Altering osteoclast numbers using CTSK models in utero affects mice offspring craniofacial morphology

Abstract

Background Bone remodelling during development and growth is important for craniofacial integrity of offspring. The aim of this study was to investigate the changes in offspring adult skull morphology when the osteoclasts number was altered in utero, using three‐dimensional (3D) geometric morphometric analysis (GMA). Materials and Methods We altered osteoclasts number in utero via two approaches. First, we generated heterozygous CtskCre;DTAfl/+ (diphtheria toxin A) mice. Second, we altered Ctsk expression in vivo by injecting pregnant wild‐type dams at embryonic day (E) 12.5 with in vivo siRNA specific for Ctsk. Mice were collected at 6 weeks and analysed using geometric morphometric analysis via computed tomography, histomorphometry and gene expression analysis. Results Altering osteoclasts number in utero affected the offspring adult skull morphology. Decreased Ctsk and osteoclast numbers were associated with a decrease in cranial vault height and an increase in mandibular body length. Changes in size and shape were observed with an increased number of osteoclasts in CtskCre;DTAfl/+ mice, including an increase in cranial vault height, as well as a shortening of mandibular body length and ramus height. Conclusion The findings of this study suggest that modulation of osteoclast numbers during pre‐ and post‐natal development may be a previously unknown factor in the aetiology of skeletal malocclusions. An improved understanding of the factors affecting bone homeostasis during development and growth may help in the development of future therapies that would target the early intervention of skeletal malocclusion.

Treatment with an inhibitor of matrix metalloproteinase 9 or cathepsin K lengthens embryonic lower jaw bone

“…This could be useful in developing treatments to regulate jaw length in utero or postnatally. Further supporting such an approach, a new study in mice found that altering CTSK expression in utero resulted in mandibular changes 39 . If these drugs were to be used in utero, as demonstrated in our in ovo experiments, off‐target effects would need to be better understood.…”

“…Further supporting such an approach, a new study in mice found that altering CTSK expression in utero resulted in mandibular changes. 39 If these drugs were to be used Our future studies will elucidate the precise mechanisms by which osteoclast-secreted proteolytic enzymes influence jaw length, information which will potentially help identify other currently available drugs which could be used to treat craniofacial malformations in an effective and minimally invasive manner.…”

Osteoclast differentiation and dynamic mRNA expression during mice embryonic palatal bone development

“…Ctsk (encoding cathepsin K) is a marker of mature OCLs. Ctsk deficiency reduces the number of osteoclasts and affects bone morphology 20 . The absence of Fos (encoding transcription factor AP-1 subunit C-Fos) in mice induces substantial osteopetrosis that is caused by the absence of OCLs 44 .…”

“…Research on embryonic OCLs mainly focuses on endochondral osteogenesis, while reports on intramembranous osteogenesis are rare. At present, some sporadic studies on intramembranous osteoblasts and OCLs in the embryonic stage suggest that OCLs may play a role in promoting bone matrix maturation and determining bone morphology [18][19][20] . However, the differentiation process of embryonic secondary palatal bone (PPMX and PPP) OCLs and their relationship to intramembranous osteogenesis remain unclear.…”

TGF-β Signaling in Cranial Neural Crest Affects Late-Stage Mandibular Bone Resorption and Length

“…It is well-established that osteoblast lineage cells such as osteocytes influence osteoclastogenesis and osteoclast function, and there is growing evidence that bone resorption by osteoclasts is critical to mandibular development (9)(10)(11). It is therefore logical that in addition to its long-known role in facial and jaw osteogenesis, NCM also regulates jaw length by controlling bone resorption, which has been demonstrated in both mice and birds (5,12,13). The primary cell type known to play a role in bone resorption is mesoderm-derived osteoclasts, thus not an NCM-derived cell.…”