Craniofacial and Dental Defects in the Col1a1 Jrt/+ Mouse Model of Osteogenesis Imperfecta

Abstract

Certain mutations in the COL1A1 and COL1A2 genes produce clinical symptoms of both osteogenesis imperfecta (OI) and Ehlers-Danlos syndrome (EDS) that include abnormal craniofacial growth, dental malocclusion, and dentinogenesis imperfecta. A mouse model (Col1a1^Jrt/+) was recently developed that had a skeletal phenotype and other features consistent with moderate-to-severe OI and also with EDS. The craniofacial phenotype of 4- and 20-wk-old Col1a1^Jrt/+ mice and wild-type littermates was assessed by micro–computed tomography (µCT) and morphometry. Teeth and the periodontal ligament compartment were analyzed by µCT, light microscopy/histomorphometry, and electron microscopy. Over time, at 20 wk, Col1a1^Jrt/+ mice developed smaller heads, a shortened anterior cranial base, class III occlusion, and a mandibular side shift with shorter morphology in the masticatory region (maxilla and mandible). Col1a1^Jrt/+ mice also had changes in the periodontal compartment and abnormalities in the dentin matrix and mineralization. These findings validate Col1a1^Jrt/+ mice as a model for OI and EDS in humans.

Keywords

Ehlers-Danlos syndrome craniofacial abnormalities bone bone development tooth calcification dentin

Introduction

Osteogenesis imperfecta (OI) is a hereditary disorder of connective tissue with a cumulative incidence of 1 in 20,000 (Rauch and Glorieux 2004). OI is caused by dominant mutations affecting collagen α chains (COL1A1 and COL1A2), which in the most severe forms of OI typically arise de novo. Recessive mutations affecting other genes such as CRTAP, LEPRE, PPIB, SERPINF1, and FKBP10 are found in a small subset of patients (Sillence et al. 1979; Cabral et al. 2005; van Dijk et al. 2009; Homan et al. 2011; Kelley et al. 2011). Patients with OI typically suffer from bone fragility and muscle weakness and have blue sclera and hearing loss (Rauch and Glorieux 2004). More specifically, patients with OI types III and IV suffer from severe cranial growth impairment (Chang et al. 2007), malocclusion, and various facial profile alterations (Rizkallah et al. 2013). OI type III, in particular, is characterized by a triangular shape of the face, attributable to a small chin and wide malar bones.

Ehlers-Danlos syndrome (EDS) is also a hereditary connective tissue disorder with an incidence of 1 in 5,000 (Pyeritz 2000). EDS results from mutations affecting the COL1A1 and COL1A2 genes—the same genes affected in the dominant form of OI—as well as from gene mutations in ADAMTS2, COL2A1, COL5A1, COL5A2, and PLOD1 (Wenstrup et al. 1996; Richards et al. 1998; Plancke et al. 2009). Characteristic of patients with EDS are skin hyperextensibility and joint hypermobility (Pyeritz 2000), including repeated laxation of the temporomandibular joint. In the dentition and the periodontium, there is hypoplasia of tooth enamel, short and deformed tooth roots, and fragile gingiva and periodontitis that may lead to premature tooth loss (Létourneau et al. 2001; Ancillao et al. 2012).

Certain mutations in the COL1A1 and COL1A2 genes produce clinical symptoms of both OI and EDS, where patients present with abnormal craniofacial growth, dental malocclusion, and dentinogenesis imperfecta (Norton and Assael 1997; Cabral et al. 2005; Waltimo-Siren et al. 2005; Chang et al. 2007; De Coster et al. 2007; Rizkallah et al. 2013). Recently, a mouse model generated by the N-ethyl-N-nitrosourea–induced mutation approach has been described as reflecting combined OI and EDS (Col1a1^Jrt/+) (Chen et al. 2014). These mice have markedly decreased deposition of collagen type I by osteoblasts as well as increased bone turnover and increased bone density at the material level (Roschger et al. 2014). These bone tissue abnormalities are also present in patients with severe OI (Rauch et al. 2000; Roschger et al. 2008). The mutant mouse phenotype includes spontaneous fractures, joint and skin hyperlaxity, and increased spinal curvature, which also are features found in humans with severe OI and EDS (Chen et al. 2014). The Col1a1^Jrt/+ mouse thus provides a tool for exploring aspects of both OI and EDS (and of combined OI-EDS) pathophysiology and treatment (Chen et al. 2014).

