Changes in rat cervical collagen during gestation and after antiprogesterone treatment as measured in vivo with light-induced autofluorescence

OBJECTIVE: This study was conducted to evaluate use of light-induced autofluorescence for measuring changes in collagen of cervical connective tissue during gestation. STUDY DESIGN: In a conventional laboratory setting light-induced autofluorescence from the cervix of Charles-Dawley timed pregnant rats was measured in vivo. Eight distinct groups at various times of gestation were examined. Measurements were also performed on rats at day 17 of gestation 24 hours after treatment with RU 38486. RESULTS: The amount of light-induced autofluorescence decreases significantly as pregnancy approaches term (means of the arbitrary total counts per spectrum on day 19 vs day 21 = 2.8 × 105 vs 1.9 × 105, p< 0.01) and reaches its lowest point when the pups are engaged in the cervix (day 19 vs day 22 = 2.8 × 105 vs 0.95 × 105, p< 0.001) and during delivery (day 19 vs DELIVERY = 2.8 × 105 vs 0.83 × 105, p< 0.001). Preterm treatment with RU 38486 also caused a significant decrease in the native fluorescence compared with vehicle-injected controls (day 17 control vs day 17 RU 38486 = 2.8 × 105 vs 1.5 × 106, p< 0.001). CONCLUSION: Significant decreases in cervical collagen at parturition parallel the results of previous studies that used various indirect methods to analyze collagen content. These data support the use of light-induced autofluorescence for detecting and studying the changes in cervical and uterine connective tissue during gestation in vivo.