Growth of living fibrous tissues: from biofilms to fibrosis
Martine Ben Amar (ENS Paris)
Morphologies of soft materials in growth, swelling or drying have been extensively studied recently. Shape modifications occur as the size varies transforming ordinary spheres, cylinders and thin plates into more or less complex objects. Existence of fibers exacerbates this complexity, giving anisotropy to the growth process itself. The growth is coupled to the environment, for bacteria the substrate, in pathology the healthy tissue. In pathological situations such as wound-healing or desmoplastic tumor growth, the immune system reacts with a battery of morphogenetic gradients, making a new tissue full of collagene and eventually sending active cells. All these factors contribute to a high level of compressive stress at the origin of patterns and deformity. I will show how we can predict quantitatively these patterns on the simple drop geometry of the biofilms and on the spherical shape of tumors.
For the pathological cases, it turns out that the wrinkling process dominates the growth, deforming the tissues and exacerbating the immune system which reacts via passive (fibroblasts) and active cells (myo-fibroblasts). I will show that the consequence is a huge increase of the stiffness, which stops spontaneously when the healing is achieved but not in case of implants or tumors. Naive estimations can be given explaining difficulties encounted in drug treatments, for example.
Joint work with Min Wu.