Synthetic Hydrogels with Stiffness Gradients for Durotaxis Study and Tissue Engineering Scaffolds

Migration of cells along the right direction is of paramount importance in a number of in vivo circumstances such as immune response, embryonic developments, morphogenesis, and healing of wounds and scars. While it has been known for a while that spatial gradients in chemical cues guide the direction of cell migration, the significance of the gradient in mechanical cues, such as stiffness of extracellular matrices (ECMs), in directed migration of cells has only recently emerged. With advances in synthetic chemistry, micro-fabrication techniques, and methods to characterize mechanical properties at a length scale even smaller than a single cell, synthetic ECMs with spatially controlled stiffness have been created with variations in design parameters. Since then, the synthetic ECMs have served as platforms to study the migratory behaviors of cells in the presence of the stiffness gradient of ECM and also as scaffolds for the regeneration of tissues. In this review, we highlight recent studies in cell migration directed by the stiffness gradient, called durotaxis, and discuss the mechanisms of durotaxis. We also summarize general methods and design principles to create synthetic ECMs with the stiffness gradients and, finally, conclude by discussing current limitations and future directions of synthetic ECMs for the study of durotaxis and the scaffold for tissue engineering.

A Case of Aortoesophageal Fistula due to Esophageal Cancer Treated with Endovascular Stent Grafting / 대한내과학회지

Hemorrhage into the esophagus due to aortoesophageal communication is very rare but life-threatening with high morbidity and mortality. Because of this, most cases of aortoesophageal fistula are confirmed by autopsy. However, we report herein a case of a 62-year-old male with an aortoesophageal fistula who was successfully treated with endovascular stent-grafting. The patient had undergone esophageal stent insertion due to esophageal cancer and experienced hematemesis and hemodynamic shock due to an aortoesophageal fistula. Emergency endoscopy was unable to identify the source of the hemorrhage due to massive bleeding. Computed tomography of the chest revealed a focal pseudoaneurysm at the descending aorta and diffuse thinning of the esophageal wall, which were treated with endovascular stent-grafting. Although aortoesophageal fistulas are usually fatal, implantation of a covered stent into the esophagus may help prevent massive bleeding, providing valuable time to treat the patient.