Methods for studying oviductal physiology

A Review: Biomechanical Aspects of the Fallopian Tube Relevant to its Function in Fertility

The fallopian tube (FT) plays a crucial role in the reproductive process by providing an ideal biomechanical and biochemical environment for fertilization and early embryo development. Despite its importance, the biomechanical functions of the FT that originate from its morphological aspects, and ultrastructural aspects, as well as the mechanical properties of FT, have not been studied nor used sufficiently, which limits the understanding of fertilization, mechanotrasduction, and mechanobiology during embryo development, as well as the replication of the FT in laboratory settings for infertility treatments. This paper reviews and revives valuable information on human FT reported in medical literature in the past five decades relevant to the biomechanical aspects of FT. In this review, we summarized the current state of knowledge concerning the morphological, ultrastructural aspects, and mechanical properties of the human FT. We also investigate the potential arising from a thorough consideration of the biomechanical functions and exploring often neglected mechanical aspects. Our investigation encompasses both macroscopic measurements (such as length, diameter, and thickness) and microscopic measurements (including the height of epithelial cells, the percentage of ciliated cells, cilia structure, and ciliary beat frequency). Our primary focus has been on healthy women of reproductive age. We have examined various measurement techniques, encompassing conventional metrology, 2D histological data as well as new spatial measurement techniques such as micro-CT.

Microscale imaging of cilia-driven fluid flow

Cilia-driven fluid flow is important for multiple processes in the body, including respiratory mucus clearance, gamete transport in the oviduct, right-left patterning in the embryonic node, and cerebrospinal fluid circulation. Multiple imaging techniques have been applied toward quantifying ciliary flow. Here, we review common velocimetry methods of quantifying fluid flow. We then discuss four important optical modalities, including light microscopy, epifluorescence, confocal microscopy, and optical coherence tomography, that have been used to investigate cilia-driven flow.

Rapid effects of progesterone on ciliary beat frequency in the mouse fallopian tube

BACKGROUND

The physiological regulation of ciliary beat frequency (CBF) within the fallopian tube is important for controlling the transport of gametes and the fertilized ovum. Progesterone influences gamete transport in the fallopian tube of several mammalian species. In fallopian tubes isolated from cows, treatment with 20 micromolar progesterone caused a rapid reduction of the tubal CBF. The aims of this study were to establish methodology for studying fallopian tube CBF in the mouse, as it is an important model species, and to investigate if progesterone rapidly affects the CBF of mice at nM concentrations.

METHODS

A method to assess tubal CBF of mice was developed. Fallopian tubes were dissected and the tissue was cut in small pieces. Tissue samples with moving cilia were located under an inverted bright field microscope and held still against the bottom of a petri dish by a motorized needle system. Images were acquired over 90 minutes at 35 degrees C with a high-speed camera and used for assessing changes in the CBF in response to the addition of hormone.

RESULTS

The baseline CBF of the mouse fallopian tube was 23.3 +/- 3.8 Hz. The CBF was stable over at least 90 minutes allowing establishment of a baseline frequency, addition of hormone and subsequent recordings. Progesterone at concentrations of 20 micromolar and 100 nM significantly reduced the CBF by 10% and 15% respectively after 30 minutes compared with controls.

CONCLUSIONS

The present study demonstrates that the mouse, despite its small size, is a useful model for studying the fallopian tube CBF ex vivo. The rapid reduction in CBF by 100 nM progesterone suggests that gamete transport in the fallopian tube could be mediated by progesterone via a non-genomic receptor mechanism.

A new method for continuous recording of oviductal pressure variations in unrestrained gilts

A new method using two intraluminally placed ultra-miniature pressure sensors placed in the same isthmus of the oviduct has been developed for continuous monitoring of oviductal pressure variations during the oestrous cycle in unrestrained gilts. Each test animal was followed for 48 h during which recordings were made at frequent intervals. By using two points of registration, directions of pressure waves could be determined. This technique allows for the determination of the base pressure in the oviduct and how it varies during the oestrous cycle. Effects of different stimuli and the effect of narcosis on oviductal activity can also be directly studied.

Effects of tension and transmural stimulation on prostaglandin production by estrous rabbit oviductal isthmus

The effect of longitudinal and circular stretch on the amounts of Prostaglandin F (PGF) and Prostaglandin E (PGE) found in the fluid bathing rabbit oviductal isthmus has been investigated. It was found that the amounts of PGE and PGF measured in the bathing fluid of longitudinally or circularly stretched tissues were negatively correlated to the maturity of the animal. Prostaglandin E increased with time in the tissues under longitudinal and circular tension. Prostaglandin F also increased with time under longitudinal tension but remained fairly constant under circular tension. Increasing the load from 0.5 to 2.0 g had no significant effect on PGE found under longitudinal or circular tension or on PGF found under longitudinal tension. Under circular tension, PGF found increased. Transmural stimulation at 20 Hz increased PGE 8-fold over control values while PGF increased only 1 to 3-fold. It is suggested that distension of the rabbit oviductal isthmus results in increased PGF production, which could be important in ovum transport.

