Sericin accelerates the production of hyaluronan and decreases the incidence of polyspermy fertilization in bovine oocytes during in vitro maturation

Antioxidant sericin averts the disruption of oocyte-follicular cell communication triggered by oxidative stress

Antioxidants are free radical scavengers that increase oocyte quality and improve female fertility by suppressing oxidative stress. However, the related mechanisms remain unclear. The present study was designed to examine whether a reduction of oxidative stress from using the antioxidant sericin led to expanded cumulus cell (CC)-oocyte communication and oocyte developmental acquisition in a bovine model. We found that cumulus-oocyte complexes (COCs) matured in the presence of sericin showed a significantly increased oocyte meiotic maturation rate (P < 0.01) and accelerated subsequent blastocyst formation, as more blastocysts were found at the hatched stage (P < 0.05) compared to that in the control group. In contrast to the control group, sericin suppressed H2O2 levels in COCs, resulting in a markedly enhanced CC-oocyte gap junction communication index and number of transzonal projections, which were preserved until 18 h of oocyte maturation. These findings indicate that sericin reduces disruption of oocyte-follicular cell communication induced by oxidative stress. Sericin consistently increased intra-oocyte glutathione (GSH) levels and reduced oocyte H2O2 levels (P < 0.05), both of which were ablated when GSH synthesis was inhibited by buthionine sulfoximide (an inhibitor of GSH synthesis). Furthermore, the inhibition of GSH synthesis counteracted the positive effects of sericin on subsequent embryo developmental competence (P < 0.01). Intra-oocyte GSH levels were positively associated with blastocyst development and quality. These outcomes demonstrate new perspectives for the improvement of oocyte quality in assisted reproductive technology and may contribute to developing treatment strategies for infertility and cancer.

Effects of individual or in-combination antioxidant supplementation during in vitro maturation culture on the developmental competence and quality of porcine embryos

The oocyte maturation process requires a high supply of energy, which generates reactive oxygen species (ROS), adversely affecting oocyte and embryo development. Balancing ROS by antioxidant supplementation is essential for maintaining oocyte maturation and embryonic quality in vitro. This study aimed to evaluate the impact of four antioxidants: β-mercaptoethanol (β-ME), chlorogenic acid (CGA), curcumin and sericin, when applied individually or in combinations, during oocyte maturation on development of porcine oocytes. Cumulus-oocyte complexes were collected, cultured in maturation medium supplemented with antioxidants for 44 hr and subsequently subjected to in vitro fertilization (IVF) and culture for 7 days. Combining all four (β-ME + CGA + curcumin + sericin) or three (β-ME + CGA + curcumin) antioxidants increased blastocyst formation rates. However, sericin supplementation alone, or in combination with β-ME or CGA, failed to improve blastocyst formation rates. The total cell numbers of blastocysts from the group supplemented with three antioxidants (β-ME + CGA + curcumin) were significantly higher than those from the other groups, except for the curcumin-supplement group. There were no differences in the maturation rates and proportions of oocytes with fragmented DNA between the antioxidant-supplemented and the non-supplemented control groups. In conclusion, supplementation with three antioxidants (β-ME + CGA + curcumin) during the maturation culture enhanced blastocyst formation and improved blastocyst quality.

The effects of supplemented sericin on in vitro maturation and preimplantation development of mouse embryos: An experimental study

Background

Mouse embryo culture condition is an essential part of transgenic, reproductive and developmental biology laboratories. Mouse embryonic culture media may have a high risk of serum contamination with pathogens.

Objective

To investigate the effect of sericin as an embryo culture medium supplement on in vitro maturation (IVM), in vitro fertilization (IVF), and development of the preimplantation embryo in mice.

Materials and Methods

The effects of sericin at three concentrations (subgroups) of 0.1%, 0.5%, and 1% as a medium supplement on IVM, IVF, and in vitro development of mouse embryos were separately investigated and compared with a sericin-free (control) group. The cumulative effect of the three concentrations was evaluated for IVM + in vitro development and IVF + in vitro development as follow-up groups.

