Oolemma characteristics in relation to survival and fertilization patterns of oocytes treated by intracytoplasmic sperm injection

Abstract

The aim of this study was to analyse the various reactions displayed by the oolemma to the penetrating pipette during intracytoplasmic sperm injection (ICSI) and correlate them with clinical factors, oocyte survival and fertilization patterns. Three types of oolemma responses were observed: normal breakage, when the injection needle created an invagination that ruptured at the approximate centre of the egg; sudden breakage, when the membrane broke without creating a funnel; and difficult breakage, when the membrane did not break or broke after several penetration attempts. A total of 2928 oocytes were analysed with the following observations: 73.9% (n = 2164) experienced normal breakage, 11.8% (n = 345) sudden breakage, and 14. 3% (n = 419) difficult breakage. The survival rate and number of normally fertilized oocytes were significantly lower and the incidence of digynic oocytes was significantly higher in the sudden breakage group; furthermore, in this group a significantly shorter length of stimulation was observed along with lower serum oestradiol concentrations when compared to oocytes experiencing normal and difficult breakage patterns. These recorded patterns were predictive of the survival and fertilization ability of the injected oocytes, as well as the incidence of digyny. The link between membrane behaviour and various clinical parameters appears to indicate a correlation between the modality of stimulation and oolemma characteristics.

An oocyte score for use in assisted reproduction

“…1b). For the consideration of injection parameters, we awarded three points to oocytes in which the ICSI pipette encountered some resistance and which the removal of the pipette left a visible 'funnel' for at least 30 s; oocytes in which a considerable amount of resistance was encountered before plasma membrane rupture were awarded two points and oocytes in which no resistance to the ICSI pipette was encountered were awarded one point ( [46], Fig. 1c).…”

“…Human oocytes may contain inclusions or vacuoles which may be detrimental to the implantation potential of this material [37,38,[41][42][43]. The oocyte plasma membrane response to penetration with an ICSI pipette has also been suggested to be a useful determinant of oocyte quality [46]. Many other parameters have also been analysed in oocytes such as zona pellucida thickness, spindle birefringence and extracellular dysmorphisms [36,47,48].…”

Estimating zona pellucida hardness under microinjection to assess oocyte/embryo quality: Analytical and experimental studies

“…Following this attempt, four years later, Palermo et al (1992) first reported human pregnancies after ICSI [2]. Since then, ICSI has progressively replaced the previous techniques of gamete micromanipulation as the treatment of choice in cases of male factor infertility and those of failed conventional IVF cycles [3]. Given the widespread use of ICSI, any modifications that can improve its clinical outcomes could possibly benefit a large segment of the patient population.…”

“…Although the efficiency of ICSI has been clearly demonstrated [2,4,5], this procedure is typically associated with the degeneration of a significant percentage of treated oocytes [2,3,6,7]. The main cause of this degeneration remains unclear.…”

“…Some researchers, such as Dumoulin et al (2001) and Ebner et al (2003) have speculated that severe mechanical stress during the unusual injection procedure may be responsible for oocyte degeneration [8,9]. However, on certain occasions, some oocytes show deviations from the presumed optimal ICSI due to a possible impairment in the elasticity of the ZP, which would normally allow the formation of a distinct funnel prior to puncture [3,6]. This is characterized by either sudden breakage or delayed penetration of the zona and is likely to result in increased gamete damage [3,6,8,9].…”