Submitted to: In Vitro Cellular and Developmental Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 14, 2010
Publication Date: March 24, 2010
Citation: Talbot, N.C., Caperna, T.J., Blomberg, L., Graninger, P.G., Stodieck, L.S. 2010. The effects of space flight and microgravity on the growth and differentiation of PICM-19 pig liver stem cells. In Vitro Cellular and Developmental Biology - Animal. 46(6):502-15. Interpretive Summary: The PICM-19 pig liver stem cell line was cultured in space for nearly 16 days on STS-126 mission to assess the effects of spaceflight on the liver’s parenchymal cells - PICM-19 cells differentiate into either monolayers of fetal hepatocytes or 3-dimensional bile ductules (cholangiocytes). Semi-quantitative data included light microscopic assessments of final cell density, cell morphology, and response to glucagon stimulation, and electron microscopic assessment of the cells’ ultrastructural features and cell-to-cell connections and physical relationships. Quantitative assessments included assays of hepatocyte detoxification functions, i.e., inducible P450 activities and urea production, and quantitation of the mRNA levels of several liver-related genes. Three post-passage age groups were included; 4-day, 10-day, and 14-day old cultures. In comparing flight vs. ground control cultures 17 h after the Space Shuttle’s return to earth, no differences were found between the cultures with the exception being that some genes were differentially expressed. By light microscopy both young and older cultures, flight and ground, had grown and differentiated normally in the Opticell culture vessels. The PICM-19 cells had grown to approximately 75% confluency, had few signs of apoptosis or necrosis, and had either differentiated into monolayer patches of hepatocytes with biliary canaliculi visible between the cells, or into 3-dimensional bile ductules with well defined lumens. Ultrastructural features between flight and ground were similar with the PICM-19 cells displaying numerous mitochondria, Golgi apparatus, smooth and rough endoplasmic reticulum, vesicular bodies and occasional lipid vacuoles. Cell-to-cell arrangements were typical in both flight and ground-control samples; biliary canaliculi were well formed between the PICM-19 cells and the cells were sandwiched between the STO feeder cells. PICM-19 cells displayed inducible P450 activities. They produced urea in a glutamine-free medium and produced more urea in response to ammonia. The experiment’s aim to gather preliminary data on the PICM-19 cell line’s suitability as an in vitro model for assessments of liver function in microgravity was demonstrated and difference between flight and ground-control cultures were minor.
Technical Abstract: In order to answer the question, what effects would microgravity have on the growth, differentiation, and function on liver stem cells, the ARS-PICM-19 pig liver stem cell line was cultured in space aboard space shuttle Endeavor for the 16 days of mission STS-126. The liver is among the few organs in the body that regularly regenerates its cells, and, in cases of extreme injury, can also regenerate substantial portions of itself given sufficient time. The ARS-PICM-19 pig liver stem cell line models this capacity in vitro, i.e., in the culture dish. The PICM-19 cells were seeded into special plastic culture containers, Opticell units, so that they could be sent into space on space shuttle Endeavor. After the flight, the Opticell units were recovered and processed in the laboratory to assess what, if any, changes could be observed between the flight PICM-19 cells and ground-control Opticell cultures of PICM-19 cells that did not go into space. The results showed that there was very little difference between the flight cells, exposed to 16 days of microgravity, and the ground control cells kept on Earth. Therefore, these preliminary results showed that in vitro liver cell growth, differentiation, and function go on normally in the weightlessness of space travel. Based on these results, if astronauts suffered acute injury to their livers while in space, their livers would probably regenerate normally.