetes and evidence for CKD. Kidney biopsy should therefore be considered in patients with diabetes and progressive CKD.

Irradiated cultured apoptotic peripheral blood mononuclear cells regenerate infarcted myocardium.

BACKGROUND: Acute myocardial infarction (AMI) is followed by post AMI cardiac remodelling, often leading to congestive heart failure. Homing of c-kit+ endothelial progenitor cells (EPC) has been thought to be the optimal source for regenerating infarcted myocardium. METHODS: Immune function of viable peripheral blood mononuclear cells (PBMC) was evaluated after co-culture with irradiated apoptotic PBMC (IA-PBMC) in vitro. Viable PBMC, IA-PBMC and culture supernatants (SN) thereof were obtained after 24 h. Reverse transcription polymerase chain reaction and enzyme-linked immunosorbent assay were utilized to quantify interleukin-8 (IL-8), vascular endothelial growth factor, matrix metalloproteinase-9 (MMP9) in PBMC, SN and SN exposed fibroblasts. Cell suspensions of viable- and IA-PBMC were infused in an experimental rat AMI model. Immunohistological analysis was performed to detect inflammatory and pro-angiogenic cells within 72 h post-infarction. Functional data and determination of infarction size were quantified by echocardiography and Elastica van Gieson staining. RESULTS: The IA-PBMC attenuated immune reactivity and resulted in secretion of pro-angiogenic IL-8 and MMP9 in vitro. Fibroblasts exposed to viable and IA-PBMC derived SN caused RNA increment of IL-8 and MMP9. AMI rats that were infused with IA-PBMC cell suspension evidenced enhanced homing of endothelial progenitor cells within 72 h as compared to control (medium alone, viable-PBMC). Echocardiography showed a significant reduction in infarction size and improvement in post AMI remodelling as evidenced by an attenuated loss of ejection fraction. CONCLUSION: These data indicate that infusion of IA-PBMC cell suspension in experimental AMI circumvented inflammation, caused preferential homing of regenerative EPC and replaced infarcted myocardium.

Myocardial lipofuscin-laden lysosomes contain the apoptosis marker caspase-cleaved cytokeratin-18.

BACKGROUND: Acute coronary syndrome is related to increased circulatory concentration of soluble apoptosis specific caspase-cleaved cytokeratin-18 (ccCK-18). Potential cardiac sources of this intermediate filament derivative have not been investigated to date. MATERIALS AND METHODS: Paraffin embedded tissue of normal myocardium, and chronically damaged samples of ischaemic, congestive and hypertrophic cardiomyopathy were analysed by histology and by CK-8, CK-18, ccCK-18 immunohistochemistry (each group, n = 15). Antibody specificity of the ccCK-18 antibody M30 was checked by immunoblotting on lysed myocardium and enriched myocardial lysosomes. RESULTS: ccCK-18 and CK-18 but not CK-8 were present in all forms of cardiomyopathy, most prominently in ischaemic cardiomyopathy while only traces were detectable immunohistochemically in normal myocardium. Weak CK-18 and strong ccCK-18 staining co-localized to lysosomes with cardiac age pigment lipofuscin. Weak staining of CK-18 was detected in the cytoplasm of coronary endothelia. CONCLUSION: Our study reveals that cardiac lipofuscin-laden lysosomes contain ccCK-18, a marker of apoptosis and its precursor CK-18. This ccCK-18 pool might contribute to increased systemic levels of ccCK-18 in acute coronary syndrome thus monitoring myocardial damage.

Eotaxin-3 is involved in Churg-Strauss syndrome--a serum marker closely correlating with disease activity.

