Infertility has been reported as one of the most common reproductive impairments, affecting nearly one in six couples worldwide. A large proportion of infertility cases are diagnosed as idiopathic, signifying a deficit in information surrounding the pathology of infertility and necessity of medical intervention such as assisted reproductive therapy. Small noncoding RNAs (sncRNAs) are well-established regulators of mammalian reproduction. Advanced technologies have revealed the dynamic expression and diverse functions of sncRNAs during mammalian germ cell development. Mounting evidence indicates sncRNAs in sperm, especially microRNAs (miRNAs) and transfer RNA (tRNA)-derived small RNAs (tsRNAs), are sensitive to environmental changes and mediate the inheritance of paternally acquired metabolic and mental traits. Here, we review the critical roles of sncRNAs in mammalian germ cell development. Furthermore, we highlight the functions of sperm-borne sncRNAs in epigenetic inheritance. We also discuss evidence supporting sncRNAs as promising biomarkers for fertility and embryo quality in addition to the present limitations of using sncRNAs for infertility diagnosis and treatment.

Extracellular vesicles (EVs) are released by nearly all types of cells, and they communicate between cells by transporting bioactive molecules, including proteins, DNA, RNA, and lipids. In recent years, RNA carried by EVs, particularly the long-chain non-coding RNA (lncRNA) and circular RNA (circRNA) subtypes, has garnered interest with respect to their role in controlling tumor progression. Among them, there are increasing reports that mesenchymal stem cell-derived extracellular vesicles (MSC-EVs) maintain a recently discovered function as transporters of lncRNAs and circRNAs. However, detailed molecular functions of lncRNAs and circRNAs contained in MSC-EVs are not presently summarized, and the efficacy of MSC-EVs as molecular carriers requires further elucidation. This review summarizes the biological characteristics of EVs and the common mechanisms of lncRNAs and circRNAs contained within them. The “double-edged sword” effect and related molecular mechanism of EV-derived lncRNAs (EV-lncRNAs) and circRNAs (EV-circRNAs) between differing tumor types and MSCs are highlighted. The potential of MSC-EVs in the field of tumor diagnosis and treatment is discussed to suggest new directions for the strategy of engineering MSC-EVs as anti-tumor drug carriers.

Precisely localizing the spatial distribution of proteins within various brain cell types and subcellular compartments, such as the synapses, is essential for generating and testing hypotheses to elucidate their roles in brain function. While the fms-like tyrosine kinase-3 (Flt3) has been extensively studied in the context of blood cell development and leukemia pathogenesis, its role in the brain remains poorly understood. Previous efforts to address this issue were hindered by the low expression levels of Flt3 and the limited sensitivity of the standard immunolabeling method, which were insufficient to reliably detect Flt3 protein in brain tissue. In this study, we systematically characterized Flt3 protein localization during brain development using a highly sensitive immunolabeling method based on alkaline phosphatase (AP) polymer biochemistry. This approach revealed a previously unrecognized neuron-selective Flt3 expression pattern in both mouse and human cerebella, with a developmental increase in total protein levels accompanied by a shift from a cytosolic to a dendritic subcellular distribution. Combining AP-polymer-based immunohistochemistry (AP-IHC) for Flt3 with conventional immunostaining of cell type marker proteins revealed parvalbumin- and calbindin-positive Purkinje cells to be the main cell type expressing Flt3 in the cerebellum. To validate the versatility of the AP-IHC method for detecting low-abundance neuronal proteins, we demonstrated robust labeling of Kir2.1, a potassium channel protein, in brain tissue sections from mouse, pig, and human samples. We further applied the AP-IHC method to human stem cell-derived neurons, effectively visualizing the postsynaptic density scaffold protein PSD95 within synapses. To our knowledge, this is the first study to employ an AP-IHC method combined with other standard immunofluorescent staining to co-detect weakly expressed neuronal proteins and other cellular markers in brain tissue and cultured neurons. Additionally, our findings uncover a previously unrecognized neuron-specific pattern of Flt3 expression in the cerebellum, laying the foundation for future mechanistic studies on its role in normal brain development and neurological disorders.