Given the similarities between the cellular and bone tissue characteristics of the Col1a1^Jrt/+ mouse and severe OI in humans (Chen et al. 2014), we hypothesized that craniofacial abnormalities are present in this mouse model, as they are in severe human OI.

Materials and Methods

Mice

Animal procedures were approved by the Animal Care Committee of McGill University. Col1a1^Jrt/+ mutant mice and their wild-type (+/+) littermates were generated as described previously (Chen et al. 2014). Heads were collected at 4 and 20 wk of age and fixed in 95% ethanol for micro–computed tomography (µCT) or with an aldehyde solution for histology.

µCT

Heads from Col1a1^Jrt/+ and +/+ littermates (4 wk: n = 5 each; 20 wk: n = 10 each) were scanned by µCT (SkyScan Model 1072; Bruker MicroCT, Kontich, Belgium) with settings at 55 kV and 180 µA and using a 0.5 mm–thick aluminum filter of 0.5-mm thickness. Software-reconstructed images were used to measure the Angle occlusion classification based on the relative positions of mandibular and maxillary molars (Perlyn et al. 2006; Laurita et al. 2011) and side shift of the mandible relative to the maxilla (Nakamura et al. 2013). Craniofacial, maxillary, and mandibular bones were assessed by measuring 20 established morphometric distances using DataViewer software (Bruker MicroCT) (Perlyn et al. 2006; de Carlos et al. 2008; Laurita et al. 2011; Saito et al. 2011; Nakamura et al. 2013). Angular measurements were made to assess the relation of the maxilla and mandible relative to the skull base and skull vault and to assess the morphology of the mandible (gonial angle) using ImageJ software (National Institutes of Health, Bethesda, MD, USA) (Simon et al. 2014). Measurements were taken from recognizable anatomic landmarks on 3-dimensional digitized images (Fig. 1A, Appendix Table); these landmarks are those used for standard orthodontic cephalometry in humans (Burkhardt et al. 2003; Simon et al. 2014).

Figure 1.

Craniofacial dysmorphology in Col1a1^Jrt/+ mice. (A) Illustrations showing the landmarks used for linear and angular measurements (Table, Appendix Table) of mouse heads obtained by micro–computed tomography (µCT). Representative µCT images of 4-wk-old (B) and 20-wk-old (C) wild-type and Col1a1^Jrt/+ mice showing Angle class I occlusion and no mandibular side shift in wild-type mice, whereas the Col1a1^Jrt/+ mice have Angle class III occlusion with a mandibular side shift.

Reconstructed images were also used to assess differences in periodontal and dental tissues in 20-wk-old Col1a1^Jrt/+ mice versus +/+ littermates. A region of interest was selected that included the lower incisor, starting from the occlusal surface of the entire first molar to the inferior edge of the mandible. Periodontal space volume/tooth volume (P.V/To.V) and mineralized dentin volume/tooth volume (mD.V/To.V) of the incisor, as well as the pulp, mineralized dentin, and enamel volume of the molars, were measured using CTAn Version 3.0 (Bruker MicroCT). The periodontal space/compartment was defined as the area between the incisor tooth (starting from the cementoenamel junction) and the alveolar bone.

Light Microscopy and Transmission Electron Microscopy (TEM)

Mandibles from three 20-wk-old Col1a1^Jrt/+ mice and from 3 +/+ littermates were dissected, fixed in aldehyde, decalcified in EDTA, post-fixed with osmium tetroxide, dehydrated, and embedded in Epon epoxy resin (Cedarlane, Burlington, ON, Canada).

