Data-Driven Based Characterization of Anisotropic Mechanical Properties for Cancellous Bone From Low-Resolution CT Images.

OBJECTIVES: Exploring the anisotropic mechanical behavior of cancellous bone is crucial for in-vivo bone biomechanical analysis. However, it is challenging to characterize anisotropic mechanical behaviors under low-resolution (LR) clinical CT images due to a lack of microstructural information. The data-driven method proposed in this article accurately characterizes the anisotropic mechanical properties of cancellous bone from LR clinical CT images. METHODS: The trabecular bone cubes of sheep are used to obtain a high-resolution (HR) micro-CT and an LR clinical CT image dataset. First, an auto-encoder model is trained using HR image data. Microstructural features are extracted by the encoder. A fast super-resolution (FSR) model is trained to map LR bone cubes to the features extracted from corresponding HR samples. The pretrained FSR model is used to convert LR clinical CT images to encoded microstructural features. The features are later used to predict target histomorphological parameters, anisotropic elastic tensors, and fabric tensors based on a fully connected neural network. RESULTS: The data-driven model accurately predicts the elastic tensor and fabric tensor of trabecular bones with LR CT images with 0.6 mm/pixel spatial resolution. It was verified that LR clinical CT images could generate microstructural information using a generative deep-learning model and an up-sampling operation. SIGNIFICANCE: This study proves that clinical medical images of cancellous bone can be used for analysis of complex mechanical properties using a data-driven method, which is useful for real-time bone defect diagnosis and personalized bone prosthesis design in clinical application.

Learning Curve and Clinical Outcomes of Ultrasonic Osteotome-based En Bloc Laminectomy for Thoracic Ossification of the Ligamentum Flavum.

OBJECTIVE: Despite rapid advances in minimally invasive surgery, en bloc laminectomy remains the most common surgical approach for treating thoracic ossification of the ligamentum flavum (TOLF). However, the learning curve of this risky operation is rarely reported. Therefore, we aimed to describe and analyze the learning curve of ultrasonic osteotome-based en bloc laminectomy for TOLF. METHODS: Among 151 consecutive patients with TOLF who underwent en bloc laminectomy performed by one surgeon between January 2012 and December 2017, we retrospectively analyzed their demographic data, surgical parameters, and neurological function. Neurological outcome was evaluated with the modified Japanese Orthopaedic Association (mJOA) scale, and the Hirabayashi method was used to calculate the neurological recovery rate. The learning curve was assessed with logarithmic curve-fitting regression analysis. Univariate analysis methods were used for statistical analysis, including t-test, rank sum test, and chi-square test. RESULTS: A total of 50% of learning milestones could be reached in approximately 14 cases, and the asymptote in 76 cases. Therefore, 76 of the 151 enrolled patients were defined as the "early group," and the remaining 75 were delimitated as the "late group" for comparison. There was a significant intergroup difference in the corrected operative time (94.80 ± 27.77 vs 65.93 ± 15.67 min, P < 0.001) and the estimated blood loss (median 240 vs 400 mL, P < 0.001). The overall follow-up was 83.1 ± 18.5 months. The mJOA significantly increased from a median of 5 (IQR: 4-5) before the surgery to 10 (IQR: 9-10) at the last follow-up (P < 0.001). The overall complication rate was 37.1%, and no significant intergroup difference was found, except for the incidence of dural tears (31.6% vs 17.3%, p = 0.042). CONCLUSION: Initially, mastering the en bloc laminectomy technique using ultrasonic osteotome for TOLF treatment can be challenging, but the surgeon's experience improves as the operative time and blood loss decrease. Improved surgical experience reduced the risk of dural tears but was not associated with the overall complication rate or long-term neurological function. Despite the relatively long learning curve, en bloc laminectomy is a secure and valid technique for TOLF treatment.

Incidence, clinical features, and risk factors for acute pancreatitis following posterior instrumented fusion surgery for lumbar degenerative disease: a single-center, retrospective analysis of 20,929 patients.

