FRI459 Sperm-Carried IGF2: Towards The Discovery Of The Spark That Gives Rise To Life

Abstract

Abstract Disclosure: R. Cannarella: None. O.J. Rando: None. S. Chamayou: None. S. La Vignera: None. R.A. Condorelli: None. A.E. Calogero: None. Background. Infertility is a public health problem affecting 15% of couples of childbearing age. In half of the cases, the male factor is a primary or contributing cause. Unfortunately, despite a comprehensive diagnostic workup, the causes of male infertility remain unclear in a large percentage of cases, thus suggesting the urgent need for further research. Spermatozoa have now been shown to carry key RNAs that may play critical roles in the development of the embryo. In this contest, a potential key growth regulator is insulin-like growth factor 2 (IGF2) whose gene is highly conserved and paternally imprinted. The gene encoding for IGF2 is involved in growth and proliferation and we have already demonstrated that it is expressed in human spermatozoa (DOI: 10.3389/fendo.2022.1010796). Aim. To evaluate the impact of sperm-carried IGF2 on early embryo growth kinetics and gene expression. Materials and methods. Patients undergoing intracytoplasmic sperm injection (ICSI) for idiopathic or male factor infertility were enrolled. Couples with female factor infertility were excluded. Following clinical practice, an aliquot of the left-over semen samples used for ICSI was used to analyze the IGF2 mRNA levels. The kinetic parameters of each embryo development were recorded and correlated with the amount of IGF2 mRNA measured in the same swim-up spermatozoa used for ICSI. Transcriptome analysis of blastocyst obtained from parthenotes collected from twelve-week-old superovulated mice was performed after incubation with recombinant human IGF2 (rhIGF2) protein (Group 1, n=40) or vehicle (Group 2, n=40) or injection with Igf2 plus Gfp (encoding for a fluorescent protein) mRNAs (Group 3, n=20) or Gfp mRNA only (Group 4, n=20). Results. In total, 16 patients were enrolled and 131 embryos were collected. We found a significant negative correlation between sperm IGF2 mRNA levels and pronucleus fading time (tPN) (r= -0.2572, p= 0.0078, n=106 embryos) and between sperm IGF2 mRNA and time of 2-cell embryo (t2) (r= -0.2368, p= 0.0145, n=106 embryos). In contrast, sperm IGF2 mRNA levels did not correlate with t3, t4, t5, t6, t7, t8, t9, t morula (tM), t blastocyst (tB), and time of expanded blastocyst (tEB). On transcriptome analysis, 501 and 101 genes were differentially expressed between Group 1 and Group 2, and between Group 3 and Group 4, respectively. Pathway enrichment analysis revealed several differentially expressed genes that trigger embryo growth and development, endoderm and mesoderm differentiation, angiogenesis, and sustaining proliferative signaling. Conclusions. Sperm-carried IGF2 triggers the expression of genes involved in early embryo development and improves embryo kinetics. This evidence may shed light on the etiology of apparently idiopathic couple infertility, since low sperm-carried IGF2 levels may be responsible for the impairment of early embryo growth and development. Presentation Date: Friday, June 16, 2023