Tape Strips in Dermatology Research

A. J. Hughes; S. S. Tawfik; K. P. Baruah; E. A. O'Toole; R. F. L. O'Shaughnessy

The British Journal of Dermatology. 2021;185(1):26-35.

Conclusions

TS offer a simple and minimally invasive method to access components of the epidermis. TS have been applied broadly in dermatology research, but their widespread adoption has been limited by variability between protocols and a lack of standardization. For RNA extraction, we recommend using 20 TS and a commercial guanidinium thiocyanate lysis buffer with a scraper, then purification using a spin column kit. For psoriasis and koebnerizing dermatoses we advise caution if taking over 10 TS from nonlesional skin. There is no optimum protocol to extract protein, and methodology should be designed based on the target studied. The number of TS should correspond to the depth of target expression and abundance. For soluble proteins, we recommend starting with 10 min of sonication in PBS. For insoluble proteins, we recommend 30 min of sonication with a buffer containing 0·2% SDS in PBS. The addition of DTT should be considered if the yield is suboptimal (note that compatibility with downstream analysis kits should be checked). If both protein and RNA extraction are required from the same set of TS, TS 2–10 can be used for protein extraction and TS 11–20 for RNA. Wider sharing of protocols and yield data will allow TS to be more widely used as an alternative to biopsies.

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Funding sources
This work was supported by a clinical training research fellowship MR/T008040/1 from the Medical Research Council, UK to A.H. S.S.T. is funded by the Newton Mosharafa fund. K.P.B. is funded by Barts Charity.

Table 1. Dermatoses that have been studied in the literature by tape stripping
Dermatosis	Type of studies
Atopic eczema	WB, ELISA, PA, IM, MS-P, MS-L, qPCR/M, RNA-seq, Chr, SM, 3DM, NGS/qPCR
Psoriasis	WB, ELISA, IM, MS-P, qPCR/M, Chr, SM, 3DM
Contact dermatitis	ELISA, qPCR/M, Chr
Photodamage	WB, ELISA, MS-P, Chr
Actinic keratosis	MS-P
Melanoma	IM, qPCR/M, SM
Basal cell carcinoma	qPCR/M
Squamous cell carcinoma	qPCR/M
Cutaneous T-cell lymphoma	MSP
Pityriasis versicolor	M/C
Seborrhoeic dermatitis	M/C, NGS/q-PCR
Dermatophytoses	M/C, NGS/q-PCR
Candida balanoposthitis	M/C
Scabies	M/C
Cutaneous leishmaniasis	NGS/q-PCR
Perioral dermatitis	M/C
Rosacea	PA, M/C
Acne vulgaris	ELISA
Lichen planus	IM
Genodermatoses (Netherton syndrome, ichthyosis vulgaris, peeling skin syndrome type B, X-linked recessive ichthyosis)	ELISA, IM

WB, Western blot; ELISA, enzyme-linked immunosorbent assay or multiplex; PA, protease assay; IM, immunostaining microscopy; MS-P, mass spectrometry protein; MS-L, mass spectrometry lipid; Chr, chromatography; qPCR, quantitative real-time polymerase chain reaction; qPCR/M, qPCR or microarray; RNA-seq, RNA-sequencing; SM, staining and microscopy (keratinocytes); 3DM, 3D microscopy; M/C, microscopy and/or culture of microbes; NGS, next-generation sequencing; NGS/q-PCR, q-PCR/NGS of microbes. References are provided in Table S1 (see Supporting Information).

Table 2. Summary of different techniques used to extract specific components from tape strips (TS)
Technique	Component detected	Description	Median number of TS used^a	Range
Western blotting	Protein	Semiquantifies individual proteins by separating them by size followed by antibody-based chemiluminescence. Can only detect solubilized proteins	2	1–30
ELISA and bead-based multiplex assays	Protein	Semiquantifies individual proteins by antibody fluorescence. Can only detect solubilized proteins	5	1–35
Protease assay	Proteases	Quantification of proteases using a standardized enzyme substrate that is fluorescence tagged	7·5	3–15
Immunostaining microscopy	Protein	Detects individual proteins directly on the TS surface using antibody fluorescence. Allows visualization of proteins in situ but is less effective at quantifying the protein	1	1–9
Mass spectrometry (proteins)	Protein	Quantification of large protein sets. Proteins are fragmented and charged, then separated by their mass-to-charge ratio	15	8–30
Mass spectrometry (lipids)	Lipids	Quantification of large lipid sets. The same principal of separation by mass-to-charge ratio is applied to lipids	8	1–16
Quantitative-PCR and microarrays	RNA	Quantifies the expression of key genes	20	4–30
RNA-seq	RNA	Quantifies gene expression of the whole transcriptome using next-generation sequencing	20	16–20
Chromatography	Lipids, peptides, amino acids	Semiquantifies individual lipids, peptides or amino acids. Chromatography separates the molecule of interest, which is then detected by a method such as ultraviolet absorption	4	1–16
Staining and microscopy (keratinocytes)	Cellular morphology	2D characterization of keratinocytes	1	1–9
3D microscopy (scanning electron, laser and atomic force)	Cellular morphology	3D characterization of keratinocytes	3	1–23
Microscopy and/or culture of microbes	Bacterial, fungal or parasitic organisms	Detects and quantifies microorganisms. TS are placed directly onto a culture medium or slide (with or without a stain or potassium hydroxide digestion)	1	1–15
q-PCR or NGS of microbial species	Bacterial, fungal or parasitic organisms	Detects and quantifies microogranisms from specific DNA sequences (NGS) or RNA expression (q-PCR)	1	1–3

ELISA, enzyme-linked immunosorbent assay; q-PCR, quantitative real-time polymerase chain reaction; NGS, next-generation sequencing; ^aThe deepest TS is documented if more superficial TS were not used. Studies where TS were repeatedly pressed onto the skin are not included. References are provided in Table S1 (see Supporting Information).

Table 3. A summary of the factors that can affect protein yield
Factor	Comment
Anatomical site^57,65	The same site should be used within a study. The volar forearm is commonly used
Pressure of TS application⁷	Pressure application can be standardized by using a pressure instrument (e.g. D500 D-squame® pressure instrument, 225 g cm⁻²)
Duration of pressure applied⁷	The time that pressure is applied to each TS should be standardized, usually between 2 s and 10 s
Contaminants on the skin surface²⁸	TS number 1–2 TS are typically discarded,² although bacteria have been shown to be present up to TS 15²⁸
Stretching the skin during application⁷	A decision must be made about whether to stretch the skin in the study design
Speed of removal of TS⁶⁶	Slow speed of TS removal was shown to increase transepidermal water loss, but protein yield was not directly studied.⁶⁶ The speed of TS removal should be considered
Brand of adhesive tape^7,19,49	The same brand of TS must be used throughout the study
Hydration of the skin⁷	There have been no attempts to standardize hydration. Emollients and occlusion have been shown to alter gene expression and could therefore confound attempts to standardize this
Activity of skin disease^17,50,54	Nonlesional atopic eczema (AE) has more protein per TS than lesional AE, but less soluble protein.⁵⁰ Studies should distinguish between samples from lesional and nonlesional skin
Season⁶⁵	Exposed sites should be avoided if studies are longer than one season