PURPOSE: The aim of this study is to identify the incidence, clinical features, and risk factors for postoperative acute pancreatitis (PAP) after lumbar surgery. METHODS: We retrospectively analyzed patients who developed PAP after posterior lumbar fusion surgery. For each PAP patient, data were collected for four controls who underwent procedures in the same period and did not develop PAP. Statistical methods included univariate and multivariate analyses. RESULTS: Totally, 21 out of 20,929 patients were diagnosed with PAP (0.10%) after posterior lumbar fusion surgery. Patients with degenerative lumbar scoliosis were at higher risk of developing PAP (P < 0.05). With atypical clinical features, PAP occurred within 3 days (0-5) after surgery. PAP patients had significantly higher incidence of osteoporosis (47.6 vs. 22.6%, P = 0.030) and fusion of L1/2(42.9 vs. 4.3%, P = 0.010), lower albumin (42.2 ± 4.1 vs. 44.3 ± 3.2 g/L, P = 0.010), more fusion segments (median 4 vs. 3, P = 0.022), larger surgical invasiveness index (median 9 vs. 8, P = 0.007), longer operation duration (232 ± 109 vs. 185 ± 90 min, P = 0.041), greater estimated blood loss (median 600 vs. 400 mL, P = 0.025), lower intraoperative mean arterial pressure (87.2 ± 9.9 vs. 92.1 ± 8.8 mmHg, P = 0.024). Multivariate logistic regression analysis found three independent risk factors: fusion of L1/2, surgical invasiveness index > 8, and intraoperative mean arterial pressure < 90 mmHg. All patients were treated with conservative therapy and fully recovered after 8.1 (4-22) days. CONCLUSION: The incidence of PAP following posterior surgery for degenerative lumbar disease was 0.10%, and its clinical features were not typical. The fusion of L1/2, high surgical invasiveness index, and low intraoperative mean arterial pressure were independent risk factors for PAP after surgery for lumbar degenerative disease.

The effect of pore size on the mechanical properties, biodegradation and osteogenic effects of additively manufactured magnesium scaffolds after high temperature oxidation: An in vitro and in vivo study.

The effects of pore size in additively manufactured biodegradable porous magnesium on the mechanical properties and biodegradation of the scaffolds as well as new bone formation have rarely been reported. In this work, we found that high temperature oxidation improves the corrosion resistance of magnesium scaffold. And the effects of pore size on the mechanical characteristics and biodegradation of scaffolds, as well as new bone formation, were investigated using magnesium scaffolds with three different pore sizes, namely, 500, 800, and 1400 µm (P500, P800, and P1400). We discovered that the mechanical characteristics of the P500 group were much better than those of the other two groups. In vitro and in vivo investigations showed that WE43 magnesium alloy scaffolds supported the survival of mesenchymal stem cells and did not cause any local toxicity. Due to their larger specific surface area, the scaffolds in the P500 group released more magnesium ions within reasonable range and improved the osteogenic differentiation of bone mesenchymal stem cells compared with the other two scaffolds. In a rabbit femoral condyle defect model, the P500 group demonstrated unique performance in promoting new bone formation, indicating its great potential for use in bone defect regeneration therapy.

Development and validation of a novel thoracic spinal stenosis surgical invasiveness index: a single-center study based on 989 patients.

