Abstract for presentation at Australia and New Zealand Society of Nephrology Annual Scientific Conference

PI3K and mTOR regulate rat renal fibroblast function and differentiation

  • Miss Catherine Winbanks, Royal Melbourne Hospital, Australia
  • Miss Lauren Grimwood, Royal Melbourne Hospital, Australia
  • Mrs Anna Gasser, Royal Melbourne Hospital, Australia
  • Dr Ian Darby, Royal Melbourne Institute of Technology, Australia
  • Tim Hewitson, Royal Melbourne Hospital, Australia
  • Prof Gavin Becker, Royal Melbourne Hospital, Australia

    • Tubulointerstitial fibrosis is largely mediated by (myo)fibroblasts present in the interstitium. In this study we investigated the role of mTOR and PI3 kinase (PI3K) in their regulation.
    Fibroblasts were propagated from kidneys 7 days post-ureteric obstruction. Specific inhibitors RAD and LY294002 were used to examine the effects on cell function (kinetics, collagen synthesis) and myofibroblast differentiation (expression of α smooth muscle actin; SMA).
    LY but not RAD blocked phosphorylation of Akt, both inhibiting phosphorylation of the S6 ribosomal protein. RAD (100nM, 200nM) and LY (10µM) decreased population growth by 59±8 and 66±6%, (p<0.05 vs control) and 44±8% (p<0.05) respectively. Likewise, DNA synthesis was reduced by 50±9, 42 ±7 and 32±12% (all p<0.01 vs control). Treatment with 100nM RAD and 10µM LY in combination decreased population growth (97±2 %) and DNA synthesis (78±4%) by more than either drug alone (p<0.05). Apoptosis (TUNEL) in treated groups was not significant. Total collagen synthesis was reduced by 78±8% (100nm RAD) and 73±2% (10mM LY) (both p<0.001). Differentiation studies indicated that SMA expression was increased relative to b-actin by 1.9 (10nM RAD), 2.2 (100nM RAD), 2.4 (200nM RAD) and 2.2 (10uM LY) fold. 100nM and 200nM RAD increased the proportion of myofibroblasts, by 34%±8%, 46±12% respectively (p<0.05), with LY increasing myofibroblasts by 20±8% (p<0.05).
    In conclusion, these results highlight the potential significance of these pathways in the regulation of renal (myo)fibroblast activity. The synergistic effects of LY and RAD on proliferation suggest that mTOR signalling involves pathways other than PI3K.

    Conference Organiser - ICMS Pty Ltd