The study investigates the secretory mechanisms and intercellular transfer of microRNAs (miRNAs) in living cells. It reveals that miRNAs are secreted through a ceramide-dependent pathway involving the exosome secretion machinery. The secreted miRNAs are functional in recipient cells, enabling intercellular communication. The study shows that neutral sphingomyelinase 2 (nSMase2) regulates miRNA secretion, and that the endosomal sorting complex required for transport (ESCRT) is not necessary for this process. Secreted miRNAs, such as a tumor-suppressive miRNA, can be transferred between cells and exert gene silencing in recipient cells, leading to cell growth inhibition. The study also demonstrates that miRNAs are packaged in exosomes, which protect them from ribonucleases. The findings suggest that secretory miRNAs play a physiological role in intercellular communication and may serve as diagnostic markers for cancer. The study provides insights into the mechanisms of miRNA secretion and their biological functions, highlighting the potential of secretory miRNAs in cellular signaling and disease progression.The study investigates the secretory mechanisms and intercellular transfer of microRNAs (miRNAs) in living cells. It reveals that miRNAs are secreted through a ceramide-dependent pathway involving the exosome secretion machinery. The secreted miRNAs are functional in recipient cells, enabling intercellular communication. The study shows that neutral sphingomyelinase 2 (nSMase2) regulates miRNA secretion, and that the endosomal sorting complex required for transport (ESCRT) is not necessary for this process. Secreted miRNAs, such as a tumor-suppressive miRNA, can be transferred between cells and exert gene silencing in recipient cells, leading to cell growth inhibition. The study also demonstrates that miRNAs are packaged in exosomes, which protect them from ribonucleases. The findings suggest that secretory miRNAs play a physiological role in intercellular communication and may serve as diagnostic markers for cancer. The study provides insights into the mechanisms of miRNA secretion and their biological functions, highlighting the potential of secretory miRNAs in cellular signaling and disease progression.