Perifeersetes

Perifeersetes are a proposed class of peripheral signaling units in theoretical biology. They are defined as small, membrane-bound modules embedded in tissue matrices, situated near the periphery of organs and vessels, and capable of exchanging metabolites and signaling molecules with surrounding cells and the circulatory system. The concept is used to describe how peripheral microenvironments might coordinate systemic and local signals without invoking a single distinct cell type.

In the models that introduce them, perifeersetes are envisioned as roughly 0.5 to 2 micrometers in diameter and enclosed by a lipid bilayer. They are imagined to possess transporters, receptors, and scaffolding proteins that enable selective uptake and release of substrates. These units are described as forming dynamic networks with nearby cell types such as endothelial cells, pericytes, immune cells, and fibroblasts, thereby contributing to local regulation of blood flow, metabolism, and immune surveillance.

Functions attributed to perifeersetes include facilitating rapid substrate exchange at tissue margins, coordinating responses to injury, and shaping microenvironmental signaling that influences tissue regeneration or inflammatory processes. In some theoretical treatments, they are presented as hubs that integrate signals from the circulatory system with paracrine messages from resident cells, effectively bridging systemic and local regulation.

Perifeersetes remain speculative; there is no established empirical evidence for their existence. They are primarily discussed as an abstraction to help model complex peripheral regulation and tissue microenvironments. Critics argue that the concept risks duplicating known cell types and structures such as endothelial cells, pericytes, and extracellular vesicles rather than providing a distinct biological entity.

See also: peripheral nervous system, endothelial cells, pericytes, fibroblasts, extracellular vesicles.