Thursday, January 21, 2010

Periosteal/Perichondrial gene expression versus LSJL

Differential gene expression in the perichondrium and cartilage of the neonatal mouse temporomandibular joint.

"Genes with higher expression in the PC sample related to growth factor ligand-receptor interactions [FGF-13 (6.4x), FGF-18 (4x), NCAM (2x); PGDF receptors, transforming growth factor (TGF)-beta and IGF-1], the Notch isoforms (especially Notch 3 and 4) and their ligands or structural proteins/proteoglycans [collagen XIV (21x){Col14a1 up in LSJL}, collagen XVIII (4x), decorin (2.5x)]. Genes with higher expression in the C sample consisted mostly of known cartilage-specific genes [aggrecan (11x){up}, procollagens X (33x){up}, XI (14x){up}, IX (4.5x){up}, Sox 9{up} (4.4x) and Indian hedgehog (6.7x)]. However, the functional or structural roles of several genes that were expressed at higher levels in the PC sample are unclear [myogenic factor (Myf) 9 (9x), tooth-related genes such as tuftelin (2.5x) and dentin sialophosphoprotein (1.6x), VEGF-B (2x) and its receptors (3-4x) and sclerostin (1.7x)]. FGF, Notch and TGF-beta signalling may be important regulators of MCC proliferation and differentiation; the relatively high expression of genes such as Myf6 and VEGF-B and its receptors suggests a degree of unsuspected plasticity in PC cells."

C stands for Cartilage.  PC stands for periochondrium.

Genes upregulated in perichondrium versus cartilage also up in LSJL:


"chondrogenic stimulation by BMP-2 up-regulates VEGF-B"

Immunohistochemical analysis of Sox9 expression in periosteum of tibia and calvaria after surgical release of the periosteum.

"The purpose of the present study was to analyze histologically the bone formation in surgically released and repositioned periosteum, and to determine expression of Sox9 and type-2 collagen in periosteal bone formation of tibia and calvaria. After surgery, the released tibial periosteum formed ectopic cartilage. At 7 days, a combination of endochondral and intramembranous ossification was apparent. Some fibroblasts derived from the released periosteum showed Sox9 expression. Chondrocytes and cartilage matrix both displayed type-2 collagen expression. At 7 days, an additional new bone was formed on the calvaria. Osteoblasts and fibroblasts derived from released calvarial periosteum did not express Sox9 or type-2 collagen. Sox9 was not expressed throughout the process periosteal bone formation on the calvaria. Sox9 and type-2 collagen expression in periosteal cells after periosteum release and that the generative potential of periosteal cells of calvaria is different from that of tibia."

The surgery: "An incision was made on the periosteum and the flap was gently released. The periosteum and skin flaps were repositioned on the bone surface and sutured"  The periosteal flap was turned over.

Tibial periosteum:

"At 7 days, periosteum had undergone changes at the release site, displaying loose connective tissue. New bone formation by endochondral ossification was observed in this inflammatory tissue. These periosteal cells of the fibrous layer were markedly more abundant and had differentiated into chondroblasts and chondrocytes. Fibroblasts derived from periosteal cells displayed differentiation and proliferation. These chondrocytes and chondroblasts had formed a cartilage mass. At 14 days after surgery, periosteal bone formation appeared as a combination of intramembraneous and endochondral ossification. Chondrogenic cells derived from the periosteum had formed a cartilage mass. Hypertrophic and mature chondrocytes formed new external callus cartilage, which in turn was replaced by newly formed trabeculae of cancellous bone undergoing endochondral ossification. At 28 days after surgery, all newly formed cartilage had been changed into trabecular bone"