OBJECTIVE: Churg-Strauss Syndrome (CSS) is characterized by excessive eosinophil accumulation in peripheral blood and affected tissues with development of granulomatous vasculitic organ damage. The contribution of eosinophil-chemotactic cytokines (eotaxin family) to eosinophilia and disease activity in CSS is unknown. Thus, we compared serum levels of the eotaxin family members in CSS patients with healthy and disease controls. METHODS: Forty patients with CSS diagnosed according to ACR 1990 criteria, 30 healthy controls (HC) and 57 disease controls (28 asthma, 20 small vessel vasculitis, 9 hypereosinophilic syndrome) were studied. Clinical data were collected and serum levels of eotaxin-1, -2 and -3 were determined by ELISA. Further, immunohistochemistry was applied to identify eotaxin-3 expression in tissue biopsies from patients with CSS. RESULTS: In contrast to eotaxin-1 and -2, eotaxin-3 was highly elevated in serum samples of active CSS patients and correlated highly significantly with eosinophil counts, total immunoglobulin E (IgE) levels and acute-phase parameters. Moreover, eotaxin-3 was not elevated in other eosinophilic and vasculitic diseases. Immunohistochemical analysis revealed strong expression of eotaxin-3 in endothelial and inflammatory cells in affected tissues of active CSS patients. CONCLUSIONS: This study reveals the specific association of elevated eotaxin-3 expression with high disease activity and eosinophilia in CSS patients. Eotaxin-3 might thus be a pathogenic player, biomarker and potential therapeutic target in CSS.

Tumour necrosis factor blockade increases lymphangiogenesis in murine and human arthritic joints.

OBJECTIVE: To investigate the presence and regulation of lymphatic vessels in inflamed joints of mice with experimental arthritis as well as patients with rheumatoid arthritis (RA) and spondyloarthritis (SpA). METHODS: Lymphatic vessels and blood vessels were assessed in synovial tissue of human tumour necrosis factor transgenic (TNFtg) mice and synovial biopsies from patients with RA and SpA by immunohistochemistry for podoplanin and CD31, respectively. Assessments were performed before and after TNF blockade in all biopsies. RESULTS: Lymphatic vessels were abundantly present in the synovial tissue of hTNFtg mice as well as patients with RA and SpA. The number of lymphatic vessels was positively related to the severity of synovial inflammation. Treatment with infliximab led to an increase in the formation of lymphatic vessels in murine and human inflammatory tissue. CONCLUSIONS: This study shows that TNF blockade promotes the proliferation of lymphatic vessels in the inflamed synovium of RA and SpA. This finding leads to the assumption that promotion of lymphangiogenesis may play an important part in efflux of cells and fluid out of the inflamed tissue.

Shift of C3 deposition from localization in the glomerulus into the tubulo-interstitial compartment in the absence of secreted IgM in immune complex glomerulonephritis.

The role of secretory IgM in protecting kidney tissue from immune complex glomerulonephritis induced by 4 mg horse spleen apoferritin and 0.05 mg lipopolysaccharide has been investigated in mutant mice in which B cells do not secrete IgM, but are capable of expressing surface IgM and IgD and secreting other Ig isotypes. Glomerular size, number of glomeruli per cross-section, glomerular cellularity and urine content of protein and creatinine was comparable in treated secreted IgM (sIgM)-deficient and wild-type mice. Assessment of urinary proteins by sodium dodecyl sulphate-polyacrylamide gel electrophoresis showed a 30 kDa low molecular weight protein in treated sIgM-deficient animals only, reflecting dysfunction of proximal tubules. A shift of bound C3 from glomeruli to the tubulo-interstitial compartment in sIgM-deficient mice also suggests tubulo-interstitial damage. In contrast, local C3 synthesis within the kidney tissue did not differ between the two treated groups. Apoptosis physiologically present to maintain kidney cell homeostasis was increased slightly in treated wild-type mice. These results indicate that secretory IgM can protect the tubulo-interstitial compartment from immune complex-induced damage without having an effect on the glomerulus.

Selective p38MAPK isoform expression and activation in antineutrophil cytoplasmatic antibody-associated crescentic glomerulonephritis: role of p38MAPKalpha.

