Spermatogenesis is one of the most complex and longest processes of sequential cell proliferation and differentiation in the body, taking more than a month from spermatogonial stem cells, through meiosis, to sperm formation. The whole process, therefore, has never been reproduced in vitro in mammals, nor in any other species with a very few exceptions in some particular types of fish. Here we show that neonatal mouse testes which contain only gonocytes or primitive spermatogonia as germ cells can produce spermatids and sperm in vitro with serum-free culture media. Spermatogenesis was maintained over 2 months in tissue fragments positioned at the gas-liquid interphase. The obtained spermatids and sperm resulted in healthy and reproductively competent offspring through microinsemination. In addition, neonatal testis tissues were cryopreserved and, after thawing, showed complete spermatogenesis in vitro. Our organ culture method could be applicable through further refinements to a variety of mammalian species, which will serve as a platform for future clinical application as well as mechanistic understanding of spermatogenesis.

In bone development and regeneration, angiogenesis and bone/cartilage resorption are essential processes and are closely associated with each other, suggesting a common mediator for these two biological events. To address this interrelationship, we examined the effect of vascular endothelial growth factor (VEGF), the most critical growth factor for angiogenesis, on osteoclastic bone-resorbing activity in a culture of highly purified rabbit mature osteoclasts. VEGF caused a dose-and time-dependent increase in the area of bone resorption pits excavated by the isolated osteoclasts, partially by enhancing the survival of the cells. Two distinct VEGF receptors, KDR/Flk-1 and Flt-1, were detectable in osteoclasts at the gene and protein levels, and VEGF induced tyrosine phosphorylation of proteins in osteoclasts. Thus, osteoclastic function and angiogenesis are upregulated by a common mediator such as VEGF.z 2000 Federation of European Biochemical Societies.

Aurones are plant flavonoids that provide yellow color to the flowers of some popular ornamental plants, such as snapdragon and cosmos. In this study, we have identified an enzyme responsible for the synthesis of aurone from chalcones in the yellow snapdragon flower. The enzyme (aureusidin synthase) is a 39-kilodalton, copper-containing glycoprotein catalyzing the hydroxylation and/or oxidative cyclization of the precursor chalcones, 2',4',6',4-tetrahydroxychalcone and 2',4',6',3,4-pentahydroxychalcone. The complementary DNA encoding aureusidin synthase is expressed in the petals of aurone-containing varieties. DNA sequence analysis revealed that aureusidin synthase belongs to the plant polyphenol oxidase family, providing an unequivocal example of the function of the polyphenol oxidase homolog in plants, i.e., flower coloration.

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