Chitosan is a partially deacetylated polymer obtained from the alkaline deacetylation of chitin, which is a glucose-based unbranched polysaccharide widely distributed in nature as the main component of exoskeletons of crustaceans and insects. Chitosan has a variety of physicochemical and biological properties resulting in numerous applications. In addition to its lack of toxicity and allergenicity, its biocompatibility, biodegradability, and bioactivity make it a very attractive substance for diverse applications as a biomaterial in pharmaceutical and medical fields. Chitosan stimulates cell growth and it has been used in fibroblast culture, increasing cell proliferation. For these reasons, it is important to evaluate if this polymer has a positive effect on embryo production. The aim of this study was to evaluate porcine oocyte maturation and embryo development, comparing the effect of supplementing different concentrations of chitosan to the maturation (MM) and development media (DM). Cumulus-oocyte complexes (COC) were aspirated from ovarian follicles of slaughtered sows. The COC were matured in supplemented TCM-199 (MM) and incubated for 44 h. All incubations were performed at 38.5°C, with 5% CO2 in air and humidity at saturation. After maturation IVF was performed, frozen-thawed semen from the same boar was used and gametes were co-incubated in MTBM for 7 h. Then, putative zygotes were cultured in NCSU-23 (DM) for 144 h. The following experiments were performed: 1) addition of 0 (control), 35, 50, 100, and 150 ppm chitosan to the MM (n = 1353), 2) addition of 0, 50, 100, and 150 ppm chitosan to the DM (n = 739), 3) addition of 0, 50, 100, and 150 ppm of chitosan to the MM first and then the same concentrations to the DM (n = 702). When chitosan was added to the MM, the highest percentage of matured oocytes (metaphase II) was obtained in the 50 ppm treatment (87%, P < 0.05) when compared with the control, 100, and 150 ppm groups (78, 78, and 82%, respectively). Regarding the percentage of blastocysts, there were no differences when comparing the treatment and the control groups (ranging from 12 to 13%). After addition of chitosan to the putative zygotes in the DM, the percentage of morulae in the 150 ppm treatment was significantly increased with regard to the other groups (54 v. 46%, respectively, P < 0.05). When adding chitosan to both MM and DM, there was no effect on embryo development. It is concluded that the addition of chitosan to the MM at a concentration of 50 ppm significantly improved oocyte maturation and a concentration of 150 ppm in the DM increased the percentage of morulae. Chitosan had a positive effect on oocyte maturation and embryo development. These results justify further investigations to find out if chitosan can be useful as a supplement for chemically defined media.
Peer Review #2 of "Elevation of MPF and MAPK gene expression, GSH content and mitochondrial distribution quality induced by melatonin promotes porcine oocyte maturation and development in vitro (v0.1)"
