Hyaluronic Acid in Cultured Ovine Tracheal Cells and Its Effect on Ciliary Beat Frequency In Vitro

Abstract

Hyaluronic acid (hyaluronan, or HA) is secreted by submucosal glands, but its function in airway secretions other than influencing the rheology of mucus is not fully understood. HA is known to modulate cell behavior and to enhance sperm motility. Because sperm tails and cilia have the same microtubular structure, we studied the effect of HA on ciliary beat frequency (CBF) in vitro. CBF of cultured ovine airway epithelial cells was measured continuously by digital video microscopy. After removal of endogenous HA by hyaluronidase, cells were exposed to 50 to 100 microg/mL of HA at different times in culture. No change in CBF in response to HA was seen in cells cultured less than 7 days. After 7 days, however, 6 of 10 measured cells (from three different sheep) showed a transient CBF increase from a baseline of 6.4 +/- 0.3 Hz (mean +/- SE) to 7.4 +/- 0.4 Hz or 16% above baseline (p < 0.05). At these time points (but not before), cytochemical staining was positive for endogenous HA using a biotinylated HA-binding protein. These data suggest that HA can increase CBF of tracheal epithelial cells only late in culture when HA is able to bind to an unspecified cell surface structure. Because this binding has a physiological effect, we hypothesize that it is an HA-binding receptor, that is either transiently expressed late in culture or initially destroyed by the protease treatment for cell dispersion.

Expression of Hyaluronan Synthases and Corresponding Hyaluronan Receptors Is Differentially Regulated During Oocyte Maturation in Cattle1

“…Although RHAMM was unregulated under gonadotropins, possible functions of this HA receptor in the bovine reproductive tract could be important, because basic expression levels during IVM were found to be compared to CD44 expression. The RHAMM may mediate movement and attachment of human cumulus cells [46], or it could modulate ciliary beating of oviduct epithelia, as described for the respiratory system [30]. Recent work discovered CD44 as the essential HA receptor throughout development of the preimplantation human embryo [47] and during trophoblast implantation [48].…”

“…Known to promote cell movement, RHAMM is located both in the cell as well as at the cell surface [27]. Furthermore, the HA receptor may be involved in wound healing [28], migration of smooth muscle cells [29], and modulation of ciliary beating of the airway epithelial cells [30].…”

Hyaluronan serves a novel role in airway mucosal host defense

“…This concentration of anti-RHAMM antibody inhibited locomotion of smooth muscle cells (24). The cells were then exposed within 60 min to hyaluronan (Seikagaku or Worthington; see Results; both with an average molecular mass of 200 kDa) at 50 g/ml, previously demonstrated to increase CBF (10). As a control, the cells were exposed to 20 M ATP to ascertain their response to a known stimulator of CBF.…”

“…We have previously shown that TK from broncho-alveolar lavage is bound to secreted hyaluronan that regulates its activity (4). We have also shown that ciliated cells in culture bind endogenously produced hyaluronan and that exogenously applied hyaluronan can stimulate ciliary beat frequency (CBF) (10).…”

Cystic Fibrosis Transmembrane Conductance Regulator Can Export Hyaluronan

“…Hyaluronan plays a major role in mucosal defence because it increases the ciliary beat frequency of tracheal epithelial cells [40,41] . It is a constituent of human airway secretions and is produced mostly by ciliated surface epithelial cells, with some contributed by submucosal glands [42][43][44] .…”