Monday, August 8, 2011

Grow taller with Matrilin's?

LSJL upregulates Matrilin's 2 & 4 by approximately 3.5 fold.  It also upregulates Matrilin 3

Expression of matrilin-1, -2 and -3 in developing mouse limbs and heart.

"Throughout development matrilin-3 expression was strictly limited to cartilage, while matrilin-1 was also found in some other forms of connective tissue. Matrilin-2, albeit present around hypertrophic chondrocytes in the growth plate, was mainly expressed in non-skeletal structures."

"matrilin-1 associates with the aggrecan core protein"  It may also be involved in collagen assembly.

"In the skeleton matrilin-2 occurs only in the periosteum, perichondrium and the hypertrophic zone of the growth plate"

Matrilin-4 is processed by ADAMTS-5 in late Golgi vesicles present in growth plate chondrocytes of defined differentiation state.

"The two aggrecanases ADAMTS-4 and ADAMTS-5 play roles in the breakdown of cartilage extracellular matrix in osteoarthritis [and] mediate processing of matrilins in the secretory pathway. The matrilins are adaptor proteins with a function in connecting fibrillar and network-like components in the cartilage extracellular matrix. Cleavage resulting in processed matrilins with fewer ligand-binding subunits could make these less efficient in providing matrix cohesion. In this study, the processing and degradation of matrilin-4 during cartilage remodeling in the growth plate of the developing mouse long bones were studied in greater detail.  ADAMTS-5 and a matrilin-4 neoepitope, revealed upon ADAMTS cleavage, colocalize in prehypertrophic/hypertrophic chondrocytes while they are not detected in proliferating chondrocytes of the growth plate. ADAMTS-5 and the cleaved matrilin-4 are preferentially detected in vesicles derived from the Golgi apparatus. The matrilin-4 neoepitope was not observed in the growth plate of ADAMTS-5 deficient mice. In the growth plate ADAMTS-5, and not ADAMTS-4, has a physiological function in the intracellular processing of matrilins and potentially of other extracellular matrix proteins."

"Aggrecan has a modular structure and ADAMTSs cleave its core protein at distinct sites either in the interglobular domain, located between the N-terminal globular domain G1 and domain G2, or in the long region of the core protein substituted with chondroitin sulfate chains"

"Matrilin-4 is expressed in all cartilaginous regions of the maturing mouse joint, including proliferating and hypertrophic cells of the growth plate"<-maybe the increase in matrilin-4 expression in LSJL could indicate new growth plate formation.

According to Molecular structure, processing, and tissue distribution of matrilin-4., osteoblasts showed low levels of matrilin 4 whereas the joint surface, where there's chondrocytes and cartilage, expressed matrilin 4 at much higher levels.  Thus, indicating that such a large increase of MATN4 levels could be due to new chondrogenesis.

Although according to Normal skeletal development of mice lacking matrilin 1: redundant function of matrilins in cartilage?, MATN1 and MATN3 are only expressed in cartilage which makes it disturbing that MATN1 is not expressed in LSJL at over 2-fold.

Increased expression of matrilin-3 not only in osteoarthritic articular cartilage but also in cartilage-forming tumors, and down-regulation of SOX9 via epidermal growth factor domain 1-dependent signaling.

"Differential proteomics analysis revealed matrilin-3 (MATN3) as a candidate regulator of the cartilaginous phenotype. Its capacity to modulate gene expression was investigated in human HCS-2/8 chondrosarcoma cells and transfected chondrocytes.
Increased expression of the cartilage-specific matrix protein MATN3 was specifically observed in enchondromas and conventional chondrosarcomas. A substantial fraction of MATN3 was found in cytoplasmic structures of tumor cells, as demonstrated by immunohistochemistry. Analyses of intracellular MATN3 revealed that it corresponded to an imperfectly maturated MATN3 polypeptide, both in HCS-2/8 human chondrosarcoma cells and in transfected human chondrocytes. Moderately increased expression of MATN3 resulted in its intracellular retention. Antibody-mediated blockade of soluble, extracellular MATN3 in HCS-2/8 cell cultures resulted in increased expression of MATN3 and the chondrogenic transcription factor SOX9. Conversely, increased ectopic expression of MATN3 resulted in decreased expression of MATN3 and SOX9 in primary chondrocytes, while a mutant MATN3 lacking its first epidermal growth factor (EGF)-like domain failed to down-regulate SOX9.
Aberrant expression and processing of MATN3 are hallmarks of conventional cartilaginous neoplasms. A particular step in the maturation of MATN3 limits its processing through the secretion machinery, resulting in its intracellular accumulation upon increased expression. Soluble, secreted MATN3, however, down-regulates SOX9 at the messenger RNA and protein levels. The first EGF-like domain of MATN3 is a critical determinant of its regulatory activity toward SOX9."

