Does hyaluronan improve embryo implantation?

PURPOSE OF REVIEW: Taking into consideration the increasing interest on hyaluronan and its biological as well as physiological properties, this review will focus on the role of this molecule in human embryo implantation. RECENT FINDINGS: Several studies have been performed up to date in order to assess whether the addition of hyaluronan in the human embryo culture system can improve pregnancy and implantation rates, including one retrospective and six randomized controlled trials. On the one hand, four of those studies showed significant increase in clinical pregnancy and/or implantation rates after using embryo transfer medium containing high concentration of hyaluronan. On the other hand, three studies did not demonstrate any significant improvement in clinical pregnancy and implantation rates. However, regardless of statistical significance, almost all studies demonstrate higher pregnancy and implantation rates after using embryo transfer medium containing high concentration of hyaluronan. SUMMARY: Up to date, the results regarding the role of hyaluronan in human embryo implantation are still conflicting and, thus, further prospective randomized clinical trials are necessary to draw solid conclusions.

Cryopreservation of human embryos by vitrification or slow freezing: a systematic review and meta-analysis.

OBJECTIVE: To examine the literature systematically in order to identify prospective comparative trials answering the following question: Is vitrification of human embryos associated with a higher postthawing survival rate as compared with slow freezing? DESIGN: Systematic review and meta-analysis. SETTING: University-based hospital. PATIENT(S): Not applicable. INTERVENTION(S): Vitrification versus slow freezing for cryopreservation of human embryos. MAIN OUTCOME MEASURE(S): Postthawing survival rate. RESULT(S): Four eligible studies were identified, three of which were randomized controlled trials. Overall, the current review summarizes information from 8,824 cryopreserved human cleavage stage embryos/blastocysts (vitrification: n = 7,482; slow freezing: n = 1,342). Survival rate of cleavage stage embryos was significantly higher after vitrification as compared with slow freezing (odds ratio 15.57, 95% confidence interval 3.68-65.82; random effects model). Postthawing survival rate of vitrified blastocysts was significantly higher compared with that observed with slow freezing (odds ratio 2.20, 95% confidence interval 1.53-3.16; fixed effects model). CONCLUSION(S): Vitrification appears to be associated with a significantly higher postthawing survival rate than slow freezing. Further prospective trials are necessary to confirm the above results and, in addition, allow the evaluation of the two cryopreservation methods in terms of pregnancy achievement.

Evaluation of a transfer medium containing high concentration of hyaluronan in human in vitro fertilization.

OBJECTIVE: To examine whether a high concentration of recombinant hyaluronan in the embryo transfer (ET) medium can influence pregnancy rates in humans. DESIGN: Retrospective, matched group study. SETTING: Private and university hospital in vitro fertilization (IVF) units. PATIENT(S): Couples undergoing IVF or intracytoplasmic sperm injection (ICSI) were divided in two groups. In group 1 (402 patients), ET was performed with an ET medium containing a high concentration of recombinant hyaluronan in the presence of recombinant human serum albumin (HSA). In group 2 (425 couples), ET was performed with a medium containing a lower concentration of hyaluronan and HSA. INTERVENTION(S): IVF and ICSI. MAIN OUTCOME MEASURE(S): The two groups were compared for pregnancy rates according to the woman's age, the technique used (IVF or ICSI), the number of embryos transferred, and the day of ET. RESULT(S): Between the two groups, no statistically significant differences were observed in the total pregnancy rates after IVF or ICSI. Similarly, the pregnancy rates did not differ between the two groups when subdivided according to the woman's age, the number of embryos transferred (one to four), or the day of ET (2, 3, or 5 after oocyte pick up). CONCLUSION(S): The use of an ET medium with a high concentration of hyaluronan does not appear to have any statistically significant effect on pregnancy rates.

The effects of sperm quality on embryo development after intracytoplasmic sperm injection.

PURPOSE: To explore the possible relationship between sperm quality and embryo development, pregnancy and implantation rates, in patients undergoing intracytoplasmic sperm injection (ICSI). METHODS: Fertilization and cleavage rates, quality of embryos, blastocyst development, pregnancy and implantation rates were analyzed in 1020 embryos from 219 couples undergoing first ICSI treatment cycle. The couples were allocated in five groups, according to semen parameters: Group 1: patients with normal semen parameters, Group 2: patients with mild oligo-astheno-teratozoospermia, Group 3: patients with severe oligo-astheno-teratozoospermia, Group 4: patients with obstructive azoospermia, Group 5: patients with non-obstructive azoospermia. RESULTS: Fertilization and cleavage rates, quality of embryos as well as blastocyst development rates were significantly reduced, as semen quality decreased. However, no significant differences were observed in clinical pregnancy and implantation rates. CONCLUSION: Overall, a negative relationship was observed between semen quality and embryo development, even before activation of the embryonic genome, suggesting that sperm can affect embryogenesis from a very early stage.