Megalin-mediated deterministic pseudotransduction in proximal tubules fundamentally challenges current understanding of AAV kidney transduction

Genetic kidney diseases are promising targets for gene therapy. Emerging AAV capsids that reportedly enable effective gene delivery to proximal tubules (PTs) following intravenous injection have raised hopes for treating diseases affecting renal tubules. Despite these promising developments, the scientific literature contains contradictory and non-reproducible findings, which prompted us to conduct a detailed and rigorous investigation of the mechanisms of AAV vector-mediated PT transduction. Here we provide compelling evidence that previously reported effective PT transduction following intravenous AAV-GFP or AAV-mCherry administration largely reflects megalin-mediated deterministic pseudotransduction rather than stochastic vector-mediated gene delivery. We demonstrate that this process is mediated by megalin-dependent uptake of circulating reporter proteins released from transduced organs including the liver and filtered through the glomeruli. These observations highlight the ongoing challenge of achieving true proximal tubule transduction via systemic AAV delivery and caution against relying on small reporters like GFP or mCherry, which can produce misleading signals.