Differential Expression of Intestinal Genes in Opossums with High and Low Responses to Dietary Cholesterol

High and low responding opossums (Monodelphis domestica) differ in their plasma very low density lipoprotein and low density lipoprotein (VLDL+LDL) cholesterol concentrations when they consume a high cholesterol diet, which is due in part to absorption of a higher percentage of dietary cholesterol in high responders. We compared the expression of a set of genes that influence cholesterol absorption in high and low responders fed a basal or a high cholesterol and low fat (HCLF) diet. Up-regulation of the ABCG5, ABCG8, and IBABP genes by the HCLF diet in high and low responders may reduce cholesterol absorption to maintain cholesterol homeostasis. Differences in expression of the phospholipase genes (PLA2 and PLB) and phospholipase activity were associated with differences in cholesterol absorption when opossums were fed cholesterol-enriched diets. Higher PLA2 and PLB mRNA levels and higher phospholipase activity may increase cholesterol absorption in high responders by enhancing the release of cholesterol from bile salt micelles for uptake by intestinal cells

Quantitative in situ hybridization with enhanced sensitivity in soft, bone and tooth tissue using digoxigenin tagged RNA probes

Uvod: Kvantitativna neradioaktivna in situ hibridizacija je moćna tehnika za lokalizaciju ekspresije transkripata mRNA. Ove metode omogućavaju otkrivanje mRNA uz visoku rezoluciju na razini jedne jedine stanice. Dosad najšire opisani neradioaktivni protokoli rabili su deblje kriostatske rezove mekog tkiva i lokalizirali visoko zastupljene gene bez kvantificiranja. Materijali i metode: Mi smo razvili metodu neradioaktivne in situ hibridi-zacije pomoću tankih rezova demineraliziranog koštanog tkiva uklopljenog u parafin, uz otkrivanje nisko zastupljenih gena i kvantifikaciju in situ signala. Naš protokol zasniva se na optimalnoj sintezi digoksigeninom obilježenih DNA probi za vizualiziranje vrlo nisko zastupljenih gena u mekom, koštanom i zubnom tkivu uklopljenom u parafin. Naša nova tehnika prikazuje in situ signal uz umnožavanje i pojačanje boje kroz reakciju alkalnefosfataze. Rezultati: Osjetljivost je na razini radioaktivnih protokola, a rezolucija je na razini pojedine stanice, štoje bolje nego kod radioaktivnih protokola. Kvantificiranje in situ hibridizacijskog signala, što se ranije radilo pomoću radioaktivnog ili fluorescentnog obilježavanja, sad je moguće s alkalnom fosfatazom pomoću naše tehnike i programa ImageJ. Zaključak: Prikazani primjeri pokazuju kako slijedeća metoda ima bolju dokazanu rezoluciju i jednaku osjetljivost kao radioaktivno obilježene metode u različitim tkivima s mogućom kvantifikacijom;to pak pokazuje da se ova metoda općenito može rabiti u istraživačkim kao i u kliničkim laboratorijima.Introduction: Quantitative non-radioactive in situ hybridization is a powerful technique for localizing the expression of mRNA transcripts. These methods enable mRNAs to be detected with great resolution on a single cell level. Up to date the most published non-radioactive protocols used thick cryostat sections in soft tissue localizing high abundant genes without quantification. Material and methods: We developed a non-radioactive in situ hybridization method using thin sections of demineralized bone paraffin embedded tissue with low abundant gene detection and in situ signal quantification. Our protocol is based on the optimal synthesis of digoxigenin labeled RNA probes to visualize very low abundant genes in soft, bone and tooth paraffin embedded tissues. Our new technique visualizes an in situ signal with amplification and enhanced color by developing alkaline phosphatase reaction. Results: The sensitivity is at the level of radioactivity and the resolution is at the level of a single cell, which is better than with radioactivity. Quantification of in situ hybridization signal, previously used with radioactive or fluorescent labeling, is now possible with alkaline phosphatase using our technique and ImageJ program. Conclusion: The presented examples show that the following method has better proven resolution and equivalent sensitivity to radioactive labeled methods in different tissues with quantification ability, thus indicating that this method can generally be used in research and clinical laboratories

