Calcium-containing scaffolds induce bone regeneration by regulating mesenchymal stem cell differentiation and migration.

BACKGROUND: Osteoinduction and subsequent bone formation rely on efficient mesenchymal stem cell (MSC) recruitment. It is also known that migration is induced by gradients of growth factors and cytokines. Degradation of Ca2+-containing biomaterials mimics the bone remodeling compartment producing a localized calcium-rich osteoinductive microenvironment. The aim of our study was to determine the effect of calcium sulfate (CaSO4) on MSC migration. In addition, to evaluate the influence of CaSO4 on MSC differentiation and the potential molecular mechanisms involved. METHODS: A circular calvarial bone defect (5 mm diameter) was created in the parietal bone of 35 Balb-C mice. We prepared and implanted a cell-free agarose/gelatin scaffold alone or in combination with different CaSO4 concentrations into the bone defects. After 7 weeks, we determined the new bone regenerated by micro-CT and histological analysis. In vitro, we evaluated the CaSO4 effects on MSC migration by both wound healing and agarose spot assays. Osteoblastic gene expression after BMP-2 and CaSO4 treatment was also evaluated by qPCR. RESULTS: CaSO4 increased MSC migration and bone formation in a concentration-dependent manner. Micro-CT analysis showed that the addition of CaSO4 significantly enhanced bone regeneration compared to the scaffold alone. The histological evaluation confirmed an increased number of endogenous cells recruited into the cell-free CaSO4-containing scaffolds. Furthermore, MSC migration in vitro and active AKT levels were attenuated when CaSO4 and BMP-2 were in combination. Addition of LY294002 and Wortmannin abrogated the CaSO4 effects on MSC migration. CONCLUSIONS: Specific CaSO4 concentrations induce bone regeneration of calvarial defects in part by acting on the host's undifferentiated MSCs and promoting their migration. Progenitor cell recruitment is followed by a gradual increment in osteoblast gene expression. Moreover, CaSO4 regulates BMP-2-induced MSC migration by differentially activating the PI3K/AKT pathway. Altogether, these results suggest that CaSO4 scaffolds could have potential applications for bone regeneration.

Nitric-oxide inhibits nyctinastic closure through cGMP in Albizia lophantha leaflets.

Nitric oxide (NO) is a highly reactive radical that acts as a direct or indirect cellular signalling molecule in plant growth, development and environmental responses. Here we studied the contribution of NO to the control of leaflet movements during nyctinastic closure. For this purpose, we tested the effect of NO donors and an NO scavenger, all supplied in light, on Albizia lophantha leaflet closure after transferral to darkness. Exogenous NO, applied as four donors [sodium nitroprusside (SNP), diethylammonium (Z)-1-(N,N-diethylamino) diazen-1-ium-1,2-diolate (DEA-NONOate), S-nitroso-N-acetylpenicillamine (SNAP) and S-nitrosoglutathione (GS-NO)], inhibited nyctinastic leaflet closure while the application of an NO scavenger [2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO)] plus SNP cancelled the effect of the latter. The inclusion of Nω-nitro-l-arginine methyl ester (l-NAME) or sodium tungstate in the incubation media enhanced nyctinastic closure and also resulted in a decrease in the nitrate plus nitrite released by leaflets into the incubation solution. These results support the notion that NO is involved in regulating the nyctinastic closure of A. lophantha leaflets. Cellular perception of NO did not appear to be mediated by calcium. Pharmacological application of inhibitors of soluble guanylate cyclase (sGC) [1H-[1,2,4]-oxadiazole-[4,3-a]-quinoxalin-1-one (ODQ) and 6-anilino-5,8-quinolinequinone (Ly83583)], phosphodiesterase type 5 (PDE5) (Sildenafil) and the cyclic guanosine monophosphate (cGMP) analogue 8-bromoguanosine-3',5'-cyclomonophosphate sodium salt (8-Br-cGMP) indicated that cGMP was downstream of the NO signalling cascade during nyctinastic closure.

Evaluación de un efecto anticonceptivo de la Persea americana en un modelo experimental en ratas / Evaluation of an effect contraceptive of the pesea American in an experimental model in rats

Con el propósito de explorar nuevos productos para el control de la fecundidad a partir de la flora medicinal nativa, se desarrolló un Modelo Experimental en ratas para evaluar un efecto anticonceptivo post-coital (antiimplantación de embriones), del extracto acuoso total de las semillas de la Persea americana (palta). Para este estudio se utilizaron ratas hembras de la cepa Sprague Dawly, en las cuales el Ciclo Estral fue controlado diariamente mediante frotis vaginales. Se estandarizó el procedimiento de evaluación de la no implantación en el útero de ratas control de preñez, explorando el número de cuerpos lúteos y el número de implantaciones, y se desarrolló el Test de Antiimplantación en el útero de ratas tratadas con la P. americana para evaluar el efecto anticonceptivo. Una primera experiencia mostró una actividad de antiimplantación embrionaria con promedios de 13 por ciento, 24 por ciento, 44 por ciento y 45 por ciento a dosis de 0.001, 0.01, 0.1 y 1 g/Kg de peso, respectivamente. Los controles positivos de preñez, en los cuales solamente se administró el vehículo, mostraron promedios de 23 por ciento de no implantaciones. En una segunda experiencia con las mismas dosis, en la que se hicieron ajuste en las condiciones de habitat, se mostró una actividad de antiimplantación con promedios de 11 por ciento, 18 por ciento, 27 por ciento y 37 por ciento, respectivamente; los controles positivos de preñez mostraron un promedio de 8 por ciento de ausencia de implantaciones. Se discute las posibilidades de este Modelo para la exploración y estudio de otros productos con actividad anticonceptiva, así como las perspectivas de la Persea americana en este propósito

Determinaciòn in vitro del porcentaje de mortalidad de Leishmania amazonensis por compuestos puros utilizado el Mètodo de MTT / Annual reports 1993 / In vitro mortality of Leishmania amazonensis whith pure compounds by using MTT Method

Tres alcaloides isoquinòlicos, curine isochondodendrine e isotetrandrine fueron probados contra la forma Leishmania amazonensis in vitro usando el mètodo MTT sal de bromuro de 3-(4,5 dimetil tiazol -2 il)- 2,5- difenil tetrazolio, mètodo calorimètrico ràpido, ùtil para evaluar la supervivencia parasitaria ante la acciòn de compuestos puros seleccionados de acciòn antileishmaniàsica. El cambio de transmitancia fue leìdo utilizando el Lector de Elisa Bio-Rad EIA reader a 570 nm. El porcentaje de mortalidad fue calculado usando el log-probita a diferentes concentraciones de los compuestos puros a 100 ug/ml y 25 ug/ml. Curine demostrò mayor porcentaje de mortalidad a todas las diluciones, lo mismo que isotetrandrine resultò con un mayor porcentaje de mortalidad a todas las diluciones. A la concentraciòn de 100 ug/ml curine e isotetrandrine presentaron 100 por ciento de mortalidad, mientras que isochondendrine 90 por ciento de mortalidad. Tambièn a 50 ug/ml curine e isotetrandrine presentaron 100 por ciento de mortalidad e isochondendrine 50 por ciento de mortalidad. A la concentraciòn de 25 ug/ml curine, isotetrandrine e isochondondendrine presentaron 80 por ciento, 50 por ciento y 10 de mortalidad. Los resultados sugeren que el mètodo MTT podrìa ser ùtil para probar la actividad de compuestos puros contra Leishmania amazonensis