Enhancement of sperm-zona pellucida (ZP) binding capacity by activation of protein kinase A and C pathways in certain infertile men with defective sperm-ZP binding

Notoginsenoside R1 protects boar sperm during liquid storage at 17°C

Reactive oxygen species (ROS) damage mammalian sperm during liquid storage. Notoginsenoside R1 (NR1) is a compound isolated from the roots of Panax notoginseng; it has powerful ROS-scavenging activities. This work hypothesized that the antioxidant capacity of NR1 could improve boar sperm quality and fertility during liquid storage. During liquid storage at 17°C, the supplementation of semen extender with NR1 (50 μM) significantly improved sperm motility, membrane integrity and acrosome integrity after 5 days of preservation. NR1 treatment also reduced ROS and lipid peroxidation (LPO) levels at day 5 (p <0.05). Higher glutathione (GSH), superoxide dismutase (SOD), catalase (CAT) levels and sperm-zona pellucida binding capacity were observed in the 50 μM NR1 group than those in the control group at day 7 (p <0.05). Importantly, statistical analysis of the fertility of 200 sows indicated that addition of NR1 to the extender improved the fertility parameters of boar spermatozoa during liquid storage at 17°C (p <0.05). These results demonstrate the practical feasibility of using 50 μM NR1 as an antioxidant in boar extender during liquid storage at 17°C, which is beneficial to both spermatozoa quality and fertility.

Deficiency in Sperm-Egg Protein Interaction as a Major Cause of Fertilization Failure

Complete elucidation of fertilization process at molecular level is one of the unresolved challenges in sexual reproduction studies, and understanding the molecular mechanism is crucial in overcoming difficulties in infertility and unsuccessful in vitro fertilization. Sperm-oocyte interaction is one of the most remarkable events in fertilization process, and deficiency in protein-protein interactions which mediate this interaction is a major cause of unexplained infertility. Due to detection of how the various defects of sperm-oocyte interaction can affect fertilization failure, different experimental methods have been applied. This review summarizes the current understanding of sperm-egg interaction mechanism during fertilization and also accumulates the different types of sperm-egg interaction abnormalities and their association with infertility. Several detection approaches regarding sperm-egg protein interactions and the associated defects are reviewed in this paper.

Traditional intracytoplasmic sperm injection provides equivalent outcomes compared with human zona pellucida-bound selected sperm injection

The capability of human zona pellucida (ZP) to bind selectively to normal functional sperm with normal chromatin has been reported widely in the literature. The aim of this study was to evaluate whether ZP–binding sperm selection may represent a method to retrieve superior spermatozoa for intracytoplasmic sperm injection (ICSI). Patients were divided into two groups: a ZP-ICSI and a conventional ICSI group. In the ZP-ICSI group, spermatozoa for injection were selected after ZP–sperm incubation and spermatozoa that were tightly bound to the ZP were used for ICSI (ZP-ICSI). Clinical outcomes of ZP-ICSI were compared with the outcomes of traditional scientist-selected sperm injection (conventional ICSI). Results did not show any significant difference in fertilization, pregnancy, implantation and take-home-baby rates between conventional ICSI and ZP-ICSI. However, when data relative to patients who received ZP-ICSI were analyzed, an interesting result was observed: higher sperm concentration and morphology correlated with higher ZP–sperm binding. Additionally, patients with higher ZP–sperm binding seem to have improved pregnancy and take-home-baby rates. In conclusion, this study shows that ZP-ICSI is not a superior method compared with conventional ICSI. However, clinical ICSI outcomes were apparently improved in the presence of good ZP–sperm binding. We therefore speculate that sperm competence to ICSI could be reduced when the sperm's ability to bind the ZP is impaired.

Dynamic alterations in the expression and localization of ACTL7a during capacitation in mouse spermatozoa

OBJECTIVE

To demonstrate that capacitation in mouse spermatozoa involves alterations in the expression and localization of ACTL7a.

DESIGN

Determine the alteration in the expression level and localization of ACTL7a in the induction of capacitation in mouse spermatozoa.

SETTING

The Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences, Peking Union Medical College, People's Republic of China.

ANIMAL(S)

ICR (Institute of Cancer Research) mice.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Western blot, indirect immunostaining.

RESULT(S)

The expression of ACTL7a is upregulated via the PKA pathway and undergoes remodeling during the early period of capacitation in mouse spermatozoa.

