Abstract 433: Difference in pAAV/D377Y-mPCSK9-induced Expression of mPCSK9 Between Male and Female Mice

Objective: The recombinant adeno-associated viral vector serotype 8 (AAV8) expressing the gain-of-function mutation of mouse proprotein convertase subtilisin/kexin type 9 (PCSK9) is a new model for the induction of hypercholesterolemia and atherosclerosis development. AAV8 tends to preferentially infect hepatocytes and the liver-specific promoter should ensure expression of PCSK9 results in reduced hepatic low-density lipoprotein receptor levels. However, the tissue distribution of adeno-associated viral vectors can differ between male and female mice. Therefore, we set out to investigate differences in PCSK9 expression and hypercholesterolemia development in male and female mice using the AAV8-PCSK9 model. Approach and Results: Male and female C57BL/6 mice were retro-orbitally injected with a low-dose (3x10 10 vector genomes) of AAV8-PCSK9 and fed a high-fat diet for 8 weeks. Inoculation of male mice with low dose AAV8-PCSK9 dramatically elevated both serum PCSK9 and cholesterol levels, which was not observed in female mice. Increasing the inoculation dose of AAV8-PCSK9 threefold (9x10 10 vector genomes) in female mice induced serum cholesterol and PCSK9 concentration to levels equivalent with low-dose inoculated male mice. Although increasing the dose of AAV8-PCSK9 induces a hypercholesterolemia phenotype in female mice, it did not result in an increased amount of AAV8 virus nor increased mRNA expression of mPCSK9 in female livers but did increase mRNA expression of mPCSK9 in the brains of these mice. Conclusions: Our data demonstrate that AAV8-PCSK9 inoculation results in differences between male and female mice in the localization and production of mPCSK9. These differences do not hinder the use of female mice in hypercholesterolemia and atherosclerosis studies when AAV8-PCSK9 doses are taken into consideration. However, localization to and production of AAV8-PCSK9 in organs besides the liver in female mice may introduce confounding factors into studies and should be considered during experimental design.