BACKGROUND CONTEXT: Surgical invasiveness indices have been established for general spine surgery (surgical invasiveness index [SII]), spine deformity, and metastatic spine tumors; however, a specific index for thoracic spinal stenosis (TSS) has not been developed. PURPOSE: To develop and validate a novel invasiveness index, incorporating TSS-specific factors for open posterior TSS surgery, which may facilitate the prediction of operative duration and intraoperative blood loss, and the stratification of surgical risk. STUDY DESIGN: A retrospective observational study. PATIENT SAMPLE: Overall, 989 patients who underwent open posterior TSS surgeries at our institution during the past 5 years were included. OUTCOME MEASURES: The operation duration, estimated blood loss, transfusion status, major surgical complications, length of hospital stay, and medical expenses. METHODS: We retrospectively analyzed the data of 989 consecutive patients who underwent posterior surgery for TSS between March 2017 and February 2022. Among them, 70% (n=692) were randomly placed in a training cohort, and the remaining 30% (n=297) automatically constituted the validation cohort. Multivariate linear regression models of operative time and log-transformed estimated blood loss were created using TSS-specific factors. Beta coefficients derived from these models were used to construct a TSS invasiveness index (TII). The ability of the TII to predict surgical invasiveness was compared with that of the SII and assessed in a validation cohort. RESULTS: The TII was more strongly correlated with operative time and estimated blood loss (p<.05) and explained more variability in operative time and estimated blood loss than the SII (p<.05). The TII explained 64.2% of operative time and 34.6% of estimated blood loss variation, whereas the SII explained 38.7% and 22.5%, respectively. In further verification, the TII was more strongly associated with transfusion rate, drainage time, and length of hospital stay than SII (p<.05). CONCLUSIONS: By incorporating TSS-specific components, the newly developed TII more accurately predicts the invasiveness of open posterior TSS surgery than the previous index.

Thirty-day unplanned reoperations of thoracic spine surgery: 10 years of data from a single center with 3242 patients.

BACKGROUND CONTEXT: Unplanned reoperation is a useful quality indicator for spine surgery. However, the rates of a 30-day unplanned reoperation in patients undergoing thoracic spinal surgery are not well established. PURPOSE: To assess the rates, reasons, and risk factors of 30-day unplanned reoperations for thoracic spine surgeries in a single center study. STUDY DESIGN: A retrospective observational study. PATIENT SAMPLE: A total of 3242 patients who underwent thoracic spinal surgery at our institution in the past decade were included. OUTCOME MEASURES: The incidence, chief reasons, and risk factors for unplanned reoperations within 30 days after thoracic spinal surgery. METHODS: We retrospectively analyzed the data of all patients who underwent thoracic spinal surgery between January 2012 and December 2021. Statistical methods, including univariate and multivariate analyses, were performed to assess the incidence, reasons, and risk factors for thoracic degenerative diseases, spinal tumors, kyphosis deformity, and spinal trauma. RESULTS: Of the 3242 patients who underwent thoracic spinal surgery, 107 (3.30%) required unplanned reoperations within 30 days due to epidural hematoma (1.17%), wound complications (0.80%), implant complications (0.43%), inadequate decompression (0.25%), and other causes (0.65%). Patients with degenerative disease (3.88%), spinal tumor (2.98%), and kyphosis deformity (3.33%) had significantly higher incidences of reoperation than those with spinal trauma (1.47%). Unplanned reoperations were classified as hyperacute (30.84%), acute (31.76%), and subacute (37.38%). After univariate analysis, several factors were associated with unplanned reoperation in the 4 cohorts of thoracic spine diseases (p<.05). Multivariate logistic regression analysis revealed that upper thoracic spine surgery (p=.001), concomitant dekyphosis (p=.027), and longer activated partial thromboplastin time (p=.025) were risk factors of unplanned reoperation for thoracic degenerative disease. Whereas American Society of Anesthesiologists (ASA) grade III (p=.015), combined approach (p=.016), and operation time longer than 420 min (p=.042) for spinal tumor, and similar ankylosing spondylitis (p=.023) and operation time longer than 340 min (p=.041) were risk factors of unplanned reoperation for kyphosis deformity. CONCLUSIONS: The unplanned reoperation rate for thoracic spine surgery was 3.30%, with epidural hematoma and wound complications being the most common reasons. However, upper thoracic spine surgery, concomitant dekyphosis, underlying coagulation disorder, longer operation time, higher ASA grade, and comorbidities of ankylosing spondylitis led to an increased risk of unplanned reoperation within 30 days of thoracic spine surgery.

Experimentally characterizing the spatially varying anisotropic mechanical property of cancellous bone via a Bayesian calibration method.

