microenvironment

Microenvironment, in biology, refers to the immediate surroundings in which cells or tissues exist, including the extracellular matrix, soluble factors, and neighboring cells. It is distinct from the broader organismal or environmental context, though it interacts with systemic signals. The microenvironment shapes cell behavior by providing signals that regulate proliferation, differentiation, survival, and migration. Components include the extracellular matrix, blood vessels, resident stromal cells such as fibroblasts and adipocytes, immune cells, and signaling molecules like cytokines, chemokines, and growth factors. Mechanical properties such as stiffness and the presence of gradients of oxygen, nutrients, and metabolites also influence cellular responses.

In oncology, the tumor microenvironment encompasses cancer cells plus stromal elements, immune infiltrates, vasculature, ECM, and acellular factors. It is dynamic and spatially heterogeneous, contributing to tumor growth, invasion, metastasis, and response or resistance to therapy. Hypoxia, acidity, and metabolic coupling between cancer and stromal cells are common features. Targeting the microenvironment—through anti-angiogenic therapies, immune-modulation, or ECM remodeling—complements cancer cell–directed treatments.

In healthy tissues, microenvironments include stem cell niches and tissue-specific milieus that balance regeneration and homeostasis. Disruption of microenvironmental cues can lead to impaired function or disease. Studying microenvironments employs histology, imaging, single-cell and spatial transcriptomics, and in vitro models such as co-cultures, organoids, and engineered matrices. In tissue engineering, recreating relevant microenvironments is essential for guiding cell fate and tissue formation.