Enhancing Chondrocyte Biosynthetic Activities: Harnessing the Power of Loading-Induced Evolved Temperature

Chondrocytes within articular cartilage possess the capacity to perceive and react to signals generated by the typical load-bearing actions of daily life, such as walking or running. Articular cartilage is predominantly oriented toward compression-based functionality, and thus the application of such stimuli dominates the field of cartilage regeneration. Nonetheless, despite its potential significance, physiological variations in temperature within the cartilage, associated with mechanical deformation of this tissue, and their biological consequences are still poorly studied. This thesis aims to comprehensively investigate the impact of a transient temperature increase on chondrocyte functionality in knee cartilage. Drawing on an original in vitro investigation of cartilage thermo-mechanobiology, this thesis unearths the hidden influence of temperature increase on this exquisite tissue, shedding new light on the complex interplay between mechanical and thermal stimuli on chondrocyte function.Employing a biomimetic approach, we commence by probing into the cellular effects of temperature increase during cyclic loading, unmasking its profound significance in the realm of cartilage mechanobiology. The research findings provide robust evidence substantiating that the synergy between mechanical signals and a biomimetic thermal increase elicits a remarkable amplification in the accumulation of major chondrogenic markers. Furthermore, this distinctive thermo-mechanical combination engenders a significant upregulation of temperature-gated (TREK1) and mechano-gated ion channels (TRPV4), further elucidating underlying thermo-mechanotransduction mechanisms. Expanding on these insights, we next shift our focus to the intricate relationship between loading-induced evolved temperature and hypoxia, another pivotal factor known to significantly influence chondrocyte function. Utilizing a state-of-the-art bioreactor and chondrocyte-laden hydrogels (specifically, single network covalent-based hydrogels) under controlled conditions, we further elucidate this complex relationship. Our findings challenge the traditional paradigm of solely focusing on mechanical attributes in cartilage, highlighting the influential role of multiple, co-existing stressors on chondrocyte behavior.Beyond investigations using conventional, covalently-crosslinked hydrogels, we extend our endeavors to the field of biomaterials by developing double network supramolecular hydrogels. These hydrogels use dynamic host-guest links to mimic hyaline cartilage's natural dynamism, fostering a favorable environment for cell encapsulation, as illustrated by enhanced mRNA transcription and synthesis of cartilage-related proteins. Next, through external application of load, heat, and hypoxia, we observe synergistic enhancements in chondrocyte biosynthetic activity (predominantly in collagen and aggrecan expression), surpassing the effects observed in conventional (single network covalent-based) hydrogels subjected to the same conditions. Our novel approach presents a unique and compelling perspective on the inextricable interplay between biomimetic temperature evolution, hypoxia and cartilage mechanobiology, propelling the significance of thermo-mechanical cues and matrix dynamism to the forefront of bio-engineering strategies for cartilage repair.