Sex hormones impact early maturation and immune response in the arteriovenous fistula mouse model

Arteriovenous fistulae (AVF) fail to mature more frequently in female patients compared with male patients, leading to inferior outcomes and decreased utilization. Since our mouse AVF model recapitulates sex differences in human AVF maturation, we hypothesized that sex hormones mediate these differences during AVF maturation. C57BL/6 mice (9-11 wk) were treated with aortocaval AVF surgery and/or gonadectomy. AVF hemodynamics were measured via ultrasound (days 0-21). Blood was col-lected for FACS and tissue for immunofluorescence and ELISA (days 3 and 7); wall thickness was assessed by histology (day 21). Inferior vena cava shear stress was higher in male mice (P = 0.0028) after gonadectomy, and they had increased wall thickness (22.0 +/- 1.8 vs. 12.7 +/- 1.2 lm; P < 0.0001). Conversely, female mice had decreased wall thickness (6.8 +/- 0.6 vs. 15.3 +/- 0.9 lm; P = 0.0002). Intact female mice had higher proportions of circulating CD3+ T cells on day 3 (P = 0.0043), CD4+ (P = 0.0003) and CD8+ T cells (P = 0.005) on day 7, and CD11b+ monocytes on day 3 (P = 0.0046). After gonadectomy, these differences disap-peared. In intact female mice, CD3+ T cells (P = 0.025), CD4+ T cells (P = 0.0178), CD8+ T cells (P = 0.0571), and CD68+ mac-rophages (P = 0.0078) increased in the fistula wall on days 3 and 7. This disappeared after gonadectomy. Furthermore, female mice had higher IL-10 (P = 0.0217) and TNF-a (P = 0.0417) levels in their AVF walls than male mice. Sex hormones mediate AVF maturation, suggesting that hormone receptor signaling may be a target to improve AVF maturation. NEW & NOTEWORTHY After arteriovenous fistula creation, females have lower rates of maturation and higher rates of failure than males. In a mouse model of venous adaptation that recapitulates human fistula maturation, sex hormones may be mecha-nisms of the sexual dimorphism: testosterone is associated with reduced shear stress, whereas estrogen is associated with increased immune cell recruitment. Modulating sex hormones or downstream effectors suggests sex-specific therapies and could address disparities in sex differences in clinical outcomes.