A Comprehensive Guide for Cell Type-Specific Transduction in Skin Using Adeno-Associated Virus as Delivery Vector

Abstract

The hair follicle cycles between growth, regression, and rest phases. This cyclic activity is regulated by the activation and quiescence of hair follicle stem cells (HFSCs). Recent studies indicate that the crosstalk between HFSCs and the stem cell niche play an important role in regulating HF maintenance. Due to the complex architecture and diverse skin cell types consisting of the skin, it is often challenging to study how a specific cell type of interest influences the microenvironment of HFSC niche. To enhance our understanding of the relationship between HFSCs and their neighboring cells, it is necessary to develop an investigation tool which can target and manipulate specific skin cell types without disturbing the sensitive microenvironment. The goal of this study was to evaluate transduction patterns of AAV with different conditions, ranging from serotypes, promoters, dosage, and timing of injection. Given these findings, we established the system by which AAV vectors can show targeted transduction of specific cell types in the skin. We first prepared the AAVs incorporated with a reporter transgene and injected intradermally on the back skin of mice. Next, we evaluated their transduction efficiency via fluorescence microscopy and quantified the labeled cells. Immunohistochemistry with different skin cell markers was performed to identify which skin cell types were infected by our AAV candidates. As a result, the pattern of AAV transduction in skin varied depending on capsid serotype, promoter, and the timing of injection. The adult injection of AAV8-CAG-GFP showed the most widespread transduction, while AAV6-CAG-GFP and AAV-PHP.S-EF1a targeted arrector pili muscle with a high frequency. The P0 injection of AAV overall showed a significant improvement in transduction efficiency, compared to the adult injection. Importantly, the P0 injection of AAV6-EF1a-DTA-mCherry was highly efficient to transduce APM. In addition, the P0 injection of AAV-PHP.S-EF1a-DTA-mCherry showed tissue-specific transduction in dermal papilla and arrector pili muscle. Our study demonstrates that the combination of different conditions can achieve a cell-type specific transduction of AAV in mice skin. With a variety of conditions, AAV can induce cell-type-specific transduction in the skin, including dermal fibroblasts, adipocytes, APM and DP. Such a system will serve as valuable tool for dissecting the crosstalk among different skin cell populations and provide new windows for conducting future studies in hair growth and wound regeneration.