OBJECTIVE: Crescentic glomerulonephritis (crGN) is a frequent and life-threatening manifestation of antineutrophil cytoplasmatic antibody-associated vasculitis. Up-regulation of proinflammatory cytokines contributes to renal damage by activation of p38 mitogen-activated protein kinases (MAPKs). However, it is unclear which of the four p38MAPK isoforms are expressed, activated and hence of major importance in crGN. METHODS: Kidney biopsies of patients with antineutrophil cytoplasmatic antibody-positive crGN and control samples were investigated for the expression and phosphorylation of p38MAPK isoforms and downstream target kinase MAPKAP2 by immunohistochemistry. Expression and functional activation of p38MAPK isoforms by TNF was also assessed in a human podocyte cell line by reverse transcription-polymerase chain reaction, immunoblotting and kinase array. RESULTS: Strong expression of p38MAPKalpha, beta and gamma isoforms was found in glomerular podocytes and crescents. Infiltrating leucocytes showed predominant p38MAPKalpha expression. Activation of p38MAPK and its downstream mediator MAPKAP2 was found in crGN confined to glomerular podocytes, crescents and inflammatory infiltrates. Interestingly, corticosteroid treatment before kidney biopsy diminished p38MAPK activation in crGN. Activated p38MAPK co-localised with alpha, beta and gamma isoforms in podocytes and crescents, while leucocytes showed mainly p38MAPKalpha activation. In a human podocyte cell line mRNA and protein of all four p38MAPK isoforms was expressed but only p38MAPKalpha was activated upon challenge with TNF. CONCLUSIONS: This study shows selective p38MAPK isoform expression and activation in crGN. Podocytes and podocyte-induce crescent formation is the main source of p38MAPK activation in crGN. TNF is a potent and selective activator of the alpha-isoform in podocytes, which therefore appears as a main contributor to proinflammatory signalling in the glomerulum of crGN.

Decrease of proteinuria in a patient with adult-onset Still's disease and glomerulonephritis after anti-TNFalpha therapy.

We report the case of a 41-year-old man diagnosed with Still's disease. Multiple disease-modifying anti-rheumatic drug (DMARD) therapies failed to induce disease remission or to prevent progressive joint destruction. The man presented with active arthritis and classical Still's rash accompanied by fever. Anti-tumour necrosis factor-alpha (TNFalpha) therapy was planned but during the medical check-up prior to the biological therapy, renal insufficiency with marked proteinuria (PU) was discovered. With PU of 912 mg/24 h a renal biopsy was performed and a histopathological evaluation revealed the diagnosis of a residual mesangio-proliferative immunocomplex-based glomerulonephritis (GN). After excluding contraindications, infliximab therapy was initiated and a good response of the arthritis was documented after 6 weeks. A significant decrease in PU (279 mg/24 h) was noted after the third infliximab infusion. Because of an allergic reaction during the fifth dose, the infliximab was discontinued. During the time frame without anti-TNFalpha therapy, active joint disease reoccurred and the proteinuria increased significantly. Because of the active disease entanercept therapy was initiated. The arthritis diminished and the PU was reduced markedly within 4 weeks. In the follow-up period of 12 months a good response to therapy was sustained. As described by other investigators, the joint disease showed a rapid and sustained response to anti-TNFalpha therapy. The decrease in proteinuria during biological therapy was notable. It was concluded that the significant decrease in PU in this patient was achieved by eliminating the inflammatory activity of the underlying kidney disease.

Chondrocyte number and proteoglycan synthesis in the aging and osteoarthritic human articular cartilage.

