P0859ACTIVATE ENDOGENOUS HYDROXYMETHYLATION TO RESTORE ERYTHROPOIETIN PRODUCTION IN FIBROTIC KIDNEYS

Abstract Background and Aims Our previous studies have shown that DNA methyltransferases (Dnmt) and Epo hypermethylation are upregulated in myofibroblasts in fibrotic murine kidneys. Demethylation leads to redifferentiation of myofibroblasts into pericytes. Furthermore, nontoxic doses of 5-azacytidine can restore EPO production and ameliorate anemia in mice with kidney fibrosis. Physiologic hydroxymethylation in zygotes is mediated by the 10 − 11 translocation enzymes (Tet1, Tet2, and Tet3). Method The mouse model of unilateral ureteral obstruction (UUO)-induced kidney fibrosis has been found to display enhanced Tet1 and Tet3 mRNA expression at day 7 and marked increase with the disease progression. Results According to the results, Tet expression significantly increased in fibrotic kidney. To study the effect of myofibroblast-specific Tet3 knockout in murine models of renal fibrosis. Tet3F/F mice were generated by a targeting vector with floxed region contains exons 8-9 of Tet3, which included the coding region for the conserved Fe2+-binding motif of dioxygenase. Gli1CreERT2/+;Tet3F/F mice were used to induce knockout of Tet3 in pericytes and myofibroblasts after tamoxifen administration. Tet3F/F mice were used as the control. Oral gavage of tamoxifen 8 mg/day for 3 days was used to activate Cre recombinase in Gli1+ pericytes and myofibroblasts in adult mice (6-8 week). After two-week washout period, mice were subjected to UUO for 7 or 14 days. The body weight, plasma creatinine and BUN levels showed no significant differences between groups in mice after induction and also UUO surgery. Plasma levels of BUN and creatinine were maintained within the normal range by normally functioning contralateral kidneys after UUO surgery. In UUO kidneys, knockout of Tet3 decreased renal α-SMA and Col1a1 expression. But plasma hematocrit and renal Epo mRNA level were not different between groups. In addition to Gli1CreERT2/+ mice we also used Pdgfrb-rtTATg;LC1Tg mice to breed with Tet3F/F mice for inducible knockout of Tet3. The plasma creatinine, BUN, and hematocrit were no different between groups after UUO surgery again. Conclusion Overall, these findings suggested increased Tet3 in myofibroblasts may play an important role in myofibroblast activation and fibrosis. Further studies need to explore the mechanisms.