CD13 is a marker for onychofibroblasts within nail matrix onychodermis: Comparison of its expression patterns in the nail unit and in the hair follicle

Abstract

CD13 may be a marker for onychofibroblasts within nail matrix onychodermis. We demonstrate CD13 expression in the specialized mesenchymes of both nail and hair.

The concept of nail matrix onychodermis (onychomatricodermis) in the nail unit: Histology and elastin immunohistochemistry

“…We also recently found differences in protein expression patterns within the onychodermis. We demonstrated stronger CD13 expression in the mesenchyme below the nail matrix compared with the mesenchyme below the nail bed, suggesting that CD13 might be a marker for onychofibroblasts within the nail matrix onychodermis . We also previously showed that fibrillin is only weakly expressed in the mesenchyme below the nail matrix, in contrast to its strong expression in the dermis of lateral nail fold .…”

“…However, the characteristics of these specialized mesenchymal cells in vivo, including their location and markers for these cells, had not been determined. Through our previous and present studies, we showed in vivo histological, histochemical and immunohistochemical properties of a distinct population of mesenchymal cells in the onychomatricodermis and some similarities between these cells and the cells of the FDP of hair follicles. Further studies are needed to evaluate the function of onychofibroblasts within the onychomatricodermis and whether the onychomatricodermis serves a role in nail formation analogous to that of the FDP in hair formation.…”

“…Furthermore, we recently found different protein expression patterns within the onychodermis itself. We demonstrated stronger CD13 expression in onychofibroblasts within the mesenchyme below the nail matrix compared with the mesenchyme below the nail bed . We also observed weak expression of fibrillin, an extracellular matrix (ECM) protein, in the mesenchyme beneath the nail matrix, in contrast to its strong expression in the dermis of lateral nail fold .…”

CD10 and the nail

“…These cells were therefore called onychofibroblasts and the dermal tissue was called onychodermis by Lee's group . These authors have now shown that CD13, an alanyl aminopeptidase (aminopeptidase N) with a wide substrate spectrum, stains onychofibroblasts as well as perifollicular connective tissue cells, but the matrix onychofibroblasts stain more intensely for CD13 than do those of the nail bed …”

“…[6][7][8] These authors have now shown that CD13, an alanyl aminopeptidase (aminopeptidase N) with a wide substrate spectrum, stains onychofibroblasts as well as perifollicular connective tissue cells, but the matrix onychofibroblasts stain more intensely for CD13 than do those of the nail bed. 9 Although the enzyme function of CD10 is clearly defined and many cells and tissues are identified that contain CD10, it is yet unknown what CD10 exactly does in the nail matrix and bed connective tissue. CD10 is expressed in onychomatricoma and may also be used as a marker to define excision specimens of the nail in ingrown nail surgery.…”