For light microscopy, images of 4 toluidine blue–stained cross-sections of each hemimandible at the level of the first molar were obtained from each mouse and analyzed histomorphometrically using ImageJ software (National Institutes of Health). Histomorphometry included P.V/To.V, blood vessel number (BldV.N), and blood vessel cross-sectional area (BldV.A). To reduce the uncertainty of misidentifying small cross-sectioned profiles in the periodontal compartment, only larger blood vessels that had cross-sectional areas greater than 500 µm in one dimension were included in the analysis. Also measured were mD.V/To.V and predentin volume/mineralized dentin volume (preD.V/mD.V). Mineralized dentin can be readily distinguished in histological sections from unmineralized predentin in decalcified samples because of increased toluidine blue staining in mineralized dentin attributable to noncollagenous protein accumulation after binding to minerals.

TEM images of 80 nm–thick sections cut on an ultramicrotome were stained with uranyl acetate and lead citrate and viewed using a Tecnai 12 transmission electron microscope (FEI, Hillsboro, OR, USA) operating at 120 kV.

Statistical Analyses

Craniofacial, periodontal, and dental measurements were reported as mean ± standard deviation. Data were assessed for normal distribution using the Shapiro-Wilk test and for homogeneity of the variance using the Levene test. Differences between groups (Col1a1^Jrt/+ mice v. +/+ littermates) were assessed using the Student’s 2-tailed unpaired t test, modified 2-tailed unpaired t test (with Welch correction), or Mann-Whitney U test. Origin 7.0 software (OriginLab, Northampton, MA, USA) and SPSS 23 software (IBM SPSS, Chicago, IL, USA) were used for statistical analyses. In all experiments, P < 0.05 was considered significant (indicated by an asterisk).

Results

Craniofacial, maxillary, and mandibular morphometric measurements of Col1a1^Jrt/+ mice and +/+ littermates were obtained at 4 and 20 wk of age. At both time points, morphometric measurements revealed that the Col1a1^Jrt/+ mice had generally smaller heads, which correlated with their visibly smaller body size (Chen et al. 2014) (Table).

Table.

Morphometric Measurements in Length (mm) of Craniofacial, Maxillary, and Mandibular Bones in 4- and 20-wk-Old Col1a1^Jrt/+ Mice and +/+ Littermates.

