Daily Cosmetic Research Analysis

BACKGROUND: Hydroquinone is widely used for its hypopigmenting effects in treating hyperpigmentation disorders. However, its topical application has been linked to adverse effects, notably exogenous ochronosis, raising concerns about its safety and mechanisms of action. OBJECTIVES: To elucidate the metabolic pathway of hydroquinone in human melanocytes and to clarify the role of tyrosinase in the development of exogenous ochronosis. METHODS: We conducted an in vitro investigation using human tyrosinase to analyse the metabolism of hydroquinone. The study involved assessing the oxidation of hydroquinone in the presence of L-DOPA and L-cysteine, measuring the production of dopaquinone and its subsequent derivatives, including 2-S-cysteinyl-hydroquinone (Cys-HQ) and hydroquinone-pheomelanin (HQ-PM). RESULTS: Our findings demonstrate that human tyrosinase effectively oxidizes hydroquinone primarily via dopaquinone, with L-cysteine facilitating the formation of Cys-HQ. Further oxidation of Cys-HQ leads to the production of HQ-PM. Notably, the results indicate that tyrosinase activity is crucial for the induction of exogenous ochronosis by hydroquinone. Additionally, while high-molecular-weight hydroquinone derivatives may remain within melanosomes, low-molecular-weight metabolites can penetrate the dermis, potentially triggering the polymerization of ochronotic particles similar to those seen in exogenous ochronosis. CONCLUSIONS: Tyrosinase plays a significant role in hydroquinone-induced exogenous ochronosis, suggesting that hydroquinone acts as a 'pseudo' substrate for this enzyme. The findings highlight the importance of using tyrosinase inhibitors to reduce the risk of exogenous ochronosis, while cautioning against other melanogenesis inhibitors that may have similar side effects. Hyperpigmentation means that some parts of the skin become darker than others. This happens when the skin makes too much of the pigment ‘melanin’. Sunlight, hormonal changes or some medicines can cause the skin to make extra melanin. Hydroquinone is a chemical in some prescription creams. It is used to lighten dark spots on the skin. Hydroquinone can work, but it can also cause problems. One serious side effect is that it can cause dark patches on the skin. Researchers from Germany, France and Japan studied how skin cells react to hydroquinone. They wanted to learn about an enzyme called tyrosinase. This enzyme helps make melanin and dark spots. The researchers found that tyrosinase changes hydroquinone through a process called oxidation. This process can make a compound called hydroquinone-melanin. The skin gets rid of large hydroquinone compounds. But smaller ones can go deeper into the skin. This can cause these small compounds and dark patches to build up. The findings suggest that tyrosinase helps form dark spots when people use hydroquinone. True tyrosinase blockers are safe for treating hyperpigmentation. But substances changed by tyrosinase may cause dark spots and make hyperpigmentation worse.

BACKGROUND: Despite numerous treatment modalities for striae distensae (SD), a definitive gold standard therapy remains unidentified. AIMS: This study aims to evaluate and compare the efficacy of injectable poly-L-lactic acid (PLLA) with a 1565-nm non-ablative fractional laser (NAFL) in treating SD located in the abdominal area. METHODS: 40 women with SD were randomly assigned to one of four treatment groups: (1) control, (2) PLLA, (3) 1565-nm NAFL, and (4) a combination of PLLA and 1565-nm NAFL. Participants, except those in the control group, underwent three treatment sessions at monthly intervals. Antera 3D imaging was used to collect data at baseline (T0) and 3 months post-treatment (T4). Collagen fibers were analyzed via immunohistochemical staining, while elastic fibers were assessed using picrosirius red and Masson staining at both T0 and T4. RESULTS: The overall efficacy scores for the PLLA, 1565-nm NAFL, and PLLA + 1565-nm NAFL groups were 5.70 ± 1.25, 3.60 ± 2.12, and 6.70 ± 2.21, respectively. Post-treatment evaluations demonstrated substantial decreases in SD volume from T0 to T4, with reductions of -1.96 ± 1.53 in the PLLA group, -0.70 ± 0.67 in the 1565-nm NAFL group, and -1.48 ± 1.35 in the PLLA + 1565-nm NAFL group. The combined and PLLA groups exhibited significant reductions in area compared to the 1565-nm NAFL and control groups. Histological analysis confirmed the presence of PLLA particles in the treated area without inflammatory reactions 1 month post-final injection. CONCLUSIONS: PLLA injections are more effective than 1565-nm NAFL in SD treatment, enhancing collagen production without inducing inflammation in treated skin. TRIAL REGISTRATION: Clinicaltrials.gov: NCT05827913.

BACKGROUND: Lip augmentation using dermal fillers is increasingly popular, but often requires large volumes and regular touch-ups, whereas poor techniques and product selection can result in unnatural-looking lips. The RHA collection was designed to have less rigidity, allowing the products to adapt to facial animation. In particular, RHA3 has been approved in Europe for lip volumization. OBJECTIVES: The authors of this study aimed to evaluate the effectiveness and safety of RHA3 vs an active comparator for lip augmentation in the US population. METHODS: This was a randomized, controlled, double-blinded, multicenter clinical study. The primary endpoint aimed to demonstrate the noninferiority of RHA3 vs the comparator using the Teoxane Lip Fullness Scale (TLFS), assessed by the blinded live evaluator, 12 weeks after treatment. Secondary objectives included improvement on the TLFS, Global Aesthetic Improvement Scale, patient satisfaction, and natural look/feel of the lips up to 52 weeks. Safety assessment covered adverse events (AEs), common treatment reactions, and injection site pain. RESULTS: A total of 202 patients were enrolled. RHA3 was considered statistically noninferior to the comparator for lip augmentation among patients with TLFS Grades 1 to 3. It provided sustained lip volume enhancement over time, with high rates of aesthetic improvement and patient satisfaction. Most RHA3-treated patients achieved a natural look and feel of the lips that was maintained throughout the study period. Most AEs were mild to moderate, with no late-onset reactions or angioedema reported. CONCLUSIONS: RHA3 was effective for lip augmentation, providing sustained aesthetic improvement, high satisfaction, and good tolerability. These findings support the use of RHA3 as a uniquely dynamic option for natural-looking lip augmentation.