OBJECTIVE: To correlate the number of chondrocytes in healthy and osteoarthritic human articular cartilage with age, and to evaluate the influence of donor age on total proteoglycan synthesis. METHODS: Chondrocytes were isolated from human articular cartilage derived from hip joints with and without osteoarthritic lesions. The cell number was normalised to cartilage sample wet weight. In addition, the influence of age on chondrocyte numbers was assessed histomorphometrically. Chondrocytes were grown as monolayer cultures for seven days in a chemically defined serum-free basal medium. Total proteoglycan synthesis was measured by [(35)S]sulphate incorporation into newly synthesised macromolecules. RESULTS: Chondrocyte numbers in healthy cartilage decreased significantly with advancing age (r = -0.69, p<0.0001). In contrast to healthy specimens, chondrocyte numbers were decreased in osteoarthritic cartilage irrespective of and unrelated to age, and differed markedly, by an average of 38%, from the cell numbers found in healthy individuals (p<0.0001). Regarding synthesis of matrix macromolecules, no dependence on patients' age, either in healthy or in osteoarthritic specimens, could be observed. CONCLUSIONS: Under the experimental conditions employed, chondrocytes from healthy and osteoarthritic joints synthesised comparable amounts of cartilage macromolecules, independent of age or underlying osteoarthritic disease. Thus the decrease in chondrocyte number in aging and osteoarthritic joints could be a crucial factor in limiting tissue replenishment.

A rare cause of anemia due to intestinal tuberculosis in a renal transplant recipient.

A renal transplant recipient with stable allograft function presented with massive hemorrhagic diarrhea and severe anemia. No microbial infection could be found in stool cultures. Early colonoscopy showed severe colitis with ulceration. Histological samples confirmed granulomatous inflammation with acid-resistant Ziehl-Neelson-positive microorganisms of mycobacterial type. Polymerase chain reaction (PCR) analysis of native mucosal biopsies specified the infectious organism as Mycobacterium tuberculosis complex. The patient responded well to antimycobacterial therapy and was still asymptomatic after 6 months with a stable graft function. Our case shows that tuberculosis can be a severe clinical problem in transplant recipients. Most of the patients with intestinal tuberculosis, reported to literature, were diagnosed post mortem or after explorative laparotomy and bowel resection. Thus, intestinal tuberculosis should be considered when a transplant recipient shows abdominal symptoms with no clear evidence of another infection. Proper diagnosis and treatment resulted in a beneficial outcome in our patient.

Expression of bone morphogenetic protein 6 in healthy and osteoarthritic human articular chondrocytes and stimulation of matrix synthesis in vitro.

OBJECTIVE: To elucidate the role of bone morphogenetic protein 6 (BMP-6) in human articular cartilage, we investigated whether BMP-6 is expressed in adult human articular chondrocytes and analyzed the potential stimulatory effects of BMP-6 on these cells. In addition, we investigated whether osteoarthritic (OA) and normal cartilage chondrocytes behave differently. METHODS: Endogenous expression of the BMP-6 gene was examined by reverse transcription-polymerase chain reaction. BMP-6 protein was detected by Western immunoblotting. Chondrocytes were grown as monolayer cultures for 7 days in a chemically defined serum-free medium, in the absence or presence of recombinant BMP-6. Proteoglycan (PG) synthesis was measured by (35)S-sulfate incorporation into newly synthesized macromolecules. Cell proliferation was assessed by (3)H-thymidine incorporation. RESULTS: BMP-6 was expressed in both healthy and OA chondrocytes at the messenger RNA and protein levels. Total PG synthesis was significantly increased after BMP-6 stimulation of healthy (mean +/- SEM 191 +/- 11%; P < 0.001) and OA (150 +/- 25%; P < 0.03) chondrocyte cultures. A direct comparison between healthy and OA samples revealed no significant difference. The proliferation rates of normal and OA chondrocytes were not affected by BMP-6 treatment. CONCLUSION: BMP-6 is endogenously expressed in chondrocytes obtained from OA and normal adult human articular cartilage. Furthermore, BMP-6 has the potential to stimulate total PG synthesis in human articular chondrocytes derived from normal as well as OA joints. We conclude that the presence of BMP-6 in adult human articular cartilage indicates a functional role for this growth factor in the maintenance of joint integrity.

Nesidioblastosis in adults: a challenging cause of organic hyperinsulinism.