Results

In the IVM group, compared to the control group, the number of oocysts reaching the MII stage was significantly higher when 1% sericin was used (161/208 = 77.4%). No significant results were observed in the IVF and in vitro development groups with different concentrations of sericin compared to the control group. Among the follow-up groups, in the IVM + in vitro development group, the number of oocytes was higher after passing the IVM and IVF and reaching the blastocysts stage when 1% sericin was used, compared with other sericin subgroups. A significant difference was also noted when compared with the control group (p = 0.048). The IVF + in vitro development study group, on the other hand, did not show any significant relationship.

Conclusion

It can be concluded that 1% sericin can be used as a supplement in mouse embryo cultures to improve the IVM rate. Also, based on the findings, sericin appears to be an effective supplement which can have a positive effect on the development of embryos derived from IVM.

The effects of sericin on cryopreserved sperm cells and subsequent embryo development in mice

BACKGROUND

Sericin, because of its ability to remove free radicals and its antioxidant properties, has been used to successfully cryopreserve various mammalian cell types. However, the effects of sericin on cryopreservation of mouse sperm has not been reported.

OBJECTIVE

The current study intended to determine the protective role of different concentrations of sericin (0, 0.25, 0.5, and 0.75%) on mouse spermatozoa during cryopreservation, in addition to its effect on in vitro fertilization and subsequent embryo development.

MATERIALS AND METHODS

Mouse sperm from epididymides were frozen in cryoprotective agent with 18% raffinose, 3% skim milk, and different concentrations of sericin (0, 0.25, 0.5, 0.75%). Thawed sperm were used for in vitro fertilization. The obtained embryos were cultured in Ksom medium for 6 days. The post-thawed motility, viability, fertilizing ability, and subsequent development to the 2-cell embryo and blastocyst stages were evaluated.

RESULTS

Our findings show that frozen-thawed sperm cells with 5% sericin indicate significantly (p≤0.0001) percentages of survivability and motility, the best fertilizing ability, as well as 2-cell embryo and blastocyst development compared to the other treated groups. There was no significant difference in survivability (p=0.8781), fertilizing ability (p=0.2458) and development of 2-cell (p=0.5136) and blastocysts embryos (p=0.0896) between 0.75% sericin and control groups.

CONCLUSION

Supplementation by 0.5% sericin in cryoprotective agent improved frozen-thawed mouse epididymal sperm cell quality and resulted in increased embryo development.

Effect of supplemented sericin on the development, cell number, cryosurvival and number of lipid droplets in cultured bovine embryos

Sericin was investigated as an alternative to fetal bovine serum (FBS) for bovine embryo culture. In vitro matured oocytes were developed using 0.05%, 0.1% or 0.15% sericin. The developmental rate, cryosurvival rate and blastulation time of these embryos were compared with those of embryos developed using 5% FBS. The number of lipid droplets was compared among the blastocysts developed using 5% FBS, using 0.05% sericin and in vivo. The rate of cleavage and blastocyst formation was similar among all groups. Blastulation occurred significantly earlier in the embryos developed using 5% FBS than in those developed using sericin at any concentration (P < 0.05). At 72 h after thawing, the cryosurvival rate of the blastocysts developed using 5% FBS and 0.05% sericin were significantly higher compared with those developed using 0.1% and 0.15% sericin (P < 0.05). The blastocysts developed using 0.05% sericin and in vivo produced a significantly fewer number of medium and large lipid droplets than those developed using 5% FBS. These results suggest that the blastocysts developed using 0.05% sericin show characteristics similar to those of the blastocysts developed in vivo and that the use of sericin as an alternative to FBS is feasible.

Processing and characterization of silk sericin from Bombyx mori and its application in biomaterials and biomedicines

Bombyx mori silk is composed of 60-80% fibroin, 15-35% sericin and 1-5% non-sericin component including wax, pigments, sugars and other impurities. For two decades, the protein-based silk fibroin was extensively used in the research and development of medical biomaterials and biomedicines. Sericin is frequently ignored and abandoned as a byproduct or waste in the processing of traditional silk fabrics, silk floss or modern silk biomaterials. However, similar to fibroin, sericin is not only a highly useful biological material, but also a lot of biological activity. Moreover, the non-sericin component present with sericin in the cocoon shell also has a strong biological activity. In this review, the extraction and recovery methods of sericin and the non-sericin component from the cocoon layer are reported, and their composition, properties and biological activity are described to produce a comprehensive report on biomedical materials and biological drugs. In addition, related problems or concerns present in the research and development of sericin are discussed, and a potential application of sericin in sustainable development is also presented.

