This week, I attended a life sciences webinar hosted by SEDS-Canada and SGAC. The webinar focused on inducing microgravity on cell cultures to study genetic changes to various types of cells.
Here is the webinar for reference, in case you are interested:
Specifically, one of the speakers (who I have the pleasure of working with at SEDS-Canada!) is working on studying natural killer cells under induced microgravity conditions.
The human immune system has two branches: innate immunity and adaptive immunity. When a new virus or bacteria first enters your body, the innate immune system elicits the first response. The innate immune system consists of cell types that recognize and destroy extracellular pathogens (like various bacterial species) and intracellular viruses. On the other hand, the role of the adaptive immune system is to secrete antibodies to fight an infection and to retain memory cells that can recognize future exposure to specific pathogens. Natural killer cells function in the innate immune system to kill cells that have been infected with an intracellular virus. They do this by releasing cytotoxic enzymes perforin and granzyme. Perforin makes holes in the cell's plasma membrane, and granzyme upregulates death signals within the cell.
On the webinar, it was discussed that the immune system undergoes dysregulation when astronauts are exposed to microgravity. Dysregulation can occur in two different ways: hyperactivation or decreased activity. Some aspects of the immune system, including natural killer cells, are decreased in their function. This leads to a lack of infected cells monitoring in the human body. Regular pathogens for the common cold, for example, become more frequently infectious in space because they are no longer destroyed by natural killer cells. However, some aspects of the immune system can become upregulated and increase in function. Too many proinflammatory molecules are then released by immune cells, causing inflammation and other issues seen in astronauts.
Current research in this field is focused on simulating microgravity conditions on a variety of human immune cell cultures to discover the underlying genetic changes that are leading to functional differences in these cells. To simulate microgravity on cell culture experiments, a Random Positioning Machine (RPM) is used. It generates conditions of microgravity by rotating a cell culture to continuously change its orientation faster than the cells can respond to gravity. Specifically, the clinostat rotates a subject around a horizontal axis to achieve this. However, due to centrifugal forces experienced by cells closer to the edge of a culture dish, the clinostat can never truly emulate microgravity conditions. The only way to truly assess changes to a cell culture in microgravity is to test on the ISS or use a CubeSAT.
Clinostat Videos:
A video of a 2D clinostat. The clinostat is 2D because the rotation occurs along one plane.
This is a video of a 3D clinostat, which rotates in two planes.