Ageing of the somatosensory system at the periphery: age‐related changes in cutaneous mechanoreceptors

Abstract

Decline of tactile sensation associated with ageing depends on modifications in skin and both central and peripheral nervous systems. At present, age‐related changes in the periphery of the somatosensory system, particularly concerning the effects on mechanoreceptors, remain unknown. Here we used immunohistochemistry to analyse the age‐dependent changes in Meissner's and Pacinian corpuscles as well as in Merkel cell‐neurite complexes. Moreover, variations in the neurotrophic TrkB‐BDNF system and the mechanoprotein Piezo2 (involved in maintenance of cutaneous mechanoreceptors and light touch, respectively) were evaluated. The number of Meissner's corpuscles and Merkel cells decreased progressively with ageing. Meissner's corpuscles were smaller, rounded in morphology and located deeper in the dermis, and signs of corpuscular denervation were found in the oldest subjects. Pacinian corpuscles generally showed no relevant age‐related alterations. Reduced expression of Piezo2 in the axon of Meissner's corpuscles and in Merkel cells was observed in old subjects, as well was a decline in the BDNF‐TrkB neurotrophic system. This study demonstrates that cutaneous Meissner's corpuscles and Merkel cell‐neurite complexes (and less evidently Pacinian corpuscles) undergo morphological and size changes during the ageing process, as well as a reduction in terms of density. Furthermore, the mechanoprotein Piezo2 and the neurotrophic TrkB‐BDNF system are reduced in aged corpuscles. Taken together, these alterations might explain part of the impairment of the somatosensory system associated with ageing.

Peripheral Mechanobiology of Touch—Studies on Vertebrate Cutaneous Sensory Corpuscles

“…Piezo2 has been also detected in human Merkel cells and Meissner´s corpuscles axon, in an age-dependent manner [ 137 , 138 ]. Recently we have also detected Piezo2 in the axon of human cutaneous Pacinian corpuscles (García-Piqueras, J. et al, unpublished).…”

A novel player in the field: Merkel disc in touch, itch and pain

“…It should be noted that while it is largely agreed that the total number of Merkel cells per touch dome decreases with age in mice, the lifespan of individual Merkel cells remains highly debated. Lineage tracing studies showed that Merkel cells were replaced every 2 months in touch domes .…”

The capsule of human Meissner corpuscles: immunohistochemical evidence

“…Because Meissner corpuscles undergo developmental (Feito et al ) and postnatal age‐dependent changes (Garcia‐Piqueras et al ), we also investigated whether the CD34‐positive capsule that surrounds most Meissner corpuscles varied with age. Prenatal Meissner corpuscles lack a capsule, and the first evidence of a well‐defined capsule was at 23 years old.…”

“…The present study was designed to investigate whether human cutaneous Meissner corpuscles possess a complete or partially differentiated capsule and whether the capsules have endoneurial or perineurial characteristics. Furthermore, we analysed the occurrence of age‐dependent changes in the capsule, as these types of changes occur in other corpuscular constituents (Feito et al ; Garcia‐Piqueras et al ).…”