Prognostic effects of histology-based tumour microenvironment scores in resected distal bile duct cancer.

AIMS: Histology-based tumour microenvironment (TME) scores are useful in predicting the prognosis of gastrointestinal cancer. However, their prognostic roles in distal bile duct cancer (DBDC) have not been previously studied. This study aimed to evaluate the prognostic significance of the TME scores using the Klintrup-Mäkinen (KM) grade, tumour stroma percentage (TSP) and the Glasgow microenvironment score (GMS) in resected DBDC. METHODS AND RESULTS: Eighty-one patients with DBDC who underwent curative resection were enrolled. DBDC was graded according to KM grade, TSP and GMS. A high KM grade was found in 19 patients (24%) and a high TSP was found in 47 patients (58%). A high TSP was significantly correlated with a low KM grade (P < 0.001). The distribution of the GMS, which was developed by combining the KM grade and TSP, was as follows: 0 (n = 19, 24%), 1 (n = 19, 24%) and 2 (n = 43, 52%). A low KM grade, high TSP and high GMS were significantly associated with short overall survival (OS) (P < 0.001) and relapse-free survival (RFS) (P < 0.001). Furthermore, multivariate analysis showed that a low KM grade [hazard ratio (HR) = 3.826; confidence interval (CI) = 1.650-8.869; P = 0.014], high TSP (HR = 2.193; CI = 1.173-4.100, P = 0.002) and high GMS (HR = 7.148; CI = 2.811-18.173) were independent prognostic factors for short RFS; a low KM grade (HR = 4.324; CI = 1.594-11.733) and high GMS (HR = 6.332; CI = 2.743-14.594) were independent prognostic factors for short OS. CONCLUSION: Histology-based TME scores, including the KM grade, TSP and GMS, are useful for predicting the survival of patients with resected DBDC.

Direct numerical simulation of transitional flow in a stenosed carotid bifurcation.

The blood flow dynamics of a stenosed, subject-specific, carotid bifurcation were numerically simulated using the spectral element method. Pulsatile inlet conditions were based on in vivo color Doppler ultrasound measurements of blood velocity. The results demonstrated the transitional or weakly turbulent state of the blood flow, which featured rapid velocity and pressure fluctuations in the post-stenotic region of the internal carotid artery (ICA) during systole and laminar flow during diastole. High-frequency vortex shedding was greatest downstream of the stenosis during the deceleration phase of systole. Velocity fluctuations had a frequency within the audible range of 100-300Hz. Instantaneous wall shear stress (WSS) within the stenosis was relatively high during systole ( approximately 25-45Pa) compared to that in a healthy carotid. In addition, high spatial gradients of WSS were present due to flow separation on the inner wall. Oscillatory flow reversal and low pressure were observed distal to the stenosis in the ICA. This study predicts the complex flow field, the turbulence levels and the distribution of the biomechanical stresses present in vivo within a stenosed carotid artery.

Force-induced activation of talin and its possible role in focal adhesion mechanotransduction.

It is now well established that cells can sense mechanical force, but the mechanisms by which force is transduced into a biochemical signal remain poorly understood. One example is the recruitment of vinculin to reinforce initial contacts between a cell and the extracellular matrix (ECM) due to tensile force. Talin, an essential linking protein in an initial contact, contains at least one vinculin-binding site (VBS) that is cryptic and inactive in the native state. The N-terminal five-helix bundle of talin rod is a stable structure with a known cryptic VBS1. The perturbation of this stable structure through elevated temperature or destabilizing mutation activates vinculin binding. Although the disruption of this subdomain by transmitted mechanical force is a potential cue for the force-induced focal adhesion strengthening, the molecular basis for this mechanism remains elusive. Here, molecular dynamics (MD) is employed to demonstrate a force-induced conformational change that exposes the cryptic vinculin-binding residues of VBS1 to solvent under applied force along a realistic pulling direction. VBS1 undergoes a rotation of 62.0 +/- 9.5 degrees relative to its native state as its vinculin-binding residues are released from the tight hydrophobic core. Charged and polar residues on the VBS1 surface are the site of force transmission that strongly interact with an adjacent alpha-helix, and in effect, apply torque to the VBS1 to cause its rotation. Activation was observed with mean force of 13.2 +/-8.0 pN during constant velocity simulation and with steady force greater than 18.0 pN.

A coarse-grained model for force-induced protein deformation and kinetics.

Force-induced changes in protein conformation are thought to be responsible for certain cellular responses to mechanical force. Changes in conformation subsequently initiate a biochemical response by alterations in, for example, binding affinity to another protein or enzymatic activity. Here, a model of protein extension under external forcing is created inspired by Kramers' theory for reaction rate kinetics in liquids. The protein is assumed to have two distinct conformational states: a relaxed state, C(1), preferred in the absence of external force, and an extended state, C(2), favored under force application. In the context of mechanotransduction, the extended state is a conformation from which the protein can initiate signaling. Appearance and persistence of C(2) are assumed to lead to transduction of the mechanical signal into a chemical one. The protein energy landscape is represented by two harmonic wells of stiffness kappa(1) and kappa(2), whose minima correspond to conformations C(1) and C(2). First passage time t(f) from C(1) to C(2) is determined from the Fokker-Plank equation employing several different approaches found in the literature. These various approaches exhibit significant differences in behavior as force increases. Although the level of applied force and the energy difference between states largely determine equilibrium, the dominant influence on t(f) is the height of the transition state. Distortions in the energy landscape due to force can also have a significant influence, however, exhibiting a weaker force dependence than exponential as previously reported, approaching a nearly constant value at a level of force that depends on the ratio kappa(1)/kappa(2). Two model systems are used to demonstrate the utility of this approach: a short alpha-helix undergoing a transition between two well-defined states and a simple molecular motor.

Transitional flow at the venous anastomosis of an arteriovenous graft: potential activation of the ERK1/2 mechanotransduction pathway.

We present experimental and computational results that describe the level, distribution, and importance of velocity fluctuations within the venous anastomosis of an arteriovenous graft. The motivation of this work is to understand better the importance of biomechanical forces in the development of intimal hyperplasia within these grafts. Steady-flow in vitro studies (Re = 1060 and 1820) were conducted within a graft model that represents the venous anastomosis to measure velocity by means of laser Doppler anemometry. Numerical simulations with the same geometry and flow conditions were conducted by employing the spectral element technique. As flow enters the vein from the graft, the velocity field exhibits flow separation and coherent structures (weak turbulence) that originate from the separation shear layer. We also report results of a porcine animal study in which the distribution and magnitude of vein-wall vibration on the venous anastomosis were measured at the time of graft construction. Preliminary molecular biology studies indicate elevated activity levels of the extracellular regulatory kinase ERK1/2, a mitogen-activated protein kinase involved in mechanotransduction, at regions of increased vein-wall vibration. These findings suggest a potential relationship between the associated turbulence-induced vein-wall vibration and the development of intimal hyperplasia in arteriovenous grafts. Further research is necessary, however, in order to determine if a correlation exists and to differentiate the vibration effect from that of flow related effects.