Mechanoresponsive stem cells acquire neural crest fate in jaw regeneration.

During both embryonic development and adult tissue regeneration, changes in chromatin structure driven by master transcription factors lead to stimulus-responsive transcriptional programs. A thorough understanding of how stem cells in the skeleton interpret mechanical stimuli and enact regeneration would shed light on how forces are transduced to the nucleus in regenerative processes. Here we develop a genetically dissectible mouse model of mandibular distraction osteogenesis-which is a process that is used in humans to correct an undersized lower jaw that involves surgically separating the jaw bone, which elicits new bone growth in the gap. We use this model to show that regions of newly formed bone are clonally derived from stem cells that reside in the skeleton. Using chromatin and transcriptional profiling, we show that these stem-cell populations gain activity within the focal adhesion kinase (FAK) signalling pathway, and that inhibiting FAK abolishes new bone formation. Mechanotransduction via FAK in skeletal stem cells during distraction activates a gene-regulatory program and retrotransposons that are normally active in primitive neural crest cells, from which skeletal stem cells arise during development. This reversion to a developmental state underlies the robust tissue growth that facilitates stem-cell-based regeneration of adult skeletal tissue.

Endochondral ossification is required for haematopoietic stem-cell niche formation.

Little is known about the formation of niches, local micro-environments required for stem-cell maintenance. Here we develop an in vivo assay for adult haematopoietic stem-cell (HSC) niche formation. With this assay, we identified a population of progenitor cells with surface markers CD45(-)Tie2(-)alpha(V)(+)CD105(+)Thy1.1(-) (CD105(+)Thy1(-)) that, when sorted from 15.5 days post-coitum fetal bones and transplanted under the adult mouse kidney capsule, could recruit host-derived blood vessels, produce donor-derived ectopic bones through a cartilage intermediate and generate a marrow cavity populated by host-derived long-term reconstituting HSC (LT-HSC). In contrast, CD45(-)Tie2(-)alpha(V)(+)CD105(+)Thy1(+) (CD105(+)Thy1(+)) fetal bone progenitors form bone that does not contain a marrow cavity. Suppressing expression of factors involved in endochondral ossification, such as osterix and vascular endothelial growth factor (VEGF), inhibited niche generation. CD105(+)Thy1(-) progenitor populations derived from regions of the fetal mandible or calvaria that do not undergo endochondral ossification formed only bone without marrow in our assay. Collectively, our data implicate endochondral ossification, bone formation that proceeds through a cartilage intermediate, as a requirement for adult HSC niche formation.

Denervation during mandibular distraction osteogenesis results in impaired bone formation.

Mandibular distraction osteogenesis (DO) is mediated by skeletal stem cells (SSCs) in mice, which enact bone regeneration via neural crest re-activation. As peripheral nerves are essential to progenitor function during development and in response to injury, we questioned if denervation impairs mandibular DO. C57Bl6 mice were divided into two groups: DO with a segmental defect in the inferior alveolar nerve (IAN) at the time of mandibular osteotomy ("DO Den") and DO with IAN intact ("DO Inn"). DO Den demonstrated significantly reduced histological and radiological osteogenesis relative to DO Inn. Denervation preceding DO results in reduced SSC amplification and osteogenic potential in mice. Single cell RNA sequencing analysis revealed that there was a predominance of innervated SSCs in clusters dominated by pathways related to bone formation. A rare human patient specimen was also analyzed and suggested that histological, radiological, and transcriptional alterations seen in mouse DO may be conserved in the setting of denervated human mandible distraction. Fibromodulin (FMOD) transcriptional and protein expression were reduced in denervated relative to innervated mouse and human mandible regenerate. Finally, when exogenous FMOD was added to DO-Den and DO-Inn SSCs undergoing in vitro osteogenic differentiation, the osteogenic potential of DO-Den SSCs was increased in comparison to control untreated DO-Den SSCs, modeling the superior osteogenic potential of DO-Inn SSCs.

Six- and twelve-month results from first human experience using everolimus-eluting stents with bioabsorbable polymer.