	4 wk^a		20 wk^b
Measurement	+/+	Col1a1^Jrt/+	+/+	Col1a1^Jrt/+
Craniofacial
Cranial length (Cr.L)	21.5 ± 0.5	20.9 ± 0.6	23.6 ± 0.4	22.9 ± 0.4^c
Anterior cranial base length (An.Cr.B.L)	5.5 ± 0.2	4.5 ± 0.3^c	6.4 ± 0.2	5.6 ± 0.2^c
Skull height (S.H)	8.6 ± 0.5	8.0 ± 0.4	10.3 ± 0.6	9.8 ± 0.5^c
Internasal distance (Inter-N.D)	3.1 ± 0.2	3.0 ± 0.2	3.4 ± 0.1	3.3 ± 0.2
Interorbitary distance (Inter-O.D)	4.2 ± 0.2	4.1 ± 0.2	4.3 ± 0.1	4.2 ± 0.1
Interzygomatic distance (Inter-Z.D)	12.1 ± 0.2	11.7 ± 0.2^c	12.4 ± 0.3	12.1 ± 0.3^c
Bitemporal distance (Inter-T.D)	10.5 ± 0.2	10.5 ± 0.4	10.8 ± 0.4	10.4 ± 0.2^c
Maxillary
Maxillary length (Mx.L)	10.8 ± 0.2	10.2 ± 0.4	11.8 ± 0.3	11.5 ± 0.2^c
Palatine length (P.L)	12.2 ± 0.4	11.5 ± 0.4^c	14.2 ± 0.3	13.5 ± 0.1^c
Anterior cranial height (An.Cr.H)	2.2 ± 0.1	2.2 ± 0.1	2.8 ± 0.1	2.7 ± 0.1
Upper incisor height (U.I.H)	3.3 ± 0.1	3.2 ± 0.2	4.0 ± 0.1	3.9 ± 0.2
Intermolar distance (Mx.M.D)	3.7 ± 0.1	3.7 ± 0.1	3.9 ± 0.1	3.6 ± 0.1^c
Position relative to skull base (Pr-E-So)	105.8 ± 3.1	107.2 ± 3.7	113.4 ± 1.5	105.0 ± 2.2^c
Position relative to skull vault (Pr-E-OIS)	136.2 ± 2.5	138.4 ± 2.3	150.0 ± 2.2	143.6 ± 1.9^c
Position relative to skull vault (Bu-E-OIS)	129.0 ± 2.5	131.4 ± 2.9	137.2 ± 1.1	132.6 ± 2.7^c
Mandibular
Effective mandibular length (Ef.Mn.L)	10.2 ± 0.3	9.3 ± 0.3^c	11.2 ± 0.2	10.4 ± 0.2^c
Mandibular plain (Mn.P)	9.4 ± 0.3	8.1 ± 0.5^c	10.5 ± 0.2	9.4 ± 0.2^c
Mandibular axis (Mn.Ax)	4.1 ± 0.1	3.9 ± 0.2	5.2 ± 0.2	4.5 ± 0.3^c
Lower incisor height (L.I.H)	4.1 ± 0.1	4.1 ± 0.1	4.5 ± 0.1	4.5 ± 0.1
Anterior mandibular height (An.Mn.H)	2.1 ± 0.1	2.1 ± 0.1	2.1 ± 0.1	2.2 ± 0.1
Ascending ramus length (As.R.L)	5.0 ± 0.1	4.3 ± 0.3^c	5.8 ± 0.1	5.3 ± 0.2^c
Posterior mandibular height (Po.Mn.H)	4.6 ± 0.2	4.1 ± 0.3^c	4.9 ± 0.2	4.5 ± 0.3^c
Intermolar distance (Mn.M.D)	3.6 ± 0.1	3.6 ± 0.1	3.9 ± 0.1	3.7 ± 0.1^c
Position relative to skull base (Id-E-So)	57.0 ± 1.9	53.2 ± 4.8	60.3 ± 0.9	59.0 ± 1.7
Gonial angle (Co-Go-Me)	82.4 ± 4.2	83.0 ± 1.9	87.7 ± 2.2	91.8 ± 2.5^c

Data are shown as mean ± standard deviation.

P value was calculated using the Mann-Whitney U test (n = 5 for each group).

P value was calculated using a 2-sample t test (n = 10 for each group).

P < 0.05.

At 4 wk, Col1a1^Jrt/+ mice had a shorter anterior cranial base length, interzygomatic distance, palatine length, effective mandibular length, mandibular plain, ascending ramus length, and posterior mandibular height as compared to +/+ littermates (Fig. 1, Table, and Appendix Table). The remainder of the morphometric values was similar between age-matched groups. Three-dimensional reconstructions of µCT images revealed that 2 out of 5 Col1a1^Jrt/+ mice presented with Angle class III occlusion with mandibular dentition positioned mesially in relation to maxillary dentition, whereas +/+ littermates had normal Angle class I occlusion (Fig. 1B). Angular measurements indicated that both the 4-wk-old Col1a1^Jrt/+ mice and their +/+ littermates had no significant differences between groups in terms of the positions of the maxilla and mandible relative to the skull base and skull vault. Gonial angle readings were also similar, indicating similar mandibular morphology.

