Cryopreservation of blue catfish stem cells for conserving genetic resources and xenogeneic transplantation

Abstract

In the United States, channel catfish (Ictalurus punctatus) ♀ × blue catfish (I. furcatus) ♂ hybrids now account for 70% of total freshwater aquaculture production. Hybrid fry production can be improved by cryopreserving valuable male and female gamete resources from blue catfish. Our long-term goal is to develop cryopreservation protocols for spermatogonial and oogonial stem cells (SSCs and OSCs) for gene banking and xenogenesis applications, which will increase gamete availability, improve options for genetic improvement of blue catfish, and increase hybrid fry output. Stem cells frozen in germplasm repositories would help facilitate this initiative beyond traditional cryopreservation of sperm and eggs. The effects of using various permeating and nonpermeating cryoprotectants, concentrations, freezing rates, and antioxidants/antifreeze proteins on post-thaw live cell production and viability of both blue catfish SSCs and OSCs were examined. The choice of permeating or non- permeating cryoprotectant notably impacted post-thaw SSC and OSC production and viability. By using the top-performing cryoprotectant at its target concentration for each cell type, the amount of live cells after thawing greatly increases. The best freezing rate was -1 °C/min overall, and post-thaw production and viability decreased at rates of -2.5, 5, and -10 °C/min. Combining antioxidants and antifreeze proteins by adding hypotaurine with either AFPI 1.0 µg/mL or AFPIII 0.1 µg/mL to the cryomedia maximizes the number of live SSCs after freezing. Together, these findings show that catfish SSCs and OSCs can be successfully frozen for future cell transplantation into channel catfish or other hosts. This may become a very valuable resource for catfish genetic enhancement programs and hybrid catfish aquaculture.