MSC-Derived Exosomes and Exosome-Educated Macrophages Can Differentially Improve Ligament Healing

Each year, ligament injuries sideline thousands of athletes and regular citizens. Recovery is long and painful, and sometimes a return to full function is never realized due to scar formation--a factor that makes ligament injuries prone to further damage. A new, exosome-based study published on Tuesday (November 3, 2020) in Stem Cells may lead to a welcome solution in the future. The open-access article is titled “Exosome‐Educated Macrophages and Exosomes Differentially Improve Ligament Healing.” (See image at left and, in larger view, at bottom). This study demonstrates how certain exosomes and exosome-educated macrophages can each promote ligament healing and reduce scarring. Exosomes are tiny sub-cellular membrane-bounded sacs that are released by all cells studied thus far and that can shuttle proteins and genetic information between cells. Macrophages are a type of white blood cell that typically kills microorganisms and removes dead cells, but can also stimulate the action of other immune system cells. “Educated macrophages” (EEMs) are macrophages that have been “educated” by interaction with information-conveying exosomes—in this case, mesenchymal stromal cell (MSC)-derived exosomes. Last year, the team behind the current study, researchers at the University of Wisconsin-Madison (UW-Madison), released another study (also published as an open-access article in Stem Cells) (https://stemcellsjournals.onlinelibrary.wiley.com/doi/full/10.1002/stem.2988) that showed how treating an Achilles tendon with EEMs reduces inflammation and improves tendon strength. The EEMs were generated by exposing CD14+ macrophages to MSC-derived exosomes. "Our previous study was done on a mouse model," said Ray Vanderby, PhD, Professor of Orthopedics and Rehabilitation at UW-Madison.