Spermatogenesis generates mature male gametes and is critical for the proper transmission of genetic information between generations. However, the developmental landscapes of human spermatogenesis remain unknown. Here, we performed single-cell RNA sequencing (scRNA-seq) analysis for 2,854 testicular cells from donors with normal spermatogenesis and 174 testicular cells from one nonobstructive azoospermia (NOA) donor. A hierarchical model was established, which was characterized by the sequential and stepwise development of three spermatogonia subtypes, seven spermatocyte subtypes, and four spermatid subtypes. Further analysis identified several stage-specific marker genes of human germ cells, such as HMGA1, PIWIL4, TEX29, SCML1, and CCDC112. Moreover, we identified altered gene expression patterns in the testicular somatic cells of one NOA patient via scRNA-seq analysis, paving the way for further diagnosis of male infertility. Our work allows for the reconstruction of transcriptional programs inherent to sequential cell fate transition during human spermatogenesis and has implications for deciphering male-related reproductive disorders.

Objective. To observe redifferentiation of dedifferentiated chondrocytes after transplantation into the joint, and to evaluate the ability of dedifferentiated chondrocytes transduced with adenovirus containing bone morphogenetic protein 4 (BMP-4) to redifferentiate in vitro and in vivo in a rabbit model of articular cartilage defects.Methods. Monolayer and pellet culture systems were used to evaluate the redifferentiation of dedifferentiated chondrocytes transduced with BMP-4. A rabbit model of partial-thickness articular cartilage defects was used to evaluate cartilage repair macroscopically and histologically, 6 and 12 weeks after transplantation with first-passage, fifth-passage, or transduced fifthpassage chondrocytes. Histologic grading of the repaired tissue was performed. Expression of BMP-4 and the ability of transplanted cells to recover a chondrocytic phenotype were also assessed. Conclusion. Some dedifferentiated chondrocytes can redifferentiate after transplantation into the loadbearing joint. BMP-4 can be used to induce redifferentiation of dedifferentiated chondrocytes in vitro and in vivo, which could help enhance articular cartilage repair. Results. BMP-4-expressing dedifferentiated

The expression pattern of sNHE suggested that this protein may be involved in the regulation of sperm motility, and aberration of its expression in sperm may contribute to the pathogenesis of asthenozoospermia.

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