"Most chondrogenic tumors are benign (enchondromas) and are comparable with differentiated chondrocytes with respect to their gene expression profile and matrix composition"

"extracellular MATN3 can down-regulate the expression of both SOX9 mRNA and its own mRNA."<-Sox9 was still upregulated in LSJL despite upregulation of MATN3.

Matrilin-3 switches from anti- to pro-anabolic upon integration to the extracellular matrix.

"Matrilin-3 (MATN3) is an almost cartilage specific, pericellular protein acting in the assembly of the ECM of chondrocytes. In the past, MATN3 was found required for cartilage homeostasis, but also involved in osteoarthritis-related pro-catabolic functions. [MATN3's] concentration as a circulating protein in articular fluids of human osteoarthritic patients was determined and its functions as a recombinant protein produced in human cells were investigated with particular emphasis on the physical state under which it is presented to chondrocytes. MATN3 down-regulated cartilage extracellular matrix (ECM) synthesis and up-regulated catabolism when administered as a soluble protein. When artificially immobilized, MATN3 induced chondrocyte adhesion via a α5β1 integrin-dependent mechanism, AKT activation[Akt is phosphorylated with LSJL] and favored survival and ECM synthesis.  MATN3 bound directly to isolated α5β1 integrin in vitro. TGFβ1 stimulation of chondrocytes allowed integration of exogenous MATN3 into their ECM and ECM-integrated MATN3 induced AKT phosphorylation and improved ECM synthesis and accumulation. The integration of MATN3 to the pericellular matrix of chondrocytes critically determines the direction toward which MATN3 regulates cartilage metabolism. MATN3 plays either beneficial or detrimental functions in cartilage."

"MATN3A, but not MATN3B, exerted up-regulation of catabolism and down-regulation of anabolism within 48 h"

"MATN3 does not arise from outside the cartilage but from the pericellular matrix of chondrocytes"

Matrilin-3 Induction of IL-1 receptor antagonist Is required for up-regulating collagen II and aggrecan and down-regulating ADAMTS-5 gene expression.

"The effects of recombinant human (rh) MATN3 protein were examined in C28/I2 immortalized human chondrocytes, primary human chondrocytes (PHCs), and primary mouse chondrocytes (PMCs)."

"rhMATN3 protein induced gene expression of IL-1Ra in C28/I2 cells, PHCs, and PMCs in a dose- and time-dependent manner. Treatment of C28/I2 cells and PHCs with MATN3 protein stimulated gene expression of COL2A1 and ACAN. Conversely, mRNA levels of COL2A1 and ACAN were decreased in MATN3 KO mice. MATN3 protein treatment inhibited IL-1β-induced MMP-13, ADAMTS-4 and ADAMTS-5 in C28/I2 cells and PHCs. Knocking down IL-1Ra abolished the MATN3-mediated stimulation of COL2A1 and ACAN and inhibition of ADAMTS-5, but had no effect on MATN3 inhibition of MMP-13 mRNA."

"MATN3 KO mice have relatively normal skeletal development"

Matrilin-3 activates the expression of osteoarthritis-associated genes in primary human chondrocytes.

"we tested the matrilin-3-dependent induction of osteoarthritis-associated genes in primary human chondrocytes. Matrilin stimulation leads to the induction of MMP1, MMP3, MMP13, COX-2, iNOS, IL-1beta, TNFalpha, IL-6 and IL-8. ADAMTS4 and ADAMTS5 [participate] in the in vitro degradation of matrilin-3. [There's] a matrilin-3-dependent feed-forward mechanism of matrix degradation, whereby proteolytically-released matrilin-3 induces pro-inflammatory cytokines as well as ADAMTS4 and -5 indirectly via IL-1beta. ADAMTS4 and ADAMTS5, in turn, cleave matrilin-3 and may release more matrilin-3 from the matrix, which could lead to further release of pro-inflammatory cytokines and proteases in cartilage."

It seems as though Matrilin-3 is involved in endochondral ossification.

" IL-6 release can be induced by collagen II, but not by collagen I [in chondrocytes]"  Type II collagen induced the release of the other interleukin's IL8 and IL1B in relatively similar quantities to MATN3.  However MATN3 increased TNFa levels more than Type II Collagen.

"ADAMTS4 and ADAMTS5 cleave matrilin-3 and may release more matrilin-3 from the matrix"

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