Genes, forces, and forms: Mechanical aspects of prenatal craniofacial development

Abstract

Current knowledge of molecular signaling during craniofacial development is advancing rapidly. We know that cells can respond to mechanical stimuli by biochemical signaling. Thus, the link between mechanical stimuli and gene expression has become a new and important area of the morphological sciences. This field of research seems to be a revival of the old approach of developmental mechanics, which goes back to the embryologists His (1874), Carey (1920), and Blechschmidt (1948). These researchers argued that forces play a fundamental role in tissue differentiation and morphogenesis. They understood morphogenesis as a closed system with living cells as the active part and biological, chemical, and physical laws as the rules. This review reports on linking mechanical aspects of developmental biology with the contemporary knowledge of tissue differentiation. We focus on the formation of cartilage (in relation to pressure), bone (in relation to shearing forces), and muscles (in relation to dilation forces). The cascade of molecules may be triggered by forces, which arise during physical cell and tissue interaction. Detailed morphological knowledge is mandatory to elucidate the exact location and timing of the regions where forces are exerted. Because this finding also holds true for the exact timing and location of signals, more 3D images of the developmental processes are required. Further research is also required to create methods for measuring forces within a tissue. The molecules whose presence and indispensability we are investigating appear to be mediators rather than creators of form.

Pressure from the lips and the tongue in children with class III malocclusion

“…More importantly, Sinsel et al(1998;1999) revealed that paralysis of the midfacial musculature can result in decreased anterioposterior growth of the snout and nasofrontal sutural growth activity. Actually, mechanical forces play a fundamental role in tissue differentiation and morphogenesis (Radlanski and Renz, 2006). The findings from this study (Figs.3 and 4) show that perioral forces exerted on the primary dentition of class III malocclusion were apparently less than the normal (P<0.01), especially for the upper anterior teeth region with negligible pressure which may cause less bone apposition in this area.…”

Engineering functional anisotropy in fibrocartilage neotissues

“…Past work has found the critical period of TMJ morphogenesis to coincide with the onset of buccal, or mouth, cavity motion during embryogenesis [42]. Others have identified the link between molecular signaling and mechanical stimulation to be fundamental to the development of the fetal mandible and overall craniofacial growth [43]. This suggests that a similar interplay between stimuli is likewise essential for development of the TMJ.…”

A comparative study of craniofacial measurements between Ryukyuan and mainland Japanese females using lateral cephalometric images

“…Studies on animal models and human genetic disorders have led to increased knowledge about the processes of craniofacial morphogenesis and genes related to these processes (Wilkie and Morriss-Kay, 2001;Cohen, 2002;Kuratani, 2005;Radlanski and Renz, 2006). However, the common genetic factors that explain facial variation among human individuals or facial difference among populations remain unclear.…”