CONCLUSION(S)

ACTL7a is an essential component of capacitation in mouse spermatozoa. The alteration in the expression and localization of ACTL7a may be the primary biochemical event in the induction of capacitation in mouse spermatozoa.

Defective protein kinase A and C pathways are common causes of disordered zona pellucida (ZP)--induced acrosome reaction in normozoospermic infertile men with normal sperm-ZP binding

OBJECTIVE

To determine association between defective protein kinases C (PKC) and A (PKA) and disordered zona pellucida (ZP)-induced acrosome reaction (DZPIAR) in normozoospermic infertile men with normal sperm-ZP binding.

DESIGN

Sperm from DZPIAR infertile men were treated without (control) or with (test) phorbol myristate acetate (PMA, PKC activator) or dibutyryl cyclic AMP (dbcAMP, PKA activator) under in vitro standard culture condition. The ZP-induced AR was assessed and compared between control and test.

SETTING

Public and private hospital-based clinical assisted reproduction technology (ART) centers.

PATIENT(S)

A total of 51 DZPIAR infertile men were involved in this study.

INTERVENTION(S)

None.

MAIN OUTCOMES MEASURE(S)

Sperm-ZP binding and the ZP-induced IAR.

RESULT(S)

Both PMA and dbcAMP enhanced ZP-induced AR up to a normal level (≥25%) in some subjects with DZPIAR: 29 (57%) with PMA and 27 (53%) with dbcAMP. Overall 35 (69%) had the ZP-induced AR enhanced to normal by PMA or dbcAMP but 16 (31%) had little or no response to either agent. Fourteen men responded to the two activators differently: 8 effective only with PMA and 6 effective only with dbcAMP.

CONCLUSION(S)

Defective upstream of PKC and PKA pathways are highly associated with disordered ZPIAR in normozoospermic infertile men with normal sperm-ZP binding.

Diagnostic tools in male infertility-the question of sperm dysfunction

Sperm dysfunction is the single most common cause of infertility, yet what is remarkable is that, there is no drug a man can take or add to his spermatozoa in vitro to improve fertility. One reason for the lack of progress in this area is that our understanding of the cellular and molecular workings of the mature spermatazoon is limited. However, over the last few years there has been considerable progress in our knowledge base and in addressing new methods to diagnose sperm dysfunction. We review the current state of the field and provide insights for further development. We conclude that: (i) there is little to be gained from more studies identifying/categorizing various populations of men using a basic semen assessment, where an effort is required in making sure the analysis is performed in an appropriate high quality way; (ii) technological development is likely to bring the reality of sperm function testing closer to implementation into the clinical pathways. In doing this, these assays must be robust, cheap (or more appropriately termed cost effective), easy to use and clinically useful; and (iii) clinical necessity, e.g., the need to identify the highest quality spermatozoon for injection is driving basic research forward. This is an exciting time to be an andrologist and, likely, a fruitful one.

Delineation of downstream signalling components during acrosome reaction mediated by heat solubilized human zona pellucida

BACKGROUND

Human egg is enveloped by a glycoproteinaceous matrix, zona pellucida (ZP), responsible for binding of the human spermatozoa to the egg and induction of acrosomal exocytosis in the spermatozoon bound to ZP. In the present manuscript, attempts have been made to delineate the downstream signalling components employed by human ZP to induce acrosome reaction.

METHODS

Heat-solubilized human ZP (SIZP) was used to study the induction of acrosome reaction in capacitated human spermatozoa using tetramethylrhodamine isothiocyanate conjugated Pisum sativum agglutinin (TRITC-PSA) in absence or presence of various pharmacological inhibitors. In addition, intracellular calcium ([Ca2+]i) levels in sperm using Fluo-3 acetoxymethyl ester as fluorescent probe were also estimated in response to SIZP.

RESULTS

SIZP induces acrosomal exocytosis in capacitated human sperm in a dose dependent manner accompanied by an increase in [Ca2+]i. Human SIZP mediated induction of acrosome reaction depends on extracellular Ca2+ and involves activation of Gi protein-coupled receptor, tyrosine kinase, protein kinases A & C and phosphoinositide 3 (PI3)- kinase. In addition, T-type voltage operated calcium channels and GABA-A receptor associated chloride (Cl-) channels play an important role in SIZP mediated induction of acrosome reaction.

CONCLUSIONS

Results described in the present study provide a comprehensive account of the various downstream signalling components associated with human ZP mediated acrosome reaction.