BACKGROUND: Everolimus, an active immunosuppressive and antiproliferative agent of the same family as sirolimus (rapamycin), has demonstrated significant reduction of neointimal proliferation in animal studies. The First Use To Underscore restenosis Reduction with Everolimus (FUTURE) I trial was the first in-human experience to evaluate the safety and efficacy of everolimus-eluting stents (EES), coated with a bioabsorbable polymer, compared with bare metal stents (BMS). METHODS AND RESULTS: FUTURE I was a prospective, single-blind, randomized trial that enrolled 42 patients with de novo coronary lesions (EES 27, BMS 15). Patient and lesion characteristics were comparable between the groups. Major adverse cardiac event rates were low at 30 days and 6 months, without any early or late stent thrombosis for either group (P=NS). Between 6 and 12 months, there were no additional reports of major adverse cardiac events. The 6-month angiographic in-stent restenosis rate was 0% versus 9.1% (1 patient) (P=NS), with an associated late loss of 0.11 mm versus 0.85 mm (P<0.001), and the in-segment restenosis rate was 4% (1 patient) and 9.1% (1 patient) (P=NS) for EES and BMS, respectively. Intravascular ultrasound analysis revealed a significant reduction of percent neointimal volume in EES compared with BMS (2.9+/-1.9 mm3/mm versus 22.4+/-9.4 mm3/mm, P<0.001). There was no late stent malapposition in either group. The safety and efficacy of the EES appeared to be sustained at 12 months. CONCLUSIONS: In this initial clinical experience, EES with bioabsorbable polymer demonstrated a safe and efficacious method to reduce in-stent neointimal hyperplasia and restenosis.

Chronic arterial responses to polymer-controlled paclitaxel-eluting stents: comparison with bare metal stents by serial intravascular ultrasound analyses: data from the randomized TAXUS-II trial.

BACKGROUND: Polymer-controlled paclitaxel-eluting stents have shown a pronounced reduction in neointimal hyperplasia compared with bare metal stents (BMS). The aim of this substudy was to evaluate local arterial responses through the use of serial quantitative intravascular ultrasound (IVUS) analyses in the TAXUS II trial. METHODS AND RESULTS: TAXUS II was a randomized, double-blind study with 536 patients in 2 consecutive cohorts comparing slow-release (SR; 131 patients) and moderate-release (MR; 135 patients) paclitaxel-eluting stents with BMS (270 patients). This IVUS substudy included patients treated with one study stent who underwent serial IVUS examination after the procedure and at 6-month follow-up (BMS, 152 patients; SR, 81; MR, 81). The analyzed stented segment (15 mm) was divided into 5 subsegments in which mean vessel area (VA), stent area (SA), lumen area (LA), intrastent neointimal hyperplasia area (NIHA), and peristent area (VA-SA) were measured. NIHA was significantly reduced in SR (0.7+/-0.9 mm2, P<0.001) and MR (0.6+/-0.8 mm2, P<0.001) compared with BMS (1.9+/-1.5 mm2), with no differences between the two paclitaxel-eluting release formulations. Longitudinal distribution of neointimal hyperplasia throughout the paclitaxel-eluting stent was uniform. Neointimal growth was independent of peristent area at postprocedure examination in all groups. There were progressive increases in peristent area from BMS to SR to MR (0.5+/-1.7, 1.0+/-1.8, and 1.4+/-2.0 mm2, respectively; P<0.001). The increase in peristent area was directly correlated with increases in VA. CONCLUSIONS: Both SR and MR paclitaxel-eluting stents prevent neointimal formation to the same degree compared with BMS. However, the difference in peristent remodeling suggests a release-dependent effect between SR and MR.

Optimism, positive affectivity, and salivary cortisol.

