Increased expression of branched-chain amino acid (BCAA) transaminase 1 (BCAT1) often correlates with tumor aggressiveness and drug resistance in cancer. We have recently reported that BCAT1 was overexpressed in a subgroup of T-cell acute lymphoblastic (T-ALL) samples, especially those with NOTCH1 activating mutations. Interestingly, BCAT1-depleted cells showed pronounced sensitivity to DNA-damaging agents such as etoposide; however, how BCAT1 regulates this sensitivity remains uncertain. Here, we provide further clues on its chemo-sensitizing effect. Indeed, BCAT1 protein regulates the non-homologous end joining (c-NHEJ) DNA repair pathway by physically associating with the KU70/KU80 heterodimer. BCAT1 inhibition during active repair of DNA double-strand breaks (DSBs) led to increased KU70/KU80 acetylation and impaired c-NHEJ repair, a dramatic increase in DSBs, and ultimately cell death. Our results suggest that, in T-ALL, BCAT1 possesses non-metabolic functions that confer a drug resistance mechanism and that targeting BCAT1 activity presents a novel strategy to improve chemotherapy response in T-ALL patients.

Chronic low-grade inflammation and oxidative stress induced by the exposome represent key drivers of skin aging and related imperfections. The development of experimental models suitable for studying these metabolic processes is therefore of primary importance for the cosmetic industry. In recent years, the role of specialized pro-resolving mediators (SPMs) in the resolution of inflammation has been highlighted; however, in vitro skin models to investigate them are still lacking. In this work, we developed an ex vivo human skin culture model that allows the quantification of maresin 1 (MaR1) production by measuring its concentration in the conditioned culture medium using an ELISA-based assay. The presence and survival of MaR1-synthesizing immune cells, namely Langerhans cells and leukocytes, were quantified during the first days of culture. The model’s ability to modulate MaR1 production was assessed in response to treatment with its precursor, docosahexaenoic acid (DHA), and with a DHA-rich cosmetic ingredient named Isochrysis Galbana Extract. Results demonstrated that the model produces MaR1 even in the absence of stimulation and responds to treatments with a further increase in MaR1 production. Furthermore, the tissue-to-medium ratio required to obtain MaR1 concentrations suitable for effective ELISA quantification was optimized. This model establishes a reproducible and scalable experimental platform for quantifying SPMs and evaluating DHA-based formulations, supporting both cosmetic research and mechanistic investigations.

Background: The cosmetic industry is a rapidly expanding, high-value sector that drives continuous research into biologically active compounds and advanced delivery technologies aimed at improving skin health. Objective: To investigate the biological activity of apple-derived extracellular vesicles (ADEVs) and to evaluate strategies to enhance the transcutaneous penetration of ADEV-based formulations. Methods: In vitro, purified ADEVs were characterized in terms of size distribution and concentration. Their internalization was assessed in different cell types, and gene expression analysis was performed in treated cellular models. Ex vivo, PKH26-labeled ADEVs were applied to human surgical skin samples, either alone or in combination with microneedling (MN) using different procedural protocols. Fluorescence distribution was quantified in both epidermal and dermal compartments. Results: ADEV characterization showed a size range of 102–160 nm and a particle concentration of 9.48 × 10¹¹ particles/mL, together with morphological features consistent with EVs. ADEVs demonstrated efficient cellular internalization in vitro and modulated the expression of selected target genes (CDH5, NOS3, KLF2, and KLF4). In the ex vivo model, fluorescence signal associated with PKH26-labeled ADEV-based formulations was detected within human skin layers. A significant treatment effect was observed in both epidermal (F = 33.57, p < 0.001) and dermal compartments (F = 7.57, p = 0.018), with the highest fluorescence signal consistently detected when EV application was preceded by MN (MN + EVs). Notably, ADEV-based formulation alone also induced a significant increase in the epidermis compared with untreated controls, although of lower magnitude than that observed following MN pre-treatment. Conclusions: These findings support a controlled evaluation of microneedling as a strategy to enhance the distribution of ADEV-based formulations within human skin, highlighting the importance of application sequence. More broadly, this work contributes to the development of standardized and reproducible delivery approaches, while underscoring the need for further methodological refinement to achieve vesicle-specific tracking in complex tissues.