Movie S2 This is similar to movie 1, but with a more direct interaction. This is to indicate the heterogeneous nature of the nerve interactions with keratinocytes Movie S3 A 3-D resolution of nerve fiber innervation of keratinocytes showing synaptic bouton-like structure penetrating and exiting keratinocytes; corresponds to figure 2dMovie S4 A bottom to top Z projection of the sample from figure 2d and Movie 3, indicating that the nerve fiber could be within one or
| QUESTIONS ADDRESSEDA deregulation of miR expression in skin-associated diseases such as psoriasis and atopic dermatitis has been reported previously.
4,5However, to our knowledge, no study has been published yet, showing that specific secretory miRs become deregulated in the course of skin ageing and are involved in human skin cell crosstalk. Thus, we analysed, if secreted miRs might play a role in age-related dysfunctions.
| EXPERIMENTAL DESIGNWe generated miR profiles of interstitial fluid collected from younger and older volunteers after suction blistering and identified agedependent differences in miR levels (eg miR-126). In vitro, we analysed whether miR-126 is age-dependently secreted by dermal endothelial cells and incorporated by other skin cells.
| RESULTS
| Secretory miR levels during skin ageingTo investigate the levels of secreted miRs during skin ageing, human interstitial fluid of the skin was analysed. 6 Quantitative PCR-based microRNA profiling was performed, and 175 miRs were detected with a C t -value <40 which was sufficient to be considered in the following analysis ( Figure S1 and Table S1). Setting a threshold of 1.5-fold regulation (up/down), we identified 61 miRs that were regulated in an age-related manner in suction blister fluids collected from young and old volunteers. The results could be confirmed in an independent experiment for three selected miRs (miR-100, miR-126 and miR-223)
| Age-related miR-100 , miR-126 and miR-223 levels in cultured endothelial cellsIn vitro analysis was performed to delineate whether the age-related miR expression changes are triggered during cellular ageing. We cultivated dermal endothelial cells isolated from volunteers aged between 22 and 73 years and determined miR-100, miR-126 and miR-223 abundance in the supernatant 48 hours after cell seeding. All three miRs were significantly decreased in the supernatant of endothelial cell populations isolated from aged volunteers compared to the younger cell population ( Figure S2A-C). In contrast, intra-cellular miR levels detected for miR-100 and miR-126 (miR-223 was not analysed) in the intra-cellular compartment remain stable throughout age ( Figure S3A-B).*contributed equally to this work F I G U R E 1 Age-related miR expression changes in human suction blister fluids of the skin. A-C: Different miRs were selected from miRNA profiling for validation from qRT-PCR profiling. The suction blister fluid of 20 healthy volunteers of two different age groups (18-28 years and 66-75 years) was collected, and the suction blister fluids of 2 volunteers ...