Functionalisation of PLLA nanofiber scaffolds using a possible cooperative effect between collagen type I and BMP-2: impact on growth and osteogenic differentiation of human mesenchymal stem cells

Mesenchymal stem cell differentiation of osteoblasts is triggered by a series of signaling processes including integrin and bone morphogenetic protein (BMP), which therefore act in a cooperative manner. The aim of this study was to analyze whether these processes can be remodeled in an artificial poly-(l)-lactide acid (PLLA) based nanofiber scaffold. Matrices composed of PLLA-collagen type I or BMP-2 incorporated PLLA-collagen type I were seeded with human mesenchymal stem cells (hMSC) and cultivated over a period of 22 days, either under growth or osteoinductive conditions. During the course of culture, gene expression of alkaline phosphatase (ALP), osteocalcin (OC) and collagen I (COL-I) as well as Smad5 and focal adhesion kinase (FAK), two signal transduction molecules involved in BMP-2 or integrin signaling were analyzed. Furthermore, calcium and collagen I deposition, as well as cell densities and proliferation, were determined using fluorescence microscopy. The incorporation of BMP-2 into PLLA-collagen type I nanofibers resulted in a decrease in diameter as well as pore sizes of the scaffold. Mesenchymal stem cells showed better adherence and a reduced proliferation on BMP-containing scaffolds. This was accompanied by an increase in gene expression of ALP, OC and COL-I. Furthermore the presence of BMP-2 resulted in an upregulation of FAK, while collagen had an impact on the gene expression of Smad5. Therefore these different strategies can be combined in order to enhance the osteoblast differentiation of hMSC on PLLA based nanofiber scaffold. By doing this, different signal transduction pathways seem to be up regulated

How useful could Arabic documentary sources be for reconstructing past climate?

Trees, corals, ice cores and documentary evidence provide high-resolution proxies that allow past climate to be reconstructed (Jones et al., 2009). Documentary evidence includes all forms of written historical information about past climate or weather, but its use for climate reconstruction is restricted to locations for which there is a rich documentary legacy. Several climate analyses and reconstructions have been undertaken using documentary evidence from Europe (Brázdil et al., 2005; 2010), North and South America (Dupigny-Giroux and Mock, 2009; Prieto and García-Herrera, 2009; Neukom et al., 2010), Asia (Ge et al., 2005; 2010; Aono and Kazui, 2008; Hirano and Mikami, 2008) and oceanic areas (García-Herrera et al., 2005). The Islamic World is a region for which such sources could also be used to reconstruct past climate, as indeed they have been widely used for astronomy and geophysics. Astronomers have used the observations made by Arab astronomers for centuries, with some remarkable examples. Historical eclipse observations, recorded by various ancient and mediaeval cultures including Arabs, have enabled changes in the Earth’s rate of rotation to be monitored with fair precision as far back as around 700 AD (Stephenson, 2003). Rada and Stephenson (1992) catalogued meteor showers using mediaeval Arab chronicles and Ahn (2003) investigated the spatial distribution of meteor streams crossing the orbit of the Earth from the tenth to the fourteenth centuries using chronicles from Korea, Japan, China, Arabia and Europe. Documentary sources from Iberia have been used to identify and date such astronomical phenomena as eclipses and comets (Vernet, 1982), naked-eye sunspots (Vaquero and Gallego, 2002) and aurora sightings (Vaquero and Gallego, 2001). The work of Basurah (2006) provides descriptions for 18 aurora displays on various dates at low latitudes in the Mediterranean area taken from Islamic chronicles (ninth to sixteenth centuries). In seismology, Arabic chronicles were extensively used to prepare the Seismic Catalogue of the Iberian Peninsula (Martínez and Mezcua, 2002) and to study seismic activity in Syria and Palestine (Ambraseseys, 2005). However, the use of these sources to recover climate information is, to the best of our knowledge, still very limited (Bulliet, 2009; Jones et al., 2009). Here we describe a preliminary inquiry based on Arabic documentary sources from Iraq. We would stress the antiquity of the documents used, with dates in the period 816–1009 AD. The sources consulted are Arabic chronicles that narrate the social, political and religious history of different regions in a form very characteristic of Arab culture.Peer reviewe