Birefrincence in the sperm head: a new tool to increase the oingoing pregnancy rate

Human spermatozoa possess characteristics of birefringence due to the anisotropy of their protoplasmic texture. As confirmed by the analysis performed by transmission electron microscopy (TEM), in the mature sperm nucleus there is a strong intrinsic birefringence associated to nucleoprotein filaments which are ordered in rods and longitudinally oriented. A similar type of birefringence is observed in the mature acrosomal complex due to the presence of subacrosomal protein filaments which are longitudinally oriented. The same is true for large portions of the tail texture, in which the microtubular organization of the axoneme and the chondriome in the midpiece are birefringent. Based on these observations, the application of polarization microscopy to the ICSI technique has been proposed as a novel tool for sperm selection. The results obtained are presented in this study