ABSTRACT
During pregnancy, hyaluronic acid (HA) concentration in the human cervix is very low, but increases rapidly at the onset of labour. HA has a high affinity for water molecules and hence can maintain tissue hydration. HA can stimulate collagenase production in rabbit cervix, and also stimulates migration and function of polymorphonuclear leukocytes in the tissues. It is an endogenous regulator of interleukin-1 (IL-1). We hypothesized that HA plays an essential role during cervical ripening. The effect of exogenous application of HA (20 mg) on non-pregnant and pregnant (day 23) rabbit cervices was compared with controls. HA induced cervical ripening in both pregnant and non-pregnant animals, and cervical water content was significantly increased. Tissue collagen was markedly decreased. The localization and distribution of HA and HA receptor CD44 was determined in non-pregnant and pregnant human cervical connective tissue using biotinylated HA binding protein and CD44 monoclonal antibodies. Both were widely distributed in the connective tissues, especially around the blood vessels and cervical glands. The effect of IL-8 (50, 100, 150 and 200 ng/ml) on HA production and hyaluronidase (HAase) activity was investigated in cultures of lower uterine segment collected during elective Caesarean sections. HA production was stimulated in a dose-dependent manner; there was no effect on hyaluronidase activity. HA administration (0.5, 1 and 2 mg/ml) stimulated the activities of collagenase and gelatinase together with IL-8 production in the culture supernatants. Thus HA may play an important role in cervical ripening, being involved in the regulation of cervical tissue water content, collagenolytic enzymes and cytokines.
Subject(s)
Cervix Uteri/physiology , Hyaluronic Acid/physiology , Interleukin-8/pharmacology , Myometrium/chemistry , Administration, Intravaginal , Animals , Cervix Uteri/chemistry , Cervix Uteri/drug effects , Collagen/analysis , Collagen/drug effects , Collagen/ultrastructure , Collagenases/drug effects , Collagenases/metabolism , Culture Techniques , Dose-Response Relationship, Drug , Female , Gelatinases/drug effects , Gelatinases/metabolism , Histocytochemistry , Humans , Hyaluronan Receptors/analysis , Hyaluronic Acid/administration & dosage , Hyaluronic Acid/metabolism , Hyaluronic Acid/pharmacology , Hyaluronoglucosaminidase/metabolism , Immunohistochemistry , Interleukin-8/administration & dosage , Interleukin-8/metabolism , Myometrium/drug effects , Myometrium/enzymology , Pregnancy , Rabbits , Suppositories , Water/analysisABSTRACT
OBJECTIVE: The aim of this research was to elucidate the mechanism of action of urinary trypsin inhibitor, a Kunitz-type protease inhibitor, in suppressing uterine muscle contraction. STUDY DESIGN: An isometric uterine contraction test was used to study this inhibitory effect of urinary trypsin inhibitor on the myometrium. Oxytocin, prostaglandin F2 alpha, and lipopolysaccharide were used to stimulate myometrial contraction. Prostaglandins F2 alpha and E2 were measured in the buffer solution. Influx of calcium into uterine smooth muscle cells was assessed by digital imaging microscopy. RESULTS: After incubation with urinary trypsin inhibitor or fetal urine, myometrial contractions stimulated by oxytocin, prostaglandin F2 alpha or lipopolysaccharide were suppressed completely. The concentrations of prostaglandins F2 alpha and E2 in the buffer solution during the isometric contraction test were significantly increased by lipopolysaccharide stimulation, but when urinary trypsin inhibitor was present in the buffer solution the concentrations of prostaglandins F2 alpha or E2 did not change significantly. Preincubation with urinary trypsin inhibitor also inhibited calcium influx, resulting in no detectable change in the intracellular free calcium concentration of smooth muscle cells. CONCLUSION: We proposed that urinary trypsin inhibitor from fetal urine inhibits uterine muscle contraction by regulation of intracellular Ca++.
