O-206 Growth hormone supplementation reduces aneuploidy and improves the quality of aged oocytes by activating the JAK2-ERK1/2 pathway
Authors: Luo Y , Li J , Huang G 
Published: June 2023

Abstract

Study question
Does growth hormone (GH) supplementation improves the quality of oocytes in aged mice via reducing aneuploidy?

Summary answer
Daily injections of GH for 8 weeks reduces aneuploidy by activating JAK2-ERK1/2 pathway and improves the quality of oocyte in aged mice.

What is known already
Aging-induced low-quality oocytes, which are mainly caused by aneuploidy, decrease female fertility. However, few treatments are available to improve the poor quality of oocytes in aged women. Age-related decline in GH levels may be related to the insufficient reproductive potential in aged women. Several studies have reported that GH improves assisted reproductive technology outcomes in poor ovarian response patients, although its role is still controversial. In animal models, GH supplementation improved the oocyte quality by enhancing mitochondrial function. However, whether GH reduces the aneuploidy rate in aged oocytes, and if so the underlying mechanisms, are unclear.

Study design, size, duration
The aged (8-month-old) C57BL/6J female mice were used in the study. For the in vivo experiments, the aged mice were intraperitoneally injected with GH (GenSci, Changchun, China; 1.6 mg/kg body weight) or an equivalent volume of normal saline for 8 weeks; For the in vitro experiments, germinal vesicle (GV) oocytes from aged mice were treated with GH (200 ng/mL) or PBS in M16 medium.

Participants/materials, setting, methods
We counted oocytes by immunohistochemistry to assess ovarian reserve. The expression of growth hormone receptor and mitochondrial genes were measured by quantitative real-time PCR. Time–lapse incubator was utilized to record the developmental potential of early embryos. Immunofluorescence was performed to assess parameters of oocyte quality (mitochondrial functions, spindle/chromosome defects, and DNA damage). Chromosome spread and DNA sequencing were used to analyze aneuploidy rate. We performed quantitative proteomics analysis to identify the potential targets of GH.

Main results and the role of chance
Firstly, we found that GH promoted GHR expression in aged oocytes (30.64±1.70 vs 21.68±1.08, P &lt; 0.001). GH ameliorated aging-induced decline in ovarian reserve of aged mice, with increased ovarian index (0.040%±0.0031 vs 0.023%±0.0019, P &lt; 0.01), and number of antral follicles (8.67±1.2 vs 3.33±0.88, P &lt; 0.05) compared to the controls. In addition, GH improved the quality of aged oocytes, representing restored mitochondrial functions (P &lt; 0.05), decreased DNA damage (23.37±1.76 vs 38.35±2.52, P &lt; 0.001) . As expected, GH promoted the fertilization rate (39.9%±1.10 vs 14.4%±0.62, P &lt; 0.001) and early embryo development (P &lt; 0.01) of aged oocytes. Of note, GH recovered the spindle/chromosome defects (42.6%±2.12 vs 63.9%±1.83, P &lt; 0.01, and reduced aneuploidy rate (20.9%±1.61 vs 39.3%±1.84, P &lt; 0.01) in aged oocytes. GH activated ERK1/2 expression to decrease aneuploidy rate in aged oocytes. In addition, JAK2 might be involved in the regulation of GH on ERK1/2 expression in aged oocytes. Altogether, GH restored age-related decline in oocyte number, and decreased the occurrence rate of aneuploidy by activating JAK2-ERK1/2 pathway, thereby improving the quality of aged oocytes.

Limitations, reasons for caution
The molecular action mechanism of GH to regulate aneuploidy remains to be determined. Besides, future work should be extended to human oocyte to determine whether this mechanism is conserved between mice and humans

Wider implications of the findings
Our work expounds a theoretical basis for application of GH to improve the fertility of aged women. Besides, the results also feed new ideas for the prevention and treatment of oocyte quality decline in assisted reproductive technology.

Trial registration number
not applicable