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. Author manuscript; available in PMC: 2021 Jan 1.
Published in final edited form as: J Invest Dermatol. 2020 May 22;141(1):203–205. doi: 10.1016/j.jid.2020.04.023

Table 1.

Toolbox with Validation Parameters for Quality Assessment of General Tissue Structure

Parameter Essential Assays Expected Result Optional Assays
Morphology Histology
(H&E staining or equivalent)		  For HEE and HSE:
✔ Number of cell layers that approximate in vivo epidermis
✔ Flattening of keratinocytes and presence of keratohyalin granules in stratum granulosum
✔ Multiple layers of basket weave orthokeratotic SC
 Additional for HSE:
✔ Nuclei in the dermis indicating fibroblasts		 - Safranin-O:
SC layer quantification
- Calcium gradient
- pH gradient
- Electron microscopy
Stratification Immunohistochemistry
Immunofluorescence		  For HEE and HSE:
 Two markers per strata indicative for proper stratification:
✔ Basal layer:
 - Proliferative cells: e.g., Ki67, Click-iT EdU, or PCNA staining
 - Positive for KRT5 or KRT14
 - Negative for KRT1 or KRT10
✔ Suprabasal layers:
 - Positive for KRT1 or KRT10
 - Terminal differentiation markers: e.g., IVL, LOR, FLG, LCE, or TGM
 Additional for HSE:
✔ Basement membrane proteins		 Enzymatic activity

Abbreviations: HEE, human epidermal equivalent; HSE, human skin equivalent; PCNA, proliferating cell nuclear antigen; SC, stratum corneum.