National audience ; This paper focuses on the study of fibrosis induced by an implanted medical device and explores the possibility of characterizing this process by in situ measurement of electrical impedance. The approach combines electrical and biological characterizations of fibrotic tissue, applied to electrodes implanted in animal models. A comparative study of electrical and biological parameters collected at the same time will enable the identification of an electrical marker of fibrosis development, which can be used for establishing a monitoring method. Adopting an interdisciplinary approach, intermediate embedded prototypes, autonomous and portable by animals, will be developed to confirm the feasibility of the continuous monitoring method and finally to propose architectural solutions (embedded computing and specific electrode) applicable to a wide variety of prosthetic implants. The paper will present some initial results on the electrical model of the fibrosis and the methodology used to obtain it.