Osteogenesis imperfecta (OI) is a heritable disorder ofconnective tissue associated with fractures, osteopenia, and short stature. 01 results from mutations affecting the proal or proa2 gene of type I collagen. We describe a strain of mice with a nonlethal recessively inherited mutation (oim) that results in phenotypic and biochemical features that simulate moderate to severe human 01. Although imperfect osteogenesis has been previously observed in bovine, feline, and murine species, none of these have duplicated both the biochemical and clinical findings associated with human OI (4-7). The Mov-13 mouse, which has a transcriptional block of the proal(I) collagen gene, has provided a potential model of human 01 type II (8-13). More recently, several transgenic variants of Mov-13 and normal mice have been created as useful models of mild 01 type I or lethal OI type II (tt, 14, 15).In this report we describe a naturally occurring mouse mutation that produces phenotypic and biochemical features similar to those seen in moderate to severe human OI. We have named this mutation osteogenesis imperfecta murine (oim). Homozygous oim mice have osteopenia, fractures, and progressive skeletal deformities. Our data indicate that these mice are deficient in proa2(I) collagen because of a G deletion at nucleotide 3983 of the Cola-2 gene. This mutation results in tissue accumulation of al(I) homotrimeric collagen in the extracellular matrix. Homozygous oim mice should permit the study of type I collagen pathophysiology in a manner not possible in humans. MATERIALS AND METHODSRadiographic and Microscopic Examination. Whole-body radiographs were taken in a Faxitron x-ray machine (34 keV for 1.5 min) using Kodak OM1 film. For light microscopy, excised femurs were fixed in neutral buffered Formalin for 24 hr, decalcified in 10% (wt/vol) EDTA in 0.1 M Tris'HCl buffer, pH 6.9, for 14 days at 4°C, embedded in paraffin, sectioned, and stained with hematoxylin and eosin.Isolation and Culture of Dermal Fibroblasts. Dermis was obtained from the back of 3-to 5-day-old homozygous oim and wild-type pups. The skin was rinsed with iodine then 70o (vol/vol) ethanol, excised, and minced to 1-to 3-mm2 pieces.Explants were grown for 2 weeks in Dulbecco's modified Eagle's medium supplemented with 10%o fetal bovine serum, streptomycin at 100 jug/ml, penicillin at 100 units/ml, and amphotericin B at 0.25 jig/ml. Cultures were assayed in the second passage.Collagen and Procollagen Analysis in Vitro. Fibroblast cultures were grown several days past visual confluence in 10-cm2 dishes. The medium was then supplemented with 150 ,uM sodium ascorbate and 24 hr later the cultures were incubated for 30 min in Dulbecco's modified Eagle's medium plus 1% dialyzed fetal bovine serum, antibiotics, 100 ,uM each nonessential amino acids but no proline, and 150 ,uM sodium ascorbate (starve medium). De novo synthesized proteins were radiolabeled for 2 hr (short-label analysis) or 24 hr (steady-state analysis) with starve medium containing 20 ,uCi (1 Ci = 37 ...
Tumor necrosis factor-related, activation-induced cytokine (TRANCE), a tumor necrosis factor family member, mediates survival of dendritic cells in the immune system and is required for osteoclast differentiation and activation in the skeleton. We report the skeletal phenotype of TRANCE-deficient mice and its rescue by the TRANCE transgene specifically expressed in lymphocytes. TRANCE-deficient mice showed severe osteopetrosis, with no osteoclasts, marrow spaces, or tooth eruption, and exhibited profound growth retardation at several skeletal sites, including the limbs, skull, and vertebrae. These mice had marked chondrodysplasia, with thick, irregular growth plates and a relative increase in hypertrophic chondrocytes. Transgenic overexpression of TRANCE in lymphocytes of TRANCE-deficient mice rescued osteoclast development in two locations in growing long bones: excavation of marrow cavities permitting hematopoiesis in the marrow spaces, and remodeling of osteopetrotic woven bone in the shafts of long bones into histologically normal lamellar bone. However, osteoclasts in these mice failed to appear at the chondroosseous junction and the metaphyseal periosteum of long bones, nor were they present in tooth eruption pathways. These defects resulted in sclerotic metaphyses with persistence of club-shaped long bones and unerupted teeth, and the growth plate defects were largely unimproved by the TRANCE transgene. Thus, TRANCE-mediated regulation of the skeleton is complex, and impacts chondrocyte differentiation and osteoclast formation in a manner that likely requires local delivery of TRANCE. T he skeleton is a dynamic system throughout life, balancing the need for physical support and locomotion on the one hand with the requirement for precisely regulated concentrations of circulating mineral ions on the other. These processes begin in utero and are coordinated with growth of the individual by a unique collaboration between the cells of cartilage and bone (1). The two principal cell types in bone are osteoblasts, which secrete bone matrix, and osteoclasts, which resorb bone, and the coupled actions of both are required for normal skeletal formation and maintenance and for mineral homeostasis (2, 3).Tumor necrosis factor-related, activation-induced cytokine (TRANCE) is a member of the tumor necrosis factor family that was initially discovered as a factor expressed on T cells that supports the survival and activity of antigen-presenting dendritic cells in the immune system (4-8). It was soon recognized that TRANCE was also the osteoclast differentiation factor produced by osteoblasts that plays an obligatory role in the formation and activation of osteoclasts, the multinucleated, monocytemacrophage lineage-derived cells that carry out bone resorption. The roles of TRANCE in the immune and skeletal systems were apparent in the phenotype of TRANCE null mice, which had severe osteopetrosis, lacked osteoclasts, and failed to form lymph nodes (7).The binding of TRANCE to its receptor (TRANCE-R), itself a member of the ...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.