Combination therapy with ONO-KK1-300-01, a cathepsin K inhibitor, and parathyroid hormone results in additive beneficial effect on bone mineral density in ovariectomized rats

A New 1,25 Dihydroxy Vitamin D Analog with Strong Bone Anabolic Activity in OVX Rats with Little or no Bone Resorptive Activity

A new 1α,25-dihydroxy vitamin D₃ analog (2-methylene-22(E)-(24R)-22-dehydro-1α,24,25-trihydroxy-19-norvitamin D₃ or WT-51) has been tested as a possible therapeutic for osteoporosis. It is 1/10th as active as 1,25(OH)₂ D₃ in binding affinity for the vitamin D receptor but is at least 200 times more active than 1,25(OH)₂ D₃ and equal to that of 2MD (2-methylene-19-nor-(20S)-1α,25(OH)₂ D₃ , an analog previously tested in postmenopausal women), in supporting bone formation by isolated osteoblasts in culture. However, in contrast to 2MD, it is virtually inactive on bone resorption in vivo. WT-51 markedly increased bone mass (lumbar and femur) in ovariectomized (OVX) female rats. Further, bone strength tested by the three-point bending system is significantly increased by WT-51. Thus, WT-51 is an attractive candidate for the treatment of postmenopausal osteoporosis. © 2019 American Society for Bone and Mineral Research.

Cathepsin K activity controls cardiotoxin-induced skeletal muscle repair in mice

BACKGROUND

Cathepsin K (CatK) is a widely expressed cysteine protease that has gained attention because of its enzymatic and non-enzymatic functions in signalling. Here, we examined whether CatK-deficiency (CatK^-/- ) would mitigate injury-related skeletal muscle remodelling and fibrosis in mice, with a special focus on inflammation and muscle cell apoptosis.

METHODS

Cardiotoxin (CTX, 20 μM/200 μL) was injected into the left gastrocnemius muscle of male wild-type (CatK^+/+ ) and CatK^-/- mice, and the mice were processed for morphological and biochemical studies.

RESULTS

On post-injection Day 14, CatK deletion ameliorated muscle interstitial fibrosis and remodelling and performance. At an early time point (Day 3), CatK^-/- reduced the lesion macrophage and leucocyte contents and cell apoptosis, the mRNA levels of monocyte chemoattractant protein-1, toll-like receptor-2 and toll-like receptor-4, and the gelatinolytic activity related to matrix metalloproteinase-2/-9. CatK deletion also restored the protein levels of caspase-3 and cleaved caspase-8 and the ratio of the BAX to the Bcl-2. Moreover, CatK deficiency protected muscle fibre laminin and desmin disorder in response to CTX injury. These beneficial muscle effects were mimicked by CatK-specific inhibitor treatment. In vitro experiments demonstrated that pharmacological CatK inhibition reduced the apoptosis of C2C12 mouse myoblasts and the levels of BAX and caspase-3 proteins induced by CTX.

CONCLUSIONS

These results demonstrate that CatK plays an essential role in skeletal muscle loss and fibrosis in response to CTX injury, possibly via a reduction of inflammation and cell apoptosis, suggesting a novel therapeutic strategy for the control of skeletal muscle diseases by regulating CatK activity.