Tape strips may be a promising, minimally invasive alternative to skin biopsies, with implications for clinical trials and practice.1 A recent study, published in the Journal of Allergy and Clinical Immunology, showed analyses of tape strips were able to identify distinct immune and barrier signatures in lesional and nonlesional skin of patients with atopic dermatitis (AD) and psoriasis, including a biomarker that distinguished AD from psoriasis with 100% accuracy.
The study included 20 adult participants with moderate to severe AD, 20 participants with psoriasis, and 20 healthy controls. Using large tape strips, the researchers collected 20 consecutive samples of lesional and nonlesional skin from participants with AD and psoriasis and skin samples from healthy controls. The tape strips were analyzed using RNA sequencing (RNA-seq) with quantitative real-time polymerase chain reaction validation of immune and barrier biomarkers.
Overall, the researchers were able to detect RNA-seq profiles in 96 of 100 samples. They identified 4123 genes differentially expressed in AD lesions and 5390 genes differentially expressed in psoriasis lesions compared with skin from healthy controls. In addition, nonlesional skin of AD was found to be similar to lesional skin compared with nonlesional skin of psoriasis, which showed larger differentiation from lesions.
Both AD and psoriasis shared increases in dendritic cell/T-cell markers (CD3, ITGAX/CD11c, CD83), as well as significantly downregulated terminal differentiation (FLG2/LCE5A), tight junction (CLDN8), and lipid biosynthesis/metabolism (FA2H/ALOXE3) products. However, AD samples showed preferential TH2 skewing (IL-13, CCL17/TARC, CCL18), whereas psoriasis had higher expression of TH17 (IL-17A/F, IL36A/IL-36G), TH1 (IFNG, CXCL9/CXCL10), and innate immunity-related (NOS2/iNOS, IL-17C) products.
Additionally, the researchers found that NOS2/iNOS expression differentiated AD and psoriasis with 100% accuracy. They also noted that more biomarkers for psoriasis and AD were found using tape strips compared with biopsies and identified several biomarkers associated with disease severity.
In an interview with The Dermatologist, corresponding author Emma Guttman, MD, PhD, discussed these findings, their implications for clinical practice, and the role of tape strips in the future of precision medicine.
The Dermatologist: What is the significance of identifying the efficacy of tape stripes?
Dr Guttman: My colleagues and I are excited about the application of tape strips. Tape strips sample the very outer layers of the epidermis and work well for identifying biomarkers of diseases with pathology that is higher up in the skin, such as in AD and psoriasis. We found they provide a very accurate picture of the phenotype of these diseases. However, it may not work well in conditions like alopecia areata because hair follicles are located deeper in the skin.
We believe that this will open a new avenue of research, such as the ability to collect samples from children for registries. We cannot sample the skin over and over again in infants and children, and collecting biopsies can even be difficult among adults. With tape strips, we can collect samples from more patients in clinical trials to analyze them for biomarkers and correlate them with disease severity.
In addition, we found a single biomarker that differentiated AD and psoriasis using tape strips. This has important relevance for selecting which treatment to use and is exciting because it can sometimes be difficult to differentiate these conditions. I can see how, in a few years, we may be able to use a single tape strip in the clinic to determine whether patients have psoriasis or AD, and to guide which treatment we would use for these patients.
The Dermatologist: In your study, the tape strips identified more biomarkers compared with biopsies. Were you surprised by this finding?
Dr Guttman: We were actually surprised to find more biomarkers with tape strips compared with biopsies, but it demonstrates that the data is of high quality. There are pros and cons for using tape strips of course. When measuring a biomarker using a biopsy, the thickness has to be diluted, which can affect how well a biopsy is able to sample a biomarker produced in the epidermis. Tape strips are able to collect a larger concentration of these biomarkers, and that is why they are very effective for diseases where the epidermis is highly affected, such as in AD and psoriasis.
The Dermatologist: Could you elaborate more on how tape strips may have a place in dermatology offices?
Dr Guttman: There are many patients whose biopsy results show they have psoriasiform dermatitis, but this is not enough information to determine whether a psoriasis or AD treatment should be used. However, with a single biomarker, we can now identify this molecularly using a noninvasive method. The tape strips are telling us more than biopsies about the pathology of patients with AD and psoriasis.
Also, I think tape strips may be useful for identifying biomarkers for inflammatory skin diseases in general. It could be used not only for psoriasis and AD, but also for contact dermatitis, ichthyosis, and even some skin cancers if they are not too deep in the skin. Similar to how biomarkers in cancer are identified in the clinic, this noninvasive method could be used for a personalized medicine approach.
The Dermatologist: What about the use of tape strips in clinical trials?
Dr Guttman: This is another exciting avenue. Thus far, biopsies are used in early studies, phase 1 and phase 2, to determine the mechanism of action and the molecular profile of a therapy, as well as the biomarkers associated with the disease. However, biopsies are invasive, painful, can cause scarring, and cannot be performed multiple times in a large sample of patients.
Tape strips open the avenue for biomarkers in phase 3 trials because this method is noninvasive and more patients are more likely to agree to the procedure. It also opens the door for personalized medicine to identify biomarkers based on age, race/ethnicity, etc.
The Dermatologist: As you mentioned earlier, personalized medicine is an important advancement for the treatment of AD due to the heterogeneity of this disease. Do you think personalized medicine will also have a place in the treatment of psoriasis?
Dr Guttman: I think there is a greater need for personalized medicine in AD. In plaque psoriasis, we have amazing treatments that target IL-17 and IL-23, for example, with 60% to 80% of patients achieving Psoriasis Area Severity Index 100 scores. For these patients, personalized medicine may not be as necessary. However, there are other types of psoriasis, such as guttate and palmoplantar, where this may be helpful for identifying a specific treatment. Also, tape strips can help us follow patients longitudinally in clinical studies.
The Dermatologist: What are some of the limitations of tape strips, and what research is needed to address these limitations?
Dr Guttman: One of the limitations of tape strips is the amount of time it takes to process them. Unlike a biopsy, where the whole sample can be processed together, tape strips have to be processed one by one, which is a little more time consuming. Also, it requires a research laboratory, and there is a technique to it. Future innovations for tape strips to save time in terms of processing, peeling fewer tapes, etc, would help advance this and would also make it easier to implement in clinical practices.
The Dermatologist: Are you involved in other studies in which you are using tape strips to assess for biomarkers?
Dr Guttman: We just published a study that identified the phenotype of AD in infants aged 0 to 5 years using tape strips.2 While we have information from biopsies about the differences in phenotype, it would be nice to compare what happens in tape strips to show that they are able to collect this information and to perform this analysis on a larger scale.
It is an exciting time in general for inflammatory skin diseases. We are seeing a lot of new developments, both in the laboratory and in the clinic, that will ultimately lead to new treatments for both children and adults.
1. He H, Bissonnette R, Wu J, et al. Tape strips detect distinct immune and barrier profiles in atopic dermatitis and psoriasis. J Allergy Clin Immunol. Published online July 21, 2020. doi:10.1016/j.jaci.2020.05.048
2. Pavel AB, Renert-Yuval Y, Wu J, et al. Tape-strips from early-onset pediatric atopic dermatitis highlight disease abnormalities in non-lesional skin. Allergy. Published online July 8, 2020. doi:10.1111/all.14490