To bioengineer ectodermal organs such as teeth and whisker follicles, we developed a three-dimensional organ-germ culture method. The bioengineered tooth germ generated a structurally correct tooth, after both in vitro organ culture as well as transplantation under a tooth cavity in vivo, showing penetration of blood vessels and nerve fibers. Our method provides a substantial advance in the development of bioengineered organ replacement strategies and regenerative therapies.

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Oligodendrocyte precursor cells (OPCs) differentiate into oligodendrocytes (OLs) in order to form myelin, which is required for the rapid propagation of action potentials in the vertebrate nervous system. In spite of the considerable clinical importance of myelination, little is known about the basic molecular mechanisms underlying OL differentiation and myelination. Here, we show that cyclin-dependent kinase (Cdk) 5 is activated following the induction of differentiation, and that the Cdk5 inhibitor roscovitine inhibits OL differentiation. The complexity of the OL processes is also diminished after knocking down endogenous Cdk5 using RNAi. We also show that the focal adhesion protein paxillin is directly phosphorylated at Ser244 by Cdk5. Transfection of a paxillin construct harboring a Ser244 to Ala mutation dramatically inhibits its morphological effects. Importantly, phosphorylation of paxillin at Ser244 reduces its interaction with focal adhesion kinase (FAK). Taken together, these results suggest that phosphorylation of paxillin by Cdk5 is a key mechanism in OL differentiation and may ultimately regulate myelination.

Although estrogens can stimulate the growth of uterine epithelial cells in vivo, there is no clear effect of estrogens on the in vitro growth of epithelial cells from reproductive tract tissues; thus, we have established a defined culture system for mouse uterine epithelial cells. Pieces of uteri from immature CD-1 mice (21-23 days of age) were treated with trypsin, and the epithelial fragments were separated, enriched by Percoll gradient centrifugation, and seeded on collagen gels prepared from rat tail tendon. Initially, the cells were cultured in a 1:1 mixture of Ham's F-12 and Dulbecco's Modified Eagle's Medium supplemented with epidermal growth factor (EGF; 10 ng/ml), insulin (10 micrograms/ml), transferrin (10 micrograms/ml), hydrocortisone (0.1 micrograms/ml), and vitamin A (10 ng/ml). The cells formed a monolayer on the collagen gel within 1-2 days, but with time, cells began to detach from the gel. Further studies revealed that the attachment and growth of these cells on collagen were markedly influenced by the calcium concentration. It was found that lowering the calcium concentration from 1.05 to 0.05-0.1 mM dramatically suppressed cell detachment; the number of cells doubled after 7 days of culture. Proliferation of uterine epithelial cells was enhanced by EGF, but not by fibroblast growth factor, platelet-derived growth factor, nerve growth factor, multiplication-stimulating activity, or somatomedin-C. The uterine epithelial cells exhibited a single class of high affinity binding sites for [125I]iodo-EGF (Kd, approximately 1.8 nM), with approximately 5 X 10(4) receptors/cell; binding was inhibited by EGF but not by the other polypeptides. This cell culture system will aid in our investigations on hormonal effects on the growth and differentiation of estrogen target cells.

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The mouse oviductal epithelium is a simple monolayer until Postnatal Day 7 and subsequently consists of differentiated secretory cells and ciliated cells. In adult oviduct, the two types of epithelial cells are unevenly distributed; ciliated cells are dominant in the ampulla and secretory cells are dominant in the isthmus. Recombinants of enzymatically separated epithelial and mesenchymal tissues of oviducts were grafted under kidney capsule for 4 wk. The recombinants developed structures with a lumen covered with a monolayer of ciliated cells and secretory cells, demonstrating that the recombinant tissues reconstructed oviductal structure. Geographically (ampulla versus isthmus) heterotypic recombinants were prepared from neonatal oviducts at Day 3. The epithelia in reconstructed oviducts took the patterns of cell distribution depending on the origin of the mesenchymal tissues. The results indicate that the mesenchyme geographically has distinct abilities to determine undifferentiated epithelial cells to ciliated cells or secretory cells in the mouse oviduct.

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SUMMARY: Mammary glands are enzymatically dissociated and the resulting tissue digest enriched for epithelial cells by isopycnic banding on a density gradient of Percoll. The cells are embedded within a rat tail collagen gel matrix and fed with the appropriate medium. Growth and differentiation are superior in such a system when compared to culture on plastic, using identical media.