The parenchyma of the submandibular gland in the adult male rat is self-renewing, with most newly formed acinar and granular duct cells believed to differentiate from the rapidly proliferating intercalated duct (ID) compartment. Since the ID cells are phenotypically diverse, based on their different expression of perinatal secretory proteins, we systemically injected tritiated thymidine for 24 hours, and followed the pattern of thymidine distribution in cells by autoradiography and immunocytochemistry of defined cellular phenotypes over a 1-month chase period. Proliferating cells were found within all parenchymal cell compartments; they were most numerous in ID, and primarily in those cells lacking immunoreactivity for the perinatal proteins SMG-B1, -C, and -D. The labeling index (LI) of the ID cells reached a peak at 7 days postinjection, and then decreased over the next 3 weeks. Concurrently, the LI increased significantly in those cells at the junctions of ID with both acini and granular ducts, and also within these larger parenchymal elements. We conclude that the ID cells not reactive for perinatal proteins proliferate to expand the ID compartment, and that ID cells at the ends of the ducts differentiate into both acinar and granular duct cells. Our data provide no evidence for the differentiation of ID cells into cells of striated ducts (SD); however, the small number of excretory duct (ED) profiles seen in our preparations showed extremely high LI (Ͼ25%), suggesting that more extensive data might reveal a precursor role for the ED in replacement of SD cells. In addition to the stepwise passage of cells from ID to other parenchymal elements at their junctions, the reported occurrence of occasional clusters of B1-positive acini (BAC) among the typical B1-negative acini had suggested an alternate pathway, in which entire segments of newly expanded ID might develop directly into a recapitulated perinatal stage of B1-reactive cell, pursuant to becoming mature acinar cells . Consistent with this suggestion, the BAC had a fourfold greater LI than typical adult acini; moreover, when analyzed by electron microscopic immunocytochemistry, they appeared similar to the novel perinatal Type III cells both ultrastructurally and in their pattern of B1-immunogold labeling. In contrast, the less common acini showing a sublingual gland phenotype had no significant difference in LI from typical acinar cells. Overall, our results emphasize the importance of the nonimmunoreactive ID cells in normal cellular replacement, and the possibility that ID can undergo en bloc differentiation into replacement acini as well as incremental addition of single cells at the boundaries of ID with acini and with granular ducts.

A histological and histochemical analyses were carried out on the entire alimentary canal of the rainbow trout Oncorhynchus mykiss. In particular the oesophageal region showed presence of terminal b-D-galactose(1-3)-N-acetylgalactosamine and a-N-acetylgalactosamine. In the anterior and posterior regions of the stomach, lining epithelium and gastric pits exhibited the presence of b-gal and a-GalNAc. In addition sialoglycoconjugates having sialic acid-bgalactose(1-3)-N-acetylgalactosamine and sialic acid-N-acetylgalactosamine as terminal triand di-saccharides, were demonstrated. In proximal and distal intestine goblet cells showed the presence of sialoglyconjugates, having sialic acid-b-gal(1-3)-GalNAc and sialic acidGalNAc as terminal sequences, belonging to N-linked chains. In the enterocytes of the entire intestine, terminal GlcNAc, a-Gal, a-fucose were found. #

We recently reported that a DNA plasmid coding p62-SQSTM1 acts as an effective anti tumor vaccine against both transplantable mouse tumors and canine spontaneous mammary neoplasms. Here we report the unexpected finding that intramuscular delivery of p62 DNA exerts a powerful anti-osteoporotic activity in a mouse model of inflammatory bone loss (i.e, ovariectomy) by combining bone-sparing and osteo-synthetic effects. Notably, the suppression of osteoporosis by p62DNA was associated with a sharp down-regulation of master inflammatory cytokines, and up-regulation of endogenous p62 protein by bone-marrow stromal cells. The present data provide a solid rational to apply p62 DNA vaccine as a safe, new therapeutic for treatment of inflammatory related bone loss diseases.

We examined the effect of PGs, particularly PGF2alpha, on basic fibroblast growth factor-2 (FGF-2) messenger RNA (mRNA) and protein in the rat osteoblastic cell line Py1a and in fetal rat calvariae. Py1a cells expressed multiple FGF-2 mRNA transcripts. PGF2alpha dose-dependently increased the 6-kb transcript at 6 h. The selective PGF2alpha agonist, fluprostenol (Flup), was more potent than PGF2alpha. Phorbol myristate acetate (10(-6) M) also increased a 6-kb mRNA at 6 h. By immunofluorescence microscopy, Flup increased perinuclear staining for FGF-2 protein at 6 h and nuclear labeling at 24 h. Immunogold labeling of calvariae revealed that treatment with Flup for 3 h caused a transition of FGF expression from matrix to cells and an increase in cytoplasmic labeling for FGF-2 protein in periosteal cells and in osteoblasts. After treatment with Flup for 24 h, nuclear labeling was marked in periosteal cells and in osteoblasts, and a further increase in cytoplasmic labeling for FGF-2 was noted in osteocytes, periosteal cells, and osteoblasts. We conclude that PGs can increase FGF-2 mRNA and protein in bone cells. Because the effect of Flup was mimicked by phorbol myristate acetate, we hypothesize that PGs' regulation of FGF-2 is mediated by a PGF2alpha-selective receptor acting through protein kinase C. Hence, effects of PGs on bone remodeling may be mediated, in part, by endogenous FGF-2.

