Fig 2: Immunohistochemical labeling of PLIN2 in human skin of patients with acne and nonacne controls (cohort 3). (a) A general view and (b) a close view of patient 1 highest expression field. (c?i) Close views of the highest expression field in the seven other patients with acne. (j) A general view of one control. (k?o) Close views of the highest expression field of the controls. Bar = 500 µm in a, e, h, i, and k. Bar = 200 µm in b, d, f, and g. Bar = 250 µm in c, m, and o. Bar = 1,000 µm in l and n. Bar = 1,000 µm in j.

Fig 3: Correlation between microcomedone index and lipid droplet proteins in cohort 1 (CSSB biopsies). (a) PLIN2 and CIDEA are expressed in a nonmetric multidimensional scaling of 50 CSSB biopsies from 23 patients on the basis of the value of the MCI in decreasing order; for each sample, the sum of corresponding MCI value and the expression values for CIDEA and PLIN2 gives 100%, and the bars represent the respective percentages for MCI, CIDEA, and PLIN2 (Fontao et al., 2020). (b) The means ± SD of CIDEA and PLIN2 expressions are determined for 50 CSSB biopsies from 23 patients, with MCI values above and below 15. Positive control for (c) PLIN2 and (d) CIDEA expressions were analyzed in human Sebo cultures, human hepatocyte cell line HepG2, mouse liver extract (liver), and human CSSB extracts from three samples. For each of the gels in c and d, after the transfer to nitrocellulose membranes, the membranes were spliced to incubate the respective pieces with (c) PLIN2 and GAPDH antibodies or (d) CIDEA and GAPDH antibodies; white lines indicate where the membranes were spliced. (e) This image shows CIDEA and GAPDH bands from a gel to explain how the densitometric assessment was performed for all protein bands of interest; as for the gels in c and d, the nitrocellulose membrane was spliced to incubate each part with CIDEA or GAPDH antibodies; when comparing CIDEA and GAPDH (housekeeping protein), the background of the gel—corresponding to the rectangle in the middle of the image—is subtracted, and the density of the protein bands are calculated by subtracting their mean gray values from that of the background. The ratio between the LD protein and GAPDH gives the expression value of the LD protein. This ratio is then multiplied by 100 when creating the graphs shown in Figure 1a and b for clarity. Statistical significance in b is set as **P < 0.01. CSSB, cyanoacrylate skin surface biopsy; LD, lipid droplet; MCI, microcomedone index; Sebo, sebocyte.

Fig 4: Summary diagram of data. PLIN2 and CIDEA are anchored on the phospholipid layer of lipid droplets. The lipid core contains mainly triglycerides, FFAs, S, as well as CWEs (Kory et al., 2016; Olzmann and Carvalho, 2019). During comedogenesis, the expression of PLIN2 and CIDEA is decreased, and a triglyceride lipase is activated, releasing FFAs from triglycerides. This process is partly reversed by topical application of SMFE. CWE, cholesterol and wax ester; FFA, free fatty acid; S, squalene; SMFE, Silybum marianum fruit extract.