Annu Int Conf IEEE Eng Med Biol Soc. 2022 Jul;2022:488-492. doi: 10.1109/EMBC48229.2022.9871419.
Human spermatozoa must swim through the female reproductive tract, where they undergo a series of biochemical and biophysical reactions called capacitation, a necessary step to fertilize the egg. Capacitation promotes changes in the motility pattern. Historically, a two-dimensional analysis has been used to classify sperm motility and clinical fertilization studies. Nevertheless, in a natural environment sperm motility is three-dimensional (3D). Imaging flagella of freely swimming sperm is a difficult task due to their high beating frequency of up to 25 Hz. Very recent studies have described several sperm flagellum 3D beating features (curvature, torsion, asymmetries, etc.). However, up to date, the 3D motility pattern of hyperactivated spermatozoa has not been characterized. The main difficulty in classifying these patterns in 3D is the lack of a ground truth reference since differences in flagellar beat patterns are very difficult to assess visually. Moreover, only around 10-20% of induced to capacitate spermatozoa are truly capacitated, i.e., hyperactivated. We used an image acquisition system that can acquire, segment, and track spermatozoa flagella in 3D+t. In this work, we propose an original three-dimensional feature vector formed by ellipses describing the envelope of the 3D+t spatio-temporal flagellar sperm motility patterns. These features allowed compressing an unlabeled 3D+t dataset to separate hyperactivated cells from others (capacitated from non-capacitated cells) using unsupervised hierarchical clustering. Preliminary results show three main clusters of flagellar motility patterns. The first principal component of these 3D flagella measurements correlated with 2D OpenCASA head determinations as a first approach to validate the unsupervised classification, showing a reasonable correlation coefficient near to 0.7. Clinical relevance- The novelty of this work is defining a 3D+t feature-based descriptor consisting of a set of ellipses enveloping the flagellar motion of human sperm for its unsu-pervised classification. This is a new promising tool to determine the viability of human sperm to fertilize the egg.
人类精子必须穿过女性生殖道，在那里它们经历一系列称为获能的生化和生物物理反应，这是受精卵子的必要步骤。获能促进了运动模式的变化。历史上，二维分析一直用于分类精子运动和临床受精研究。然而，在自然环境中，精子运动是三维的。由于其高达 25 Hz 的高拍打频率，对自由游动的精子鞭毛进行成像一直是一项艰巨的任务。最近的研究已经描述了几种精子鞭毛的 3D 拍打特征（弯曲、扭转、不对称等）。然而，到目前为止，还没有对超激活精子的 3D 运动模式进行特征描述。在 3D 中对这些模式进行分类的主要困难是缺乏地面真实参考，因为鞭毛拍打模式的差异很难通过视觉进行评估。此外，只有大约 10-20%的诱导获能的精子真正获能，即超激活。我们使用了一种可以在 3D+t 中获取、分割和跟踪精子鞭毛的图像采集系统。在这项工作中，我们提出了一种由椭圆组成的原始三维特征向量，该向量描述了 3D+t 时空鞭毛精子运动模式的包络。这些特征允许将未标记的 3D+t 数据集压缩为从其他细胞（从未获能细胞到获能细胞）中分离出超激活细胞，使用无监督层次聚类。初步结果显示了三个主要的鞭毛运动模式簇。这些 3D 鞭毛测量的第一主成分与 2D OpenCASA 头部测定相关，作为验证无监督分类的初步方法，显示出接近 0.7 的合理相关系数。临床相关性-这项工作的新颖之处在于定义了一种基于 3D+t 的特征描述符，该描述符由一组包围人类精子鞭毛运动的椭圆组成，用于其无监督分类。这是一种确定人类精子受精卵子活力的新工具。
