metaplasioiksi

Metaplasia is a reversible cellular adaptation where one mature cell type is replaced by another mature cell type. This change typically occurs in response to chronic irritation or stress. The new cell type is generally better equipped to withstand the adverse conditions than the original cell type.

A common example is squamous metaplasia of the respiratory epithelium. In response to irritants like cigarette smoke, the ciliated columnar epithelium lining the airways can transform into stratified squamous epithelium. While squamous cells are more resistant to these irritants, they lack the cilia necessary for clearing mucus and debris, which can lead to impaired lung function and increased susceptibility to infection.

Another example is intestinal metaplasia of the gastric mucosa. This occurs when the normal gastric epithelium is replaced by intestinal-type epithelium, characterized by goblet cells and absorptive cells. This transformation is often associated with chronic gastritis, particularly that caused by Helicobacter pylori infection or autoimmune gastritis, and can be a precursor to gastric adenocarcinoma.

Metaplasia itself is not necessarily a pathological process, but it can be a sign of underlying chronic disease and, in some cases, can predispose to malignancy. The process is initiated by stem cell differentiation or reprogramming of existing differentiated cells. If the causative stimulus is removed, the metaplastic cells may revert to their original form. However, prolonged exposure to the stimulus can lead to further cellular changes, including dysplasia and eventually neoplasia.