Indocyanine Green Fluorescence Imaging for Evaluation of Uterine Blood Flow in Cynomolgus Macaque

BACKGROUND Uterine blood flow is an important factor in uterine viability, but the number of blood vessels required to maintain viability is uncertain. In this study, indocyanine green (ICG) fluorescence imaging was used to examine uterine hemodynamics and vessels associated with uterine blood flow in cynomolgus macaque. METHODS The uterus of a female cynomolgus macaque was cut from the vaginal canal to mimic a situation during trachelectomy or uterine transplantation surgery in which uterine perfusion is maintained only with uterine and ovarian vessels. Intraoperative uterine hemodynamics was observed using ICG fluorescence imaging under conditions in which various nutrient vessels were selected by clamping of blood vessels. A time-intensity curve was plotted using imaging analysis software to measure the T(max) of uterine perfusion for selected blood vessel patterns. Open surgery was performed with the uterus receiving nutritional support only from uterine vessels on one side. The size of the uterus after surgery was monitored using transabdominal ultrasonography. RESULTS The resulting time-intensity curves displayed the average intensity in the regions of the uterine corpus and uterine cervix, and in the entire uterus. Analyses of the uterine hemodynamics in the cynomolgus macaque showed that uterine vessels were significantly related to uterine perfusion (P=0.008), whereas ovarian vessels did not have a significant relationship (P=0.588). When uterine vessels were clamped, ovarian vessels prolonged the time needed to reach perfusion maximum. Postoperative transabdominal ultrasonography showed that the size of the uterus was not changed 2 months after surgery, with recovery of periodic menstruation. The cynomolgus macaque has got pregnant with favorable fetus well-being. CONCLUSION Uterine vessels may be responsible for uterine blood flow, and even one uterine vessel may be sufficient to maintain uterine viability in cynomolgus macaque. Our results show that ICG fluorescence imaging is useful for evaluation of uterine blood flow since this method allows real-time observation of uterine hemodynamics.