Athletic performance relies on tendons, which enable movement by transferring forces from muscles to the skeleton. Yet how load-bearing structures in tendon sense and adapt to physical demands is not understood. Here, by performing calcium (Ca 2+ ) imaging in mechanically loaded tendon explants from rats and in primary tendon cells from rats and humans, we show that tenocytes detect mechanical forces via the mechanosensitive ion channel PIEZO1, which senses shear stresses induced by collagen-fibre sliding. Via tenocyte-targeted loss-of-function and gain-of-function experiments in rodents, we show that reduced PIEZO1 activity decreased tendon stiffness and that elevated PIEZO1 mechanosignalling increased tendon stiffness and strength, seemingly through upregulated collagen crosslinking. We also show that humans carrying the PIEZO1 E756del gain-of-function mutation display a 13.2% average increase in normalized jumping height, presumably owing to a higher rate of force generation or to the release of a larger amount of stored elastic energy. Further understanding of the PIEZO1-mediated mechanoregulation of tendon stiffness should aid research on musculoskeletal medicine and on sports performance.

The kidney regulates plasma protein levels by eliminating them from the circulation. Proteins filtered by glomeruli are endocytosed and degraded in the proximal tubule and defects in this process result in tubular proteinuria, an important clinical biomarker. However, the spatiotemporal organization of renal protein metabolism in vivo was previously unclear. Here, using functional probes and intravital microscopy, we track the fate of filtered proteins in real time in living mice, and map specialized processing to tubular structures with singular value decomposition analysis and three-dimensional electron microscopy. We reveal that degradation of proteins requires sequential, coordinated activity of distinct tubular sub-segments, each adapted to specific tasks. Moreover, we leverage this approach to pinpoint the nature of endo-lysosomal disorders in disease models, and show that compensatory uptake in later regions of the proximal tubule limits urinary protein loss. This means that measurement of proteinuria likely underestimates severity of endocytotic defects in patients.

Tendons enable movement by transferring muscle forces to the skeleton, and athletic performances critically rely on mechanically-optimized tendons. How load-bearing structures of tendon sense and adapt to physical demands is an open question of central importance to musculoskeletal medicine and human sports performance. Here, with calcium imaging in tendon explants and primary tendon cells we characterized how tenocytes detect mechanical forces and determined collagen fiber-sliding-induced shear stress as a key stimulus. CRISPR/Cas9 screening in human and rat tenocytes identified PIEZO1 as the crucial shear sensor. In rodents, elevated mechano-signaling increased tendon stiffness and strength both in vitro by pharmacological channel activation and in vivo by a Piezo1 gain-of-function mutation. Strikingly, humans carrying the PIEZO1 gain-of-function E756del mutation revealed a 16% average increase in normalized jumping height, with more effective storage of potential energy released during dynamic jumping maneuvers. We propose that PIEZO1-mediated mechano-signaling regulates tendon stiffness and impacts human athletic performance.

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Nephrotoxicity is a major cause of kidney disease and failure in drug development, but understanding of cellular mechanisms is limited, highlighting the need for better experimental models and methodological approaches. Most nephrotoxins damage the proximal tubule (PT), causing functional impairment of solute reabsorption and systemic metabolic complications. The anti-viral drug Tenofovir disoproxil fumarate (TDF) is an archetypal nephrotoxin, inducing mitochondrial abnormalities and urinary solute wasting, for reasons that were previously unclear. Here, we developed an automated, high-throughput imaging pipeline to screen the effects of TDF on solute transport and mitochondrial morphology in human-derived RPTEC/TERT1 cells, and leveraged this to generate realistic models of functional toxicity. By applying multiparametric metabolic profiling—including oxygen consumption measurements, metabolomics and transcriptomics—we elucidated a highly robust molecular fingerprint of TDF exposure. Crucially, we identified that the active metabolite inhibits complex V (ATP synthase), and that TDF treatment causes rapid, dose dependent loss of complex V activity and expression. Moreover, we found evidence of complex V suppression in kidney biopsies from humans with TDF toxicity. Thus, we demonstrate an effective and convenient experimental approach to screen for disease relevant functional defects in kidney cells in vitro, and reveal a new paradigm for understanding the pathogenesis of a substantial cause of nephrotoxicity.