Muscle satellite cell proliferation and association: new insights from myofiber time-lapse imaging

<p>Abstract</p> <p>Background</p> <p>As the resident stem cells of skeletal muscle, satellite cells are activated by extracellular cues associated with local damage. Once activated, satellite cells will re-enter the cell cycle to proliferate and supply a population of myoblasts, which will repair or replace damaged myofibers by differentiating and fusing either with an existing myofiber or with each other. There is also evidence that the orientation of cell division with respect to the myofiber may indicate or convey asymmetry in the two daughter cells. Our recent studies with time-lapse imaging of myofiber-associated satellite cells <it>in vitro </it>have yielded new data on the timing and orientation of satellite cell divisions, and revealed persistent differences in the behavior of daughter cells from planar versus vertical divisions.</p> <p>Results</p> <p>We analyzed 244 individual fiber-associated satellite cells in time-lapse video from 24 to 48 hours after myofiber harvest. We found that initial cell division in fiber culture is not synchronous, although presumably all cells were activated by the initial trauma of harvest; that cell cycling time is significantly shorter than previously thought (as short as 4.8 hours, averaging 10 hours between the first and second divisions and eight hours between the second and third); and that timing of subsequent divisions is not strongly correlated with timing of the initial division. Approximately 65% of first and 80% of second cell divisions occur parallel to the axis of the myofiber, whereas the remainder occur outside the plane of the fiber surface (vertical division). We previously demonstrated that daughter cells frequently remain associated with each other after division or reassociate after a brief separation, and that unrelated cells may also associate for significant periods of time. We show in this paper that daughter cells resulting from a vertical division remain associated with one another several times longer than do daughters from a horizontal division. However, the total average time of association between sister cells is not significantly different from the total average time of association between unrelated cells.</p> <p>Conclusions</p> <p>These longitudinal characterizations of satellite cell behavior shortly after activation provide new insights into cell proliferation and association as a function of relatedness, and indicate significant and consistent heterogeneity within the population based on these metrics.</p

Collagenase Clostridium histolyticum in the treatment of Peyronies disease: patient selection and perspectives.

The safety and efficacy of the use of collagenase Clostridium histolyticum (CCH) for the treatment of Peyronies disease has been confirmed over the past several years. However, identification of the ideal patient population for use of this treatment is not well established. Multiple studies have attempted to delineate various patient-specific factors that may predict response to treatment with CCH, with the intent of enhancing patient selection. To date, these include baseline curvature severity, duration of disease, disease phase at presentation, plaque calcification, baseline erectile function, plaque size, age, comorbid diabetes, previous penile trauma, responsiveness to first treatment cycle, baseline penile shortening or pain, prior treatment with intralesional injection, compliance with plaque modeling, and atypical curvature. In addition, other studies have sought to explore various aspects of treatment with CCH that may affect patient perspective of treatment. They have focused on patient-reported outcomes, female partner considerations, cost of treatment, and potential confounders of patient satisfaction. This review provides a summary and analysis of currently available literature on topics of patient selection and perspectives in regard to treatment of Peyronies disease with CCH

Collagenase <em>Clostridium histolyticum</em> in the treatment of Peyronie&rsquo;s disease: patient selection and perspectives

The safety and efficacy of the use of collagenase Clostridium histolyticum (CCH) for the treatment of Peyronie’s disease has been confirmed over the past several years. However, identification of the ideal patient population for use of this treatment is not well established. Multiple studies have attempted to delineate various patient-specific factors that may predict response to treatment with CCH, with the intent of enhancing patient selection. To date, these include baseline curvature severity, duration of disease, disease phase at presentation, plaque calcification, baseline erectile function, plaque size, age, comorbid diabetes, previous penile trauma, responsiveness to first treatment cycle, baseline penile shortening or pain, prior treatment with intralesional injection, compliance with plaque modeling, and atypical curvature. In addition, other studies have sought to explore various aspects of treatment with CCH that may affect patient perspective of treatment. They have focused on patient-reported outcomes, female partner considerations, cost of treatment, and potential confounders of patient satisfaction. This review provides a summary and analysis of currently available literature on topics of patient selection and perspectives in regard to treatment of Peyronie’s disease with CCH

Long bone structure and strength depend on BMP2 from osteoblasts and osteocytes, but not vascular endothelial cells.

