Copyright (c) 2009 All rights reserved. http://works.bepress.com/julia_oxford Recent documents in Julia T. Oxford en-us Tue, 27 Oct 2009 08:28:07 PDT 3600 http://works.bepress.com/julia_oxford/3 http://works.bepress.com/julia_oxford/3 Thu, 23 Apr 2009 18:21:47 PDT Collagen type XI is an essential component of the collagen fibrils within the developing skeleton. It is a quantitatively minor member of the fibrillar collagens that plays a regulatory role in the assembly of embryonic collagen fibrils as the diameter of collagen fibrils is dependent on the presence of Collagen α1(XI). However, very little is known about the role of collagen type XI in bone microarchitecture formation. In this study, skeletal mineralization was evaluated in the absence and presence of Collagen α1(XI) comparing the chondrodysplasia (cho) mouse embryo to wildtype. The data presented support a role for collagen type α1(XI) in skeletal development that is distinct from its function in nucleating the formation and limiting the diameter of cartilage type II collagen fibrils. Established characteristics of the cho mouse were apparent in the mouse included in this study, including a shortened snout, and short, wide long-bones with flared metaphyses. The cho mouse humerus was 55% the length of the wildtype humerus and approximately 35% wider at the diaphysis and metaphyses. Quantification of the differences in the humerus, vertebral column, and ribcage of the cho and wildtype mice was carried out using high-resolution three-dimensional models that were created from x-ray microcomputed tomography images. Analysis revealed differences in bone density, size and microarchitecture. The differences in skeletal properties between these mice were analyzed by determining bone mineral density (BMD) calculations and three-dimensional measures of microarchitecture (BV/TV, Tb.Th, Tb.N, Tb.Sp). Results indicated that bone mineral density was increased in the absence of collagen α1(XI) in humerus, vertebrae, and the anterior rib samples of the cho mouse. The increase in bone density correlated with an observed increase in trabecular number, trabecular thickness, and percent bone volume, as well as a decrease in trabecular separation in the humerus, ribs, and vertebrae. In contrast, cortical bone mineral density was similar in wildtype and cho mice. A function for Collagen α1(XI) in the establishment of bone microarchitecture during embryonic development is supported by this data. Future studies will focus on Collagen α1(XI) in bone formation and mineralization by osteoblasts, and new functions for Collagen α1(XI) in non-cartilaginous tissues of the skeleton. Julia T. Oxford http://works.bepress.com/julia_oxford/2 http://works.bepress.com/julia_oxford/2 Mon, 13 Apr 2009 13:50:10 PDT Collagen is an important material in tissues of living organisms. Found almost everywhere in the human body, it is important in connective tissues, bone growth, and cartilage. In this work, collagen XI and two of its isoforms, V1b and V2, present in developing cartilage, are investigated using the technique of immuno-SEM. The efficacy of this technique to examine fundamental issues related to ossification is presented. Prior work using alternative techniques has shown that both isoforms were observed in the longitudinal septa, and in a very restricted pericellular pattern in the resting zone. Prior to primary ossification, V1b was detected only in the diaphysis, primarily adjacent to the perichondrium, and not in the epiphysis. The V2-containing isoforms were most strongly expressed in areas of newly forming cartilage, and disappeared as chondrocyte maturation proceeded. The technique of immuno-SEM will yield a better understanding of protein composition and organization within the osteochondral junction. Michelle Gerritsen http://works.bepress.com/julia_oxford/1 http://works.bepress.com/julia_oxford/1 Thu, 15 Jan 2009 21:26:40 PST Type XI collagen is a quantitatively minor yet essential constituent of the cartilage extracellular matrix. The amino propeptide of the 1 chain remains attached to the rest of the molecule for a longer period of time after synthesis than the other amino propeptides of type XI collagen and has been localized to the surface of thin collagen fibrils. Yeast two-hybrid system was used to demonstrate that a homodimer of 1(XI) amino propeptide (1(XI)Npp) could form in vivo. Interaction was also confirmed using multi-angle laser light scattering, detecting an absolute weight average molar mass ranging from the size of a monomer to the size of a dimer (25,000-50,000 g/mol), respectively. Binding was shown to be saturable by ELISA. An interaction between recombinant 1(XI)Npp and the endogenous 1(XI)Npp was observed, and specificity for 1(XI)Npp but not 2(XI)Npp was demonstrated by co-precipitation. The interaction between the recombinant form of 1(XI)Npp and the endogenous 1(XI)Npp resulted in a stable association during the regeneration of cartilage extracellular matrix by fetal bovine chondrocytes maintained in pellet culture, generating a protein that migrated with an apparent molecular mass of 50-60 kDa on an SDS-polyacrylamide gel. Julia T. Oxford