Scientists have discovered a unique stem cell population in both mice and humans that could reshape how tendon and ligament injuries are treated. The research also offers new clues about spinal stenosis, though clinical applications are still a long way off.
During routine spinal surgeries, surgeons came across a cell type that could shift the future of orthopaedic medicine. These cells, found in the Achilles tendon and in major ligaments throughout the body, can both renew themselves and produce the mature cells that build and maintain tendons and ligaments.
The research, led by teams at Weill Cornell Medicine and Hospital for Special Surgery, is the first to identify this kind of stem cell in both mice and humans. Their findings, published in Cell, confirm the presence of these cells in human tissue samples collected during spinal operations. According to Weill Cornell Medicine, these tendon and ligament stem cells (TLSC) were defined by a specific set of molecular markers and showed both self-renewal and the ability to generate all types of tendon and ligament cells.
The TLSC population was found not only in spinal ligaments but also in the Achilles tendon and kneecap ligament in humans, supporting the idea of a universal stem cell type for connective tissues.
What makes these cells notable is their dual function: they serve as a reservoir for tissue repair and can produce the specialized cells that form the structure of tendons and ligaments. Studying them was not straightforward. Tendons and ligaments are difficult to analyze at the cellular level because their cells are so similar. The team had to sort through thousands of individual cells to find those with true stem cell properties, as described in the Cell paper.
The researchers found these stem cells in several places: the Achilles tendon, the patellar ligament, and other connective tissues. This suggests a widespread system for tissue maintenance and repair. Matthew Greenblatt, one of the lead investigators, says this points to a common stem cell type distributed throughout the body's connective tissues—a theory that will need more research to confirm. Before this study, only possible stem cell populations had been suggested, but this is the first clear identification of a self-renewing, multipotent stem cell for tendons and ligaments.
The picture changes when these cells are studied in disease. In patients with lumbar spinal stenosis—a condition where the spinal canal narrows and compresses nerves—these stem cells act differently. Tissue samples from affected patients had more of these stem cells, and when transplanted into mice, the cells produced more tissue than those from patients without stenosis. Molecular analysis showed increased calcium signaling in the diseased cells, which turned out to be important.
The study, published on September 7, 2026, in Cell, links abnormal TLSC activity to excessive tissue growth in lumbar spinal stenosis, suggesting these cells as a potential drug target. The authors note that some existing blood pressure medications affecting calcium channels could be repurposed for this condition, though clinical trials are needed.
When the researchers increased calcium signaling in healthy ligament cells, the cells began to grow abnormally, similar to what is seen in spinal stenosis. Reducing the signal slowed down this excessive tissue growth in mouse models. This points to a direct link between the activity of these stem cells, calcium signaling, and the thickening of spinal ligaments seen in disease. The Cell article notes that these findings provide a molecular basis for targeting TLSC in certain conditions.
There are practical implications. Medications that target calcium channels are already used to treat high blood pressure. The research team is now looking at whether these drugs could be repurposed to treat spinal stenosis—a process known as drug repositioning. So far, the evidence comes only from animal studies, and there are no clinical recommendations for patients yet. The reduction in tissue growth was seen only in mice, and it is not known if any specific drug would be safe or effective for this use in humans.
Beyond spinal conditions, this discovery could eventually help address stubborn injuries in sports and orthopaedics. Chronic Achilles tendon ruptures, rotator cuff tears, and degenerative ligament problems have long resisted effective treatments. Learning how these stem cells work might one day lead to therapies that promote real tissue repair instead of temporary fixes.
For now, these findings are a step forward in basic science, not a ready-made treatment. As Weill Cornell Medicine notes, clinical trials will be needed before any calcium-related pathway can be considered for therapy. Patients with spinal stenosis should not change their medications or start using calcium channel blockers based on this research alone.
This discovery changes how scientists think about tendon and ligament injuries, shifting the focus from broad hopes for regeneration to specific cellular targets. Identifying a common stem cell population across different tissues is a rare advance, but moving from lab results to patient care will take time and careful testing. Only clinical trials will show whether this breakthrough can lead to new treatments for people with tendon and ligament disorders.
