PIK3R2 and fibrosis: Postmortem analyses performed after 8 weeks of TAC showed that: (1) Ouabain pretreatment significantly attenuated the TAC-induced cardiac hypertrophy in the control mice but not the KO mice (Fig. 7a); (2) cardiac fibrosis measured by trichrome staining, which was evident in all TAC hearts was significantly reduced by ouabain pretreatment in the control but not the p85-KO hearts (Fig. 7b).