BACKGROUND: Nesidioblastosis in adults has been reintroduced into the differential diagnosis of organic hyperinsulinism by the description of 'noninsulinoma pancreatogenous hypoglycaemia syndrome (NIPHS)'. MATERIALS AND METHODS: Pathologic specimens of all adult patients (n = 66) operated on for organic hyperinsulinism were re-examined. Five patients fulfilled the histomorphological criteria of nesidioblastosis. Retrospective review of clinical presentation, results of 72-h fasts, intravenous tolbutamide tolerance tests, pre- and intraoperative localization studies and surgical therapy was performed. RESULTS: In contrast to NIPHS, fasting tests became positive after 8-14 h. Tolbutamide tests were positive and preoperative imaging showed negative results in all patients. At first operation distal pancreatic resections were performed in three patients, resection of the pancreatic body in one patient and biopsy of the pancreatic tail in one patient. Two of three patients with recurrent disease had to be reoperated. One patient showed a coexistence of nesidioblastosis and multiple small insulinomas and is part of a kindred with autosomal dominantly inherited 'familial islet-cell adenomatosis'. CONCLUSIONS: Surgical exploration is indicated only after thorough biochemical diagnosis. An aggressive strategy for preoperative localization including selective arterial calcium stimulation testing seems justified. There may be a combination of nesidioblastosis and islet cell tumours. A link between beta-cell hyperplasia and progression to insulinoma based on not yet known genetic causes can be suspected.

Cartilage-derived morphogenetic protein-1 and -2 are endogenously expressed in healthy and osteoarthritic human articular chondrocytes and stimulate matrix synthesis.

OBJECTIVE: We investigated whether chondrocytes derived from osteoarthritic cartilage may lose their responsiveness to cartilage-derived morphogenetic protein-1, -2 (CDMP-1, -2) and osteogenic protein-1 (OP-1) compared with healthy cells, thus leading to an impaired maintenance of matrix integrity. DESIGN: Chondrocytes were isolated from articular cartilage from patients with and without osteoarthritic lesions. Cells were grown as monolayer cultures for 7 days in a chemically defined serum-free basal medium (BM) in the presence of recombinant CDMP-1, -2, and OP-1. Glycosaminoglycan synthesis was measured by [35S]Sulfate incorporation into newly synthesized macromolecules. Cell proliferation was investigated by [3H]Thymidine incorporation. The endogenous gene expression of CDMPs/OP-1 and their respective type I and type II receptors was examined using RT-PCR. The presence of CDMP proteins in tissue and cultured cells was detected by Western immunoblots. RESULTS: mRNAs coding for CDMPs and their respective receptors are endogenously expressed not only in healthy, but also in osteoarthritic cartilage. CDMP proteins are present in both normal and osteoarthritic articular cartilage and cultured chondrocytes. CDMP-1, CDMP-2 and OP-1 markedly increased glycosaminoglycan synthesis in both healthy (P< 0.01) and osteoarthritic (P< 0.05) human articular chondrocytes. A comparison of the glycosaminoglycan biosynthetic activity between healthy and osteoarthritic samples revealed no detectable difference, neither in stimulated nor in unstimulated cultures. [(3)H]Thymidine incorporation showed that CDMPs/OP-1 did not affect cell proliferation in vitro. CONCLUSION: CDMPs and OP-1 exert their anabolic effects on both healthy and osteoarthritic chondrocytes indicating no loss in responsiveness to these growth factors in OA. The endogenous expression of CDMPs/OP-1 and their receptors suggest an important role in cartilage homeostasis.

Isolation and characterization of dermal lymphatic and blood endothelial cells reveal stable and functionally specialized cell lineages.