At 20 wk, Col1a1^Jrt/+ mice had a more severe phenotype, where again the heads were shorter in cranial length, anterior cranial base length, interzygomatic distance, and intertemporal distance compared to +/+ littermates (Fig. 1, Table, and Appendix Table). Maxillary measurements showed reductions in maxillary length, palatine length, and distance between the right and left first molar in Col1a1^Jrt/+ mice, and the mandibles showed decreased effective mandibular length, plain, and axis and ascending ramus length, posterior mandibular height, and distance between the right and left first molar. All (n = 10) Col1a1^Jrt/+ mice presented with Angle class III occlusion, whereas +/+ littermates had normal Angle class I occlusion (Fig. 1C). In addition, 7 out of 10 Col1a1^Jrt/+ mice at 20 wk had a mandibular side shift (randomly, to either side) compared to their normal littermates. As determined from angular measurements, the 20-wk-old Col1a1^Jrt/+ mice had a retrognathic maxilla relative to the skull base and skull vault compared to their +/+ littermates. Angular measurements of the mandible indicated that both age-matched groups had a normal position of the mandible relative to the skull base. These findings are in agreement with the Angle class III occlusion seen in 20-wk-old Col1a1^Jrt/+ mice compared to the Angle class I occlusion of their +/+ littermates. Gonial angles were higher in 20-wk-old Col1a1^Jrt/+ mice compared to their +/+ littermates, indicating an alteration of the mandible in 20-wk-old Col1a1^Jrt/+ mice.

The periodontal compartment was assessed by µCT in both 4- and 20-wk-old mice, where at both ages the Col1a1^Jrt/+ mice had a wider periodontal ligament space associated with the incisor as compared to +/+ littermates (Fig. 2A–F). Histomorphometry at 20 wk confirmed the increase in this compartment size, which was accompanied by an increase in BldV.N and BldV.A (Fig. 2G–K).

Figure 2.

Widened periodontal space compartment in Col1a1^Jrt/+ mice. Micro–computed tomography (µCT) cross-sectional images of 4-wk-old (A, B) and 20-wk-old (D, E) hemimandibles of representative samples from wild-type (+/+) and Col1a1^Jrt/+ mice. (C, F) Quantitative µCT demonstrates that the periodontal space volume/tooth volume (P.V/To.V) of the incisor is greater in Col1a1^Jrt/+ mice compared to +/+ mice in both age groups. (G, H) Toluidine blue–stained histology sections of the 2 samples shown in D and E, respectively. (I) In agreement with the µCT analyses, histomorphometry confirms the widening of the periodontal space compartment (P.V/To.V) in Col1a1^Jrt/+ mice compared to +/+ littermates. (J, K) In comparison to +/+ littermates, the increase in the periodontal space of the lower incisor in Col1a1^Jrt/+ mice is associated with an increase in the blood vessel number (BldV.N) and blood vessel cross-sectional area (BldV.A, µm²), with major vessels outlined in red in the histology sections (D, E). P, periodontal space compartment; To, incisor tooth. Data are mean ± standard deviation (n = 10). *P < 0.05.

µCT of the lower incisors of 20-wk-old Col1a1^Jrt/+ and +/+ mice (Fig. 3A–D) showed lower mD.V/To.V in the incisors of the mutant mice. For the molars, a similar decrease in mD.V/To.V was observed (mutant: 0.61 ± 0.01 standard error of the mean [SEM] v. wild-type: 0.66 ± 0.03 SEM; P < 0.05), and overall, molar size was smaller in the mutant mice (mutant: 1.43 ± 0.07 mm³ SEM v. wild-type: 1.66 ± 0.02 mm³ SEM; P < 0.05) (Appendix Fig. 1). In the incisors, by light microscopy, a zone of defective dentin mineralization was identified (as detected by decreased toluidine blue staining) that was most commonly found in the central portion of the crown-analog incisor dentin; histomorphometry confirmed a mineralization defect in incisor dentin of the mutant mice (Fig. 3H), which had a larger volume of unmineralized predentin compared to +/+ littermates (Fig. 3A–L). No overt differences were found for temporomandibular joint histology (Appendix Fig. 2).

Figure 3.

