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Adipocyte deposition is believed to be a primary characteristic of age-related thymic involution, but the underlying cellular and molecular mechanisms remain unknown. We show here that thymic mesenchymal stromal cells (tMSCs) have a higher tendency to differentiate into adipocytes and melanocortin-2 receptor accessory protein (MRAP) is a potential driver of tMSCs adipogenesis. Furthermore, we discover that thymosin-α1 promotes MRAP expression in tMSCs through FoxO1 signaling pathway. Additionally, the proportion of tMSCs increase in older mice compared to young mice. Importantly, MRAP is also necessary for human thymic MSCs to differentiate into adipocytes when exposed to thymosin-α1. Single-cell RNA-seq analysis of human thymus revealed an accumulation of tMSCs and adipocytes during aging, indicating a strong potential for adipogenic differentiation in age-related thymic involution. Thus, we have revealed MRAP as a key factor in promoting thymic MSCs adipogenesis triggered by thymosin-α1 and FoxO1 pathway, which may serve as potential target to hinder adiposity in age-related thymic involution. Adipocyte deposition is believed to be a primary characteristic of age-related thymic involution. Here, the authors show that MRAP is a key factor in promoting thymic MSCs adipogenesis triggered by thymosin-α1 and FoxO1 pathway, which provide a new mechanism for age-related thymic involution

BackgroundExtracellular Vesicles (EVs) derived from mesenchymal stem cells (MSCs) have gained recognition as promising therapeutic and drug delivery agents in regenerative medicine. However, their clinical application is limited by donor variability, low scalability, and inconsistent therapeutic quality. To overcome these challenges, a robust and standardized production platform is urgently needed.MethodsWe developed a scalable biomanufacturing strategy by generating and expanding MSCs from extended pluripotent stem cells (EPSC) using a suspension bioreactor culture system. A fixed-bed bioreactor was integrated for automated, continuous expansion of iMSCs and downstream EV harvesting. EVs were isolated through a streamlined protocol and characterized for size, morphology, surface markers, and bioactivity. Therapeutic efficacy was assessed in a bleomycin-induced pulmonary fibrosis mouse model.ResultsiMSC-derived EVs (iMSC-EVs) exhibited comparable characteristics to primary MSC-EVs, including a size distribution of 70–80 nm, cup-shaped morphology, and expression of canonical EV markers (CD63, CD81, TSG101). iMSCs were expanded for up to 20 days in 3D culture, yielding > 5 × 10⁸ cells per batch using a suspension bioreactor culture system and producing ~ 1.2 × 10¹³ EV particles/day in a fixed-bed bioreactor. In vivo, iMSC-EVs significantly reduced Ashcroft fibrosis scores and bronchoalveolar lavage fluid protein levels in bleomycin-injured lungs, with therapeutic efficacy comparable to primary MSC-EVs.ConclusionsThis study establishes a scalable and standardized platform for producing high-quality iMSC-EVs using bioreactor-based systems. Our approach addresses key limitations in traditional EV production and sets the stage for AI-integrated, fully automated, GMP-compliant manufacturing of therapeutic EVs suitable for clinical translation.Supplementary InformationThe online version contains supplementary material available at 10.1186/s13287-025-04507-y.

Dimethylsulfoxide (DMSO) has conventionally been used for cell cryopreservation both in research and in clinical applications, but has long-term cytotoxic effects. Trehalose, a natural disaccharide, has been proposed as a non-toxic cryoprotectant. However, the lack of specific cell membrane transporter receptors inhibits transmembrane transport and severely limits its cryoprotective capability. This research presents a method to successfully deliver trehalose into mesenchymal stem cells (MSCs) using ultrasound in the presence of microbubbles. The optimised trehalose concentration was shown to be able to not only preserve membrane integrity and cell viability but also the multipotency of MSCs, which are essential for stem cell therapy. Confocal imaging revealed that rhodamine-labelled trehalose was transported into cells rather than simply attached to the membrane. Additionally, the membranes were successfully preserved in lyophilised cells. This study demonstrates that ultrasonication with microbubbles facilitated trehalose delivery, offering promising cryoprotective capability without the cytotoxicity associated with DMSO-based methods. Subject terms: Membrane biophysics, Biomedical engineering