A recent study puts into the spotlight the mechanical factors that perform an essential responsibility in the differentiation and function of fibroblasts, which are the connective tissue cells that work towards the achievement of wound healing and scar tissue formation.

When the body is injured, it initiates a complex rescue operation. Specialized cells, called fibroblasts, located just beneath the surface of the skin leap into action. These cells enter the makeshift wound matrix, called the clot. The secretion of collagen starts in order to close the wound as quickly as possible. At the outset, this matrix is soft and rich in growth factors. The fibroblasts, then, slow progress around the matrix. As such, fibers are pulled and are reorganized. This, then, causes the matrix to grow stiffer. At a certain point, the fibroblasts stop advancing and transform into powerful contractile cells. Such cells secure themselves to the matrix and draw together the edges of the wound.

This research uncovers for the first time that a mechanical mechanism is fundamental in the transformation of cells from migrating to contractile. To make such conversion, the fibroblasts must reach the matrix in order to have access the growth factors there. Once achieved, the production of smooth-muscle proteins is stimulated.
In the past, researchers hypothesized that the fibroblasts were able to achieve such transformation through the digestion of the matrix. However, Boris Hinz, an EPFL scientist, Pierre-Jean Wipff, a doctoral student, and their colleagues have found out that the cells disengage the growth factor with the use a purely mechanical process. Through their experimentations, employing novel cell culture substrates of varying rigidity, the team of researchers discovered that at a certain point, the matrix is adequately inflexible and that some cell-exerted force causes the growth factors to be released.

Once the growth factors are discharged, the fibroblasts squeeze out the contractile proteins. This causes them to be more firmly attached to the matrix. Then, they start to contract bring about the tight pulling together of the matrix. Also, through such process, more growth factors are released. These set of growth factors are responsible for the stimulation of other fibroblasts and eventually transform them into contractile. The mechanical nature of the switch guarantees that the contraction only occurs when the matrix is ready.

As reported above, cell or tissue culture procedures were entailed. In experiments that involve tissue culture, an inverted phase contrast microscope or darkfield microscopy is of assistance in the examination of cells.
Darkfield microscopy is a type of microscope that is designed with its light source and condenser positioned facing down on the top above the stage.

In using a darkfield microscopy or every time an objective is changed, the researcher must first check if the phase rings are aligned. Specimens are put in a large container, like a tissue culture flask, and the bottom of which is viewed when using a darkfield microscopy. When not in use, a darkfield microscopy should be covered and the lights should be turned down.Original article can be found here