Ann Dermatol.  2021 Apr;33(2):108-115. 10.5021/ad.2021.33.2.108.

Characterization of the Onychomatricodermis Containing Onychofibroblasts of the Nail Unit : Histology, Immunohistochemistry, and Electron Microscopic Study

• Lee D
• Abudureyimu G
• Park JH
• Jang KT
• Kwon GY
• Shim JS

• KMID: 2513591
• DOI: http://doi.org/10.5021/ad.2021.33.2.108

Abstract

Background
We recently discovered the presence of specialized nail mesenchyme below the nail matrix and designated it as onychomatricodermis.
Objective
We did further research to characterize the histologic, histochemical, immunohistochemical and ultrastructural features of the onychomatricodermis containing onychofibroblasts in the nail unit.
Methods
Ten polydactyly nail unit specimens and 8 nail matrix biopsies were included. H&E-stained slides were reviewed. We did Alcian blue staining and Masson Trichrome staining, as well as immunohistochemical staining for type Ⅰ collagen, CD10, CD13 and CD34. In addition, polydactyly nail units were examined by transmission electron microscopy.
Results
In H&E staining, the specialized mesenchyme called onychomatricodermis was observed to be slightly distant from the undersurface of the nail matrix and be less eosinophilic area. Onychomatricodermal onychofibroblasts showed light purple abundant cytoplasm.Masson Trichrome staining revealed fewer collagen fibers within the onychomatricodermis. In Alcian blue staining the onychomatricodermis showed mucin deposition within the onychofibroblasts and around them. Immunohistochemically, type Ⅰ collagen was expressed much less in the onychomatricodermis while it was strongly expressed elsewhere in the nail unit. In nail matrix biopsy specimens onychomatricodermal onychofibroblasts expressed CD10 and CD13 strongly, and expressed CD34 as well. Ultrastructurally, collagen fibrils were found sparsely within the onychomatricodermis, whereas collagen fibrils were densely distributed in the dermis of other parts of the nail unit.
Conclusion
We demonstrated that there was less collagen expression in the onychomatricodermis containing onychofibroblasts. In addition, we found morphological and immunohistochemical features of onychomatricodermal onychofibroblasts (onychofibroblasts of Dongyoun). These findings support the presence of onychomatricodermis containing onychofibroblasts in the nail unit.

Keyword

Collagen; Onychodermis; Onychofibroblast; Onychomatricodermis