ReferenceID 3471

Inactivation of Nell-1 in Chondrocytes Significantly Impedes Appendicular Skeletogenesis

J Bone Miner Res

NELL-1, an osteoinductive protein, has been shown to regulate skeletal ossification. Interestingly, an interstitial 11p14.1-p15.3 deletion involving the Nell-1 gene was recently reported in a patient with short stature a

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Reference Id
3471
Evidence Id
20061
Core Evidence Id
20061
Source Reference Id
247
Herb2 Reference Id
HBREF000461
Subject Paper Key
HBIN022330_30352124
Pubmed Id
30352124
Doi
10.1002/jbmr.3615
Paper Title
Inactivation of Nell-1 in Chondrocytes Significantly Impedes Appendicular Skeletogenesis
Paper Abstract
NELL-1, an osteoinductive protein, has been shown to regulate skeletal ossification. Interestingly, an interstitial 11p14.1-p15.3 deletion involving the Nell-1 gene was recently reported in a patient with short stature and delayed fontanelle closure. Here we sought to define the role of Nell-1 in endochondral ossification by investigating Nell-1-specific inactivation in Col2α1-expressing cell lineages. Nell-1flox/flox ; Col2α1-Cre+ (Nell-1Col2α1 KO) mice were generated for comprehensive analysis. Nell-1Col2α1 KO mice were born alive but displayed subtle femoral length shortening. At 1 and 3 months postpartum, Nell-1 inactivation resulted in dwarfism and premature osteoporotic phenotypes. Specifically, Nell-1Col2α1 KO femurs and tibias exhibited significantly reduced length, bone mineral density (BMD), bone volume per tissue volume (BV/TV), trabecular number/thickness, cortical volume/thickness/density, and increased trabecular separation. The decreased bone formation rate revealed by dynamic histomorphometry was associated with altered numbers and/or function of osteoblasts and osteoclasts. Furthermore, longitudinal observations by in vivo micro-CT showed delayed and reduced mineralization at secondary ossification centers in mutants. Histologically, reduced staining intensities of Safranin O, Col-2, Col-10, and fewer BrdU-positive chondrocytes were observed in thinner Nell-1Col2α1 KO epiphyseal plates along with altered distribution and weaker expression level of Ihh, Patched-1, PTHrP, and PTHrP receptor. Primary Nell-1Col2α1 KO chondrocytes also exhibited decreased proliferation and differentiation, and its downregulated expression of the Ihh-PTHrP signaling molecules can be partially rescued by exogenous Nell-1 protein. Moreover, intranuclear Gli-1 protein and gene expression of the Gli-1 downstream target genes, Hip-1 and N-Myc, were also significantly decreased with Nell-1 inactivation. Notably, the rescue effects were diminished/reduced with application of Ihh signaling inhibitors, cyclopamine or GANT61. Taken together, these findings suggest that Nell-1 is a pivotal modulator of epiphyseal homeostasis and endochondral ossification. The cumulative chondrocyte-specific Nell-1 inactivation significantly impedes appendicular skeletogenesis resulting in dwarfism and premature osteoporosis through inhibiting Ihh signaling and predominantly altering the Ihh-PTHrP feedback loop. 2018 American Society for Bone and Mineral Research.
Journal
J Bone Miner Res
Publish Year
2019
Experiment Subject
nell-1col2alpha1ko mice
Experiment Type
Animal Experiment
Phenotype Related
Osteoporosis
Paper Title Cn
Paper Title En
Inactivation of Nell-1 in Chondrocytes Significantly Impedes Appendicular Skeletogenesis
Bilingual Status
semi_complete