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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Animal Biosciences & Biotechnology Laboratory » Research » Publications at this Location » Publication #308539
Title: Apical blebs on sperm-storage tubule epithelial cell microvilli: their release and interaction with resident sperm in the turkey hen oviduct

Author
item Bakst, Murray
item Bauchan, Gary

Submitted to: Theriogenology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/13/2015
Publication Date: 1/16/2015
Citation: Bakst, M.R., Bauchan, G.R. 2015. Apical blebs on sperm-storage tubule epithelial cell microvilli: their release and interaction with resident sperm in the turkey hen oviduct. Theriogenology. 83:1438-1444.

Interpretive Summary: Located at the upper end of the turkey hen’s vagina are numerous tubular structures derived from the vagina’s surface cells, collectively referred to as the sperm-storage tubules (SSTs). Following mating or artificial insemination, sperm ascend the vagina and enter the SSTs. Over the next days and weeks the sperm gradually exit the SSTs and are transported to the upper end of the oviduct to fertilize a daily succession of ova (yolks). Little is known regarding the cellular and molecular mechanisms responsible for sperm subsistence while residing within the SSTs. In this study, the relationship between the numerous hair-like surface projections from the surface of the SST lining cells (called microvilli) and sperm residing in the SSTs was examined. Some microvilli formed vesicles at their tips that were released into the SST lumen and appeared associated with or fused to surface of sperm in the SSTs. Those sperm adjacent to the cells lining the SSTs were surrounded by the SST microvilli. Based on these observations and those of other authors, it is suggested that the vesicles derived from the SST microvilli help sustain sperm storage in the SSTs by (1) supplying metabolic substrates utilized by resident sperm, (2) fusing with the sperm thereby providing fats, carbohydrates, and proteins (glycoproteins and glycolipids) that stabilizes the sperm’s membranes and reversibly suppresses sperm functions associated with fertilization, and (3) act as transport vesicles actively transporting fluid from the SST cells to the SST lumen. These observations will benefit poultry scientists studying the biological basis of prolonged oviductal sperm storage and sustained hen fertility and cell biologists examining the formation and functions of shedding vesicles.

Technical Abstract: Technical Abstract: Located at the anterior end of the turkey hen vagina are numerous discrete tubular invaginations of the surface epithelium, collectively referred to as the sperm-storage tubules (SSTs). Following mating or artificial insemination, sperm ascend the vagina, enter the SSTs, and over the ensuing days and weeks, gradually exit the SSTs and are transported to the anterior end of the oviduct to fertilize a daily succession of ova. Little is known regarding the cellular and molecular mechanisms responsible for sperm subsistence in the lumen of the SST. In this study, the origin of microvillous blebs (MvBs) on the apical tips of SST epithelial cells and their possible roles in sperm survival are examined. Regardless if sperm are present or not, transmission electron microscopy revealed two types of microvilli differentiated by the presence or absence of pleomorphic, unilaminar MvBs localized to their apical tips. While some MvBs appeared to be discharging their contents into the SST lumen, others appeared to have pinched off the microvillous stem. When SSTs contained clusters of densely packed sperm, the heads of those sperm adjacent to the SST epithelial cell surface were surrounded by microvilli. Associated with the plasmalemma of sperm throughout the SST lumina were membrane fragments and small vesicles (30 to 130 nm in diameter) some of which appeared to have fused with sperm. It is concluded that the MvBs are a form of shedding vesicle released from the SST epithelial cell microvilli by apocrine secretion. Based on observations described herein and those of other authors, it is suggested that the MvBs contribute to sustained sperm storage in the SSTs by (1) supplying metabolic substrates utilized by resident sperm, (2) serving as fusogenic vehicles providing exogenous macromolecules that reversibly suppress sperm functions associated with fertilization (decapacitation?) and stabilize the sperm plasmalemma, and (3) act as transport vesicles actively transporting fluid from the SST epithelial cells to the SST lumen.