Keeping Rhino Cells Alive in the Zoo Biobank

A Frozen Zoo

1Northfield Zoo takes part in a conservation program for an endangered rhinoceros. Besides caring for the animals, the zoo keeps a biobank: living cells from endangered animals stored in tanks of liquid nitrogen at about −196 °C. Frozen cells can be thawed and grown years later for research that may help the species. This summer, teen volunteer Beatriz Lindgren worked in the biobank lab with cell biologist Dr. Amaru Quispe.

2During a routine health check, the zoo vet took a tiny skin sample from a young rhino. In the lab, its skin cells grow in plastic dishes filled with a pink liquid called culture medium, which holds water, sugar and other nutrients. The dishes sit in a warm incubator at 37 °C. Each cell is wrapped in a thin cell membrane. Inside, mitochondria release energy from sugar, and the nucleus holds the instructions that direct the cell's work, including when to copy itself and divide.

3To learn what the cells need, Beatriz started three dishes, each with 10,000 rhino skin cells and the same amount of medium, at 37 °C. Dish A had the usual medium and normal air. Dish B had the same medium with the sugar left out, in normal air. Dish C had the usual medium, but its incubator held almost no oxygen. After 5 days she counted the cells and added a blue dye. The dye stays out of a cell whose membrane is whole, but it stains a cell whose membrane is damaged.

4Before cells are frozen, the lab mixes them with a protective liquid that helps stop sharp ice crystals from forming inside them. To show why, Dr. Quispe froze 1,000 cells with the protective liquid and 1,000 cells without it. A week later he thawed both tubes and added the blue dye.

5The vet also collected a drop of the rhino's blood. Dr. Quispe explained that the biobank does not store the rhino's red blood cells, because mature red blood cells in mammals have no nucleus.