The isolated-perfused rabbit oviduct: a simple experimental preparation

A new, simple method to study several physiological parameters in the isolated rabbit oviduct is described in detail. The whole oviduct with its supporting membranes, the ovary and part of the uterine horn, and part of the systemic blood supply were excised and perfused in vitro through cannulated blood vessels with a blood-physiological solution mixture. Autoregulation of the vasculature was demonstrated, suggesting that the preparation was viable and well oxygenated. The frequency of contractions of the ampullary and isthmic parts was decreased by prostaglandin E2 added to the perfusing solution.

Contractile patterns of isolated oviductal smooth muscle under different hormonal conditions

The isthmic portion of the human fallopian tube was excised during surgery and the ampullary-isthmic junction was identified. Muscle strips (1-mm wide) were dissected from the outer longitudinal and the inner circular layers at this region and used for isometric recordings of spontaneous contractile activity in organ bath experiments. It was found that the amplitude and the duration of individual contractions were similar during various phases of normal menstrual cycles, whereas the frequency of contractions was significantly increased during the periovulatory period in both circular and longitudinal muscle. During early pregnancy or treatment with combined oral contraceptives the motility pattern was similar to that observed in the late luteal phase, being characterized by a comparatively low contraction frequency. In the perimenopausal period, irregular patterns were frequently observed whereas preparations obtained from postmenopausal women exhibited a very weak activity with low amplitude and frequency of contractions. Similar activity was encountered in specimens from patients treated with androgens. It is concluded that endogenous estrogens stimulate human oviductal contractility while endogenous progesterone has a depressive action on tubal activity. Both effects occur with a certain delay and are prolonged for up to 3 days, i.e., the changes in the serum levels of ovarian steroids and the induced alterations of tubal contractility are out of phase.

Adrenergic responses of the various smooth muscle layers at the human uterotubal junction

The different muscle layers at the human uterotubal junction (UTJ) were mechanically separated, and 1-mm wide muscle strips were isolated and mounted in organ chambers for isometric recording of contractile activity. It was found that the adrenergic neurotransmitter noradrenalin elicited an inhibition of the spontaneous phasic activity in the inner longitudinal and the intermediate circular layers but caused a clear-cut excitatory response in the outer, spiral-shaped (uterine) layer. The excitatory response was totally blocked by treatment with phenoxybenzamine, an alpha-adrenoceptor antagonist, whereas the inhibitory effects were abolished after pretreatment with the beta-adrenoceptor antagonist propranolol. The data demonstrate a differentiated distribution of alpha- and beta-adrenoceptors in the smooth musculature at the proximal end of the tubal isthmus. It is suggested that this arrangement might serve an important purpose in the physiologic control of ovum transport in women.

Studies on ciliated epithelia of the human genital tract. II. The mucociliary wave pattern of fallopian tube epithelium

The ciliary activity of human fallopian tube epithelium was studied in vitro by using a technique which included registration of the light reflections from the mucociliary waves on the epithelial surface. In all registrations, the mucociliary waves moved toward the uterine end of the specimen. The frequencies of the reflections of the mucociliary waves ranged between 960 and 1368 cpm, with a mean of 1191 cpm (2 SD, +/- 176) and a median of 1210 cpm. Significant differences in the mucociliary wave frequencies were not observed between different parts of the fallopian tube nor between registrations performed during the follicular and luteal phases of the menstrual cycle. Scanning electron microscopy of the specimens revealed no morphologic changes of the cilia during the menstrual cycle.

Ciliary activity in the human oviduct

Ciliary activity of the human oviduct was investigated using a cinematographic technique. Oviducts from preovulatory, postovulatory and puerperal subjects were analyzed and the fimbrial, ampullary and isthmic regions were compared. It was found that cilia beat more rapidly after ovulation, this difference being significant in both ampullary and isthmic regions, but not in the fimbriae. The implications of these findings are discussed.

[Histochemical and histological investigations on the human fallopian tube under different hormonal influences. I. Demonstration of ATPase with special reference to reactive ciliated cells (author's transl)]

The localization of the Mg++-activated adenosine triphosphatase (ATPase) in the human Fallopian tube has been studied by means of histochemical methods. The samples were obtained from 18 women in the age from 23--62 years. Some of them were treated by various steroid hormones. Endosalpinx ciliary ATPase-activity represents dynein and is therefore an indicator of ciliary motility. Estrogens and gestagens have a different influence on the ATPase-activity. All cilia of one ciliated cell react in the same manner and may be regarded as a reaction unit. The relation of negative to positive ciliary borders differs characteristically in the tubal isthmus, ampulls and infundibulum and coincides with commonly known phenomena of egg transport through the oviduct. Postovulatory, reaction units increase in ampulla and infundibulum compared with the proliferative phase. The oviducts of postmenopausal women possess but a scanty outfit of reaction units. Short-time treatment with estrogen in the early secretory phase results in a great number of reaction units in all tubal segments; a similar treatment in the proliferative phase diminishes the reaction units in the ampulla. Midcycle progesterone treatment activates the ciliary ATPase in the isthmus. Low doses of lynestrenol (minipill) in the proliferative phase leads to a decrease of reaction units in all tubal segments; the pattern of ciliary reaction under low doses of lynestrenol at the time of ovulation coincides with that of the proliferative phase. Treatment with a contraceptive steroid (0,05 mg ethinylestradiol and 0,25 d-norgestrel) causes a considerable activation of the ciliary ATPase in all portions of the oviduct.