Smoothened is a master regulator of adult liver repair

When regenerative processes cannot keep pace with cell death, functional epithelia are replaced by scar. Scarring is characterized by both excessive accumulation of fibrous matrix and persistent outgrowth of cell types that accumulate transiently during successful wound healing, including myofibroblasts (MFs) and progenitors. This suggests that signaling that normally directs these cells to repair injured epithelia is deregulated. To evaluate this possibility, we examined liver repair during different types of liver injury after Smoothened (SMO), an obligate intermediate in the Hedgehog (Hh) signaling pathway, was conditionally deleted in cells expressing the MF-associated gene, αSMA. Surprisingly, blocking canonical Hh signaling in MFs not only inhibited liver fibrosis but also prevented accumulation of liver progenitors. Hh-sensitive, hepatic stellate cells (HSCs) were identified as the source of both MFs and progenitors by lineage-tracing studies in 3 other strains of mice, coupled with analysis of highly pure HSC preparations using flow cytometry, immunofluorescence confocal microscopy, RT-PCR, and in situ hybridization. The results identify SMO as a master regulator of hepatic epithelial regeneration based on its ability to promote mesenchymal-to-epithelial transitions in a subpopulation of HSC-derived MFs with features of multipotent progenitors.     

Reproducibility of constant-load treadmill testing with various treadmill protocols and predictability of treadmill test results in patients with intermittent claudication

BACKGROUND: Most trials on the reliability of constant-load treadmill testing use one pair of treadmill settings (speed, grade) only. The question of whether the results can be applied to tests with different settings is left open. Also, claudication distances measured with differing settings are not comparable, rendering the comparison of the results from different trials difficult. This study evaluates the reliability of constant-load testing with various workloads and compares them with claudication distances achieved with walking at normal speed on level ground but also evaluates whether metabolic equivalent (MET) normalization can be used to translate the results of different treadmill tests into each other. METHODS: Fifteen patients with claudication underwent repeated treadmill testing with different treadmill settings, including speeds of 2.0, 3.2, and 4.0 km/h (1.25, 2.0, and 2.5 mph, respectively) and grades of 0% and 12%. The walking capacity was also tested on level ground with a speed chosen by the individual patient. Results of virtual treadmill tests with all possible combinations of the speeds and the grades used were predicted from real tests, with MET normalization. The relationship between real and predicted claudication distances was tested with regression modeling. RESULTS: Reliability coefficients (RCs) for the absolute claudication distance (ACD) were superior to RCs for the initial claudication distance. RCs for ACD ranged between 0.61 and 0.95, with increasing values found with increasing workloads. The best coefficients for the regression of measured on predicted claudication distances were achieved with a model on the basis of a power function (r = 0.963). The model was only appropriate for the prediction of group mean results from clinical trials but cannot be applied to single patient data. For proof of concept, the model was tested with six published studies in which the claudication distances of a patient sample were double treadmill tested with different workloads. The result of the second test was predicted from the first test, and estimated and measured claudication distances were compared. The mean difference (all trials) was 7.9%, whereas the maximum difference amounted to 16.5%. CONCLUSION: For an optimal treadmill test reliability, higher workloads should be used and ACD should be preferred over initial claudication distance. MET normalization provides the basis for the comparability of treadmill test results achieved with different test conditions.     

Infrequent delivery of a long-acting PTH-Fc fusion protein has potent anabolic effects on cortical and cancellous bone.

Skeletal anabolism with PTH is achieved through daily injections that result in brief exposure to the peptide. We hypothesized that similar anabolic effects could be achieved with less frequent but more sustained exposures to PTH. A PTH-Fc fusion protein with a longer half-life than PTH(1-34) increased cortical and cancellous BMD and bone strength with once- or twice-weekly injections. INTRODUCTION: The anabolic effects of PTH are currently achieved with, and thought to require, daily injections that result in brief exposure to the peptide. We hypothesized that less frequent but more sustained exposures to PTH could also be anabolic for bone, provided that serum levels of PTH were not constant. MATERIALS AND METHODS: PTH(1-34) was fused to the Fc fragment of human IgG1 to increase the half-life of PTH. Skeletal anabolism was examined in mice and rats treated once or twice per week with this PTH-Fc fusion protein. RESULTS: PTH-Fc and PTH(1-34) had similar effects on PTH/PTHrP receptor activation, internalization, and signaling in vitro. However, PTH-Fc had a 33-fold longer mean residence time in the circulation of rats compared with that of PTH(1-34). Subcutaneous injection of PTH-Fc once or twice per week resulted in significant increases in bone volume, density, and strength in osteopenic ovariectomized mice and rats. These anabolic effects occurred in association with hypercalcemia and were significantly greater than those achievable with high concentrations of daily PTH(1-34). PTH-Fc also significantly improved cortical bone volume and density under conditions where daily PTH(1-34) did not. Antiresorptive co-therapy with estrogen further enhanced the ability of PTH-Fc to increase bone mass and strength in ovariectomized rats. CONCLUSIONS: These results challenge the notion that brief daily exposure to PTH is essential for its anabolic effects on cortical and cancellous bone. PTH-derived molecules with a sustained circulating half-life may represent a powerful and previously undefined anabolic regimen for cortical and cancellous bone.