Traditional experimental tests for characterizing bone's mechanical properties usually hypothesize a uniaxial stress condition without quantitatively evaluating the influence of spatially varying principal material orientations, which cannot accurately predict the mechanical properties distribution of bones in vivo environment. In this study, a Bayesian calibrating procedure was developed using quantified multiaxial stress to investigate cancellous bone's local anisotropic elastic performance around joints as the spatial variation of main bearing orientations. First, the bone cube specimens from the distal femur of sheep are prepared using traditional anatomical axes. The multiaxial stress state of each bone specimen is calibrated using the actual principal material orientations derived from fabric tensor at different anatomical locations. Based on the calibrated multiaxial stress state, the process of identifying mechanical properties is described as an inverse problem. Then, a Bayesian calibration procedure based on a surrogate constitutive model was developed via multiaxial stress correction to identify the anisotropic material parameters. Finally, a comparison between the experiment and simulation results is discussed by applying the optimal model parameters obtained from the Bayesian probability distribution. Compared to traditional uniaxial methods, our results prove that the calibration based on the spatial variation of the main bearing orientations can significantly improve the accuracy of characterizing regional anisotropic mechanical responses. Moreover, we determine that the actual mechanical property distribution is influenced by complicated mechanical stimulation. This study provides a novel method to evaluate the spatially varying mechanical properties of bone tissues enduring complex mechanical loading accurately and effectively. It is expected to provide more realistic mechanical design targets in vivo for a personalized artificial bone prosthesis in clinical treatment.

Thirty-day Unplanned Reoperations After Posterior Surgery for Thoracic Spinal Stenosis: A Single-center Study Based on 1948 Patients.

STUDY DESIGN: A retrospective study. OBJECTIVE: The purpose of this study is to identify the incidences, causes, and risk factors of 30-day unplanned reoperation of posterior surgery for thoracic spinal stenosis (TSS) based on 1948 patients in a single center. SUMMARY OF BACKGROUND DATA: Unplanned reoperation is suggested to be a useful quality indicator for spine surgery. However, the incidences, causes, and risk factors of 30-day unplanned reoperation in patients who underwent posterior spinal surgery for TSS have not been well-established. MATERIALS AND METHODS: We retrospectively analyzed the clinical data of patients who underwent posterior spinal surgery for TSS from January 2011 to December 2021. Statistical methods including univariate and multivariate analyses were performed to assess the incidences, causes, and risk factors. RESULTS: A total of 1948 patients who underwent posterior spinal surgery for TSS in our institution were reviewed, and 77 (3.95%) required unplanned reoperations within 30 days because of epidural hematoma (1.64%), wound-related complications (1.02%), inadequate decompression (0.41%), and implant malposition or failure (0.36%), neurological deficit (0.26%), and other causes (0.26%). After univariate analysis, seven clinical factors were associated with unplanned reoperation ( P <0.05). Multivariate logistic regression analysis showed that upper thoracic spine surgery ( P =0.010), thoracic kyphosis ≥45° ( P =0.039), and intraoperative dural injury ( P =0.047) were independent risk factors for 30-day unplanned reoperation of posterior surgery for TSS. CONCLUSIONS: The incidence of 30-day unplanned reoperations after posterior surgical treatment for TSS was 3.95%. The most common causes were epidural hematoma, wound-related complications, inadequate decompression, and implant malposition or failure. Upper thoracic spine surgery, thoracic kyphosis ≥45°, and intraoperative dural injury led to an increased risk of unplanned reoperation within 30 days after posterior spinal surgery for TSS. LEVEL OF EVIDENCE: 4.

Incidence, Risk Factors, and Outcomes of Symptomatic Bone Cement Displacement following Percutaneous Kyphoplasty for Osteoporotic Vertebral Compression Fracture: A Single Center Study.