Effect of sericin supplementation in maturation medium on cumulus cell expansion, oocyte nuclear maturation, and subsequent embryo development in Sanjabi ewes during the breeding season

The purpose of this study was to evaluate the effect of sericin with different concentrations (0% [control], 0.1%, 0.5%, 1.0%, and 2.5%) added to the IVM medium on cumulus cell expansion, oocyte nuclear maturation, and subsequent embryo development in Sanjabi ewes during the breeding season. The resumption of meiosis was assessed by the frequency of germinal vesicle breakdown and the first polar body extrusion. After IVF with fresh ram semen, presumptive zygotes were cultured 8 days in potassium simplex optimization medium supplemented by amino acids, and the percentages developing to the two-cell and blastocyst stages were measured as the indicators of early embryonic developmental competence. More cumulus-oocyte complexes matured with 0.5% sericin underwent germinal vesicle breakdown and reached metaphase II stage compared with the control cumulus-oocyte complexes matured without sericin (P ≤ 0.05). The present findings indicated that supplementation with 0.5% sericin during the maturation culture may improve the nuclear maturation and the cumulus cell expansion. Furthermore, the percentage of blastocysts obtained from 0.5% and 0.1% sericin (37.8 ± 1.76% and 34.8 ± 1.09%, respectively) was higher (P ≤ 0.05) than that of the control medium (29.60 ± 1.67%). However, addition of 1% and 2.5% of sericin to the IVM medium oocytes had a negative effect on nuclear maturation and cumulus cell expansion. Furthermore, the percentage of cleavage and blastocyst rate was significantly lower in the 1% and 2.5% sericin groups than in the control group. These findings showed that supplementation of IVM medium with 0.5% sericin may improve the meiotic competence of oocytes and early embryonic development in Sanjabi ewes during the breeding season.

Synthesis of PAMAM dendrimer-based fast cross-linking hydrogel for biofabrication

Hydrogels possess great potential in biofabrication because they allow cell encapsulation and proliferation in a highly hydrated three-dimensional environment, and they provide biologically relevant chemical and physical signals. However, development of hydrogel systems that mimic the complexity of natural extracellular matrix remains a challenge. In this study, we report the development of a binary hydrogel system containing a synthetic poly(amido amine) (PAMAM) dendrimer and a natural polymer, i.e., hyaluronic acid (HA), to form a fast cross-linking hydrogel. Live cell staining experiment and cell viability assay of bone marrow stem cells demonstrated that cells were viable and proliferating in the in situ formed PAMAM/HA hydrogel system. Furthermore, introduction of a Arginylglycylaspartic acid (RGD) peptide into the hydrogel system significantly improved the cell viability, proliferation, and attachment. Therefore, this PAMAM/HA hydrogel system could be a promising platform for various applications in biofabrication.

Maturation and fertilisation of sheep oocytes cultured in serum-free medium containing silk protein sericin

Sericin is a water-soluble component of silk and has been used as a biomaterial due to its antibacterial and ultraviolet radiation-resistant properties. This study was designed to evaluate the effect of sericin supplementation in a maturation medium on the meiotic competence and fertilisability of sheep oocytes. Cumulus-oocyte complexes (COCs) were cultured in TCM199 supplemented with sericin at various concentrations of 0 (control), 0.1, 0.25 and 0.5%, either with or without bovine serum albumin (BSA). When the COCs were matured without BSA, the supplementation of 0.1% sericin significantly increased the rates of maturation to metaphase II and the total fertilisation of oocytes compared with the other concentrations of sericin. When the COCs were matured with BSA, the beneficial effects of 0.1% sericin supplementation on the maturation and fertilisation of oocytes were not observed. Our findings indicate that supplementation with 0.1% sericin during maturation culture may improve the nuclear maturation and fertilisability of sheep oocytes. Moreover, it may be possible to replace BSA with sericin in chemically defined media without the risk of disease transmission.