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.

STRO-1+ mesenchymal precursor cells located in synovial surface projections of patients with osteoarthritis.

OBJECTIVE: To investigate the presence of mesenchymal precursor cells (MPCs) in synovial surface projections of patients with osteoarthritis (OA), to characterize their phenotype and to show their localization. METHODS: Progenitor cells in synovial surface projections were identified by immunohistochemistry, morphometric analysis and confocal laser scanning microscopy using the following phenotypic markers: STRO-1, CD34, and alpha smooth muscle actin (alpha-SMA). RESULTS: In the synovial tissue of all 21 patients with OA MPCs were detected. Immunohistochemistry and subsequent morphometric analysis showed that approximately twice as many STRO-1+ cells/mm2 were observed in synovial tissue of patients with OA as compared to healthy organ donors and that number of STRO-1+ cells/mm2 correlated with total cell number/mm2. Interestingly, in the synovial tissue of patients with OA, twice as many STRO-1+ cells/mm2 were found in synovial surface projections as compared to the sublining area without villi. Using confocal laser scanning microscopy two populations of STRO-1+ MPCs could be detected in synovial surface projections. Single STRO-1+ cells that co-expressed alpha-SMA resemble a population of pericyte precursors required to stabilize the immature vasculature. The second STRO-1+ cell population that was found lacked alpha-SMA but co-expressed CD34 on their surface with low intensity. CONCLUSION: Here we can show that in the synovial tissue of patients with OA twice as many STRO-1+ MPCs can be found in synovial surface projections as compared to the sublining area. These cells are preferentially located at the basis and in the protruding end of the synovial surface projection.

The metabolism of benzo(a)pyrene by English sole (Parophrys vetulus): comparison between isolated hepatocytes in vitro and liver in vivo.

1. Metabolites and DNA adducts of 3H-benzo(a)pyrene (BaP) formed by isolated hepatocytes from English sole (Parophrys vetulus) in vitro were compared to those in bile and liver of sole exposed i.m. to 3H-BaP. 2. English sole liver was perfused with a collagenase solution and hepatocytes were isolated with greater than 95% viability. Determination of kinetic parameters for metabolism of 3H-BaP showed a Km of 29 +/- 10 microM and an apparent Vmax of 1300 pmol BaP metabolized/10(6) cells per h. 3. Analysis of medium from hepatocyte cultures and bile by ion-pair h.p.l.c. showed significant amounts of radioactivity in regions where glucuronide and glutathione conjugates of BaP metabolites elute. No sulphate conjugates of BaP metabolites were detected. The major unconjugated metabolite formed by hepatocytes was the BaP-9,10-dihydrodiol. 4. Hydrolysis of glucuronide conjugates by beta-glucuronidase and reversed-phase h.p.l.c. analysis of chloroform-soluble metabolites showed the presence of BaP-7,8-dihydrodiol, 1-hydroxyBaP and 3-hydroxyBaP. The identities of these metabolites were confirmed by comparing their fluorescence spectra with those of standard BaP metabolites. 5. Analysis by 32P-postlabelling of the BaP-DNA adducts formed in isolated hepatocytes and liver revealed that major adducts detected are derived from the anti-7,8-dihydrodiol-9,10-epoxideBaP (anti-BaPDE) and syn-BaPDE. 6. Results show that the types of conjugated metabolites and BaP-DNA adducts formed in primary hepatocyte culture were similar to those in bile and liver of English sole exposed to BaP. Thus, isolated hepatocytes from English sole afford a reliable alternative to live fish for studies of the mechanisms of hepatic xenobiotic metabolism and DNA adduct formation in a species shown to be susceptible to induction of hepatocarcinogenesis by PAHs.