Glucocorticoid-Induced Autophagy in Osteocytes

Glucocorticoid (GC) therapy is the most frequent cause of secondary osteoporosis. In this study we have demonstrated that GC treatment induced the development of autophagy, preserving osteocyte viability. GC treatment resulted in an increase in autophagy markers and the accumulation of autophagosome vacuoles in vitro and in vivo promoted the onset of the osteocyte autophagy, as determined by expression of autophagy markers in an animal model of GC-induced osteoporosis. An autophagy inhibitor reversed the protective effects of GCs. The effects of GCs on osteocytes were in contrast to tumor necrosis factor α (TNF-α), which induced apoptosis but not autophagy. Together this study reveals a novel mechanism for the effect of GC on osteocytes, shedding new insight into mechanisms responsible for bone loss in patients receiving GC therapy. © 2010 American Society for Bone and Mineral Research

Expression and function of Dlx genes in the osteoblast lineage

AbstractOur laboratory and others have shown that overexpression of Dlx5 stimulates osteoblast differentiation. Dlx5−/−/Dlx6−/− mice have more severe craniofacial and limb defects than Dlx5−/−, some of which are potentially due to defects in osteoblast maturation. We wished to investigate the degree to which other Dlx genes compensate for the lack of Dlx5, thus allowing normal development of the majority of skeletal elements in Dlx5−/− mice. Dlx gene expression in cells from different stages of the osteoblast lineage isolated by FACS sorting showed that Dlx2, Dlx5 and Dlx6 are expressed most strongly in less mature osteoblasts, whereas Dlx3 is very highly expressed in differentiated osteoblasts and osteocytes. In situ hybridization and Northern blot analysis demonstrated the presence of endogenous Dlx3 mRNA within osteoblasts and osteocytes. Dlx3 strongly upregulates osteoblastic markers with a potency comparable to Dlx5. Cloned chick or mouse Dlx6 showed stimulatory effects on osteoblast differentiation. Our results suggest that Dlx2 and Dlx6 have the potential to stimulate osteoblastic differentiation and may compensate for the absence of Dlx5 to produce relatively normal osteoblastic differentiation in Dlx5 knockout mice, while Dlx3 may play a distinct role in late stage osteoblast differentiation and osteocyte function

Bone morphogenetic protein-2 gene controls tooth root development in coordination with formation of the periodontium

Formation of the periodontium begins following onset of tooth-root formation in a coordinated manner after birth. Dental follicle progenitor cells are thought to form the cementum, alveolar bone and Sharpey's fibers of the periodontal ligament (PDL). However, little is known about the regulatory morphogens that control differentiation and function of these progenitor cells, as well as the progenitor cells involved in crown and root formation. We investigated the role of bone morphogenetic protein-2 (Bmp2) in these processes by the conditional removal of the Bmp2 gene using the Sp7-Cre-EGFP mouse model. Sp7-Cre-EGFP first becomes active at E18 in the first molar, with robust Cre activity at postnatal day 0 (P0), followed by Cre activity in the second molar, which occurs after P0. There is robust Cre activity in the periodontium and third molars by 2 weeks of age. When the Bmp2 gene is removed from Sp7(+) (Osterix(+)) cells, major defects are noted in root, cellular cementum and periodontium formation. First, there are major cell autonomous defects in root-odontoblast terminal differentiation. Second, there are major alterations in formation of the PDLs and cellular cementum, correlated with decreased nuclear factor IC (Nfic), periostin and α-SMA(+) cells. Third, there is a failure to produce vascular endothelial growth factor A (VEGF-A) in the periodontium and the pulp leading to decreased formation of the microvascular and associated candidate stem cells in the Bmp2-cKO(Sp7-Cre-EGFP). Fourth, ameloblast function and enamel formation are indirectly altered in the Bmp2-cKO(Sp7-Cre-EGFP). These data demonstrate that the Bmp2 gene has complex roles in postnatal tooth development and periodontium formation