STUDY DESIGN: Retrospective. BACKGROUND: Symptomatic bone cement displacement (BCD) is a rare complication following percutaneous kyphoplasty (PKP) interventions for osteoporotic vertebral compression fracture (OVCF). This study aimed to investigate the incidence and the outcomes of symptomatic BCD comprehensively and identify its risk factors. METHODS: The clinical data of patients treated with PKP for OVCF between January 2012 and December 2020 were extracted. Patients who developed BCD following PKP during follow-up were divided into the symptomatic and asymptomatic groups. Patients who did not develop BCD were assigned to the control group. Univariate and multiple logistic regression analyses were used to compare the three clinical groups' features to assess the independent risk factors for the symptomatic and asymptomatic groups. RESULTS: A total of 896 patients were enrolled. Twenty-one patients (2.3%) were identified as having symptomatic BCD following PKP for OVCF, and 35 (3.9%) developed asymptomatic BCD. Compared with the control group, the symptomatic and asymptomatic groups had a higher incidence of anterior leakage, intravertebral vacuum cleft (IVC) signs, and a lower cement distribution score. The symptomatic group had a lower relative cross-sectional area (rCSA) of the paraspinal muscle (PSM), higher PSM fatty degeneration, and higher kyphotic angle (at the last follow-up) than the asymptomatic and control groups. For outcomes, the symptomatic group had a higher VAS/ODI score and a higher incidence of new vertebral fractures compared with the asymptomatic and control groups. Anterior leakage (OR: 1.737, 95% CI: 1.215-3.300), the IVC sign (OR: 3.361, 95% CI: 1.605-13.036), the cement distribution score (OR: 0.476, 95% CI: 0.225-0.904), PSM rCSA (OR: 0.953, 95% CI: 0.917-0.992), and PSM fatty degeneration (OR: 1.061, 95% CI: 1.005-1.119) were identified as independent risk factors for the symptomatic group. Anterior leakage (OR: 1.839, 95% CI: 1.206-2.803), the IVC sign (OR: 2.936, 95% CI: 1.174-9.018), and cement distribution score (OR: 0.632, 95% CI: 0.295-0.858) were independent risk factors for the asymptomatic group. CONCLUSION: The incidence of symptomatic BCD is 2.3% in patients treated with PKP. Anterior leakage, the IVC sign, and the distribution score were independent risk factors for BCD, and paraspinal muscle degeneration was a specific risk factor for symptomatic BCD. Symptomatic BCD can lead to poor outcomes.

Incidences, causes and risk factors of unplanned reoperations within 30 days of spine surgery: a single-center study based on 35,246 patients.

BACKGROUND CONTEXT: Unplanned reoperation, a quality indicator in spine surgery, has not been sufficiently investigated in a large-scale, single-center study. PURPOSE: To assess the incidences, causes, and risk factors of unplanned reoperations within 30 days of spine surgeries in a single-center study. STUDY DESIGN: Retrospective observational study. PATIENT SAMPLE: A cohort of 35,246 patients who underwent spinal surgery in our hospital were included. OUTCOME MEASURES: The rates, chief reasons, and risk factors for unplanned reoperations within 30 days of spine surgery. METHODS: We retrospectively analyzed the data for patients who underwent spine surgeries for degenerative spinal disorders, tumor, or deformity and had subsequent unplanned operations within 30 days at a single tertiary academic hospital from January 2016 to July 2021. Univariate and multivariate analyses were performed to assess the incidences, causes, and risk factors. RESULTS: Out of 35,246 spinal surgery patients, 297 (0.84%) required unplanned reoperations within 30 days of spine surgery. Patients with a thoracic degenerative disease (3.23%), spinal tumor (1.63%), and spinal deformity (1.50%) had significantly higher rates of reoperation than those with atlantoaxial (0.61%), cervical (0.65%), and lumbar (0.82%) degenerative disease. The common causes for reoperation included epidural hematoma (0.403%), wound infections (0.148%), neurological deficit (0.108%), and pedicle screw malposition (0.077%). Unplanned reoperations were classified as hyperacute (45.45%), acute (30.98%), subacute (15.82%), or chronic (7.74%). Univariate analysis indicated that 20 clinical factors were associated with unplanned reoperation (p<.05). Multivariate Poisson regression analysis revealed that anemia (p<.001), osteoporosis (p=.048), ankylosing spondylitis (p=.008), preoperative foot drop (p=.011), deep venous thrombosis (p<.001), and previous surgical history (p<.001) were independent risk factors for unplanned spinal reoperation. CONCLUSIONS: The incidence of unplanned spinal reoperations was 0.84%. The chief common causes were epidural hematoma, wound infections, neurological deficit, and pedicle screw malposition. Anemia, osteoporosis, ankylosing spondylitis, preoperative foot drop, deep venous thrombosis, and previous surgical history led to an increased risk of unplanned reoperation within 30 days of spine surgery.

