Cold Shock Protein B as an Alternative to DMSO for Oocyte Vitrification

Area of Science:

• Reproductive Biology
• Cryobiology
• Biochemistry

Background:

• Dimethyl sulfoxide (DMSO) is a common cryoprotectant for oocyte vitrification but causes toxicity.
• DMSO's concentration-dependent toxicity can impair oocyte developmental potential.
• There is a need for safer alternatives to DMSO in oocyte cryopreservation.

Purpose of the Study:

• To investigate the potential of cold shock protein B (CspB protein) as a DMSO substitute in oocyte vitrification.
• To evaluate CspB protein's efficacy in preventing ice crystallization and improving oocyte survival and developmental competence.
• To elucidate the molecular mechanisms underlying CspB protein's cryoprotective effects.

Main Methods:

• Molecular dynamics simulations to assess CspB protein's interaction with ice.
• Experimental validation of CspB protein expression, binding to oolemma, and ice inhibition.
• Oocyte vitrification using CspB protein-supplemented solutions and assessment of post-thaw survival, developmental rates, oxidative stress, mitochondrial function, and apoptosis.
• Transcriptomic analysis to identify CspB protein-mediated signaling pathways.

Main Results:

• CspB protein effectively inhibits ice crystallization and recrystallization by stabilizing the ice-water interface.
• Vitrification solutions with CspB protein (1-2 mg/mL) significantly reduced or replaced DMSO, improving mouse and bovine oocyte survival rates.
• Oocytes vitrified with an optimized CspB protein formulation (15% ethylene glycol + 2 mg/mL CspB) showed developmental competence comparable to DMSO-treated oocytes.
• CspB protein's cryoprotective mechanism involves modulating the mTOR signaling pathway, regulating oxidative stress, mitochondrial function, and apoptosis.

Conclusions:

• CspB protein serves as an effective, non-toxic alternative to DMSO in oocyte vitrification.
• This protein-based cryoprotection strategy enhances oocyte survival and developmental potential.
• CspB protein's mechanism involves direct ice inhibition and mTOR-mediated regulation of cellular stress responses.
• This approach offers a promising advancement for reproductive biotechnologies across species.