cellexpansion

Cell expansion refers to the processes by which cells increase in size or number, contributing to tissue and organ growth. It is distinct from cell division, though both processes can occur during development and growth. In plant biology, cell expansion is the main driver of growth after cells have divided: cells enlarge as water enters the vacuole, turgor pressure increases, and the cell wall loosens to accommodate enlargement. The rate and extent of expansion are regulated by hormones such as auxins, gibberellins, and brassinosteroids, and by the mechanical properties of the cell wall and surrounding tissues. Enzymes that loosen or remodel the wall, including expansins and pectinases, facilitate this process. The outcome is larger cells with relatively constant cytoplasmic composition, contributing to growth of organs such as leaves and stems.

In animals, cell expansion can refer to two related phenomena. Hypertrophy is an increase in cell size without a corresponding increase in cell number, observed in tissues like muscle under certain conditions. Ex vivo cell expansion describes increasing cell numbers in culture for research or therapeutic applications, such as expanding stem cells or immune cells. Ex vivo expansion requires defined culture media, growth factors, substrate conditions, and careful monitoring to maintain cell phenotype and genomic stability.

Applications include improving crop yield through enhanced cell expansion in meristems and generating sufficient cell material for regenerative medicine. Challenges involve controlling differentiation and function, preventing senescence and genomic instability, and ensuring safety, reproducibility, and scalability in culture-based workflows.