Primary cilia are sensory organelles that translate extracellular chemical and mechanical cues into cellular responses. Bone is an exquisitely mechanosensitive organ, and its homeostasis depends on the ability of bone cells to sense and respond to mechanical stimuli. One such stimulus is dynamic fluid flow, which triggers biochemical and transcriptional changes in bone cells by an unknown mechanism. Here we report that bone cells possess primary cilia that project from the cell surface and deflect during fluid flow and that these primary cilia are required for osteogenic and bone resorptive responses to dynamic fluid flow. We also show that, unlike in kidney cells, primary cilia in bone translate fluid flow into cellular responses in bone cells independently of Ca
2+
flux and stretch-activated ion channels. These results suggest that primary cilia might regulate homeostasis in diverse tissues by allowing mechanical signals to alter cellular activity via tissue-specific pathways. Our identification of a mechanism for mechanotransduction in bone could lead to therapeutic approaches for combating bone loss due to osteoporosis and disuse.
Apoptosis inhibition may be an effective strategy in minimizing chondrocyte and synovial cell death after exposure to anesthetics. Further investigation is clinically warranted.
Background: Open physes and trochlear/notch geometries in pediatric patients limit the safe corridor for femoral interference screw graft fixation during medial patellofemoral ligament (MPFL) reconstruction. Accordingly, interest is increasing in anchor-based fixation, but biomechanical validation is deficient. Purpose: To compare anchor-based and tenodesis screw femoral fixation of MPFL grafts in a time-zero biomechanical model. Study Design: Controlled laboratory study. Methods: Twenty-seven fresh-frozen porcine distal femurs were potted for testing in an electromechanical load frame, while bovine tendons were used for MPFL grafts. Reconstructions were performed with 1 of 3 femoral fixation strategies: 4.5-mm biocomposite double-loaded threaded anchor (DLA group), 3.9-mm biocomposite knotless threaded anchor (KA group), or traditional 7 × 23–mm biocomposite tenodesis screw (TS group). For testing, femoral specimens were oriented and secured in the mechanical testing apparatus such that actuator tensile pull re-created the normal MPFL trajectory. Specimens underwent 10 cycles of 5- to 15-N loading at 1-Hz preconditioning, followed by 1000 cycles of 10- to 50 N-loading at 1 Hz. After cyclic loading, all specimens were loaded to failure at 305 mm/min. The average cyclic construct stiffness, displacement, and load-to-failure data between the 3 groups were compared using analysis of variance (ANOVA) with the significance level set at P < .05. Results: Average cyclic construct stiffnesses were comparable across groups per repeated-measures ANOVA analysis: 68.3 ± 6.3, 71.4 ± 6.4, and 74.3 ± 7.9 N/mm for TS, DLA, and KA groups, respectively (at cycle 1000). Average construct displacements at cycles 100 and 1000 were significantly less in the anchor versus tenodesis screw groups per ANOVA and Tukey post hoc analysis: 7.7 ± 4.2 mm for the TS group versus 3.7 ± 0.4 and 4.3 ± 0.6 mm for the DLA and KA groups, respectively (at cycle 1000). There was no significant difference in ultimate failure loads between the anchor and tenodesis screw groups, but 3 of 9 TS constructs failed at loads below the average failure load of the native MPFL. Conclusion: Compared with the tenodesis group, anchor-based fixation produced constructs with equivalent cyclic stiffnesses, improved load-displacement characteristics, and had less failure load variability in the porcine cadaveric model. Clinical Relevance: Femoral fixation of the MPFL graft with a single anchor (4.5 or 3.9 mm threaded) is a viable alternative to traditional tenodesis screw fixation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.