Tendons are particularly vulnerable to overuse, as noted by Jess Snedeker, a professor of orthopaedic biomechanics at ETH Zurich. "They are designed to handle significant loads, concentrating muscle forces onto the relatively slender tendons that facilitate movement in our skeleton," he explains.
Medical professionals classify these issues as tendinopathies, which are frequently encountered by orthopedic specialists. However, effective treatment options remain scarce. While physical therapy can provide some relief, its effectiveness is often limited in severe cases. This has prompted researchers to delve deeper into the underlying mechanisms of tendon disorders to develop improved therapeutic approaches.
HIF1 Protein Emerges as a Key Contributor
A research team led by Snedeker and Katrien De Bock, a professor of exercise and health at ETH Zurich, has identified a crucial factor in this context: the HIF1 protein. This protein acts as a transcription factor, regulating the activity of specific genes within cells.
Previous research indicated elevated HIF1 levels in damaged tendons, but it was unclear whether this protein was merely associated with the condition or actively contributed to it. Through experiments involving mice and human tendon tissues, the team established that HIF1 not only correlates with tendon disease but also plays a direct role in its onset.
Direct Evidence Linking HIF1 to Tendon Damage
In their mouse experiments, researchers manipulated HIF1 levels by either keeping it constantly activated or completely deactivating it. Mice with continuously active HIF1 developed tendon issues even without excessive strain. Conversely, those with deactivated HIF1 in their tendon tissues did not experience tendon problems, even under overload conditions.
The research team also examined human tendon cells obtained during surgical procedures. In both mouse and human samples, increased HIF1 levels led to detrimental structural changes in tendons, including the formation of excessive crosslinks within collagen fibers, which are essential for tendon strength and integrity.
"This results in greater brittleness and hinders the mechanical function of tendons," says Greta Moschini, a doctoral student involved in the study. The team also noted an increase in blood vessel and nerve growth within the tendon tissue, which may explain the pain commonly associated with tendinopathy, according to Moschini.
The Importance of Early Intervention
"Our research not only sheds light on the development of the disease but also emphasizes the necessity for early treatment of tendon issues," Snedeker states. He particularly highlights the significance for young athletes, who often face tendinopathies while their conditions are still manageable.
Over time, however, the damage caused by HIF1 can accumulate, potentially becoming irreversible. "Once the damage reaches a certain point, physiotherapy may no longer be effective, and surgical intervention to remove the affected tendon may be the only option," he adds.
Exploring Targeted Treatments for Tendon Disorders
With HIF1 identified as a molecular driver of tendon diseases, a pertinent question arises: Can we develop medications to inhibit HIF1 and either prevent or reverse tendinopathy?
De Bock acknowledges the complexity of this issue. HIF1 plays a vital role in the body, responding to low oxygen levels and triggering adaptive mechanisms. "Completely inhibiting HIF1 could result in adverse side effects," she cautions.
One avenue of exploration is to specifically target HIF1 activity in tendon tissues. However, De Bock suggests a more promising approach may involve a detailed examination of the biological processes surrounding HIF1. By identifying other molecules influenced by HIF1, researchers may discover safer and more precise targets for treating tendinopathy, and this investigation is currently in progress.
