Insulin-like growth factor-1 improves in vitro meiotic resumption of dromedary camel (Camelus Dromedarius) oocytes

Abstract

Despite relatively high maturation rate of in vitro matured oocytes in the dromedary camel, however, blastocyst production is very low after in vitro fertilization (IVF). Herein, the influences of oocyte collection method (follicular aspiration vs slicing; Experiment I), the addition of Insulin-like growth factor I (IGF-I) to the maturation medium (Experiment II) on in vitro maturation (IVM) of oocyte were investigated. Although the nuclear maturation did not differ regardless of collecting method, follicular aspiration led to lower degeneration rates than those in controls (P < 0.05). The percentages of oocytes at MII were greater in the presence of IGF-1 than in its absence (71.9% vs 48.4%, respectively, P<0.05). Additionally, the percentages of degenerated oocytes were higher in the control group compared to oocytes cultured in the presence of IGF-I (23.6% vs 10.4%, respectively, P<0.05). IGF-I treatment improved the quality of MII matured oocytes as evidenced by the decrease of cathepsin B (CTSB) activity, a marker of poor quality oocytes, when compared to control ones (P < 0.05). In conclusion, follicular aspiration decreased the degeneration rate; however, it had no effect on completion of maturation. IGF-I enhanced the IVM of oocyte and decreased degeneration rate.

Keywords: IVM; camel; cathepsin B; insulin-like growth factor I; oocytes.

Figure 1. Collection of oocytes by follicular aspiration (A) or slicing with multiple blades (B).

Figure 2. Fluorescence photomicrographs show chromatin configuration in camel oocytes stained with propidium iodide (PI stain). (A) Immature oocyte having germinal vesicle; (B) Germinal vesicle break down; (C) Metaphase I; (D) Mature oocyte having metaphase II plate (MII) (white arrow) and a polar body (arrowhead); (E, F) Degenerated oocyte. (×400).

Figure 3. Effect of absence and presence of Insulin-like Growth Factor I (IGF-I) to IVM medium on cathepsin B (CTSB) activity in cumulus-oocyte complexes (COCs). Quantification of the relative fluorescence intensity of CTSB activity (A). CTSB were detected as red fluorescence dots (B). An excitation filter of 365 nm was used to detect nuclei, while an excitation filter of 550 nm was applied to observe CTSB activity. The relative fluorescence intensities of CTSB were measured using 44 and 49 COCs. *Asterisk indicates a significant difference between the groups (P < 0.01).