Vacuolation

Vacuolation is the formation or appearance of vacuoles—membrane-bound, fluid-filled spaces—in the cytoplasm of a cell. Vacuoles are normal components of plant cells, where a large central vacuole regulates turgor and stores water, ions, pigments, and metabolites. In animal cells, vacuoles may arise as lysosomes, endosomal compartments, autophagosomes, or as pathological spaces formed during cellular injury.

Causes and contexts vary. In healthy tissues, vacuoles are part of normal physiology in plants. In animal cells, cytoplasmic vacuolation is often a sign of cellular stress or injury (hydropic change), autophagy, or infection. Toxins and certain drugs can induce vacuolation; bacterial and viral infections can provoke cytoplasmic vacuolation; prion diseases can produce widespread vacuolation of brain tissue known as spongiform change.

Appearance and detection also differ. Vacuoles appear as clear, round to irregular spaces within the cytoplasm on light microscopy; they may coalesce into larger spaces. Electron microscopy reveals membrane-bound vesicles with distinct limiting membranes. Distinguishing true vacuoles from lipid droplets or dilated endoplasmic reticulum may require special staining or ultrastructural analysis.

Clinical and biological relevance. Cytoplasmic vacuolation is a histological finding rather than a disease by itself. In neuropathology, vacuolation of the neuropil is associated with spongiform changes in prion diseases; in hepatic tissue, hydropic degeneration reflects hypoxic or toxic injury; in plants, vacuoles play central roles in growth, storage, and maintaining cell turgor.