# A Sensitive Reporter Mouse Model to Study Adipocyte‐Derived Extracellular Vesicles In Vivo

## TL;DR

The study created a sensitive mouse model to track adipocyte-derived extracellular vesicles in vivo, revealing early effects of a high-fat diet on their abundance and distribution.

## Contribution

A novel and sensitive AAV-based reporter system for tracking adipocyte-derived extracellular vesicles in vivo was developed.

## Key findings

- CD63-NanoLuc and sec-NanoLuc constructs enabled detection of adipocyte-derived EVs in plasma, tissues, and urine.
- HFD increased NanoLuc activity in ATs, lungs, and kidneys specifically in CD63-NanoLuc mice.
- The reporter system detected early effects of HFD on EV abundance before significant weight gain.

## Abstract

Extracellular vesicles (EVs) affect the function of cells in living animals. Yet, cell type‐specific EV abundances and their distribution in biological fluids are technically challenging to study. Thus, we aimed to develop an in vivo EV reporter system to monitor cell‐type‐specific EVs, with a focus on adipocyte‐derived EVs. While our previously generated EV reporter construct had insufficient sensitivity, we successfully created a sensitive EV reporter using an adeno‐associated virus (AAV) vector with Cre‐activated expression of human CD63 fused to NanoLuc (CD63‐NanoLuc). Moreover, we designed a control AAV construct for monitoring constitutive secretion of NanoLuc (sec‐NanoLuc). AAV administration to mice induced adipocyte‐specific expression of both reporters. NanoLuc activity was detected in plasma. While sec‐NanoLuc was predominantly in plasma and urine, CD63‐NanoLuc was highest in adipose tissues (ATs). We challenged mice with a 2‐week high‐fat diet (HFD), which had minimal effects on body weight and adipogenic markers. Still, the HFD‐fed CD63‐NanoLuc mice, but not sec‐NanoLuc mice, showed significantly higher NanoLuc activity in ATs, lungs, kidneys and urine. Thus, our CD63‐NanoLuc and sec‐NanoLuc constructs revealed an early effect of HFD on the abundance and distribution of adipocyte‐derived EVs and provide a sensitive system for monitoring cell‐type‐specific EVs in health and disease.