Selection and Expression Stability Analysis of Housekeeping Genes for Real-Time PCR Normalization in Rhesus Macaque Peripheral Blood

(1) Background: Although the rhesus macaque (Macaca mulatta) is widely maintained in captive populations for translational research, reliable molecular tools for monitoring their physiological status remain limited—a gap that directly affects population management and health monitoring. In particular, no validated panel of housekeeping genes (HKGs) is currently available for expression analysis at the mRNA level in peripheral blood of the species. (2) Methods: Peripheral blood samples from healthy male rhesus macaques aged 4–7 years were used. The expression stability of candidate HKGs was evaluated using RefFinder based on cycle threshold (Ct) values obtained from real-time PCR. (3) Results: A panel of 29 candidate HKGs was compiled. After multistage bioinformatic and experimental selection, 22 genes were excluded. Expression stability analysis of the remaining seven genes (AHSA1, B4GALT3, CYB5R1, HPCAL1, PSMD6, SSR2, and VPS72) identified B4GALT3 and PSMD6 as the most stable. (4) Conclusions: This study presents the experimentally validated set of HKGs for expression studies in Macaca mulatta. Based on the results of expression stability analysis, the B4GALT3 and PSMD6 genes can be recommended as reference genes for studying changes in gene expression in peripheral blood.