Welcome to the Sunday Paper Club. Every Sunday, this blog will offer an analysis of a paper on space habitation and other related topics. These are my opinions on a weekly scientific paper; basically, I read the paper and write down my thoughts while I read it. They are subject to my perspectives and believes. I am open to debate, so if any reader believes I have misinterpreted something in a paper, please point it out. I'm only a student and I'm still learning how to read these papers and interpret them. All quotes and ideas are from the paper, unless otherwise noted.
This week we are reviewing the paper Modeled Microgravity Inhibits Osteogenic Differentiation of Human Mesenchymal Stem Cells and Increases Adipogenesis. I am using a new format based on the Lifehacker article Back to School: Keep an Academic Reading Journal.
Article Information
Title: Modeled Microgravity Inhibits Osteogenic Differentiation of Human Mesenchymal Stem Cells and Increases Adipogenesis
Authors: MAJD ZAYZAFOON, WILLIAM E. GATHINGS AND JAY M. MCDONALD
Date: May 2004
Journal: Endocrinology
Volume: 145
Number: 5
Article Overview
This was experiment that used mouse bone samples to see how growth was effected in a ground based, zero gravity incubator. It found that bones were vastly effected.
Quotes and Analysis
"...bone loss is the major skeletal problem that has been reported in humans after prolonged space flight and weightlessness. In the most severe forms of microgravity (MG)-induced bone loss, there is an approximately 2% decrease in bone mineral density in only 1 month, equal to that of a postmenopausal woman in 1 year" Page 2421.
Comment: Wow, that is a deal breaker for zero gravity space settlements. 1 year in space would be a 24% reduction in bone mass, you can snap a bone if you bump into something too hard. I'm really just stunned at how much the loss it...we really need gravity it seems.
"During simulated MG, the vessel wall and medium containing cells bound to microcarrier beads rotate at the same speed, producing a vector-averaged gravity comparable with that of near-earth free-fall orbit... This system was developed by NASA at the Johnson Space Center and has been previously used to simulate the effects of a MG environment on numerous cell culture systems" Page 2422.
Comment: One of the many criticisms of the International Space Station (ISS) is that the zero gravity enviroment that makes the ISS so unique can be replicated on Earth. I also thought that the criticism was only considering the Vomit Comet, but since devices like the one above exists, the criticism of the ISS becomes more powerful. That device basically manipulates the forces on a sample to get something close to zero gravity.
Translation of Page 2424: The bone did not grow in microgravity, this was proven with a fancy image measuring system and tests for calcium in the bone.
Comment: Growth is staled in microgravity, we could never put children in space for long periods of time because it would cause too much harm to their development.
"Despite all limitations and contradictory reports, until the experiments are conducted under true MG in space, validated earth-bound models will have to suffice" Page 2427.
"Our present findings suggest that modeled MG acts on the common precursor cell in the bone marrow to promote its commitment to the adipocyte lineage, at the expense of the osteoblastic lineage. These changes in gene expression were not reversible. Thirty days after readaptation to normal gravity, the expression of osteoblast gene markers (with the exception of ALP) remained lower than in the gravity control" Page 2429.
Comment: So, zero-gravity inhabitants could never return to Earth. Also, it would be cool if someone studied the effect for moving to and from zero gravity daily, they may have weaker bones and muscles.
"In support of our data, cosmonauts (n = 15) who suffer from serious bone loss in space have been reported to continue to have significant tibial bone loss 6 months after readaptation" Page 2429.
Questions Raised by the Paper:
How much of the ISS' functions can be preformed on the ground?
Is it ethical to have people become so weaken that they can never return to Earth?
Can you become so weakened by zero gravity that you can't function in zero gravity?