A plexus of lymphatic vessels guides interstitial fluid, passenger leukocytes, and tumor cells toward regional lymph nodes. Microvascular endothelial cells (ECs) of lymph channels (LECs) are difficult to distinguish from those of blood vessels (BECs) because both express a similar set of markers, such as CD31, CD34, podocalyxin, von Willebrand factor (vWF), etc. Analysis of the specific properties of LECs was hampered so far by lack of tools to isolate LECs. Recently, the 38-kD mucoprotein podoplanin was found to be expressed by microvascular LECs but not BECs in vivo. Here we isolated for the first time podoplanin(+) LECs and podoplanin(-) BECs from dermal cell suspensions by multicolor flow cytometry. Both EC types were propagated and stably expressed VE-cadherin, CD31, and vWF. Molecules selectively displayed by LECs in vivo, i.e., podoplanin, the hyaluronate receptor LYVE-1, and the vascular endothelial cell growth factor (VEGF)-C receptor, fms-like tyrosine kinase 4 (Flt-4)/VEGFR-3, were strongly expressed by expanded LECs, but not BECs. Conversely, BECs but not LECs expressed VEGF-C. LECs as well as BECs formed junctional contacts with similar molecular composition and ultrastructural features. Nevertheless, the two EC types assembled in vitro in vascular tubes in a strictly homotypic fashion. This EC specialization extends to the secretion of biologically relevant chemotactic factors: LECs, but not BECs, constitutively secrete the CC chemokine receptor (CCR)7 ligand secondary lymphoid tissue chemokine (SLC)/CCL21 at their basal side, while both subsets, upon activation, release macrophage inflammatory protein (MIP)-3alpha/CCL20 apically. These results demonstrate that LECs and BECs constitute stable and specialized EC lineages equipped with the potential to navigate leukocytes and, perhaps also, tumor cells into and out of the tissues.

Immunoadsorption in Goodpasture's syndrome.

Patients with Goodpasture's syndrome presenting with dialysis-dependent end-stage renal failure at diagnosis almost never regain independent renal function. We report a patient with a 100% crescentic lesion in whom reversal of dialysis dependence was achieved by immunoadsorption together with immunosuppression. In a second patient, early initiation of immunoadsorption was able to completely restore normal renal function as early as 1 month after the start of treatment. These data give evidence of the use of immunoadsorption as a hopeful alternative to conventional plasma exchange in patients with Goodpasture's syndrome showing advanced renal failure.

Angiosarcomas express mixed endothelial phenotypes of blood and lymphatic capillaries: podoplanin as a specific marker for lymphatic endothelium.

Angiosarcomas apparently derive from blood vessel endothelial cells; however, occasionally their histological features suggest mixed origin from blood and lymphatic endothelia. In the absence of specific positive markers for lymphatic endothelia the precise distinction between these components has not been possible. Here we provide evidence by light and electron microscopic immunohistochemistry that podoplanin, a approximately 38-kd membrane glycoprotein of podocytes, is specifically expressed in the endothelium of lymphatic capillaries, but not in the blood vasculature. In normal skin and kidney, podoplanin colocalized with vascular endothelial growth factor receptor-3, the only other lymphatic marker presently available. Complementary immunostaining of blood vessels was obtained with established endothelial markers (CD31, CD34, factor VIII-related antigen, and Ulex europaeus I lectin) as well as podocalyxin, another podocytic protein that is also localized in endothelia of blood vessels. Podoplanin specifically immunolabeled endothelia of benign tumorous lesions of undisputed lymphatic origin (lymphangiomas, hygromas) and was detected there as a 38-kd protein by immunoblotting. As paradigms of malignant vascular tumors, poorly differentiated (G3) common angiosarcomas (n = 8), epitheloid angiosarcomas (n = 3), and intestinal Kaposi's sarcomas (n = 5) were examined for their podoplanin content in relation to conventional endothelial markers. The relative number of tumor cells expressing podoplanin was estimated and, although the number of cases in this preliminary study was limited to 16, an apparent spectrum of podoplanin expression emerged that can be divided into a low-expression group in which 0-10% of tumor cells contained podoplanin, a moderate-expression group with 30-60% and a high-expression group with 70-100%. Ten of eleven angiosarcomas and all Kaposi's sarcomas showed mixed expression of both lymphatic and blood vascular endothelial phenotypes. By double labeling, most podoplanin-positive tumor cells coexpressed endothelial markers of blood vessels, whereas few tumor cells were positive for individual markers only. From these results we conclude that (1) podoplanin is a selective marker of lymphatic endothelium; (2) G3 angiosarcomas display a quantitative spectrum of podoplanin-expressing tumor cells; (3) in most angiosarcomas, a varying subset of tumor cells coexpresses podoplanin and endothelial markers of blood vessels; and (4) all endothelial cells of Kaposi's sarcomas expressed the lymphatic marker podoplanin.

