transepiteliellt

Transepiteliellt (English: transepithelial) is an adjective used in medical and biological contexts to describe processes, treatments, or transport that occur across an epithelial layer. Epithelia are sheets of cells that line body surfaces and cavities and act as selective barriers; transepithelial phenomena therefore involve passage through or across these cell layers rather than around them.

In clinical practice the term commonly appears in ophthalmology and drug delivery. Transepithelial corneal procedures, such as transepithelial photorefractive keratectomy and transepithelial corneal collagen cross-linking, preserve the corneal epithelium while delivering energy or agents to deeper stromal tissue, with the aim of reducing pain and infection risk compared with techniques that remove the epithelium. In topical drug delivery, transepithelial transport refers to movement of molecules via transcellular routes, paracellular pathways between cells, carrier-mediated uptake, endocytosis, or facilitated by enhancers, iontophoresis or nanoparticles.

In laboratory research, transepithelial electrical resistance (TEER) and permeability assays are used to quantify barrier integrity and transport across cultured epithelial layers. Clinical and experimental considerations include the balance between preserving epithelial integrity to maintain barrier function and achieving sufficient penetration for therapeutic effect; techniques that increase transepithelial permeability can raise the risk of irritation or infection. The concept is central to pharmacology, physiology and procedural techniques that target tissues protected by epithelial barriers.