On December 9, 2025, a bioreactor carrying the final samples from the “MSK-2” experiment returned to Earth. This marked the completion of a six-year program by Sechenov University aimed at studying how microgravity affects human tissues. Over this period, 11 batches of living cells were sent to the ISS, and researchers are now ready to present their conclusions: space accelerates cartilage degeneration by orders of magnitude, but a specific substance may significantly slow the process.

Cartilage: The Most Vulnerable Tissue in Space

It has long been known on Earth that extended time in microgravity leads to loss of bone mass and joint problems in astronauts. However, the underlying mechanisms remained unclear. The MSK-2 experiment modelled these effects at the cellular level by growing 3D spheroids of chondrocytes — cartilage cells — inside a bioreactor.

In orbit, the breakdown of the extracellular matrix — the structural scaffold of cartilage — occurs drastically faster than in ground-based labs. Thanks to this rapidity, researchers were able to observe processes within months that would normally take years on Earth.

Lactoferrin vs. Space

The key part of the final stage involved comparing two sample groups. One was a control group; the other was treated with lactoferrin, a protein with anti-inflammatory and protective properties. Preliminary data indicate that lactoferrin substantially reduces metabolic stress in chondrocytes and helps preserve matrix structure even under microgravity conditions.

Project scientific supervisor Pyotr Timashev emphasized that cartilage is considered one of the most vulnerable tissues during long-duration missions, which increases the risk of degenerative changes in astronauts.

What Comes Next

The samples are now being analyzed at the Institute of Regenerative Medicine at Sechenov University. Full evaluation — including morphology, metabolism and gene expression — will take several months. The results will inform:

• new preventive protocols for astronauts
• therapies for osteoarthritis and spinal disorders on Earth
• the next phase of research, involving intervertebral disc models for the upcoming Russian Orbital Station

Summary

The six-year MSK-2 experiment on the ISS has concluded. Scientists have demonstrated that microgravity accelerates cartilage degradation by tens of times, but lactoferrin can slow this process. The findings will help protect astronauts’ health and contribute to new treatments for arthritis on Earth. Space once again proves to be an accelerator of medical discovery.