Proteasome-Enriched hPPSCs-Derived EVs Attenuate Hypoxic Injury in Endothelial Cells via Proteasome-Mediated HIF-1α Degradation.

Stem cell-derived extracellular vesicles (EVs) hold therapeutic potential for hypoxia-associated injury, yet the molecular mechanisms underlying their protective effects remain incompletely defined. Herein, we performed comparative proteomic profiling of extracellular vesicles (EVs) secreted by human placenta-derived perivascular stem cells (hPPSCs) and human umbilical cord mesenchymal stem cells (hUCMSCs). We found that hPPSCs-EVs are enriched in proteasome-related proteins. Enzymatic activity assays further confirmed that proteasome activity in hPPSCs-EVs was significantly higher than that in hUCMSCs-EVs. Additionally, we observed that hPPSCs-EVs were efficiently endocytosed by human umbilical vein endothelial cells (hUVECs), leading to marked downregulation of hypoxia-inducible factor 1-alpha (HIF-1α) and intracellular ubiquitinated proteins. Importantly, this HIF-1α degradation persisted even when the host ubiquitin-proteasome system was blocked, indicating that hPPSCs-EVs can function independently of the host proteasomal pathway. These results reveal that hPPSCs-EVs deliver functional proteasomes to endothelial cells, thereby compensating for impaired protein degradation and protecting cells under hypoxic stress. Collectively, our findings provide evidence for an intercellular transfer of proteolytic capacity via stem cell-derived EVs, a mechanism that preserves endothelial proteostasis and highlights the therapeutic potential of proteasome-rich EVs for hypoxia-associated diseases.