Structural insight into SARS-CoV-2 neutralizing antibodies and modulation of syncytia.

Infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is initiated by binding of the viral Spike protein to host receptor angiotensin-converting enzyme 2 (ACE2), followed by fusion of viral and host membranes. Although antibodies that block this interaction are in emergency use as early coronavirus disease 2019 (COVID-19) therapies, the precise determinants of neutralization potency remain unknown. We discovered a series of antibodies that potently block ACE2 binding but exhibit divergent neutralization efficacy against the live virus. Strikingly, these neutralizing antibodies can inhibit or enhance Spike-mediated membrane fusion and formation of syncytia, which are associated with chronic tissue damage in individuals with COVID-19. As revealed by cryoelectron microscopy, multiple structures of Spike-antibody complexes have distinct binding modes that not only block ACE2 binding but also alter the Spike protein conformational cycle triggered by ACE2 binding. We show that stabilization of different Spike conformations leads to modulation of Spike-mediated membrane fusion with profound implications for COVID-19 pathology and immunity.

Bivalent binding of a fully human IgG to the SARS-CoV-2 spike proteins reveals mechanisms of potent neutralization.

In vitro antibody selection against pathogens from naïve combinatorial libraries can yield various classes of antigen-specific binders that are distinct from those evolved from natural infection1-4. Also, rapid neutralizing antibody discovery can be made possible by a strategy that selects for those interfering with pathogen and host interaction5. Here we report the discovery of antibodies that neutralize SARS-CoV-2, the virus responsible for the COVID-19 pandemic, from a highly diverse naïve human Fab library. Lead antibody 5A6 blocks the receptor binding domain (RBD) of the viral spike from binding to the host receptor angiotensin converting enzyme 2 (ACE2), neutralizes SARS-CoV-2 infection of Vero E6 cells, and reduces viral replication in reconstituted human nasal and bronchial epithelium models. 5A6 has a high occupancy on the viral surface and exerts its neutralization activity via a bivalent binding mode to the tip of two neighbouring RBDs at the ACE2 interaction interface, one in the "up" and the other in the "down" position, explaining its superior neutralization capacity. Furthermore, 5A6 is insensitive to several spike mutations identified in clinical isolates, including the D614G mutant that has become dominant worldwide. Our results suggest that 5A6 could be an effective prophylactic and therapeutic treatment of COVID-19.

Does Early Graft Patency Benefit from Perioperative Statin Therapy? A Propensity Score-Matched Study of Patients Undergoing Off-Pump Coronary Artery Bypass Surgery.

BACKGROUND: Decreased graft patency after off-pump coronary artery bypass grafting (OPCAB) leads to substantial increases in cardiac events. However, there is paucity of data on efficacy and safety of perioperative statin therapy for OPCAB populations. METHODS: 582 patients undergoing OPCAB in a single-institution database (October 1, 2009-September 30, 2012) were stratified by perioperative continuation of statin therapy (CS group, n=398) or not (DS group, n=184). Inverse probability weighted propensity adjustment was used to account for treatment assignment bias, resulting in a well-matched cohort. Primary outcomes were graft patency at an average of five days after operation and in-hospital mortality. Secondary outcomes included intraoperative blood loss, liver, and renal functions. RESULTS: No in-hospital death occurred in this study. Early graft patency rates after OPCAB were 98.4% (1255 of 1275 grafts) in the CS group and 98.0% (583 of 595 grafts, P=0.486) in the DS group. Secondary outcomes showed a reduction in blood loss during operation (438.53 mL versus 480.47 mL, P=0.01). Continuation of statin therapy is associated with alanine transaminase (ALT) elevation (49.67 U/L versus 34.52 U/L, P<0.001), as well as aspartate transaminase (33.54 U/L versus 28.10 U/L, P<0.001). Abnormal ALT elevation was observed in 8.9% of the CS group and 3.1% in DS (odds ratio 3.06, 95% confidence interval, 1.77 to 5.29, P<0.001). There was no significant difference in estimated glomerular filtration rate (76.28 mL/min/1.73m2 versus 76.13 mL/min/1.73m2, P=0.90). Subgroup analyses suggested that graft occlusion was less common in CS than in DS group among smoking patients (odds ratio 0.41, 95% confidence interval, 0.20 to 0.86, P=0.026). CONCLUSIONS: Perioperative continuation of statin therapy did not improve early graft patency in OPCAB patients. A lower risk of graft occlusion was observed among smoking patients. Continuous statin use correlated with liver function elevation (Clinical Trials.gov number, NCT01268917).

