Journal
JOURNAL OF ORTHOPAEDIC RESEARCH
Volume 31, Issue 4, Pages 651-657Publisher
WILEY
DOI: 10.1002/jor.22280
Keywords
osteochondroma; exostosis; skeletal dysplasias; shape analysis; mouse genetic models
Categories
Funding
- National Center for Research Resources [5P41RR012553-14]
- National Institute of General Medical Sciences [8 P41 GM103545-14]
- National Institutes of Health
- NIH/NCBC National Alliance for Medical Image Computing [U54-EB005149]
- National Cancer Institute [NIH K08CA138764]
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Individuals with multiple osteochondromas (MO) demonstrate shortened long bones. Ext1 or Ext2 haploinsufficiency cannot recapitulate the phenotype in mice. Loss of heterozygosity for Ext1 may induce shortening by steal of longitudinal growth into osteochondromas or by a general derangement of physeal signaling. We induced osteochondromagenesis at different time points during skeletal growth in a mouse genetic model, then analyzed femora and tibiae at 12 weeks using micro-CT and a point-distribution-based shape analysis. Bone lengths and volumes were compared. Metaphyseal volume deviations from normal, as a measure of phenotypic widening, were tested for correlation with length deviations. Mice with osteochondromas had shorter femora and tibiae than controls, more consistently when osteochondromagenesis was induced earlier during skeletal growth. Volumetric metaphyseal widening did not correlate with longitudinal shortening, although some of the most severe shortening was in bones with abundant osteochondromas. Loss of heterozygosity for Ext1 was sufficient to drive bone shortening in a mouse model of MO, but shortening did not correlate with osteochondroma volumetric growth. While a steal phenomenon seems apparent in individual cases, some other mechanism must also be capable of contributing to the short bone phenotype, independent of osteochondroma formation. Clones of chondrocytes lacking functional heparan sulfate must blunt physeal signaling generally, rather than stealing growth potential focally. (c) 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 31: 651657, 2013
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