Cryopreservation

A brief review of the methodology and cryoprotectants in selected fish and mammalian species

Cryopreservation is a valuable technique used to assist in the genetic improvement of cultured stocks and provide a continuous supply of good-quality semen for artificial insemination. Conserving semen by cryopreservation serves several purposes (e.g. artificial reproductive technologies and species conservation) and is also used in the clinical treatment of human infertility. However, the lifespan of cryopreserved semen is influenced by a range of factors, including storage temperature, cooling rate, chemical composition of the extender, the concentration of cryoprotectant, reactive oxygen species, seminal plasma composition and hygienic control. The choice of cryoprotectant is a vital factor underlying the success of animal semen cryopreservation. In this regard, extensive research has been carried out on various cryoprotectants, such as egg yolk, dimethyl sulfoxide, methanol, ethylene glycol and dimethylacetamide. Recent studies have also described the use of a range of new cryoprotectants for cryopreservation, including compounds of plant origin (soy), amino acids, antifreeze proteins, carbohydrates and cyclodextrins. Moreover, semen cryopreservation and storage require the use of liquid nitrogen or ultralow refrigeration methods for both long- and short-term storage. This review summarizes the general methods used for freezing semen and discusses the use of traditional and newly emerging cryoprotectants (permeable and non-permeable) for the cryopreservation of semen in selected fish and mammalian species.

A systematic review and meta-analysis of spermatozoa cryopreservation, in vitro and in vivo fertility practices in water buffalo

We explored different aspects of buffalo spermatozoa during cryopreservation. The meta-data comprised of 285 studies, published from January 2008 to March 2020. A free web tool CADIMA as well as PRISMA 2009 Flow Diagram were used for carrying out this study. The inter-reviewer agreement among studies allocated was satisfactory for criteria A (selection bias), B (performance bias), C (detection bias) and D (attrition bias), respectively. India led the percent (%) research ladder with 34.4, followed by Pakistan (29.5), Egypt (12.3), Iran (7.7), Italy (5.6), Indonesia (3.2), China (2.1), Brazil (1.4), Thailand (1.1), Philippines and Bulgaria (0.7 each), Saudi Arabia, Turkey, Vietnam, and USA (0.4 each). Among four categories of studies, Group-1 evaluated only supplements/additives/media in the freezing semen extender (n = 191/285; 67.02%); Group-2 conducted in vivo fertilization (n = 62/285; 21.75%) and Group-3 conducted in vitro fertilization/ cleavage rate/penetration rate/ blastocyst yields (n = 28/285; 9.82%) with their specific cryodiluents/media, respectively. Group-4 conducted different experimental supplements/additives/media and carried out both in vitro and in vivo fertilization simultaneously (n = 4/285; 1.40%). Conventional spermatozoa cryopreservation was reported by 51.9% studies followed by programmable fast freezing by 20.7% studies. A few leading extender types included BioXcell (3.9%); Soyamilk-skim (3.5%); and Andromed (2.1%). The study also describes French straws for semen filling, cooling temperatures, extension time, equilibration time, cryopreservation stages, thawing temperatures, seasons, thawing time, and stains used during semen evaluation assays. The study concludes that the research on spermatozoa cryopreservation of buffalo is largely conducted at quality level and a need of applying these findings for evaluation of fertility potential (in vivo and in vitro) is indispensable for effective genetic improvement.

Cloning and characterization of ApCystatin, a plant cystatin gene from Agapanthus praecox ssp. orientalis responds to abiotic stress

Plant cystatins are involved in the regulation of protein turnover and play important roles in defense mechanisms. We cloned the ApCystatin gene from Agapanthus praecox ssp. orientalis, a famous ornamental and medical plant. The complete cDNA sequence of ApCystatin is comprised of 1439 nucleotides with a 423 bp ORF encoding 140 amino acids. The mRNA level of ApCystatin was significantly up-regulated under various abiotic stress, such as salt, osmosis, oxidative and cold stresses, which suggested that ApCystatin participated in the plant's resistance to stress. The recombinant ApCystatin fusion protein expressed in E. coli transetta (DE3) cells was approximate 18 kDa. 25 μg of ApCystatin inhibited more than 95% activity of papain, suggesting ApCystatin as a papain-like protease inhibitor. As an exogenous substance, 1.60 μg/mL ApCystatin protein improved the regrowth percentage of Arabidopsis 60-h seedlings after cryopreservation from 30% to 47%. In addition, the relative survival rate of A. praecox embryogenic callus after cryopreservation also increased for 30% with addition of 1.20 μg/mL ApCystatin protein. This indicated that ApCystatin performed protective property against cryoinjury to Arabidopsis 60-h seedlings and A. praecox embryogenic callus during cryopreservation. Under various abiotic stress conditions, the recombinant ApCystatin protein showed significant advantage in growth rates at NaCl, mannitol, PEG6000, cold, acidic and alkaline conditions, compared to control. In conclusion, ApCystatin as a new member of plant cystatins exhibited protective property against cryoinjury in plant cryopreservation and abiotic stress in E. coli.