Citations

AbstractTissue engineering aims at recapitulating permissive conditions that enable cells to collaborate and form functional tissues. Applications range from human tissue modeling for diagnostic purposes to therapeutic solutions in regenerative medicine and surgery. Across this spectrum, human stem cells are the active ingredient, expandable virtually indefinitely and with the propensity to generate new tissue. Engaging lineage-specific differentiation requires a precise concerto of key spatial and temporal factors, such as soluble molecules and growth factors, but also physical and mechanical stimuli. These stimuli compete to modulate distinct developmental signaling pathways and ultimately affect the differentiation efficiency. The heart is a chemo-mechano-electrical biological system that behaves as both a sensor and an actuator. It can transduce electrical inputs to generate mechanical contraction and electrical wave propagation. Such a complex organ arises from multipart developmental events that interact with one another to self-regulate. Here, we overview the main events of heart development and the role of mechanical forces in modifying the microenvironment of the progenitor cells. We analyze the cascades regulating cardiac gene activation to illustrate how mechanotransduction is already involved in the most popular protocols for stem cell differentiation (SCD) into cardiomyocytes. We then review how forces are transmitted to embryonic stem cells by cell-substrate or cell-cell communications, and how biomaterials can be designed to mimic these interactions and help reproduce key features of the developmental milieu. Putting this back in a clinical perspective, many challenges needs to be overcome before biomaterials-based SCD protocols can be scaled up and marketed. Stem Cells 2015;33:1021–1035

Arrhythmogenic Substrate of Ventricular Arrhythmias at the AMCIntroductionCatheter ablation of ventricular arrhythmia (VA) at the fibrous aortic mitral continuity (AMC) has been described, yet the nature of the arrhythmogenic substrate remains unknown.MethodsProcedural records of 528 consecutive patients undergoing ablation of VA at Mayo Clinic, Rochester, MN, were reviewed. The electrocardiographic and electrophysiologic characteristics of patients with successful ablation at the AMC were analyzed to characterize the underlying arrhythmogenic substrate.ResultsOf the 21 patients (mean age 53.2 ± 13.4 years, 47.6% male) who underwent ablation of VA at the AMC with acute success, prepotentials (PPs) were found at the ablation sites preceding the ventricular electrogram (VEGM) during arrhythmias in 13 (61.9%) patients and during sinus rhythm in 7 (53.8%) patients. VAs with PPs were associated with a significantly higher burden of premature ventricular complexes (PVCs; 26.1 ± 10.9% vs. 14.9 ± 10.1%, P = 0.03), shorter VEGM to QRS intervals (9.0 ± 28.5 milliseconds vs. 33.1 ± 8.8 milliseconds, P = 0.03), lower pace map scores (8.7 ± 1.6 vs. 11.4 ± 0.8, P = 0.001), and a trend toward shorter V‐H intervals during VA (32.1 ± 38.6 milliseconds vs. 76.3 ± 11.1 milliseconds, P = 0.06) as compared to those without PP. A strong and positive correlation was found between V‐H interval and QRS duration during arrhythmia in those with PPs (B = 2.11, R2 = 0.97, t = 13.7, P < 0.001) but not in those without PPs.ConclusionLocal EGM characteristics and relative activation time of the His bundle suggest the possibility of conduction tissue as the origin for VA arising from the fibrous AMC. Specific identification and targeting of PPs when ablating VAs at this location may improve procedural success.

Background and purpose Mechanisms of both healing and complications, including spontaneous aneurysm rupture, remain unclear following flow diverter treatment. The aim of this study was to compare gene expression of various key molecules involved in the healing of aneurysms, between aneurysms treated with microcoils and flow diverters. Methods Saccular aneurysms were created in rabbits. Aneurysms were treated with coils (n=6) or flow diverters (n=6). Aneurysms were harvested at 4 weeks following treatment and used for gene expression and zymography experiments. Genes with a fold change of 1.2 or more were considered upregulated whereas those with a fold change of 0.8 or less were considered downregulated. Results All coil embolized aneurysms were completely occluded at follow-up. Two aneurysms were occluded and the remaining four samples were incompletely occluded in the flow diverter treated group. The following genes were expressed at lower levels in the flow diverter group compared with the coiled aneurysm group: proteinases (matrix metalloproteinases 2 and 9), cellular markers (endothelial nitric oxide synthase and smooth muscle actin), and structural proteins (collagens and fibronectin). Genes related to inflammation (tumor necrosis factor α and monocyte chemoattractant protein 1) were upregulated in flow diverter treated aneurysms compared with coil embolized aneurysms. Notably, the enzymatic activity of active matrix metalloproteinase 9 was high in aneurysms treated with flow diverters. Conclusions Our findings may provide improved understanding of rupture risk and healing following aneurysm treatment and inform development of therapies aimed at lowering rupture risk and accelerating healing.

Pancreatectomy is associated with significant morbidity and unpredictable outcome, with few diagnostic tools to determine, which patients gain the most benefit from this treatment, especially before the operation. This study aimed to define a preoperative signature panel of serum markers to indicate response to pancreatectomy for pancreatic cancer. Over 1000 patients with pancreatic cancer treated at two independent high‐volume institutions were included in this study and were divided into three groups, including resected, locally advanced and metastatic. Eight serum tumor markers most commonly used in gastrointestinal cancers were analyzed for patient outcome. Preoperative CA19‐9 independently indicated surgical response in pancreatic cancer. Patients with CA19‐9 ≥1000 U/mL generally had a poor surgical benefit. However, a subset of these patients still achieved a survival advantage when CA19‐9 levels decreased postoperatively. CEA and CA125 in the presence of CA19‐9 ≥1000 U/mL could independently predict the non‐decrease of CA19‐9 postoperatively. The combination of the three markers was useful for predicting a worse surgical outcome with a median survival of 5.1 months vs. 23.0 months (p < 0.001) for the training cohort and 7.0 months vs. 18.2 months (p < 0.001) for the validation cohort and also suggested a higher prevalence of early distant metastasis after surgery. Resected patients with this proposed signature showed no survival advantage over patients in the locally advanced group who did not receive pancreatectomy. Therefore, a preoperative serum signature of CEA+/CA125+/CA19‐9 ≥1000 U/mL is associated with poor surgical outcome and can be used to select appropriate patients with pancreatic cancer for pancreatectomy.