Relationship between the Length of Sperm Tail Mitochondrial Sheath and Fertility Traits in Boars Used for Artificial Insemination

Abstract

The length of sperm tail midpiece, occupied by the mitochondrial sheath (MS), has been correlated with reproductive traits of mice, fish, and birds; however, it is not known whether such a correlation exists in higher order species such as domestic pigs. As the mitochondria provide for sperm motility and generate the fertility-affecting reactive oxygen species (ROS), we hypothesized that MS length correlates with boar semen parameters and artificial insemination (AI) fertility. Sperm samples collected from 57 boars and used for single sire AI were labeled with ProteoStat Aggresome probe (AGG; Enzo Life Sciences) for MS imaging by epifluorescence microscopy and image-based flow cytometry (IBFC). The mean boar MS length was 7.26 ± 0.2 µm, ranging from 6.94 ± 0.18 µm to 7.65 ± 0.31 µm. The absolute longest MS measured was 9.19 µm and the shortest was 5.83 µm. Boars in the high tertile of MS length had significantly higher conception rate (CR; p = 0.05) and sperm parameters. Boars within the high tertile of average number piglets born per litter had significantly shorter MS and more varied MS length than boars in the low tertile (p = 0.04). MS length data correlated with conventional sperm parameters including percent viable and intact acrosomes (p = 0.03), basal:induced oxidation ratio (measure of intracellular ROS levels; p = 0.02) and Comp DNA (chromatin integrity; p = 0.06) along with many flow cytometric AGG parameters in IBFC. Sperm head AGG intensity median absolute deviation had a negative correlation with total born (r = −0.423 p = 0.004). These data reveal a complex relationship between sperm MS length and aggresome abundance to sperm parameters and boar reproductive success in AI service.

Human live spermatozoa morphology assessment using digital holographic microscopy

“…The longer tail may correspond with motility 20 , 21 but not with the speed of spermatozoa 20 . The length of the midpiece has been shown to correlate with reproductive traits in humans 22 , boars 23 and other species 21 . On the other hand, a longer midpiece does not denote a well-organized mitochondrial sheath.…”

Mammalian Cell-Free System Recapitulates the Early Events of Post-Fertilization Sperm Mitophagy

“…These PACRG-containing aggresomes are then removed through macroautophagic pathways. In this sense, mitochondrial sheaths of mammalian spermatozoa are similar to aggresomes and are detectable using aggresome-detecting probes [ 8 , 38 ]. Thus, the whole sperm mitochondrial sheath may be recognized as a large aggresome by the oocyte autophagy machinery.…”

An Exploration of Current and Perspective Semen Analysis and Sperm Selection for Livestock Artificial Insemination

“…Furthermore, the potential for biomarker-based analysis is extensive as new sperm quality biomarkers continue to be identified [ 30 , 32 , 33 , 34 , 41 , 42 ]. New advancements to flow cytometry also allow for the dissemination of image-based flow cytometry (IBFC); this technology captures images of each single cell at high speeds (500 to 2000 sperm/second) and allows for characterizing biomarker localization at subcellular level (e.g., between sperm head and tail or within their respective sub-compartments), which is not possible in regular flow cytometry [ 43 , 44 ].…”

“…Coupled with artificial intelligence methods such as machine learning, IBFC in animal andrology may eventually lead to development of label-free approaches to semen analysis [ 45 ]. In this scenario, images from IBFC could have features extracted from ground truth images from biomarker characterization to train neural networks for differentiating fertile and infertile spermatozoa within an ejaculate based solely on bright field data with no need for sample labeling and fluorescence detection, an example is provided in Figure 1 [ 41 ]. Algorithms created by this type of research could then be utilized on bare bone image-based flow cytometers with no need of expensive lasers or on CASAs used in andrology labs daily.…”