Dentin defect in 20-wk-old Col1a1^Jrt/+ mice. (A–C) Micro–computed tomography (µCT) cross-sectional images of the lower incisors of representative samples from +/+ littermates and Col1a1^Jrt/+ mice show a dentin mineralization defect (asterisk) in the mutant mice. (D) Quantification by µCT indicates that the incisor tooth of Col1a1^Jrt/+ mice has lower mineralized dentin volume/tooth volume (mD.V/To.V) compared to +/+ littermates. (E–G) Light microscopy of the same regions shown in A to C after sample decalcification confirms the dentin defect (asterisks/dashed line) in Col1a1^Jrt/+ mice. (H) Histomorphometry of the sections confirms the dentin defect (asterisks/dashed line) in Col1a1^Jrt/+ mice, where lower mD.V/To.V is observed. (I–K) Higher magnification of the regions shown in E to G showing the lack of mineralization (increased predentin [PD]) in some areas (asterisk) of the lower incisor in Col1a1^Jrt/+ mice. (L) Histomorphometry of the sections confirms the dentin defect (asterisks/dashed line) in Col1a1^Jrt/+ mice, where lower predentin volume/mineralized dentin volume (preD.V/mD.V) is observed. Data are mean ± standard deviation (n = 10). *P < 0.05. Den, dentin; En, Enamel; EnS, enamel space after decalcification of the sample.

TEM of the dentin defect revealed a generalized layering phenomenon in the ultrastructure of dentin, where electron-dense, variably spaced protein-rich bands of the dentin extracellular matrix alternated with lighter regions of the matrix (Fig. 4A). A wider band of an increased-density matrix was found at the boundary of predentin and dentin, with the electrons denser extending out into predentin along individual and separated collagen fibril tracks, and collagen fibrils appeared smaller in diameter (Fig. 4B, C). In surrounding intramembranous alveolar bone observed by TEM, the collagen fibril diameter also appeared smaller, but no other obvious differences in bone histology were observed (Fig. 4D, E).

Figure 4.

Transmission electron microscopy of abnormal dentin and bone ultrastructure in Col1a1^Jrt/+ mice. (A, B) Col1a1^Jrt/+ mice have an abundant collagenous dentin matrix (Den), but with readily apparent abnormalities in dentin as compared to wild-type mice (C). The abnormalities appear as a series of sequential electron-dense layers/bands (asterisks) in the mineralized dentin region and as a widened and irregular electron-dense mineralization front at the predentin (PD)–dentin (bracket) junction. In these teeth in which mineral is no longer present because of the sample preparation decalcification procedure used prior to sectioning, the increased electron density arises from increased stained organic content, here considered to represent increased noncollagenous protein accumulating at these abnormal sites. Here, such staining frequently associates with isolated smaller collagen fibrils extending well into predentin (arrows) and with a widened mineralization front (brackets). (D, E) Similarly as in predentin, in the osteoid (Os), collagen fibrils in the mutant mice were smaller in diameter in the surrounding intramembranous alveolar bone than in their wild-type littermates, but no other obvious differences in the bone ultrastructure were noted. MM, mineralized matrix region (here decalcified); Ob, osteoblast; OP, odontoblast process.

Discussion

Collagen secretion and assembly are integral parts of mineralized tissue cell activity in which the Col1a1 promoter has a modular design used for stage-specific gene expression (Dacic et al. 2001). In this study, we report on alterations in the craniofacial phenotype and tooth dentin in a recently developed mouse model (the Col1a1^Jrt/+ mouse) (Chen et al. 2014) having a dominant mutation in the Col1a1 gene, which results in features of OI and EDS. We show that, over time, Col1a1^Jrt/+ mice present class III dental occlusion; a mandibular side shift; and short craniofacial, maxillary, and mandibular morphometric indices. We also show that Col1a1^Jrt/+ mice develop a wider periodontal space with changes in its vascularization and abnormalities in the dentin structure and mineralization as compared to their normal littermates.

