Caspase-2 is required for skeletal muscle differentiation and myogenesis.

Caspase activation plays a crucial role in skeletal muscle differentiation. We previously found that caspase-2 activity increases during skeletal muscle cell differentiation; however, its direct effect on differentiation has not been fully investigated. Here, we found that caspase-2 activity transiently increased more than two-fold within 24h following induction of differentiation. Both pharmacological inhibition and shRNA-mediated knockdown of caspase-2 suppressed myogenic differentiation and dramatically impaired myotube formation. Furthermore, shRNA-mediated knockdown prevented induction of p21 and altered cell cycle profiles. Interestingly, caspase-3 activity was also dramatically reduced following caspase-2 inhibition or ablation. Moreover, caspase-2 and p21 were localized to the nucleus during early differentiation. Given the nuclear localization of caspase-2 and p21, as well as the impairment in p21 induction in caspase-2 knockdown cells, we propose that the role of caspase-2 is to regulate p21 induction at the onset of differentiation, which may regulate the myogenic program. Collectively, these results highlight a novel function for caspase-2 in myocyte differentiation and myogenesis.

How the concept of biochemical response influenced the management of primary biliary cholangitis over time.

BACKGROUND: Criteria assessing biochemical response to ursodeoxycholic acid (UDCA) are established risk stratification tools in primary biliary cholangitis (PBC). We aimed to evaluate to what extent liver tests influenced patient management during a three decade period, and whether this changed over time. METHODS: 851 Dutch PBC patients diagnosed between 1988 and 2012 were reviewed to assess patient management in relation to liver test results during UDCA treatment. To do so, biochemical response at one year was analysed retrospectively according to Paris-1 criteria. RESULTS: Response was assessable for 687/851 (81%) patients; 157/687 non-responders. During a follow-up of 8.8 years (IQR 4.8-13.9), 141 died and 30 underwent liver transplantation. Transplant-free survival of non-responders (60%) was significantly worse compared with responders (87%) (p < 0.0001). Management was modified in 46/157 (29%) non-responders. The most frequent change observed, noted in 26/46 patients, was an increase in UDCA dosage. Subsequently, 9/26 (35%) non-responders became responders within the next two years. Steroid treatment was started in one patient; 19 patients were referred to a tertiary centre. No trend towards more frequent changes in management over time was observed (p = 0.10). CONCLUSION: Changes in medical management occurred in a minority of non-responders. This can largely be explained by the lack of accepted response criteria and of established second-line treatments for PBC. Nevertheless, the observation that response-guided management did not increase over time suggests that awareness of the concept of biochemical response requires further attention,particularly since new treatment options for PBC will soon become available.