Hyaluronidase modifies the biomechanical properties of the rat cervix and shortens the duration of labor independent of myometrial contractility

OBJECTIVE: To investigate the effect of intracervical hyaluronidase on the biomechanical properties of the cervix and on uterine contractility. STUDY DESIGN: Sprague-Dawley rats (n = 33, term day 22) were injected with hyaluronidase (100 IU) or saline solution on day 18 of gestation (n = 8-9/group). On day 21, labor was induced with mifepristone (8 mg/rat). Injection-to-delivery times were recorded. Biomechanical properties of the cervix were assessed using stretch-tension analysis. Myometrial contractility was investigated in response to hyaluronidase (0.2-200 IU/mL), oxytocin (10(-10)M to 10(-5)M), and potassium chloride (60 mM). RESULTS: Delivery times were shorter in the hyaluronidase group (P = .03). Cervices of the treated animals showed higher measures of elasticity and plasticity (P = .02 for both). Myometrial sensitivity to hyaluronidase, oxytocin, or potassium chloride was not affected by the cervical application of hyaluronidase (P > .05 for all). CONCLUSION: Cervical hyaluronidase treatment shortens labor and alters the biomechanical properties of the cervix, independent of the myometrium.