Mutational spectrum of Barrett's stem cells suggests paths to initiation of a precancerous lesion.

The precancerous lesion known as Barrett's oesophagus can evolve to oesophageal adenocarcinoma in decades-long processes of regenerative growth. Here we report the isolation and propagation of distinct, patient-matched stem cells of Barrett's, gastric and oesophageal epithelia that yield divergent tumour types following in vitro transformation and xenografting. Genomic analyses reveal a broad mutational spectrum unique to Barrett's stem cells that likely reflects their risk for oncogenesis. Remarkably, 25% of cases show no cancer-related genomic changes, suggesting that Barrett's initiates without driver mutations. Most cases, however, sustain patterns of deletions almost identical to adenocarcinoma though tumour-associated gene amplifications were absent. Notably, those suspected of low-grade dysplasia have p53 mutations or undergo amplifications of proto-oncogenes and receptor tyrosine kinases, implicating these events in lethal transitions. Our findings suggest paths for the initiation and progression of Barrett's and define a discrete stem cell underlying its regenerative growth whose eradication could prevent oesophageal adenocarcinoma.

c-Abl promotes osteoblast expansion by differentially regulating canonical and non-canonical BMP pathways and p16INK4a expression.

Defects in stem cell renewal or progenitor cell expansion underlie ageing-related diseases such as osteoporosis. Yet much remains unclear about the mechanisms regulating progenitor expansion. Here we show that the tyrosine kinase c-Abl plays an important role in osteoprogenitor expansion. c-Abl interacts with and phosphorylates BMPRIA and the phosphorylation differentially influences the interaction of BMPRIA with BMPRII and the Tab1-Tak1 complex, leading to uneven activation of Smad1/5/8 and Erk1/2, the canonical and non-canonical BMP pathways that direct the expression of p16(INK4a). c-Abl deficiency shunts BMP signalling from Smad1/5/8 to Erk1/2, leading to p16(INK4a) upregulation and osteoblast senescence. Mouse genetic studies revealed that p16(INK4a) controls mesenchymal stem cell maintenance and osteoblast expansion and mediates the effects of c-Abl deficiency on osteoblast expansion and bone formation. These findings identify c-Abl as a regulator of BMP signalling pathways and uncover a role for c-Abl in p16(INK4a) expression and osteoprogenitor expansion.

A crucial role for bone morphogenetic protein-Smad1 signalling in the DNA damage response.

DNA damage and the elicited cellular response underlie the etiology of tumorigenesis and ageing. Yet, how this response integrates inputs from cells' environmental cues remains underexplored. Here we report that the BMP-Smad1 pathway, which is essential for embryonic development and tissue homeostasis, has an important role in the DNA damage response and oncogenesis. On genotoxic stress, Atm phosphorylates BMPs-activated Smad1 in the nucleus on S239, which disrupts Smad1 interaction with protein phosphatase PPM1A, leading to enhanced activation and upregulation of Smad1. Smad1 then interacts with p53 and inhibits Mdm2-mediated p53 ubiquitination and degradation to regulate cell proliferation and survival. Enhanced Smad1 S239 phosphorylation, and Smad1 mutations causing S239 substitution were detected in oesophageal and gastric cancer samples, respectively. These findings suggest that BMP-Smad1 signalling participates in the DNA damage response via the Atm-p53 pathway, thus providing a molecular mechanism whereby BMP-Smad1 loss-of-function leads to tumorigenesis, for example, juvenile polyposis and Cowden syndromes.

