Métaplasie

Métaplasie refers to a reversible change in which one differentiated cell type is replaced by another differentiated cell type. This transformation typically occurs in response to chronic irritation or stress. The new cell type is usually better equipped to handle the altered environment. For example, squamous metaplasia is common in the respiratory tract when exposed to irritants like cigarette smoke. The normal ciliated columnar epithelium of the airways may be replaced by stratified squamous epithelium, which is more resistant to injury but lacks the cilia that help clear mucus and debris. Another example is Osseous metaplasia, where bone or cartilage forms in soft tissues where it is not normally present, such as in the healing of a chronic inflammatory lesion. Endometrial metaplasia can occur in the uterus, where glandular epithelium is replaced by squamous epithelium. While metaplasia itself is a reversible adaptation, the underlying cause of the stress should ideally be removed. If the stress persists, metaplasia can sometimes progress to dysplasia and eventually to malignancy, although metaplasia itself is not considered a cancerous change. The process involves changes in gene expression that lead to the differentiation of stem cells or progenitor cells into a different cell lineage.