When we think of wounds, we don’t typically think of them as part of normal, healthy function. Micro-wounds, however, form when white blood cells have to cross the barrier in our blood vessels to get to an injury or infection. These micro-wounds happen all the time, and our cells heal these wounds efficiently and elegantly.
One of the most important barriers in our body is that created by the vascular endothelium. Vascular endothelial cells line all of our blood vessels—from the largest vessels to the smallest capillaries—and function in fluid filtration, hormone trafficking, and recruitment and trafficking of blood and stem cells. The movement of cells, for example white blood cells, across the vascular endothelium and out of circulation creates “micro-wounds” that can compromise the integrity of the tissue. A recent paper describes how these micro-wounds are healed, based on a model in which the vascular endothelium senses a loss of tension upon micro-wounding and triggers its own repair. Martinelli and colleagues tracked micro-wounds that were created by either transmigrating white blood cells or by mechanical disruption by a probe, and found that ventral lamellipodia are generated by endothelial cells to close the micro-wounds. These lamellipodia are enriched in Rac1 effector proteins, and require reactive oxygen species (ROS) and Arp2/3 for efficient wound closing. Images above show probe-induced wounding of an endothelial cell, followed by wound healing. The wound initially expanded to 20um across (80 seconds), with multiple nodes of ventral lamellipodia (blue arrowheads) and ventral F-actin waves forming around the wound and closing it.
Martinelli, R., Kamei, M., Sage, P., Massol, R., Varghese, L., Sciuto, T., Toporsian, M., Dvorak, A., Kirchhausen, T., Springer, T., & Carman, C. (2013). Release of cellular tension signals self-restorative ventral lamellipodia to heal barrier micro-wounds originally published in the Journal of Cell Biology, 201 (3), 449-465 DOI: 10.1083/jcb.201209077