The anatomical and functional dimensions of bone marrow topography have been at the forefront of modern bone and immunological research for many years and remain a source of complexity and perplexity due to the multitude of microhabitats within this microenvironment. In fact, research has uncovered fascinating functional aspects of bone marrow residents, and the bone marrow niche has been identified as the foremost reservoir of a variety of cells including hematopoietic, skeletal and endothelial stem/progenitor cells. The physical interactions of the marrow residents, combined with the release of cytokines and growth factors, organize well-defined operative compartments, which preserve bone and immune cell homeostasis. In a simplistic view, both the hematopoietic and bone marrow stromal (mesenchymal) stem/progenitor cell populations dwell at the interface between the endosteum and the bone marrow area (endosteal niche) and in the perivascular space (vascular niche). Indeed, the tantalizing hypothesis of bone marrow regulatory dependency on these niches is supported by current research insofar as the increase in the number of osteoblasts results in a concomitant increase in the hematopoietic population, indicating that the osteoblasts and the endosteal niche are key components of HSC maintenance. On the other hand, impaired function of the vascular niche compromises the endosteal niche's ability to support hematopoiesis. These fascinating discoveries indicate that there are strong ties between bone marrow inhabitants within the confines of the bone marrow itself. When these ties fail, niche-niche communication suffers and results in reduced bone formation, enfeebled hematopoiesis and unrestrained HSC migration through blood circulation. This study focused on the extraordinary homeostatic equilibrium and function of both bone and immune cells within the spatially defined microenvironment of bone marrow. But how important is the anatomically outlined scenery in which the bone marrow entity supports and hosts the hematopoietic elements?

Bone morphogenetic protein 2 (BMP-2) is one of the most potent regulators of osteoblast differentiation and bone formation. R-Smads (Smads 1/5/8) are the major transducers for BMPs receptors and, once activated, they are translocated in the nucleus regulating transcription target genes by interacting with various transcription factors. Runx-2 proteins have been shown to interact through their C-terminal segment with Smads and this interaction is required for in vivo osteogenesis. In particular, recruitment of Smads to intranuclear sites is Runx-2 dependent, and Runx-2 factor may accommodate the dynamic targeting of signal transducer to active transcription sites. Previously, we have shown, by in vitro and in vivo experiments, that BMP-2 up-regulated FGF-2 which is important for the maximal responses of BMP-2 in bone. In this study, we found that endogenous FGF2 is necessary for BMP-2 induced nuclear accumulation and co-localization of Runx-2 and phospho-Smads1/5/8, while Runx/Smads nuclear accumulation and co-localization was reduced in Fgf2-/- osteoblasts. Based on these novel data, we conclude that the impaired nuclear accumulation of Runx-2 in Fgf2-/- osteoblasts reduces R-Smads sub-nuclear targeting with a consequent decreased expression of differentiating markers and impaired bone formation in Fgf2 null mice.

Parathyroid hormone (PTH) increases Fibroblast growth factor receptor-1 (FGFR1) and Fibroblast growth factor-2 (FGF-2) expression in osteoblasts and the anabolic response to PTH is reduced in Fgf2−/− mice. This study examined whether candidate factors implicated in the anabolic response to PTH were modulated in Fgf2−/− osteoblasts. PTH increased Runx-2 protein expression in Fgf2+/+ but not Fgf2−/− osteoblasts. By immunocytochemistry, PTH treatment induced nuclear accumulation of Runx-2 only in Fgf2+/+ osteoblasts. PTH and FGF-2 regulate Runx-2 via activation of the cAMP response element binding proteins (CREBs). Western blot time course studies showed that PTH increased phospho-CREB within 15 min that was sustained for 24 h in Fgf2+/+ but had no effect in Fgf2−/− osteoblasts. Silencing of FGF-2 in Fgf2+/+ osteoblasts blocked the stimulatory effect of PTH on Runx-2 and CREBs phosphorylation. Studies of the effects of PTH on proteins involved in osteoblast precursor proliferation and apoptosis showed that PTH increased cyclinD1-cdk4/6 protein in Fgf2+/+ but not Fgf2−/− osteoblasts. Interestingly, PTH increased the cell cycle inhibitor p21/waf1 in Fgf2−/− osteoblasts. PTH increased Bcl-2/Bax protein ratio in Fgf2+/+ but not Fgf2−/− osteoblasts. In addition PTH increased cell viability in Fgf2+/+ but not Fgf2−/− osteoblasts. These data suggest that endogenous FGF-2 is important in PTH effects on osteoblast proliferation, differentiation and apoptosis. Reduced expression of these factors may contribute to the reduced anabolic response to PTH in the Fgf2−/− mice. Our results strongly indicate that the anabolic PTH effect is dependent in part on FGF-2 expression.

Bone microenvironment is a complex dynamic equilibrium between osteoclasts and osteoblasts and is modulated by a wide variety of hormones and osteocyte mediators secreted in response to physiological and pathological conditions. The rate of remodeling involves tight coupling and regulation of both cells population and is regulated by a wide variety of hormones and mediators such as parathyroid hormone, prostaglandins, thyroid hormone, sex steroids, etc. It is also well documented that bone formation is easily influenced by the exposure of osteoblasts and osteoclasts to chemical compounds. Currently, humans and wildlife animals are exposed to various environmental xenoestrogens typically at low doses. These compounds, known as endocrine disruptor chemicals (EDCs), can alter the systemic hormonal regulation of the bone remodeling process and the skeletal formation. This review highlights the effects of the EDCs on mammalian bone turnover and development providing a macro and molecular view of their action.