Fig. 5. Stiffness and strength regulation of murine tendons by PIEZO1.

a, Schematic of our in vitro experiment with tendon explants subjected to recurrent sham (control) or 5 μM Yoda1 stimulations. To investigate the changes over time, each tendon fascicle was cut in two, the first half was tested at day 0 and the second half after the stimulation paradigm at day 16. b, Comparison of the ramp-to-failure tests between day 0 and day 16 shows higher Δ stiffness (control -2.22 N/%, Yoda1 +1.94 N/%) and Δ strength (control +0.23 N, Yoda1 +0.55 N) after Yoda1-treatment, with no difference in Δ diameter (n=32 fascicles, 4 rats), Mann-Whitney test. c, mRNA expression of genes encoding collagen crosslinking enzymes (Lox and Plod2) and type I collagen (Col1a1) in tendon explants 48 h after four-times stretching to 2% (normalized to static control using the 2^–ddCT method, n=20, 7 rats) or 5 μM Yoda1 stimulation (normalized to sham control using the 2^–ddCT method, n=8, 4 rats), one sample t-test. d, Positional tendons: ramp-to-failure tests with tail tendon fascicles show an increased stiffness but unaffected diameter in Piezo1GOF mice (n=13 mice, 10 heterozygous and 3 homozygous, 6 fascicles tested per mouse) compared to wild-type littermate controls (n=9 mice, 6 fascicles tested per mouse) from 6 litters in total. e, Load-bearing tendons: ramp-to-failure curves of plantaris tendons from littermates demonstrate a tendon phenotype in Piezo1GOF mice with (f) increased stiffness and strength but unaffected diameter. n=8 Piezo1GOF mice (6 heterozygous and 2 homozygous) and n=7 wild-type littermate controls were analysed from 3 litters in total. Unless indicated otherwise, statistics was performed with linear mixed effects models (mouse ID as random effect and litter as fixed effect, Bonferroni-Holm correction). Replicates are biological. Data are means±SEM.