Transcriptome Profiling of Osteoblasts in a Medaka (Oryzias latipes) Osteoporosis Model Identifies Mmp13b as Crucial for Osteoclast Activation

Abstract

Matrix metalloproteases (MMPs) play crucial roles in extracellular matrix (ECM) modulation during osteoclast-driven bone remodeling. In the present study, we used transcriptome profiling of bone cells in a medaka model for osteoporosis and bone regeneration to identify factors critical for bone remodeling and homeostasis. This identified mmp13b, which was strongly expressed in osteoblast progenitors and upregulated under osteoporotic conditions and during regeneration of bony fin rays. To characterize the role of mmp13b in bone remodeling, we generated medaka mmp13b mutants by CRISPR/Cas9. We found that mmp13b mutants form normal numbers of osteoblasts and osteoclasts. However, osteoclast activity was severely impaired under osteoporotic conditions. In mmp13b mutants and embryos treated with the MMP13 inhibitor CL-82198, unmineralized collagens and mineralized bone matrix failed to be degraded. In addition, the dynamic migratory behavior of activated osteoclasts was severely affected in mmp13b mutants. Expression analysis showed that maturation genes were downregulated in mmp13b deficient osteoclasts suggesting that they remain in an immature and non-activated state. We also found that fin regeneration was delayed in mmp13b mutants with a concomitant alteration of the ECM and reduced numbers of osteoblast progenitors in regenerating joint regions. Together, our findings suggest that osteoblast-derived Mmp13b alters the bone ECM to allow the maturation and activation of osteoclasts during bone remodeling in a paracrine manner. Mmp13b-induced ECM alterations are also required to facilitate osteoblast progenitor recruitment and full regeneration of bony fin rays.

A Collagen10a1 mutation disrupts cell polarity in a medaka model for metaphyseal chondrodysplasia type Schmid

“…RNA sequencing and bioinformatics analysis were performed by Novogene (Singapore) and as described previously. 84 GO term and KEGG pathway analyses were performed on differentially expressed genes identified with a threshold of p<0.05, using g:Profiler (version e109_eg56_p17_1d3191d) with g:SCS multiple testing correction method applying a significance threshold of 0.05. 85 Blinding was not performed.…”

High Bone Mass Disorders: New Insights From Connecting the Clinic and the Bench

“…(126) To date, there is a vast library of transgenic reporter and mutant zebrafish available that has been shown to accurately model various skeletal diseases (Zebrafish Information Network [ZFIN]; www.zfin.org), allowing bone cell populations to be imaged, FACS isolated, or manipulated. (124,127,128) Zebrafish can also model high BMD (84,(129)(130)(131) ; eg, an osteopetrosis-like phenotype in mmp9 À/À ;mmp13b À/À double mutant fish, (78) CSF1R-related dysosteosclerosis (OMIM 618476), (132,133) and PTDSS1-related Lenz-Majewski hyperostotic dysplasia (OMIM 151050). (134) Exploiting the zebrafish lifespan to understand spatiotemporal and molecular causes of HBM Initial zebrafish development is rapid with the first skeletal progenitor cells in the form of neural crest cells appear around the first day of development.…”

“…( 126 ) To date, there is a vast library of transgenic reporter and mutant zebrafish available that has been shown to accurately model various skeletal diseases (Zebrafish Information Network [ZFIN]; www.zfin.org ), allowing bone cell populations to be imaged, FACS isolated, or manipulated. ( 124 , 127 , 128 ) Zebrafish can also model high BMD ( 84 , 129 , 130 , 131 ) ; eg, an osteopetrosis‐like phenotype in mmp9 −/− ; mmp13b −/− double mutant fish, ( 78 ) CSF1R ‐related dysosteosclerosis (OMIM 618476), ( 132 , 133 ) and PTDSS1 ‐related Lenz–Majewski hyperostotic dysplasia (OMIM 151050). ( 134 )…”