Human menstrual blood-derived stem cells (MenSCs), a major class of mesenchymal stem cells (MSCs), modulate intercellular signals via paracrine factors. Previous studies found that MenSC-derived secretomes exert protective effects against liver fibrosis. However, the underlying mechanisms of these observations remain unclear.
Extracellular Matrix Protein 1 (ECM1), identified in MenSCs culture medium using mass spectrometry, was employed to stably overexpress ECM1-HA or silence in MenSCs using lentiviral vectors. These genetically engineered cells were either intravenously injected into the carbon tetrachloride (CCl4)-induced liver fibrosis mice or co-cultured with hepatic stellate cells (HSCs)-LX-2. The interaction between ECM1 and low-density lipoprotein receptor-related protein 1α (LRP1α) was confirmed using Co-Immunoprecipitation (Co-ip), Duolink Proximity Ligation Assays (PLA) and pull-down. LRP1 deficient mice were generated via intravenous administration of adeno-associated-virus-8. The downstream molecular mechanisms were characterized by non-target metabolomics and multiplex immunohistochemical staining. RNA sequencing was performed to evaluate the genetic alterations in various genes within the MenSCs.
MenSC-secreted ECM1 exhibits potential to ameliorate liver fibrosis by inactivating HSCs, improving liver functions, and reducing collagen deposition in both cellular and mouse model of the CCl4-induced liver fibrosis. Mechanistically, a novel interaction was identified that ECM1 directly bound to cell surface receptor LRP1α. Notably, the antifibrotic efficacy of MenSC was negated in LRP1-deficient cells and mice. Moreover, the ECM1-LRP1 axis contributed to the alleviation of liver fibrosis by suppressing AKT/mTOR while activating the FoxO1 signaling pathway, thereby facilitating pyrimidine and purine metabolism. Additionally, ECM1-modified MenSCs regulate the transcription of intrinsic cytokine genes, further mitigating liver fibrosis.
These findings highlight an extensive network of ECM1-LRP1 interaction, which serve as a link for providing promising insights into the mechanism of MenSC-based drug development for liver fibrosis. Our study also potentially presents novel avenues for clinical antifibrotic therapy.
© 2025. The Author(s).

ABSTRACT Direct targeting of the oncoprotein MYC has long been attempted in cancer therapy, with limited success. We here identify a novel co-regulatory feedback loop of MYC and G1 to S phase transition protein 1 (GSPT1), where MYC promotes transcription of GSPT1, and GSPT1 senses stop codon of MYC to promote its translation. We report on the first-in-class dual MYC/GSPT1 protein degrader, GT19630. GT19630 significantly induced integrated stress response, abrogated oxidative phosphorylation through inhibition of the TCA cycle and induced cell death. Protein degradation of MYC was critical for efficacy of GT19630. GT19630 induced profound anti-proliferative effects and apoptosis agnostic to TP53 in a broad range of cancer cells, and is highly active in vivo in multiple, therapy-resistant hematologic and solid tumor models. Dual MYC/GSPT1 degradation was well tolerated in humanized Crbn I391V mice. In conclusion, we propose a novel treatment approach by directly targeting the MYC-GSPT1 axis in MYC-driven cancers. Statement of significance MYC has been considered an undruggable protein. We found a targetable, novel positive co-regulatory feedback of MYC and GSPT1, a key translation terminator. The dual MYC/GSPT1 degrader GT19630 is highly active in MYC-driven tumors, with moderate effects on humanized Crbn mice, providing opportunities to improve treatment outcome of MYC-driven cancers.

Osteoporosis is characterized by reduced bone mass due to imbalanced bone metabolism. Exosomes derived from bone mesenchymal stem cells (BMSCs) have been shown to play roles in various diseases. This study aimed to clarify the regulatory function and molecular mechanism of BMSCs-derived exosomes in osteogenic differentiation and their potential therapeutic effects on osteoporosis. Exosomes were extracted from BMSCs. Bone marrow-derived macrophages (BMDMs) were cultured and internalized with BMSCs-derived exosomes. Real-time quantitative PCR was used to detect the expression of macrophage surface markers and tripartite motif (TRIM) family genes. BMDMs were co-cultured with human osteoblasts to assess osteogenic differentiation. Western blot was performed to analyze the ubiquitination of triggering receptor expressed on myeloid cell 1 (TREM1) mediated by TRIM25. An ovariectomized mice model was established to evaluate the role of TRIM25 and exosomes in osteoporosis. Exosomes were successfully isolated from BMSCs. BMSCs-derived exosomes upregulated TRIM25 expression, promoting M2 macrophage polarization and osteogenic differentiation. TRIM25 facilitated the ubiquitination and degradation of TREM1. Overexpression of TREM1 reversed the enhanced M2 macrophage polarization and osteogenic differentiation caused by TRIM25 overexpression. TRIM25 enhanced the protective effect of BMSCs-derived exosomes against bone loss in mice. These findings suggested that BMSCs-derived exosomes promoted osteogenic differentiation by regulating M2 macrophage polarization through TRIM25-mediated ubiquitination and degradation of TREM1. This mechanism might provide a novel approach for treating osteoporosis.
© 2024. The Author(s).

Facial nerve (FN) injury seriously affects human social viability and causes a heavy economic and social burden. Although mesenchymal stem cell-derived exosomes (MSC-Exos) promise therapeutic benefits for injury repair, there has been no evaluation of the impact of MSC-Exos administration on FN repair. Herein, we explore the function of MSC-Exos in the immunomodulation of macrophages and their effects in repairing FN injury. An ultracentrifugation technique was used to separate exosomes from the MSC supernatant. Administrating MSC-Exos to SD rats via local injection after FN injury promoted axon regeneration and myelination and alleviated local and systemic inflammation. MSC-Exos facilitated M2 polarization and reduced the M1-M2 polarization ratio. miRNA sequencing of MSC-Exos and previous literature showed that the MAPK/NF-κb pathway was a downstream target of macrophage polarization. We confirmed this hypothesis both in vivo and in vitro. Our findings show that MSC-Exos are a potential candidate for treating FN injury because they may have superior benefits for FN injury recovery and can decrease inflammation by controlling the heterogeneity of macrophages, which is regulated by the p38 MAPK/NF-κb pathway.

The tumor suppressor TP53 is frequently inactivated in a mutation-independent manner in cancers and is reactivated by inhibiting its negative regulators. We here cotarget MDM2 and the nuclear exporter XPO1 to maximize transcriptional activity of p53. MDM2/XPO1 inhibition accumulated nuclear p53 and elicited a 25- to 60-fold increase of its transcriptional targets. TP53 regulates MYC, and MDM2/XPO1 inhibition disrupted the c-MYC-regulated transcriptome, resulting in the synergistic induction of apoptosis in acute myeloid leukemia (AML). Unexpectedly, venetoclax-resistant AMLs express high levels of c-MYC and are vulnerable to MDM2/XPO1 inhibition in vivo. However, AML cells persisting after MDM2/XPO1 inhibition exhibit a quiescence- and stress response-associated phenotype. Venetoclax overcomes that resistance, as shown by single-cell mass cytometry. The triple inhibition of MDM2, XPO1, and BCL2 was highly effective against venetoclax-resistant AML in vivo. Our results propose a novel, highly translatable therapeutic approach leveraging p53 reactivation to overcome nongenetic, stress-adapted venetoclax resistance.