Exogenous interleukin-1 beta stimulation regulates equine tenocyte function and gene expression in three-dimensional culture which can be rescued by pharmacological inhibition of interleukin 1 receptor, but not nuclear factor kappa B, signaling

The modulating role of uniaxial straining in the IL-1β and TGF-β mediated inflammatory response of human primary ligamentocytes

Biomechanical (over-)stimulation, in addition to inflammatory and fibrotic stimuli, severely impacts the anterior cruciate ligament (ACL) biology, contributing to the overall chronic nature of desmopathy. A major challenge has been the lack of representative two-dimensional (2D) in vitro models mimicking inflammatory processes in the presence of dynamic mechanical strain, both being crucial for ligament homeostasis. Physiological levels of strain exert anti-inflammatory effects, while excessive strain can facilitate inflammatory mechanisms. Adhering to the 3Rs (Replacement, Reduction and Refinement) principles of animal research, this study aims to investigate the role of a dynamic biomechanical in vitro environment on inflammatory mechanisms by combining a Flexcell culture system with primary human ligamentocytes for the study of ligament pathology. Primary ligamentocytes from OA patients were cultured under animal-free conditions with human platelet lysate, and exposed to either IL-1β or TGF-β3 to simulate different inflammatory microenvironments. Cells were subjected to different magnitudes of mechanical strain. Results showed that cells aligned along the force axis under strain. This study highlights the critical role of the mechanical microenvironment in modulating inflammatory and fibrotic cellular responses in ligamentocyte pathology, providing valuable insights into the complex interplay between biomechanical stimuli and cytokine signaling. These findings not only advance our understanding of ligament biology but also can pave the way for the development of more targeted therapeutic strategies for ligament injuries and diseases, potentially improving patient outcomes in orthopedic medicine.

Equine Embryonic Stem Cell-Derived Tenocytes are Insensitive to a Combination of Inflammatory Cytokines and Have Distinct Molecular Responses Compared to Primary Tenocytes

Tissue fibrosis following tendon injury is a major clinical problem due to the increased risk of re-injury and limited treatment options; however, its mechanism remains unclear. Evidence suggests that insufficient resolution of inflammation contributes to fibrotic healing by disrupting tenocyte activity, with the NF-κB pathway being identified as a potential mediator. Equine embryonic stem cell (ESC) derived tenocytes may offer a potential cell-based therapy to improve tendon regeneration, but how they respond to an inflammatory environment is largely unknown. Our findings reveal for the first time that, unlike adult tenocytes, ESC-tenocytes are unaffected by IFN-γ, TNFα, and IL-1β stimulation; producing minimal changes to tendon-associated gene expression and generating 3-D collagen gel constructs indistinguishable from unstimulated controls. Inflammatory pathway analysis found these inflammatory cytokines failed to activate NF-κB in the ESC-tenocytes. However, NF-κB could be activated to induce changes in gene expression following stimulation with NF-κB pharmaceutical activators. Transcriptomic analysis revealed differences between cytokine and NF-κB signalling components between adult and ESC-tenocytes, which may contribute to the mechanism by which ESC-tenocytes escape inflammatory stimuli. Further investigation of these molecular mechanisms will help guide novel therapies to reduce fibrosis and encourage superior tendon healing.