Persistent histones in immature sperm are associated with DNA fragmentation and affect paternal contribution of sperm: A study of aniline blue staining, fluorescence in situ hybridization (FISH) and DNA nick translation

Methodology of aniline blue staining of chromatin and the assessment of the associated nuclear and cytoplasmic attributes in human sperm

In this chapter, the laboratory methods for detection of sperm biomarkers that are aimed at identifying arrested sperm development are summarized. These probes include sperm staining with aniline blue for persistent histones, representing a break in the histone-transition protein-protamine sequence, immunocytochemistry with cytoplasmic sperm proteins, highlighting cytoplasmic retention during spermiogenesis, DNA nick translation testing for DNA chain fragmentation due to various reasons, for instance low HspA2 chaperone protein levels, and consequential diminished DNA repair. Finally, we briefly provide references on our work on sperm hyaluronan binding, abnormal Tybergerg sperm morphology, and the increased levels of chromosomal aneuploidies in sperm with developmental arrest. A very interesting aspect of the biomarker field is the discovery (Sati et al, Reprod Biomed Online 16:570-579, 2008) that the various nuclear and cytoplasmic defects detected by the biomarkers are related, and may simultaneously occur within the same spermatozoa as evidenced by a combination of biomarkers, such as aniline blue staining (persistent histones) coupled with cytoplasmic retention, DNA fragmentation, Caspase-3, Tygerberg abnormal morphology, and increased levels of chromosomal aneuploidies. We show examples of this >80% overlap in staining patterns within the same spermatozoa.

Efficacy of hyaluronic acid binding assay in selecting motile spermatozoa with normal morphology at high magnification

BACKGROUND

The present study aimed to evaluate the efficacy of the hyaluronic acid (HA) binding assay in the selection of motile spermatozoa with normal morphology at high magnification (8400x).

METHODS

A total of 16592 prepared spermatozoa were selected and classified into two groups: Group I, spermatozoa which presented their head attached to an HA substance (HA-bound sperm), and Group II, those spermatozoa that did not attach to the HA substance (HA-unbound sperm). HA-bound and HA-unbound spermatozoa were evaluated according to the following sperm forms: 1-Normal morphology: normal nucleus (smooth, symmetric and oval configuration, length: 4.75+/-2.8 μm and width: 3.28+/-0.20 μm, no extrusion or invagination and no vacuoles occupied more than 4% of the nuclear area) as well as acrosome, post-acrosomal lamina, neck, tail, besides not presenting a cytoplasmic droplet or cytoplasm around the head; 2-Abnormalities of nuclear form (a-Large/small; b-Wide/narrow; c-Regional disorder); 3-Abnormalities of nuclear chromatin content (a-Vacuoles: occupy >4% to 50% of the nuclear area and b-Large vacuoles: occupy >50% of the nuclear area) using a high magnification (8400x) microscopy system.

RESULTS

No significant differences were obtained with respect to sperm morphological forms and the groups HA-bound and HA-unbound. 1-Normal morphology: HA-bound 2.7% and HA-unbound 2.5% (P = 0.56). 2-Abnormalities of nuclear form: a-Large/small: HA-bound 1.6% vs. HA-unbound 1.6% (P = 0.63); b-Wide/narrow: HA-bound 3.1% vs. HA-unbound 2.7% (P = 0.13); c-Regional disorders: HA-bound 4.7% vs. HA-unbound 4.4% (P = 0.34). 3. Abnormalities of nuclear chromatin content: a-Vacuoles >4% to 50%: HA-bound 72.2% vs. HA-unbound 72.5% (P = 0.74); b-Large vacuoles: HA-bound 15.7% vs. HA-unbound 16.3% (P = 0.36).

CONCLUSIONS

The findings suggest that HA binding assay has limited efficacy in selecting motile spermatozoa with normal morphology at high magnification.

"Physiologic ICSI": hyaluronic acid (HA) favors selection of spermatozoa without DNA fragmentation and with normal nucleus, resulting in improvement of embryo quality

OBJECTIVE

To evaluate the role of hyaluronic acid (HA) for sperm selection before intracytoplasmic sperm injection (ICSI).

DESIGN

Three prospective studies.

SETTING

Private assisted reproduction center in Italy.

PATIENT(S)

Study 1: 20 men. Study 2: 15 men. Study 3: 206 couples treated with ICSI on a limited number of oocytes per patient (1-3) in accordance with Italian IVF law.

INTERVENTION(S)

Study 1: determination of sperm DNA fragmentation of HA-bound spermatozoa versus spermatozoa in polyvinylpyrrolidone (PVP). Study 2: assessment of nuclear morphology of HA-bound spermatozoa versus spermatozoa in PVP. Study 3: randomized study comparing conventional PVP-ICSI to ICSI in which the spermatozoa are selected for their capacity to bind to HA (HA-ICSI).

MAIN OUTCOME MEASURE(S)

Study 1: sperm DNA fragmentation rate. Study 2: sperm nucleus normalcy rate according to motile sperm organellar morphology examination criteria. Study 3: fertilization, embryo quality and development, and implantation and pregnancy.

RESULT(S)

Spematozoa bound to HA show a significant reduction in DNA fragmentation (study 1) and a significant improvement in nucleus normalcy (study 2) compared with spermatozoa immersed in PVP. Furthermore, injection of HA-bound spermatozoa (HA-ICSI) significantly improves embryo quality and development (study 3).

CONCLUSION(S)

Hyaluronic acid may optimize ICSI outcome by favoring selection of spermatozoa without DNA fragmentation and with normal nucleus. Furthermore, HA may also be used to speed up the selection of spermatozoa with normal nucleus during intracytoplasmic morphologically selected sperm injection (IMSI).