The importance of bone morphogenetic protein 2 (BMP2) in the skeleton is well known. BMP2 is expressed in a variety of tissues during development, growth and healing. In this study we sought to better identify the role of tissue-specific BMP2 during post-natal growth and to determine if BMP2 knockout affects the ability of terminally differentiated cells to create high quality bone material. We targeted BMP2 knockout to two differentiated cell types known to express BMP2 during growth and healing, early-stage osteoblasts and their progeny (osterix promoted Cre) and vascular endothelial cells (vascular-endothelial-cadherin promoted Cre). Our objectives were to assess post-natal bone growth, structure and strength. We hypothesized that removal of BMP2 from osteogenic and vascular cells (separately) would result in smaller skeletons with inferior bone material properties. At 12 and 24 weeks of age the osteoblast knockout of BMP2 reduced body weight by 20%, but the vascular knockout had no effect. Analysis of bone in the tibia revealed reductions in cortical and cancellous bone size and volume in the osteoblast knockout, but not in the vascular endothelial knockout. Furthermore, forelimb strength testing revealed a 30% reduction in ultimate force at both 12 and 24 weeks in the osteoblast knockout of BMP2, but no change in the vascular endothelial knockout. Moreover, mechanical strength testing of femurs from osteoblast knockout mice demonstrated an increased Young's modulus (greater than 35%) but decreased post-yield displacement (greater than 50%) at both 12 and 24 weeks of age. In summary, the osteoblast knockout of BMP2 reduced bone size and altered mechanical properties at the whole-bone and material levels. Osteoblast-derived BMP2 has an important role in post-natal skeletal growth, structure and strength, while vascular endothelial-derived BMP2 does not

A modeling study to estimate prostate cancer-specific mortality on active surveillance for men with favorable intermediate-risk prostate cancer: Results from the SEARCH cohort.

PurposeLimited data exist to help surgeons decide between active surveillance (AS) versus treatment for men with favorable intermediate risk (FIR) prostate cancer. To estimate the theoretical excess risk of prostate cancer-specific mortality (PCSM) with AS versus radical prostatectomy (RP), we determined the risk of PCSM in FIR men undergoing RP and modeled the PCSM risk for AS using a range of increased PSCM scenarios ranging from 1.25x to 2x higher relative to RP.Materials and methodsWe retrospectively reviewed data from men undergoing RP from 1988 to 2017 at 8 Veterans Affairs hospitals within the SEARCH cohort. Men with FIR PC were identified using the NCCN risk criteria. Risk of PCSM at 5, 10, and 15 years after RP was estimated. Using these estimates, PCSM was then modeled for AS using a range of increased risk of PCSM relative to RP ranging from 1.25x to 2x higher.ResultsFor the 920 FIR men identified, 5-, 10-, and 15-year survival estimates for PCSM after RP were 99.9%, 99.0%, and 97.8%, respectively. If the risk of PCSM on AS were 1.25-2x greater than RP, there would be 0.54%-2.17% excess risk of PCSM at 15 years.ConclusionsThe risk of death for FIR after RP is very low. Assuming even modestly increased PCSM with AS versus RP, the excess risk of death for AS in FIR is low even up to 15 years. These data support the consideration of AS as a relatively safe alternative to RP in FIR men, though prospective randomized trials are needed to validate these findings

Deletion of BMP2 was evaluated in osteogenic cells (Osx-Cre) and vascular cells (VEC-Cre).

<p>(A) First, Cre activation was verified by examination of cortical bone (ulna) and muscle from transverse cross-sections through the mid-forelimb. In control samples the bone is completely black. The Osx-Cre mouse has a GFP::Cre fusion protein which demonstrated the current expression of Cre in some osteocytes within the bone and osteoblasts lining the bone surface (open white arrowheads). The VEC-Cre mouse was crossed with mTmG reporter mouse and demonstrated Cre activation within muscle and periosteum compartments surrounding the bone (filled white arrowheads). (B) Confirmation of the BMP2 protein deletion was done using immunohistochemistry. In the control sample BMP2 expression was seen in the muscle (blue filled arrows) and bone-lining cells (thin black arrows). Using the Osx-Cre BMP2 expression was absent in the bone lining cells, but abundantly expressed throughout the muscle compartment (blue filled arrows). In contrast, using the VEC-Cre expression of BMP2 was limited to osteoblasts lining the bone surface (thin black arrows). Images are representative of 3–5 sections from 3–6 animals/group.</p

Whole body DXA results at 12 and 24 weeks for WT and cKO male mice.

<p>(A) Body weight was significantly reduced in the Osx-Cre cKO and unchanged for VEC-Cre mice. (B) Percent fat was not significantly reduced in the 12- and 24week old Osx-Cre cKO male mice (although it did reach significance at 24 weeks when male and female data were pooled (ANOVA)). (C) Osx-Cre cKO male mice showed a significant reduction in BMC at the 12-week time point, with a non-significant trend at 24 weeks (which was significant when male and female data were pooled (ANOVA)). BMC was unchanged for VEC-Cre mice at either time point.</p

In vivo microCT results from tibia midshaft and metaphyseal regions.

z<p>p<0.05 BMP2 fl/fl; VEC-Cre+ vs. BMP2 fl/fl; VEC-Cre−.</p>a<p>p<0.05 BMP2 fl/fl; Osx-Cre+ vs. BMP2 fl/fl; Osx-Cre−.</p

MicroCT was used to assess structural properties of the tibia at 12/16 and 24 weeks.

<p>(Osx-Cre data shown at 12 weeks, VEC-Cre data shown at 16 weeks.) Osx-Cre cKO mice had (A) shorter tibia and (B) reduced cortical bone volume with no change in (C) cancellous BV/TV or (D) cortical TMD. VEC-Cre mice showed no differences in any parameter. (E) Illustrations of cortical bone geometry show a smaller marrow cavity in the Osx-Cre cKO mice.</p