Genetic changes induced in human cells in Space Shuttle experiment (STS-95)

Area of Science:

• Space Biology
• Radiation Biology
• Genetics

Background:

• Previous space experiments suggest microgravity may enhance space radiation's biological effects.
• Assessing synergistic effects of radiation and microgravity is crucial for human spaceflight radiation risk.
• Human tumor HCT-116 cells, with a DNA mismatch repair defect, were used to detect potential genetic changes.

Purpose of the Study:

• To determine if human cells exhibit synergistic effects between space radiation and microgravity.
• To evaluate the mutation frequencies in human cells exposed to spaceflight conditions.
• To assess the potential for genetic damage during long-term space missions.

Main Methods:

• Human tumor HCT-116 cells were cultured aboard the Space Shuttle Discovery (STS-95) for 9 days.
• Post-flight, single-cell clones were isolated, and microsatellite repetitive sequences were analyzed for mutations using PCR.
• Mutation frequencies for microsatellite loci and ouabain-resistant phenotypes were assessed.

Main Results:

• Microsatellite mutation frequencies in the spaceflight samples were comparable to ground controls.
• Ouabain-resistant mutation frequencies also showed no significant difference between spaceflight and ground samples.
• Cells treated with bleomycin in space did not exhibit significantly different mutation frequencies compared to ground controls.

Conclusions:

• Under the conditions of this mission, neither space radiation nor microgravity induced excess mutations in human cells.
• The study found no evidence of a synergistic effect between space radiation and microgravity on human cell genetic stability.
• Current spaceflight radiation levels (approx. 20 mSv) and microgravity did not cause detectable genetic mutations in HCT-116 cells.