Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15219, USA.
Mol Ther. 2011 Jun;19(6):1079-89. doi: 10.1038/mt.2011.3. Epub 2011 Mar 1.
Recombinant adeno-associated virus serotype 9 (rAAV9) vectors show robust in vivo transduction by a systemic approach. It has been proposed that rAAV9 has enhanced ability to cross the vascular endothelial barriers. However, the scientific basis of systemic administration of rAAV9 and its transduction mechanisms have not been fully established. Here, we show indirect evidence suggesting that capillary walls still remain as a significant barrier to rAAV9 in cardiac transduction but not so in hepatic transduction in mice, and the distinctively delayed blood clearance of rAAV9 plays an important role in overcoming this barrier, contributing to robust cardiac transduction. We find that transvascular transport of rAAV9 in the heart is a capacity-limited slow process and occurs in the absence of caveolin-1, the major component of caveolae that mediate endothelial transcytosis. In addition, a reverse genetic study identifies the outer region of the icosahedral threefold capsid protrusions as a potential culprit for rAAV9's delayed blood clearance. These results support a model in which the delayed blood clearance of rAAV9 sustains the capacity-limited slow transvascular vector transport and plays a role in mediating robust cardiac transduction, and provide important implications in AAV capsid engineering to create new rAAV variants with more desirable properties.
重组腺相关病毒血清型 9（rAAV9）载体通过全身给药方式具有强大的体内转导能力。有人提出 rAAV9 具有增强穿过血管内皮屏障的能力。然而，全身给予 rAAV9 的科学基础及其转导机制尚未完全建立。在这里，我们提供间接证据表明，在小鼠心脏转导中，毛细血管壁仍然是 rAAV9 的重要屏障，但在肝脏转导中并非如此，而 rAAV9 的明显延迟清除在克服这一屏障方面发挥了重要作用，从而导致了强大的心脏转导。我们发现，rAAV9 在心脏中的跨血管转运是一个容量限制的缓慢过程，并且在没有 caveolin-1 的情况下发生，caveolin-1 是介导内皮细胞胞吞作用的小窝主要成分。此外，反向遗传学研究鉴定出二十面体三重衣壳突起的外区域是 rAAV9 延迟清除的潜在罪魁祸首。这些结果支持了一种模型，即 rAAV9 的延迟清除维持了容量限制的缓慢跨血管载体转运，并在介导强大的心脏转导中发挥作用，并为 AAV 衣壳工程提供了重要启示，以创建具有更理想特性的新型 rAAV 变体。