When first reported (Chen et al. 2014), it was described that the Col1a1^Jrt/+ mouse model reflects the moderate-to-severe types of OI classification: OI types III and IV. Our finding of craniofacial abnormalities in this model is similar to those reported in humans with severe OI (Waltimo-Siren et al. 2005; Chang et al. 2007; Rizkallah et al. 2013), where a concave triangular facial profile was described and where a detailed cephalometric radiographic analysis of 29 adults with OI types III and IV revealed deficiencies in the anterior cranial base as well as shorter maxillary, palatine, and mandibular lengths compared to age- and sex-matched controls (Waltimo-Siren et al. 2005). Despite the shortened mandible, its relative anterior position to the maxilla in these patients is attributed to bending of the cranial base and closing (anti-clockwise) growth rotation of the mandible, leading to the class III dental occlusion pattern that is characteristic of severe OI. The results of our study indicate that Col1a1^Jrt/+ mice have a similar occlusion pattern to that seen in patients with OI types III and IV, with the maxilla retruded in relation to the cranial base. While some changes were observed at 4 wk of age, the mutant mouse phenotype was much more prominent at 20 wk of age. This is likely mainly related to the relative timing of growth processes that occur after 4 wk since the ontogenic trajectories for the growth of craniofacial bones variably continue well beyond this time (Gonzalez et al. 2013). More specifically for the mandible, we did observe linear length changes at 4 wk of age, despite the fact that this particular bone has reached almost 95% of its adult size at this time (Swiderski and Zelditch 2013). Thus, the substantially greater changes observed at 20 wk of age in both linear and angular measurements arising from alterations in the continued developmental growth processes of various craniofacial bones in growing Col1a1^Jrt/+ mice suggest additional functional/biomechanical contributions to the phenotype. The latter possibility is supported by studies showing changes in the mandibular morphology of mice fed a soft food diet (Renaud et al. 2010) and in edentulous p63 mutant mice missing teeth (thus, having no biomechanical forces from tooth occlusion) (Paradis et al. 2013).

We also observed a functional mandibular side shift in the older (20 wk) Col1a1^Jrt/+ mice, similar to what was reported in a recent clinical study (Ierardo et al. 2015). The functional mandibular side shift in Col1a1^Jrt/+ mice might result from the disproportion between the widths of intermaxillary molars and intermandibular molars relative to +/+ littermates. Thus, it seems that the Col1a1^Jrt/+ mice adopt a shifted mandible position to provide for better occlusion between maxillary and mandibular molars to chew food more efficiently (Rizkallah et al. 2013). A mandibular side shift might also occur in the Col1a1^Jrt/+ mice because of temporomandibular joint laxity and hypermobility, a symptom commonly found in patients with EDS (Ancillao et al. 2012).

We show here that the bones of the masticatory complex (maxilla and mandible) were severely affected in the older Col1a1^Jrt/+ mice; in patients, this results in the “triangular face” characteristic of patients with OI (Chang et al. 2007). Based on our findings here in mice, this feature in humans is most likely related to defective developmental growth patterns and/or (although in our opinion less likely) to the biomechanical effects of loading produced from chewing cycles (occlusion) on growth patterns of bone (Paschetta et al. 2010). Indeed, bone growth can be controlled by both genetic and environmental stimuli (Hallgrimsson et al. 2007), and in the latter case, biomechanical masticatory forces play a major role in directing maxillary and mandibular growth (Corruccini and Beecher 1982; von Cramon-Taubadel 2011). Since the bone of Col1a1^Jrt/+ mice is of low quality and friable (Chen et al. 2014), it seems reasonable to consider that biomechanical loading from altered chewing cycles might indeed negatively influence maxillary and mandibular bone growth.

The Col1a1^Jrt/+ mice have a widened periodontal ligament space, a phenomenon that is often seen when occlusal forces exceed the adaptive capacity of periodontal tissue (traumatic occlusion) (Newmann et al. 2003). Widening in the periodontal space can be caused by fluctuations in compression and tension of the periodontal ligament, resulting in resorption of adjacent alveolar bone. While likely not connected to the jaw phenotype, but since Col1a1^Jrt/+ mice have low bone quality (Chen et al. 2014), normal physiological biting forces are likely traumatic to the periodontium in the Col1a1^Jrt/+ mice. The increase that we observed in BldV.N and BldV.A might be related to a reparative feedback mechanism to increase vascularization and local metabolism rates in an attempt to overcome widening of the periodontal ligament caused by abnormal occlusion.

