An avian tarsometatarsal (TMT) skeleton spanning from the base of toes to the intertarsal joint is a compound bone developed by elongation and lateral fusion of three cylindrical periosteal bones. Ontogenetic development of the TMT skeleton is likely to recapitulate the changes occurred during evolution but so far has received less attention. In this study, its development has been examined morphologically and histologically in the chick, Gallus gallus. Three metatarsal cartilage rods radiating distally earlier in development became aligned parallel to each other by embryonic day 8 (ED8). Calcification initiated at ED8 in the midshaft of cartilage propagated cylindrically along its surface. Coordinated radial growth by fabricating bony struts and trabeculae resulted in the formation of three independent bone cylinders, which further became closely apposed with each other by ED13 when the periosteum began to fuse in a back-to-back orientation. Bone microstructure, especially orientation of intertrabecular channels in which blood vasculature resides, appeared related to the observed rapid longitudinal growth. Differential radial growth was considered to delineate eventual surface configurations of a compound TMT bone, but its morphogenesis preceded the fusion of bone cylinders. Bony trabeculae connecting adjacent cylinders emerged first at ED17 in the dorsal and ventral quarters of intervening tissue at the mid-diaphyseal level. Posthatch TMT skeleton had a seemingly uniform mid-diaphysis, although the septa persisted between original marrow cavities. These findings provide morphological and histological bases for further cellular and molecular studies on this developmental process. Anat Rec, 293:1527Rec, 293: -1535
The existence of progenitor/mesenchymal stem cells (MSCs) was demonstrated previously in human primary/deciduous teeth. In this study, we examined dental pulp cells from root portion (root cells) of primary teeth without discernible root resorption and compared them with pulp cells from the crown portion (crown cells). Root cells and crown cells were characterized and compared to each other based on progenitor/MSC characteristics and on their generation efficiency of induced pluripotent stem (iPS) cells. Root cells and crown cells included cells manifesting typical progenitor/MSC properties such as osteogenic and adipogenic differentiation potential and clonogenicity. Interestingly, root cells showed a higher expression level of embryonic stem cell marker, KLF4, than crown cells. Moreover, the number of colony-forming unit-fibroblast and cell proliferation rate were higher for root cells than crown cells, and the efficiency of generating iPS cells from root cells was approximately four times higher than that from crown cells. Taken together, these results suggest that root cells from primary teeth show the MSC-like properties and thus could be a potent alternative source for iPS cell generation and the subsequent transplantation therapy.
Fibrillin microfibrils are integral components of elastic fibers and serve as a scaffold for elastin deposition. However, microfibrillar fibers (MFs) are not necessarily committed to develop into so-called elastic fibers. In dermis, elastin-free oxytalan MFs originating from the dermoepidermal junction are continuous to elaunin-type MFs (with a small amount of elastin) in the deeper papillary dermis, whereas the reticular dermis contains elastic fibers, or MFs embedded largely in elastin. In this study, we have investigated temporospatial patterns of elastin deposition on the MFs in tarsometatarsal presumptive dermis. While the earliest expression of elastin was demonstrated immunohistochemically as early as embryonic day 4 (ED4) in the wall of cardiac outflow and pharyngeal arch arteries, its deposition in the tarsometatarsus was first detected at ED6 in the deeper mesenchyme and at ED13 in the subectodermal mesenchyme. In the latter tissue, MFs had been organized perpendicularly to the covering ectoderm by ED4, well before an overt accumulation of collagenous matrix. Elastin deposition was observed initially in a punctate manner at ED13 and afterward became continuous along MFs. However, a characteristic spaced array of subectodermal vertical MFs was disorganized by ED17. These findings suggest that elastin deposition in the subectodermal MFs is not deployed by continuous, orderly propagation from elastic fibers in the deeper mesenchyme but occurs de novo in multiple foci along vertical MFs. Moreover, the present chronology of elastin deposition indicates that subectodermal, elastin-free MFs function as a transient, but primary fibrous structure in the presumptive dermis before the accumulation of collagenous matrix.
Whole-mount staining with Alcian blue for cartilage and alizarin red for bone has been widely used for visualizing the skeletal patterns of embryos and small adult vertebrates. The possibility of decalcification by the acidic Alcian blue solution is known, but standard staining protocols do not always avoid this issue. We investigated the effects of acidity on the stainability of developing bones in stage 36 chick embryos and developed an optimal procedure for obtaining reliable results with minimal decalcification. The diaphyses of long bone rudiments and the maxillofacial membranous bones progressively lost their stainability with alizarin red when the chick embryos were soaked for long periods in the preceding acidic Alcian blue staining solution for cartilage. Unless the acidity was neutralized with an alkaline solution, the remaining acidity in the specimens rendered the pH sufficiently low to prevent the subsequent alizarin red staining of the bones. These findings indicate that the mineralizing bones at the early stages of development are labile to acidity and become decalcified more substantially during the staining process than previously appreciated. The following points are important for visualizing such labile mineralizing bones in chick embryos: 1) fixing with formaldehyde followed by soaking in 70% ethanol, 2) minimizing the time that the specimens are exposed to the acidic Alcian blue solution, and 3) neutralizing and dehydrating the specimens by an alkaline-alcohol solution immediately after the cartilage staining. When the exact onset and/or an early phase of ossification are of interest, the current double-staining procedure should be accompanied by a control single-staining procedure directed only toward bone.
Lysyl oxidase (LOX) plays a critical role in the formation of cross-linkages in extracellular matrix molecules. Thus, it is essential for the biogenesis and homeostasis of the connective tissue matrix. During development, collagen fibres and elastic system fibres emerge and accumulate in a temporospatial manner in the presumptive dermis of chicks. In this study, we investigated LOX mRNA expression by laser capture microdissection and RT-qPCR and LOX protein localization by immunohistochemistry. The picrosirius polarization method was used to investigate a relation between collagen accumulation and LOX expression. PCR analysis showed that the expression of LOX mRNA in the presumptive dermis became apparent at embryonic day 13 and increased considerably by ED17. Immunohistochemical staining for LOX in the dermis was very low at all stages of development. Accumulation of collagen fibres was seen in the dermis on ED10, and higher wavelengths of birefringence became evident by ED13. Our findings suggest that the temporal pattern of LOX mRNA expression correlates with collagen fibre accumulation in the dermis of the developing chick limb bud, whereas LOX expression was relatively constant at the protein level.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.