[Podoplanin--a specific marker for lymphatic endothelium expressed in angiosarcoma]. / Podoplanin--ein spezifischer Marker für Lymphgefässendothelien wird in Angiosarkomen exprimiert.

AIMS: Angiosarcomas apparently derive from endothelia of the blood vasculature, however occasionally their histologic features suggest mixed origin from blood and lymphatic endothelia. In the absence of specific positive markers for lymphatic endothelia the precise distinction between these components was not possible so far. Here we provide evidence that podoplanin, a approximately 38 kD membrane glycoprotein of podocytes is a specific marker of lymphatic endothelium that was used to identify the relative fraction of tumor cells with lymphatic or blood vascular endothelial phenotype in vascular tumors. METHODS: Podoplanin was localized in normal human skin and kidney cortex by immunohistochemistry on paraffin sections, double immunofluorescence on frozen sections with PAL-E, immunoelectron microscopy and by immunoblotting. 45 vascular tumors (29 benign lesions, 11 angiosarcomas and 5 gastrointestinal Kaposi's sarcomas) were evaluated for podoplanin expression. Complementary staining was obtained with established endothelial markers (CD 31, CD 34, Factor VIII related antigen, UEA I) and with podocalyxin, another podocytic protein mainly present in endothelia of blood vessels. RESULTS: In human tissues podoplanin is specifically expressed in the endothelium of lymphatics, but not in blood vasculature or in hemangiomas. This expression is preserved in endothelia of all benign lymphatic tumorous lesions and all Kaposi's sarcomas examined. By contrast 10 out of 11 G3 angiosarcomas contained only variable fractions of podoplanin-expressing tumor cells. Most tumor cells coexpressed podoplanin and markers of blood vessel phenotype. CONCLUSIONS: (1) Podoplanin is a selective marker of lymphatic endothelium; (2) G3 angiosarcomas display a quantitative spectrum of podoplanin-expressing tumor cells; (3) In the majority of angiosarcomas tumor cells coexpress podoplanin and endothelial markers of blood vessels; (4) All endothelial cells of Kaposi's sarcomas expressed the lymphatic marker podoplanin.

Podoplanin, novel 43-kd membrane protein of glomerular epithelial cells, is down-regulated in puromycin nephrosis.

Puromycin aminonucleoside nephrosis (PAN), a rat model of human minimal change nephropathy, is characterized by extensive flattening of glomerular epithelial cell (podocyte) foot processes and by severe proteinuria. For comparison of expression of glomerular membrane proteins of normal and PAN rats, a membrane protein fraction of isolated rat glomeruli was prepared and monoclonal antibodies were raised against it. An IgG-secreting clone designated LF3 was selected that specifically immunolabeled podocytes of normal but not of PAN rats. The antigen of LF3 IgG was identified as a 43-kd glycoprotein. Molecular cloning of its cDNA was performed in a delta gt11 expression library prepared from mRNA of isolated rat glomeruli. The predicted amino acid sequence indicated a 166-amino-acid integral membrane protein with a single membrane-spanning domain, two potential phosphorylation sites in its short cytoplasmic tail, and six potential O-glycosylation sites in the large ectodomain. High amino acid sequence identities were found to membrane glycoproteins of rat lung and bone and mouse thymus epithelial cells as well as to a phorbol-ester-induced protein in a mouse osteoblast cell line and to a canine influenza C virus receptor. In PAN, expression of this 43-kd protein was selectively reduced to < 30%, as determined by quantitative immunogold electron microscopy, immunoblotting, and Northern blotting. These data provide evidence that transcription of the 43-kd transmembrane podocyte glycoprotein is specifically down-regulated in PAN. To indicate that this protein could be associated with transformation of arborized foot processes to flat feet (Latin, pes planus) we have called it podoplanin.