I Love Histology and Herpetology

Gekko gecko (Tokay Gecko), locally known to Indonesians as Tokek, is a member of Suborder Lacertilia which can be found from northeast India to southern China and throughout Southeast Asia. There are two identified subspecies of Tokek, those are G. g. gecko (Linnaeus, 1758) and G. g. azhari (Mertens, 1955), the latter is endemic to Bangladesh. This arboreal lizard naturally lives in tropical rain forest but some of them have entered human habitation (Kongbuntad et al., 2016). The taxonomical classification of G. gecko displayed on Integrated Taxonomic Information System (ITIS) is as followed:  Kingdom       : Animalia  Phylum            : Chordata  Subphylum    : Vertebrata  Class              : Reptilia  Order             : Squamata  Suborder        : Gekkota  Family   ...

Aggrecan (Acan) belongs to the chondroitin sulfate proteoglycans of the lectican family, namely hyalectans family. Members of this family are vital components of extracellular matrix (Adams et al., 2007; Aspberg, 2012). Acan, one of the chondrocyte specific markers, is essential for cartilage function and skeletal development (Nirmal & Nair, 2013). Acan acts as the main compressive macromolecule in cartilage tissue, making bone capable to withstand physical loading, showing how important this molecule is in maintaining cartilage integrity (Lee et al., 2010). In the precartilaginous anlagen, the condensed mesenchymal cells express versican which is then down-regulated during chondrogenic differentiation as Acan is up-regulated (Lauinga et al., 2014). Chondrocytes in the proliferative zone produce a large amount of extracellular matrix predominantly consisting of type II collagen and Acan. When chondrocytes differentiate into pre-hypertrophic and hypertrophic chondrocytes, there is a...

Matrix Gla protein (MGP) is a member of the mineral-binding Gla protein family with the molecular weight of 10-kD and known to be involved in cartilage mineralization during development. MGP is expressed in chondrocytes, endothelial cells and vascular smooth muscle cells (Dan et al., 2012; Yao et al., 2009). The five γ-carboxyglutamic acid (Gla) residues of this protein possess high affinity for ions such as calcium and phosphate (Newman et al., 2001; Beazley et al., 2013) which enable it to prevent extracellular matrix calcification by binding the minerals thus limiting the amount of free calcium ions available to initiate calcification (Yagami et al., 1999; Dan et al., 2012). It has been reported that MGP does not only inhibit cartilage mineralization, but it also blocks chondrocyte maturation and both types of ossification (Yagami et al., 1999). Mineralization begins in matrix vesicles which is associated with MGP and at sites with accumulated proteoglycan. MGP inhibits calcium infl...

Chondrocytes express chondrocyte-specific extracellular matrix proteins such as type II, IX, XI collagens and aggrecan, while the hypertrophic chondrocytes tend to produce matrix high in type I and X collagens (Cancedda et al., 1995; Erlebacher et al., 1995; Hall & Miyake, 1995; Niu et al., 2016). Type II collagen is encoded by the type II procollagen gene (Col2a1) (Hering et al., 2014; Cruet-Hennequart et al., 2015) and its expression is usually used as an early key marker of chondrogenic cells (Mori-Akiyama et al., 2003; Xu et al., 2008). In mouse embryo, Sox9 is co-expressed with Col2a1, suggesting that direct activation of Col2a1 by Sox9 is crucial in activating genes that encode cartilage extracellular matrix proteins (Lefebvre & de Crombrugghe, 1998; Lefebvre et al., 1998; Grogan et al., 2008). Chondrocytes begin to synthesize type II collagen in the form of a procollagen molecule with a triple-helical α1 (II) chains. This procollagen molecule has an amino and carboxyl pr...

Skeletal tissues express bone morphogenetic proteins (BMPs) which act as regulators of skeletal development and maintenance of bone mass in adults (Gamer et al., 2009). BMPs belong to the transforming growth factor-β superfamily (Bahamonde & Lyons, 2001) and are expressed throughout the developing skeleton, influencing cell type specification, cell differentiation and apoptosis during endochondral ossification. At the earliest stages of osteogenesis, BMPs are required for mesenchymal condensation and at the later stages, BMPs-receptor complexes stimulate chondrocyte proliferation and differentiation (Gamer et al., 2010).  BMP3 molecule is structurally related to BMPs but it acts as a negative regulator of osteogenesis (Bahamonde & Lyons, 2001; Gamer et al., 2010; Huang et al., 2007). BMP3 is mainly produced by osteoblasts and osteocytes (Long & Ornitz, 2013). This molecule is present within bone and accounts for almost 65% of total BMP (Zhang et al., 2015; Zhou et al., ...