9233 Sperm-carried IGF2: a Spark Contributing To Embryo Growth And Development
Authors: Cannarella Rossella , Rando Oliver J , Condorelli Rosita A , Sandrine Chamayou , Romano Simona , Guglielmino Antonino , Yin Qiangzong , Gustafsson Hans Tobias , Mancuso Francesca , Bellucci Catia , Luca Giovanni , La Vignera Sandro , Calogero Aldo E 
Published: October 2024

Disclosure: R. Cannarella: None. O.J. Rando: None. R.A. Condorelli: None. C. Sandrine: None. S. Romano: None. A. Guglielmino: None. Q. Yin: None. H. Gustafsson: None. F. Mancuso: None. C. Bellucci: None. G. Luca: None. S. La Vignera: None. A.E. Calogero: None.

Background: Sperm RNAs can regulate early embryo development. A potential key regulator of growth is insulin-like growth factor 2 (IGF2), a highly conserved paternally-imprinted gene involved in cell growth and proliferation that is expressed in human spermatozoa. Animal research supports the positive impact of IGF2-supplemented cultures on embryo quality. However, the role of sperm-carried IGF2 in the early development of the human embryo is unknown. Objective: To study whether sperm-carried IGF2 mRNA influences the morphokinetics of the human embryo. Design: Prospective, uncontrolled, observational pilot study. Setting: University-affiliated fertility center. Subjects: We enrolled 16 patients undergoing assisted reproductive techniques (ART) for idiopathic or male factor infertility and 10 healthy fertile controls with proven paternity. Couples with female factor infertility due to reduced oocyte reserve were excluded, while those with tubal factor or anovulation were included. Main Outcome Measure(s): After clinical use, an aliquot of the sperm samples employed for ART was used to evaluate IGF2 mRNA levels. Embryo kinetics were recorded and correlated with the amount of IGF2 mRNA, correcting for female age, body mass index (BMI), anti-Müllerian hormone (AMH) levels, and oocyte quality. To provide mechanistic insights into the human data, a transcriptome analysis was performed of parthenotes obtained from twelve-week-old superovulated mice injected with Igf2 mRNA plus Gfp mRNA (experimental group, n=20) or Gfp mRNAs (control group, n=20). Pathway enrichment analysis was then performed using g:Profiler g:GOSt and EnrichR. Results: Sperm IGF2 mRNA negatively correlated with time to 2-cell stage (t2), t3, t4, t5, and time to expanded blastocyst (tEB), independently of maternal age, BMI, AMH, and oocyte quality. IGF2 mRNA index &gt;4.9 predicted the ability of the embryo to reach the blastocyst stage at day 5, with a sensitivity of 100% and specificity of 71.6% (AUC 0.845; p&lt;0.001). The distribution of sperm IGF2 levels differs significantly between morphologically good or poor embryos, with the lowest levels more frequently associated with morphologically poor embryos (61.9%) than with good ones (38.1%) (p=0.0091). Furthermore, sperm-derived IGF2 levels were significantly lower in subfertile men compared to fertile controls with proven paternity. Transcriptome analysis of Igf2-injected embryos demonstrated differential expression of 101 genes activating pathways regulating early embryo development. Conclusion: Sperm-carried IGF2 mRNA can support early embryo development, independently of female factors. Larger studies are needed to confirm this finding and to investigate its role as a clinical marker to predict the chances of obtaining blastocysts that can be implanted in infertile couples undergoing ART.