Mathematical Analysis of Mandibular Morphogenesis by Micro‐CT‐Based Mouse and Alizarin Red S‐Stained‐Based Human Studies During Development

Abstract

Prenatal development of the mandible is an important factor in its postnatal function. To examine quantitatively normal and abnormal developmental changes of the mandible, we here evaluated morphological changes in mineralizing mandibles by thin-plate spline (TPS) including bending energy (BE) and Procrustes distance (PD), and by Procrustes analyses including warp analysis, regression analysis, and discriminant function analysis. BE and PD were calculated from lateral views of the mandibles of mice or of human fetuses using scanned micro-computed tomography (CT) images or alizarin red S-stained specimens, respectively. BE and PD were compared (1) between different developmental stages, and further, to detect abnormalities in the data sets and to evaluate the deviation from normal development in mouse fetuses, (2) at embryonic day (E) 18.5 between the normal and deformed mandibles, the latter being caused by suturing the jaw at E15.5, (3) at E15.5 and E18.5 between normal and knockout mutant mice of receptor tyrosine kinaselike orphan receptor (Ror) 2. In mice, BE and PD were large during the prenatal period and small after postnatal day 3, suggesting that the mandibular shape changes rapidly during the prenatal and early postnatal periods. In humans, BE of the mandibles peaked at 16-19 weeks of gestation, suggesting the time-dependent change in the mandibular shape. TPS and Procrustes analyses statistically separated the abnormal mandibles of the sutured or Ror2 mutant mouse fetuses from the normal mandible. These results suggest that TPS and Procrustes analyses are useful for assessing the morphogenesis and deformity of the mandible. Anat Rec, 295:313-327, 2012 The mammalian mandible is a complex morphological structure formed by various morphogenetic components of different embryological origins. These morphogenetic components were assembled during development to form the final structure (Atchley, 1993). The mandible originates from cells of the neural crest that migrate to the first mandibular arch and form the embryonic mesenchyme, which later develops into skeletal, dental, and connective tissues. The mesenchymal cells aggregate and produce condensations before undergoing differentiation to produce the morphogenetic components of the mandible (Atchley and Hall, 1991). The mandible consists of two symmetrical halves (right and left), each formed by a dentary bone with four morphogenetic regions: the mandibular body (ramus) and three processes (coronoid, condylar, and angular).Establishing normative expectations for experimentally induced changes in size and shape will be an important innovation in three-dimensional (3-D) micro-computed tomography (CT)-based morphological assessments, especially in quantifying differences in the values of those parameters between sets of developing mandibles as a primary aim. Nondestructive methods such as micro-magnetic resonance imaging (Pieles et al., 2007) and micro-CT (Johnson et al., 2006;Boughner et al., 2008;Nagase et al., 2008;Parsons et al., 2008;Hallgrimss...

Statistical analyses in trials for the comprehensive understanding of organogenesis and histogenesis in humans and mice

“…To examine the deformation of 2D morphology in biological structures, the minimized total BE can be used as an index because the minimized BE represents the minimized curvature of the plate (35), therefore, the thin-plate spline can be useful to compare the morphological difference during organ development between two developmental stages or two individuals. A difference in mandible shape could be detected between Ror2-knockout and heterozygous or wildtype mice at E18.5 using BE, while BE revealed no difference between the Ror2 heterozygous and wildtype mice, which have similar morphology (36). The thin-plate spline is also used for registration between the medical images by selection of the landmarks, i.e.…”

“…Similarly, the Procrustes distance is the sum of the squared distances between corresponding landmarks on the images, and can be used to examine the shape difference by comparing the configurations of the landmarks between two structures (35,36).…”

Micro‐computed tomography imaging and analysis in developmental biology and toxicology

“…Various anatomical components of the mouse embryo head have been examined after staining with OT and embedding in paraffin; these being the trigeminal ganglion (Aoyagi et al, ) and Meckel's cartilage (Aoyagi et al, ). A highly detailed mathematical analysis of mandibular shape in fixed GD 14.5–18.5 embryos from wild‐type and knockout mice of receptor tyrosine kinase‐like orphan receptor 2 showed that these mandibles could be separately identified (Rafiq et al, ). In another knockout mouse for a protein kinase A regulatory subunit ( Prkar1a ), micro‐CT showed qualitative and quantitative changes in the neural crest‐derived bones of the face on GD 17.5 (Jones et al, ).…”