"At 3 days after surgery, periosteal cells proliferated and changed into fibroblasts. These fibroblasts showed Sox9 expression but no type-2 collagen expression. At 7 days after surgery, a small number of fibroblasts from the released periosteum were immunostained for Sox9. Sox9 immunostaining was observed in fibroblasts surrounding ectopic cartilage and differentiated chondrocytes. Chondrogenic cells from the released periosteum were positive for type-2 collagen. At 14 days after surgery, Sox9 immunostaining was observed in fibroblasts and chondrocytes, but not in hypertrophic chondrocytes. Type-2 collagen was expressed around chondrocytes and hypertrophic chondrocytes"

Calvarial[skull cap] periosteum:

"At 3 days, inflammatory tissue and rich vascularization were found. Periosteal cells were attached to the bone surface at the release site and were connected to adjacent cells. At 7 days after surgery, periosteum contained loose connective tissue. Additional bone formation started on the calvarial bone surface. Many osteoblasts were localized on the bone surface and induced bone matrix formation. Fibroblasts derived from the periosteum were concentrated on the bone surface and had differentiate into osteoblasts. At 14 days after surgery, bone formation was continuing by intramembraneous ossification. New trabecular bone contained many osteocytes. Osteoblasts on calvarial bone produced extracellular bone matrix and induced calcification of the bone. At 28 days after surgery, additional bone formation was continuously apparent. New trabecular bone consisted of osteocytes, osteoblasts and extracellular bone matrix "

"Expression of Sox9 or type-2 collagen was not detected in cells derived from the periosteum throughout the experiment"

"Microscopical (A, B) and electron microscopical (C, D) observations of tibial (A, C) and calvarial (B, D) periosteum. Periosteum (P) is connective tissue covering the bone surface (Bone). It comprises of a fibrous layer (FL) and an osteogenic layer (OL). The comparatively thick outer fibrous layer is made up of dense connective tissue. The less well-defined inner osteogenic layer contains osteogenic cells. Scale bars A, B: 20mm; C, D: 5mm."

"Photomicrograph of released periosteum after toluidine blue staining. (A) Released tibial periosteum (RP) consisting of the fibrous layer and part of the osteogenic layer. The fibrous layer is released from the bone (Bone), and the osteogenic layer is damaged by the surgical procedure. Few osteogenic cells are present in the inner layer. Osteogenic cells are not present on the surface of the cortex bone. (B) Released calvarial periosteum (RP) consisting the fibrous layer containing a few fibroblasts and collagen fibers. Released calvarial periosteum is thinner than tibial periosteum. Osteogenic cells are not present on the surface of cortical bone (Bone)."

Identification of unique molecular subdomains in the perichondrium and periosteum and their role in regulating gene expression in the underlying chondrocytes.

"Both the perichondrium and the periosteum are reported to have two morphologically distinct layers. While the inner layer is proposed to contribute to appositional growth of cartilage and bone the outer fibroblastic layer is thought to perform a structural role by offering attachment sites for tendons and ligaments "

"Fgf18[produced by the perichondrium and regulated by Runx2 and TGFb1 is required both for chondrocyte proliferation and for osteogenesis, acting through two distinct receptors"

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12 day chick tibia showing the distinction between the periosteum and perichondrium.

"localized to this inner cambial layer of the perichondrium, including Tsp2[upregulated in perichondrium downregulated in periosteum], MafB[perichondrium specific gene]{down}, Dkk3{up}, THBS2{UP}, and galectin-1[perichondrium specific gene]. We also observed that cellular retinoic acid binding protein-I (CRABP-I){up as Crabp1} and Undulin (COL14A1){up} are expressed in the outer layer of the perichondrium"

Genes specific to periosteum(inner layer): "B-Tubulin{LSJL upregulates Tubulin Beta 6}, Neuronal protein 3.1 (P311), Y-box binding protein 1 (YBX-1), Type V collagen(Col5a1), Retinoic acid induced 14 (RAI14), alpha2 chain of type I collagen and Decorin "

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EFEMP1 a gene associated with stature was reported to be sporadically detected in the periosteum and perichondrium.  matn4 is upregulated by LSJL.

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