Gene expression profile analysis and identification of the effects triggered by essential sandalwood oil on human skin explants

The purpose of the present study was to establish at the molecular level, a genetic profile of the biological activity of essential sandalwood oil from Santalum album, produced under standardized conditions. The model system under investigation is based on living human skin explants. This protocol permits to compare ex vivo the effects of SO at the histological level as well as the changes of gene expression as a function of SO concentration and duration of treatment. In the present report, Sandalwood oil (S. album) was applied to living human skin explants to evaluate the sustained activity of the oil through gene expression profiling. Transcriptomic analysis showed a number of metabolic pathways and biological activities triggered by treatments previously described for aloe, curcumin and luteolin. No inflammatory responses accompanied the beneficial activities. The most intriguing impact was the natural effect on the retinoic acid (vitamin A) metabolism. Furthermore, we found that mechanisms normally acting in more specialized cell types such as immune cells, adipocytes, nerve cells, or hair follicles were activated in human skin explants in response to sandalwood oil. Thus, the oil may have the potential of further beneficial activities such as its antibacterial activity among other protective mechanisms. These results corroborate at a molecular level the rationale for clinical studies with sandalwood oil and support recent studies of patients with eczema (atopic dermatitis) or acne, which is often accompanied by bacterial growth on skin of Propionibacterium acnes. The wood was obtained from managed plantations of Santalum album grown in the Kununurra district of Western Australia. The plantations were owned by Santanol. The essential oil was extracted from the rich heartwood of plantation trees that were 15 years old. Oil was obtained through the steam distillation of wood chips loaded into commercial size stainless steel distillation pots. The effluent was cooled and condensed into a collection vessel and the top layer containing the oil was collected. The quality of the oil complies with that set out in ISO 3518/2002 – Oils of Sandalwood (Santalum album L.). The study was approved by an ethics committee and performed in accordance with the Declaration of Helsinki after the patient had given informed consent. A full-thickness human skin biopsy was obtained after plastic surgery from a healthy female donor (49-year-old Caucasian). Microarray data were quantified and normalized according to Agilent protocol (GeneExtraction Feature V10.5.5.1), and deposited in the public domain (NCBI PubMed Omnibus ).Subsequently, the fold-change (FC) between treated versus untreated condition was calculated by the following ratios: transcript intensity of treated samples versus transcript intensity of control samples. The selection of genes of interest were identified in sequential steps: a) Controls were considered unchanged if their expression was between 0.8 and 1.25 fold-change at two time points, 9h (early) and 24h (late). b) In order to take into account the effect of the tested product (P), only gene transcripts that were not subjected to modulation caused by the excipient (almond oil) were considered. Therefore, genes with an FC ≥1.25 between excipient and control values (intensities higher than background) in at least two out of three similar conditions (for each permutation between treated samples and controls), were removed. The remaining genes were then filtered for either FC ≥1.25 and <1.45, and for FC ≥1.45 between P and control values (intensities higher than background) in at least two out of three similar conditions (for each permutation between all treated samples and controls) for either P1 (2%) or P3 (0.4%) at either one (9h or 24h) or both time points. P1 and P3 were chosen based on the histology results. contributor: GENEX, 1 Chemin de Saulxier, 91160 Longjumeau, FRANCE contributor: SANTANOL, 17-21 Couslon Way, Canning Vale, WA, 6155, AUSTRALIA