OBJECTIVES: Research on stress and salivary cortisol has focused almost exclusively on the effects of negative psychological conditions or emotional states. Little attention has been drawn to the impact associated with positive psychological conditions, which have been shown recently to have significant influences on neuroendocrine regulation. The aim of this study is to examine the impact of optimism and positive affect on salivary cortisol with the effects of their negative counterparts controlled for. DESIGN: Optimism and pessimism, and positive and negative affectivity were studied in relation to the diurnal rhythm of salivary cortisol in a group of 80 Hong Kong Chinese, who provided six saliva samples over the course of a day on two consecutive days. The separate effects of optimism and positive affect on two dynamic components of cortisol secretion, awakening response, and diurnal decline were examined. METHODS: Optimism and pessimism were measured using the Chinese version of the revised Life Orientation Test while generalized affects and mood states were assessed by the Chinese Affect Scale. An enzyme-linked immunoabsorbent assay kit (EIA) developed for use in saliva was adopted for the biochemical analysis of cortisol. Testing of major group differences associated with positive psychological conditions was carried out using two-way (group by saliva collection time) ANOVAs for repeated measures with negative psychological conditions and mood states as covariates. RESULTS: Participants having higher optimism scores exhibited less cortisol secretion in the awakening period when the effect of pessimism and mood were controlled. This effect was more apparent in men than in women who had higher cortisol levels in the awakening period. Optimism did not have similar effect on cortisol levels during the underlying period of diurnal decline. On the other hand, higher generalized positive affect was associated with lower cortisol levels during the underlying period of diurnal decline after the effects of negative affect and mood states had been controlled. Generalized positive affect did not significantly influence cortisol secretion during the awakening period. CONCLUSIONS: These findings suggest that positive psychological resources including optimism and generalized positive affect had higher impact on cortisol secretion than their negative counterparts, and point to the need for increased attention to the potential contribution of positive mental states to well-being.

Coronary intervention with a heparin-coated stent and aspirin only.

OBJECTIVES: To determine the safety and efficacy of a post-stenting anti-platelet regimen of aspirin without additional ticlopidine or clopidogrel after successful heparin-coated stent implantation. METHODS: A prospective, non-randomized, multi-center pilot study of patients undergoing percutaneous coronary intervention, including those with acute coronary syndromes and small vessels with one-month clinical follow-up, was undertaken. Patients received a heparin-coated stent and were treated with aspirin only. RESULTS: Over a period of 6 months, a total of 122 patients were recruited in 6 centers. Their mean age was 57.2 10.0 years, 79% were male and 31% had unstable angina. Most (75%) had single-vessel disease, predominantly of the left anterior descending artery (51%), with a mean reference diameter of 2.44 mm 0.44 mm at baseline and 2.48 0.41 mm post stenting. At a 1-month clinical follow-up, no major adverse cardiovascular events (including subacute stent thrombosis) had occurred. Five patients were readmitted to hospital for symptoms unrelated to the interventional procedure. CONCLUSIONS: Heparin-coated stent implantation using an antiplatelet regimen of aspirin only, appears to be safe and feasible. A randomized trial of a larger number of patients appears warranted.

Highly permeable silicon membranes for shear free chemotaxis and rapid cell labeling.

Microfluidic systems are powerful tools for cell biology studies because they enable the precise addition and removal of solutes in small volumes. However, the fluid forces inherent in the use of microfluidics for cell cultures are sometimes undesirable. An important example is chemotaxis systems where fluid flow creates well-defined and steady chemotactic gradients but also pushes cells downstream. Here we demonstrate a chemotaxis system in which two chambers are separated by a molecularly thin (15 nm), transparent, and nanoporous silicon membrane. One chamber is a microfluidic channel that carries a flow-generated gradient while the other chamber is a shear-free environment for cell observation. The molecularly thin membranes provide effectively no resistance to molecular diffusion between the two chambers, making them ideal elements for creating flow-free chambers in microfluidic systems. Analytical and computational flow models that account for membrane and chamber geometry, predict shear reduction of more than five orders of magnitude. This prediction is confirmed by observing the pure diffusion of nanoparticles in the cell-hosting chamber despite high input flow (Q = 10 µL min(-1); vavg ~ 45 mm min(-1)) in the flow chamber only 15 nm away. Using total internal reflection fluorescence (TIRF) microscopy, we show that a flow-generated molecular gradient will pass through the membrane into the quiescent cell chamber. Finally we demonstrate that our device allows us to expose migrating neutrophils to a chemotactic gradient or fluorescent label without any influence from flow.

The contribution of bifunctional SkipDewax pretreatment solution, rabbit monoclonal antibodies, and polymer detection systems in immunohistochemistry.

