The Human Cutaneous Sensory Corpuscles: An Update

Sensory corpuscles of human skin are terminals of primary mechanoreceptive neurons associated with non-neuronal cells that function as low-threshold mechanoreceptors. Structurally, they consist of an extreme tip of a mechanosensory axon and nonmyelinating peripheral glial cells variably arranged according to the morphotype of the sensory corpuscle, all covered for connective cells of endoneurial and/or perineurial origin. Although the pathologies of sensitive corpuscles are scarce and almost never severe, adequate knowledge of the structure and immunohistochemical profile of these formations is essential for dermatologists and pathologists. In fact, since sensory corpuscles and nerves share a basic structure and protein composition, a cutaneous biopsy may be a complementary method for the analysis of nerve involvement in peripheral neuropathies, systemic diseases, and several pathologies of the central nervous system. Thus, a biopsy of cutaneous sensory corpuscles can provide information for the diagnosis, evolution, and effectiveness of treatments of some pathologies in which they are involved. Here, we updated and summarized the current knowledge about the immunohistochemistry of human sensory corpuscles with the aim to provide information to dermatologists and skin pathologists.

Verification and characterisation of human digital Ruffini's sensory corpuscles

Ruffini's corpuscles are present as long fusiform encapsulated sensory structures in different tissues including the skin. Although physiological analyses strongly suggest their existence in glabrous digital skin, such localisation remains unconfirmed. Here, we have investigated the occurrence of typical Ruffini's corpuscles in 372 sections of human digital skin obtained from 186 subjects of both sexes and different ages (19-92 years). S100 protein, neuron-specific enolase and neurofilament proteins were detected, and the basic immunohistochemical profile of these corpuscles was analysed. Fewer than 0.3 Ruffini's corpuscles/mm² were detected, with density distribution across the fingers being F4 > F3 > F2 > F1 > F5 and absolute values being F2 > F1 > F3 > F4 > F5. Axons displayed neuron-specific enolase immunoreactivity, glial cells forming the core contained S100 protein, and the capsule was positive for CD34 but not Glut1, demonstrating an endoneurial origin. Present results demonstrate the existence of Ruffini's corpuscles in human glabrous digital skin at very low densities. Moreover, the identified Ruffini's corpuscles share the basic immunohistochemical characteristics of other dermal sensory corpuscles.