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Background and objectives: Exosomes, which are small nanoscale vesicles capable of secretion, have garnered significant attention in recent years because of their therapeutic potential, particularly in the context of kidney diseases. Notably, human umbilical cord mesenchymal stem cell-derived exosomes (hucMSC-Exos) are emerging as promising targeted therapies for renal conditions. The aim of this study was to investigate the therapeutic effects of hucMSC-Exos on diabetic kidney disease (DKD) both in vivo and in vitro. Additionally, this study seeks to elucidate cellular and molecular differentials, as well as the expression of relevant signaling pathways, through single-cell RNA sequencing. This endeavor was designed to enhance our understanding of the connection between hucMSC-Exos and the pathogenesis of DKD. Methods and results: The study commenced with the extraction and characterization of hucMSC-Exos, including the determination of their concentrations. Animal experiments were conducted to evaluate the therapeutic potential of hucMSC-Exos in a DKD mouse model. Subsequently, single-cell sequencing was employed to investigate the molecular mechanisms underlying the efficacy of extracellular vesicles in ameliorating DKD. These findings were further substantiated by cell-based experiments. Importantly, the results indicate that hucMSC-Exos can impede the progression of DKD in mice, with macrophage activation playing a pivotal role in this process. Conclusions: The in vivo experiments conclusively established hucMSC-Exos as a pivotal component in preserving renal function and retarding the progression of DKD. Our utilization of single-cell sequencing technology, in conjunction with in vivo and in vitro experiments, provides compelling evidence that M2 macrophages are instrumental in enhancing the amelioration of diabetic nephropathy.

As valuable land in the ocean, coral islands are not only important bases for making use of marine resources and protecting marine rights and interests, but also important for breakthrough research in many fields of earth science. Hence, the economical and efficient determination of the underground structure of coral islands has become significant in coral island engineering geology, but remains challenging for traditional marine geophysical prospecting and drilling methods. While ambient noise tomography with dense arrays has been widely used in continental regions, its applicability to coral islands remains undetermined. In this study, based on the data recorded by a dense array on an isolated coral island in the South China Sea, we analyzed the ambient noise characteristics and obtained a 3D subsurface structure of the coral island using ambient noise tomography. We made the following findings: ① The ambient noise frequencies can be roughly categorized into three levels: < 1, 1–5, and > 5 Hz. The spectral characteristics of the noise below 5 Hz were consistent at different stations, but there were significant differences in the characteristics of the noise above 5 Hz. ② For ambient noise frequencies below 5 Hz, cross-correlation functions with high quality could be obtained with only 24 h of waveform data. However, it was difficult to extract meaningful cross-correlation functions for ambient noise frequencies above 5 Hz. ③ The surface-wave velocity in the coral island was higher toward the sea and lower toward the lagoon, which was consistent with the high degree of cementation of the outer reef flat stratum on the seaward side. ④ There were two low-velocity horizons at depths of 25–75 and 200–300 m, which were in good agreement with the high-porosity horizons that were revealed by drilling core samples, reflecting the weathering history of the reef. Our research demonstrates that ambient noise tomography is a potentially economical, efficient, and environmentally friendly method for the geological prospecting of coral reefs.