Distal airway stem cells yield alveoli in vitro and during lung regeneration following H1N1 influenza infection.

The extent of lung regeneration following catastrophic damage and the potential role of adult stem cells in such a process remains obscure. Sublethal infection of mice with an H1N1 influenza virus related to that of the 1918 pandemic triggers massive airway damage followed by apparent regeneration. We show here that p63-expressing stem cells in the bronchiolar epithelium undergo rapid proliferation after infection and radiate to interbronchiolar regions of alveolar ablation. Once there, these cells assemble into discrete, Krt5+ pods and initiate expression of markers typical of alveoli. Gene expression profiles of these pods suggest that they are intermediates in the reconstitution of the alveolar-capillary network eradicated by viral infection. The dynamics of this p63-expressing stem cell in lung regeneration mirrors our parallel finding that defined pedigrees of human distal airway stem cells assemble alveoli-like structures in vitro and suggests new therapeutic avenues to acute and chronic airway disease.

PKCdelta mediates Nrf2-dependent protection of neuronal cells from NO-induced apoptosis.

A chemical inhibitor library of 84 compounds was screened to investigate the signaling pathway(s) leading to activation of Nrf2 in response to nitric oxide (NO). We identified the protein kinase C delta (PKCdelta) inhibitor rottlerin as the only compound that reduced NO-induced ARE-luciferase reporter activity and diminished NO-induced up-regulation of two Nrf2/ARE-regulated proteins - NAD(P)H:quinone oxidoreductase-1 (NQO1) and hemeoxygenase-1 (HO-1) in SH-Sy5y cells. Rottlerin also sensitized neuroblastoma cells and mouse primary cortical neurons to NO-induced apoptosis. Stable over-expression of PKCdelta augmented NO-induced, ARE-dependent gene expression of HO-1 in SH-Sy5y cells, which were more protected from NO killing. Conversely, NO-induced ARE-dependent gene expression was reduced in PKCdelta-knockdown SH-EP cells, which displayed greater sensitivity to apoptosis. PKCdelta(-/-) cortical neurons exhibited increased NO-induced apoptosis and less HO-1 mRNA and protein induction compared with wild type neurons. Hence, PKCdelta is an important positive modulator of NO-induced Nrf2/ARE-dependent signaling that counteracts NO-mediated apoptosis in neuronal cells.

PKC delta phosphorylates p52ShcA at Ser29 to regulate ERK activation in response to H2O2.

Both PKC delta and ShcA have been implicated in cell response to oxidative stress [Y. Hu, X. Wang, L. Zeng, D.Y. Cai, K. Sabapathy, S.P. Goff, E.J. Firpo, B. Li, Mol Biol Cell., 16 (2005) 3705-3718, B. Li, X. Wang, N. Rasheed, Y. Hu, S. Boast, T. Ishii, K. Nakayama, K.I. Nakayama, S.P., Goff, Genes Dev, 18 (2004) 1824-1837, E. Migliaccio, M. Giorgio, S. Mele, G. Pelicci, P. Reboldi, P.P. Pandolfi, L. Lanfrancone, P.G. Pelicci, Nature, 402 (1999) 309-313], yet their relationship in the response has not been studied. Here we report that PKC delta interacts with ShcA and this interaction is promoted by H(2)O(2). PKC delta and ShcA are also colocalized in the cytoplasm and displayed co-translocation in response to H(2)O(2). Activated PKC delta was able to phosphorylate ShcA at Ser29, as determined by mass spectrometry. These results suggest that ShcA, p66 and p52, are substrates that interact with PKC delta. This phosphorylation is critical in H(2)O(2) induced ERK activation as reconstitution with ShcA Ser29A failed to rescue ERK activation of ShcA-/- MEFs, while ShcA could. In line with this conclusion, inhibition of PKC delta with inhibitors is able to diminish H(2)O(2) induced ERK activation in MEFs. These results suggest that the interaction between PKC delta and ShcA and the phosphorylation of ShcA at Ser29 play important roles in ERK activation in cell response to H(2)O(2).