Abstract Body: The perivascular adipose tissue (PVAT), fat that surrounds many blood vessels, is capable of modulating vascular tone through multiple modalities. Despite increasing research interest, PVAT remains less understood compared to other vascular layers. We hypothesized that the transcriptome and cell population of thoracic aorta PVAT (taPVAT) differ between hypertensive and normotensive rats. To test this hypothesis, we performed single-nucleus RNA-sequencing (snRNA-seq) on twenty-five taPVAT samples from male and female Dahl SS rats, fed either control (Con) chow or a high-fat diet (HFD) for 8 or 24 weeks. Mean arterial pressure (MAP) measurements showed elevated values in female rats fed a HFD for 24 weeks with a trend towards increasing blood pressure in male rats (Fig. 1a). Our analysis included at least three taPVAT samples per treatment group, resulting in 71,813 high-quality sequenced nuclei, representing eight major cell types (Fig. 1b) and twenty-eight cell sub-types. Within each cell type, the differences in population and gene expression across diet, diet duration, and sex were examined. The most substantial population proportion differences were observed across diet duration, with fewer differences noted across diet and sex (Fig. 1c). The total number of differentially expressed genes (DEGs) (adjusted p-value ≤ 0.05, |log₂(fold change)| ≥ 1) across diet, diet duration, and sex were 191, 424, and 119, respectively. Interestingly, in the taPVAT from HFD fed rats, the gene Csmd1 (CUB and Sushi multiple domains 1) was consistently upregulated across nearly all cell types. Whereas Scd (stearoyl-CoA desaturase), which is involved in fatty acid biosynthesis, was frequently the most downregulated gene. Pathway enrichment analysis revealed that the DEGs related to the HFD were associated with a decrease in lipid and fatty acid biosynthetic processes. DEGs related to rats fed a HFD for twenty-four weeks versus eight weeks were linked to an enrichment in inflammatory response and extracellular matrix organization pathways, and in HFD fed male rats compared to females, there was enrichment for leukocyte aggregation and peptidyl-cysteine modification pathways. In conclusion, our findings help paint a more detailed picture of the molecular and cellular changes in taPVAT associated with hypertension.