Meckel's chondrocytes, derived from the ectomesenchyme, have the potential to transform into other phenotypes. In this study, we transplanted cell pellets of Meckel's chondrocytes into isogenic mouse spleens and analyzed their phenotypic transformation into osteogenic cells using histological and immunohistochemical methods. With the increasing duration of transplantation, chondrocytes were incorporated into splenic tissues and formed a von Kossa-positive calcified matrix containing calcium and phosphoric acid, similar to that of intact bone. Type I, II, and X collagens, and the bone-marker proteins osteocalcin, osteopontin, osteonectin, and bone morphogenetic protein-2 (BMP-2) were immunolocalized in the matrix formed by the transplanted chondrocytes. Osteopontin and osteonectin were detected in the calcified matrix at earlier stages than osteocalcin and BMP-2. Type II collagen was expressed during the first week of transplantation, and type X collagen-positive cells appeared scattered during the initial stage of calcification, these collagens being later replaced by type I collagen formed by osteocyte-like cells. Electron microscopic observations revealed that chondrocytes surrounded by the calcified matrix transformed into spindle-shaped osteocytic cells accompanying the formation of bone-type thick-banded collagen fibrils. These results suggest that phenotypic switching of Meckel's chondrocytes can occur under in vivo conditions at a cellular morphological level.

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The microstructure of lingual papillae on the dorsal surface of the tongue of adult Egyptian fruit bats was examined by light microscopy (LM) and scanning electron microscopy (SEM). This elongated tongue with a rounded apex is approximately 3 cm long - including the 1.7cm length of the anterior free part of the tongue - which facilitates considerable freedom of movement. The surface of the tongue has four types of lingual papillae: two types of mechanical papillae - filiform and conical papillae, and two types of gustatory papillae - fungiform and vallate papillae. Most numerous are filiform papillae with well developed keratinized processes represented by four morphological subtypes - small, giant, elongated, and bifid papillae. Our observations showed the small and giant filiform papillae to be present in the anterior part of the tongue and tilted to the back of the tongue. In the posterior part of the tongue, the filiform papillae with elongated processes were arranged on each side of the tongue and oriented perpendicularly to the median line of tongue. This arrangement of filiform papillae is considered to be useful for the efficient uptake of semiliquid food as it can be collected toward the median line of the tongue. Gustatory fungiform papillae were distributed among filiform papillae on the border of the apex and the anterior part of the body of the tongue and also on the posterior part of the tongue, while three vallate papillae surrounded by conical papillae were found on the root of the tongue. There were also taste buds along the ducts of the posterior lingual glands in the posterior-lateral part of the tongue. These morphological features are discussed in relation to adaptation to food uptake in the Egyptian fruit bat.

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The nerve growth factor-induced gene B-β (NGFI-Bβ, Nurr1) is a member of the nuclear receptor superfamily that is expressed predominantly in the central nervous system. We used an antibody against the human NGFI-Bβ to observe the protein expression in neuronal cells in the retina, cerebral neocortex, and midbrain of humans and rats. To provide further insight into the role of NGFI-Bβ in the differentiation of neuronal cells, we also examined the expression of NGFI-Bβ in rat ontogeny. A few cells in the midbrain showed the expression of NGFIBβ from 12 days of gestation, and NGFI-Bβ positive cells increased in the neocortex, claustrum, thalamus and hypothalamus in the subsequent fetal days. NGFI-Bβ-positive cells appeared in the inner nuclear layer of the retina at 18 days of gestation and also in the ganglion cell layer after birth. An immunohistochemical study on the expression of proliferating cell nuclear antigen (PCNA) demonstrated that NGFI-Bβ-positive cells were not proliferating cells. These findings suggest that NGFI-Bβ plays an important role during the postmitotic differentiation of neuronal cells in the brain and retina.

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The general sugar expression pattern was studied in 9 normal full-term human placentas by the use of 21 individual lectins in combination with immunohistochemistry for various markers to understand the function of the placenta as the site of feto-maternal interactions. In mature intermediate and terminal villi, the brush border of the syncytiotrophoblast layer strongly expressed GlcNAc (as stained by WGA, S-WGA, DSL lectins) but weakly expressed sialic acid (Mal II, SNA). The cytoplasm of the syncytiotrophoblast layer showed weak expressions of GlcNAc and Gal/GalNAc with granular patterns. The cytotrophoblast layer, as also recognized by PCNA and HAI-1, typicaly expressed GlcNAc (LEL etc.) and Gal/GalNAc (MAL I). We found that the cytotrophoblast layer became very thin but largely maintained its continuity in the mature villi. The basement membranes of both the trophoblast layer and the endothelial layer strongly and continuously expressed mannose (Con A, LCA) and galactose (ECL, RCA I). Although endothelial cells almost exclusively expressed sialic acid and fucose, UEA I showed a heterogeneous reactivity with endothelial cells within the same vessels. No uniform expression pattern of any sugar was seen in stromal components except for Hofbauer cells, which usually expressed GlcNAc (LEL and DSL etc.). Thus, the sugar expression analysis by lectin histochemistry combined with immunohistochemistry proved helpful to understand the sugar chain related functions of the placenta under both normal and pathological conditions.

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We isolated adherent fibroblastic cells after collagenase and dispase treatment of human dental pulp. When human dental pulp cells (hDPCs) were cultured in the presence of basic fibroblast growth factor (bFGF), the ratio of hDPCs in the S-phase was significantly higher in comparison with incubation without bFGF. The ratio of hDPCs expressing STRO-1 as a marker of stem cell populations increased approximately eightfold in the presence of bFGF as opposed to that in the absence of bFGF. We demonstrated the characterization and distinctiveness of the hDPCs and showed that, when cultured with the medium containing serum and bFGF, they were highly proliferative and capable of differentiating in vitro into osteoblasts, chondrocytes, and adipocytes. Furthermore, the in vitro differentiation was confirmed at both the protein and gene expression levels. Transplantation of hDPCs - expanded ex vivo in the presence of bFGF into immunocompromised mice - revealed the formation of bone, cartilage, and adipose tissue. The donor hDPC-derived cells were labeled in the bone tissues located near the PLGA in the subcutaneous tissues of recipient mice using a human-specific Alu probe. When cultured with a serum-free medium containing bFGF, the hDPCs strongly expressed STRO-1 immunoreactive products and sustained self-renewal, and thus were almost identical in differentiation potential and proliferation activity to hDPCs cultured with the medium containing serum and bFGF. The present results suggest that the hDPCs cultured in the presence of bFGF irrespective of the presence or absence of the bovine serum are rich in mesenchymal stem cells or progenitor cells and useful for cell-based therapies to treat dental diseases.

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Transferrin binding protein (TfBP) is a cytoplasmic glycoprotein that was originally isolated from the chick oviduct. As we previously demonstrated the constitutive expression of TfBP in the avian nervous system, in this study we examined whether TfBP is expressed in the reptilian nervous system. In accordance with previous findings in the chicken, oligodendrocytes were most prominently labeled by antiserum to TfBP. Great variability was observed between different regions of the central nervous system (CNS) in terms of TfBP-labeled oligodendrocyte numbers. In the retina, TfBP was localized specifically in the cells that are morphologically oligodendrocytes and present in the optic nerve and the ganglion cell layer. TfBP staining was also seen in the Schwann cells of peripheral nerves. Furthermore, choroid plexus cells and capillary endothelial cells similarly exhibited strong reactions. These results may reflect the fact that the homology of nervous system genes is conserved between close phylogenetic lines, and proove the potential of TfBP as a marker for oligodendrocytes in avian as well as reptile.

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