Dermal filler (Hyaluronic acid) (HA)

The term 'Filler' primarily refers to dermal fillers, which are injectable substances used in aesthetic and reconstructive medicine to restore volume, enhance facial contours, and smooth wrinkles [1, 11]. The most clinically relevant type is composed of hyaluronic acid (HA), a naturally occurring glycosaminoglycan that provides structural support and hydration to the extracellular matrix [1, 3]. While 'Filler' is not a canonical biological target like a receptor or enzyme, it serves as the essential substrate for pharmacological interventions such as hyaluronidase, an enzyme used to dissolve HA-based fillers in cases of overfilling or medical emergencies like vascular occlusion [2, 12]. These fillers can also interact with biological receptors such as CD44, which regulates cell proliferation and homeostasis [4, 7]. Historically, 'filler cells' was also used as a colloquial name for glial cells (astrocytes) in the brain, reflecting an outdated view of them as passive structural support, though they are now known to be active regulators of synaptic function [6]. In modern biotechnology, fillers represent a major class of medical devices and pharmaceutical products rather than a specific molecular signaling target [8, 11].

Other names

Soft tissue fillerHyaluronan fillerInjectable fillerFiller cells (astrocytes)Dermal volumizer

Dermal fillers primarily act as physical volumizing agents in the skin's extracellular matrix to restore lost tissue volume; they are specifically targeted for enzymatic degradation by hyaluronidase, which catalyzes the hydrolysis of glycosidic bonds within the hyaluronic acid polymer [2, 5, 12].