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<p>Vitamin D receptor (VDR) regulates musculoskeletal biology, but its adult, tissue-specific roles are difficult to resolve with germline or conventional conditional knockouts. We developed recombinant adeno-associated viral vectors (rAAVs) to drive Cre recombinase selectively in bone or muscle and used them to delete <i>Vdr</i> postnatally in <i>Vdr</i><sup><i>fl/fl</i></sup> mice. To engineer a muscle-selective vector, we screened AAV9 constructs carrying candidate muscle promoters and identified tMCKΔ63 as the most selective&#xa0;promoter. Packaging this cassette in the myotropic AAVMYO capsid further reduced off-target skeletal expression while preserving strong muscle transduction. Local intramuscular delivery of AAVMYO–tMCKΔ63 enabled unilateral targeting with minimal systemic spread. In parallel, a bone-selective AAV8-Sp7 vector supported skeletal delivery. These vectors produced tissue-restricted <i>Vdr</i> deletion in <i>Vdr</i><sub><i>muscle</i></sub><sup><i>AAV</i></sup> and <i>Vdr</i><sub><i>bone</i></sub><sup><i>AAV</i></sup> mice. Muscle-targeted VDR loss reduced grip strength (–9.27%, <i>p</i> &lt; 0.01) and endurance (–16.58%, <i>p</i> &lt; 0.05). Bone-targeted deletion caused modest but significant skeletal changes, including increased cortical thickness ( + 7%, <i>p</i> &lt; 0.05) and higher vertebral stiffness ( + 27%, <i>p</i> &lt; 0.001), without effects on body weight or tibial strength. This scalable, crossbreeding-independent strategy enables compartment-specific functional studies in floxed models, including genes with embryonic lethality or complex tissue interactions. It also provides a general framework for iterative capsid-promoter optimization to maximize specificity in vivo across diverse tissues.</p>

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Bone- and muscle-targeted adeno-associated viral vectors enable tissue-selective vitamin D receptor knockdown in mice

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年7月29日

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  • Alexandra K. O’Donohue,
  • Julian Chu,
  • Nicholas Norris,
  • Hsien-Yin Kao,
  • Josephine Yu,
  • Lucinda R. Lee,
  • Dirk Grimm,
  • Jenny E. Gunton,
  • Aaron Schindeler

摘要

Vitamin D receptor (VDR) regulates musculoskeletal biology, but its adult, tissue-specific roles are difficult to resolve with germline or conventional conditional knockouts. We developed recombinant adeno-associated viral vectors (rAAVs) to drive Cre recombinase selectively in bone or muscle and used them to delete Vdr postnatally in Vdrfl/fl mice. To engineer a muscle-selective vector, we screened AAV9 constructs carrying candidate muscle promoters and identified tMCKΔ63 as the most selective promoter. Packaging this cassette in the myotropic AAVMYO capsid further reduced off-target skeletal expression while preserving strong muscle transduction. Local intramuscular delivery of AAVMYO–tMCKΔ63 enabled unilateral targeting with minimal systemic spread. In parallel, a bone-selective AAV8-Sp7 vector supported skeletal delivery. These vectors produced tissue-restricted Vdr deletion in VdrmuscleAAV and VdrboneAAV mice. Muscle-targeted VDR loss reduced grip strength (–9.27%, p < 0.01) and endurance (–16.58%, p < 0.05). Bone-targeted deletion caused modest but significant skeletal changes, including increased cortical thickness ( + 7%, p < 0.05) and higher vertebral stiffness ( + 27%, p < 0.001), without effects on body weight or tibial strength. This scalable, crossbreeding-independent strategy enables compartment-specific functional studies in floxed models, including genes with embryonic lethality or complex tissue interactions. It also provides a general framework for iterative capsid-promoter optimization to maximize specificity in vivo across diverse tissues.