Expression data from the dermis of human stretched scars and patient-matched healthy dermis from occipital scalps

It is well accepted that elevated mechanical tension of the skin surrounding a healing wound stimulates a fibrotic cascade of events and contributes to an increased size of scars. A laxity paradox in the field of hair transplantation describes a phenomenon opposing this view. During Strip Follicular Unit Transplantation (Strip FUT), surgeons remove a strip of scalp skin (approximately 5 cm x 10 cm, depending on the number of hair follicles required) from the occipital scalp, which is then used to harvest hair follicles that will be transplanted into the balding frontal scalp. Most patients with normal scalp skin laxity heal with narrow normotrophic scars, while a small number of patients (14%) with very loose scalp skin, and so low residual skin tension, heal with post operating scar widening (4 - 12 mm). These scars, referred to as stretched scars in the hair transplantation field, often require revision surgery or secondary hair grafting into the scar. We hypothesise that stretched scars present a unique transcriptional signature different from other types of scars. To determine the gene expression profile of stretched scars, we used Affymetrix microarrays to perform profiling of fibrotic dermis and the surrounding patient-matched healthy dermis. We collected full-thickness skin samples from 3 patients who had their stretched scars excised for aesthetic reasons. The samples were approximately 1 cm x 2 cm and consisted of mature (at least 4 years old) and wide (at least 5 mm) scars and the surrounding healthy skin. All scars formed post-surgically on occipital scalps after excision of skin needed for harvesting hair follicles during a Follicular Unit Transplantation (FUT) surgery. The scar and healthy dermis were dissected from 20 µm-thick sections of the sample and RNA was isolated using RNeasy Plus Mini Kit (Qiagen). RNA was used to synthesize first-strand complementary DNA (cDNA) using Nugen Ovation V2. This was then converted to double-stranded cDNA, and used as a template for in vitro transcription to generate cRNA using the Nugen Encore Biotin Module. The cRNA was then transferred for hybridization and scanning onto the GeneChip™ Human Genome U133 Plus 2.0 Array. Transcriptomic Analysis Console (TAC) was used to perform a one-way ANOVA on the dataset to identify 442 transcripts that were significantly (P < 0.01) and differentially (fold change <- 1.5 or > 1.5) regulated between the dermis of stretched scars and the surrounding healthy skin. We used Ingenuity Pathway Analysis (IPA) to find the diseases & functions that these differentially expressed genes were involved in and define transcripts of proteins that are expressed extracellularly.