RESUMO
Abstract: cranial sutures are specialized structures composed of the sutural mesenchyme, the overlying scalp, the dura and osteogenic fronts. Each one of these structures express important proteins for osteogenic maturation, membranous ossification of skull bones, and homeostasis of cranial sutures in a differential, spatial and temporal manner. These proteins include fibroblast growth factor (FGF) and its receptors (FGFR), the transforming growth factor beta (TGF-beta), bone morphogenetic proteins (BMPs), as well as transcription factors TWIST and MSX2, among others. The alteration in the expression of one or more of these proteins causes multiple pathological conditions; one of them is the premature closure of one or more cranial sutures, known as craniosynostosis. This malformation is commonly treated with surgery. However, advances in the fields of molecular and cellular biology have allowed to conduct research on some proteins involved in the development of craniosynostosis. The results of these studies can lead to future preventive therapeutic strategies that may be used as a complement to the surgical treatment of craniosynostosis. Possible strategies include the use of specific drugs that can regulate the expression and activation of FGF signaling pathways, TGF-beta or BMPs, to prevent or avoid craniosynostosis or re-synostosis after a surgery.
Resumen: las suturas craneales son estructuras especializadas compuestas por el mesénquima sutural, el pericráneo suprayacente, la duramadre y los frentes osteogénicos. Cada una de estas estructuras expresan de forma diferencial, espacial y temporalmente, proteínas importantes para la maduración osteogénica, la osificación membranosa de los huesos calvarios y la homeostasis de las suturas craneales. Estas proteínas incluyen el factor de crecimiento fibroblástico (FGF) y sus receptores (FGFR), el factor de crecimiento transformante beta (TGF-beta), las proteínas morfogenéticas óseas (BMPs), así como factores de transcripción TWIST y MSX2, entre otros. La alteración en la expresión de una o varias de estas proteínas provoca múltiples condiciones patológicas, una de ellas es el cierre prematuro de una o varias suturas craneales, conocido como craneosinostosis. Esta malformación es comúnmente tratada con cirugía. Sin embargo, los avances en los campos de la biología molecular y celular han permitido investigar algunas proteínas que participan en el desarrollo de la craneosinostosis. Los resultados de estos estudios pueden generar futuras estrategias terapéuticas preventivas o que complementen los tratamientos quirúrgicos de la craneosinostosis. Algunas estrategias posibles son el uso de fármacos específicos que puedan regular la expresión y activación de las vías de señalización del FGF, el TGFbeta o de las BMPs, para prevenir la craneosinostosis o evitar la resinostosis tras una cirugía.
Assuntos
Humanos , Suturas Cranianas/crescimento & desenvolvimento , Craniossinostoses/metabolismo , Craniossinostoses/terapia , Proteínas Morfogenéticas Ósseas , Fatores de Crescimento de Fibroblastos , Terapia de Alvo Molecular , Fator de Crescimento Transformador betaRESUMO
Many studies have documented genetic differentiation of physiological ecotypes along environmental gradients in the temperate zone, but this topic has received little attention in tropical plants. We collected cuttings of Psychotria horizontalis (Rubiaceae) from Atlantic and Pacific coastal areas in central Panama, which differed twofold in annual rainfall, and grew them under common conditions in a screened, open-air growing house for 14 months. Plants from the wetter (Atlantic) region showed significantly higher stomatal conductance, but photosynthetic rates were similar in both groups, leading to higher water use efficiency in plants from the drier (Pacific) region. Responses of stomatal conductance to atmospheric humidity were similar in both groups. Anatomical studies show that plants from the wetter region had a higher mesophyll surface area per unit leaf area (A(mes)/A(leaf)) than plants from the drier region (17.2 versus 13.9), and also had a higher stomatal density (161.5 versus 98.0 mm(-2)) and fewer trichomes (2.0 versus 18.7 mm(-2)). The proportion of palisade cell surface area that was exposed to intercellular airspaces is higher in plants from the Pacific coast than from the Atlantic coast, such that the total palisade cell surface area exposed to the intercellular airspaces is similar in plants from the two regions (A(mes)/A(leaf) = 1.7). Paired plants transplanted into natural forest understory conditions showed considerable variability among sites, but plants from the drier region consistently had lower stomatal conductance than plants from the wetter region. After 20 months in the field, plant growth was similar regardless of plant origin, but plants of Pacific coast origin had longer roots and more (but smaller) leaves than plants of Atlantic coast origin. Stomatal density in field-grown plants was higher in plants of Atlantic (135.9 mm(-2)) than Pacific (90.1 mm(-2)) origin. An understanding of genetically based adaptations to local environmental conditions is important for predicting the consequences of climatic change and forest fragmentation.