A newly characterized Hippo-IGF2 signaling axis governs both developmental organ sizing and regenerative capacity. In mouse liver, Igf2 drives rapid fetal and neonatal growth but is directly transcriptionally silenced by Hippo pathway activation postnatally — essentially locking in adult organ size. Chronic liver injury reverses this by inactivating Hippo signaling, re-inducing Igf2 to fuel regeneration. Critically, aged mice lose this regenerative induction, but ectopic Igf2 expression fully restores it. Whole-body Hippo activation or Igf2 deletion produced globally miniaturized animals with proportionally small organs, confirming IGF2's systemic role as a circulating hormone compensating for local deficits.
This finding reframes IGF2 — long studied as a fetal growth factor and imprinted oncogene — as a precision effector downstream of the Hippo tumor-suppressor pathway, linking developmental growth control to aging-associated regenerative decline. The observation that aged liver regeneration fails specifically at the Igf2 induction step, and that this is pharmacologically rescuable, has real translational weight. Age-related liver dysfunction and impaired post-injury recovery are clinically significant; a targetable molecular bottleneck is valuable. That said, all data are murine, and IGF2 reactivation carries inherent oncogenic risk — the pathway's tumor-suppressive role via Hippo must be carefully navigated. This is paradigm-shifting for organ-size biology and meaningfully advances regenerative aging research, though human validation and safety profiling remain essential next steps.