CONTEXT: In immunohistochemistry, nonstandardized antigen retrieval protocols and fluids, poor-quality antibodies, and the presence of endogenous biotin frequently lead to incorrect results. Recently, advanced reagents including bifunctional SkipDewax pretreatment solution (BSPS), rabbit monoclonal (RM) antibodies, and biotin-free polymer detection systems (PDSs) have been developed, which, it is claimed, resolve these problems. OBJECTIVES: To determine whether BSPS, RM antibodies, and biotin-free PDSs improve the accuracy of immunohistochemistry; to optimize a new protocol consisting of a combination of BSPS, RM antibodies, and PDSs; and to compare it with a conventional protocol. DESIGN: The efficacies of BSPS, RM antibodies, and PDSs were compared with those of their respective conventional reagents using multitissue spring-roll sections. The new protocol was compared with a conventional protocol using Ki-67 immunostaining of 49 colorectal carcinoma specimens. RESULTS: For antigen retrieval, BSPS resulted in similar or better tissue staining than an EDTA solution, but the efficacy of BSPS decreased when it was reused. Most RM antibodies resulted in a greater proportion of positive cells than the corresponding non-RM antibodies, which did not produce satisfactory results in the absence of antigen retrieval. The PDSs Bond, ChemMate, and SuperPicture resulted in a high percentage of positive cells, good staining intensities, and low backgrounds. Other PDSs, except that from Ventana, resulted in high backgrounds and false positivity. The new combined protocol resulted in better Ki-67 staining than the conventional assay. CONCLUSIONS: Bifunctional SkipDewax pretreatment solution, RM antibodies, and PDSs improve staining quality and diagnostic accuracy of immunohistochemistry assays and provide a foundation for standardization.

Polymer-based, paclitaxel-eluting TAXUS Liberté stent in de novo lesions: the pivotal TAXUS ATLAS trial.

OBJECTIVES: The goal of this research was to assess non-inferiority of the next-generation TAXUS Liberté stent (Boston Scientific Corp., Natick, Massachusetts) versus the TAXUS Express stent (Boston Scientific Corp.). BACKGROUND: The introduction of drug-eluting stents (DES) has shifted clinical practice towards more complex lesion subsets, prompting the need for more deliverable DES. TAXUS Liberté was designed to combine the established polymer-based, paclitaxel-elution TAXUS technology with the more advanced Liberté stent platform. METHODS: The TAXUS ATLAS study is a global, prospective, single-arm trial evaluating outcomes in de novo coronary lesions visually estimated to be 10 to 28 mm in length in vessels 2.5 to 4.0 mm in diameter. The control group is an entry-criteria-matched population of TAXUS Express patients from the TAXUS IV and V trials. The primary end point is non-inferiority of TAXUS Liberté versus TAXUS Express for 9-month target vessel revascularization. RESULTS: Despite similar inclusion criteria, quantitative coronary angiography-determined baseline lesion characteristics were significantly more complex for TAXUS Liberté than TAXUS Express. The primary non-inferiority end point was met with the 1-sided 95% confidence bound of 2.98% less than the pre-specified non-inferiority margin of 3% (p = 0.0487). CONCLUSIONS: Despite the treatment of more complex lesions with TAXUS Liberté, the primary end point was met, demonstrating that TAXUS Liberté is non-inferior to TAXUS Express. The successful transfer of the proven TAXUS technology to the more advanced TAXUS Liberté platform was demonstrated. (TAXUS ATLAS: TAXUS Liberté-SR Stent for the Treatment of De Novo Coronary Artery Lesions; http://www.clinicaltrials.gov/ct/show/NCT00371709?order=1; NCT00371709).

The NUGGET study: NIR ultra gold-gilded equivalency trial.

This study should clarify whether the gold-coated NIROYAL stent is equivalent to the stainless steel NIR stent. Patients were randomized to either NIR stent (n = 298) or a NIROYAL stent (n = 305). The primary endpoint was the minimum lumen diameter of the target lesion at 6 months postprocedure. Secondary endpoints focused on clinical events. At 30 days, adverse events were similar in both groups. At 6 months, the minimal lumen diameter was 1.83/1.64 mm (P < 0.001; 95% CI = 0.08-0.30) and the angiographic restenosis rate was 20.6%/37.7% (P < 0.001; 95% CI = -24.7 to -9.3) for NIR/NIROYAL. The 6-month MACE rates were NIR 7.4% and NIROYAL 10.5% (95% CI = -7.7 to 1.4). Compared to stainless steel stent, the NIROYAL stent demonstrated a smaller minimal lumen diameter, a higher late loss (i.e., higher neointimal hyperplasia in spite of a significantly better initial gain), with higher restenosis and similar MACE rates at 6 months.