Cryopreservation of shortnose sturgeon (Acipenser brevirostrum) ovarian tissue

Abstract

There are many factors that risk the survival of wild sturgeon populations; namely, illegal poaching for caviar and anthropogenic consequences such as habitat destruction. In fact, based on their classification by the IUCN, sturgeon are considered one of the most endangered vertebrate groups worldwide. Therefore, the need for a largescale conservation effort is growing. Cryopreservation is used as a method of preserving important genetic material for conservation purposes by storing biological samples at very low temperatures. Thus, the work presented here is aimed to optimize cryopreservation protocols with a focus on shortnose sturgeon (Acipenser brevirostrum) ovarian tissue. Shortnose sturgeon were specifically chosen as they are locally accessible, smaller in size than other sturgeon species, and have a lower endangerment status. I examined the effectiveness of three different cryoprotectants for their use in cryopreserving oogonial cells: dimethyl sulfoxide (DMSO), ethylene glycol (EG), and glycerol (GLY). Additionally, the antioxidant melatonin was also included at three different concentrations (0.01 mM, 0.1 mM, and 1 mM) in hopes of mitigating freezing injury and enhancing post-thaw cell viability which I assessed using a Luminescent ATP Determination kit. When comparing only the three cryoprotectants without any further supplementation, EG was found to be the least effective cryoprotectant, whereas DMSO was most effective in samples from fish #1 and GLY was most effective in samples from fish #2. However, post-thaw analysis following melatonin supplementation to the cryomedia revealed that there was no one treatment group that stood out from the rest. Alternatively, the four samples with the highest post-thaw ATP concentration all resulted in statistically equal values and were treated with either DMSO + 0.1 mM melatonin, EG + 0.01 mM melatonin, GLY + 0.01 mM melatonin, or GLY without any further supplementation. These results suggest that the addition of melatonin has a favourable effect on viability during the freezing. Overall, the work presented here represents an endeavour to conserve sturgeon populations by using cryopreservation to maintain the integrity and viability of genetic samples.