The Col1a1^Jrt/+ mice have focal regions of increased predentin thickness associated with a defect in tooth mineralization, as occurs in dentinogenesis imperfecta in patients with OI type IV (Koreeda-Miura et al. 2003). Besides these focal, wide-tract defects in mineralization occurring deep within dentin, the banding pattern also observed by TEM in decalcified sections was evidence of repeated cycles of abnormal irregular mineralization. The banded patterns demarcated by cyclic accumulation of noncollagenous proteins as lines/planes within dentin indicate intermittent “stop and go”–type mineralization rather than the continuous gradual process that is thought normally to occur. The mineralization front also showed an abnormal accumulation of electron-dense (stained) material that associated with smaller collagen fibrils. Immunohistochemical studies have shown abundant plasma fibronectin in dentin of patients with OI (Lukinmaa 1988); however, the dense material that we observed seems more likely to be an accumulation of noncollagenous dentin matrix proteins (and possibly small proteoglycans) regulating mineralization and secreted locally by odontoblasts. As reported for endochondral bone (Chen et al. 2014), we also observed here smaller collagen fibril diameters by TEM in intramembranous alveolar bone, consistent with the notion proposed by Chen et al. (2014) that the incorporation of mutant collagen molecules into the fibrils, along with other fibril size–limiting factors, might lead to the decreased quality and mechanical properties of the mutant bone.

In conclusion, in the absence of obvious changes in temporomandibular joint growth and morphology, Col1a1^Jrt/+ mice over time developed smaller heads, a shortened anterior cranial base, class III occlusion, and evidence of a mandibular side shift. In addition, Col1a1^Jrt/+ mice had changes in the periodontal compartment and abnormalities in the dentin matrix and mineralization. These findings validate Col1a1^Jrt/+ mice as a model for OI and EDS in humans.

Author Contributions

H. Eimar, contributed to conception, design, data acquisition, analysis, and interpretation, drafted and critically revised the manuscript; F. Tamimi, F. Rauch, contributed to conception, design, data analysis, and interpretation, critically revised the manuscript; J.-M. Retrouvey, contributed to conception, design, and data interpretation, critically revised the manuscript; J.E. Aubin, contributed to conception, data analysis, and interpretation, critically revised the manuscript; M.D. McKee, contributed to conception, design, data acquisition, analysis, and interpretation, critically revised the manuscript. All authors gave final approval and agree to be accountable for all aspects of the work.

Footnotes

Acknowledgements

The authors thank Yu Ling Zhang, Sami Abdullah, and Lydia Malynowsky for technical support. Drs. Tamimi, Retrouvey, and McKee are members of the FRQ-S Network for Oral and Bone Health Research.

This work was supported by the Canadian Institutes of Health Research, the Natural Sciences and Engineering Research Council of Canada, the Fondation de l’Ordre des Dentistes du Québec, and the Fonds de la Recherche du Québec-Santé.

The authors declare no potential conflicts of interest with respect to the authorship and/or publication of this article.

A supplemental appendix to this article is published electronically only at .

References

Ancillao

Galli

Celletti

Castori

Albertini

Camerota

. 2012. Temporomandibular joint mobility in adult females with Ehlers-Danlos syndrome, hypermobility type (also known as joint hypermobility syndrome). J Cranio Max Dis. 1(2):88–94.

Burkhardt

McNamara

Jr. Baccetti

. 2003. Maxillary molar distalization or mandibular enhancement: a cephalometric comparison of comprehensive orthodontic treatment including the pendulum and the herbst appliances. Am J Orthod Dentofacial Orthop. 123(2):108–116.

Cabral

Makareeva

Colige

Letocha

Yeowell

Pals

Leikin

Marini

. 2005. Mutations near amino end of alpha1(I) collagen cause combined osteogenesis imperfecta/Ehlers-Danlos syndrome by interference with n-propeptide processing. J Biol Chem. 280(19):19259–19269.

Chang

Lin

Hsu

. 2007. The craniofacial characteristics of osteogenesis imperfecta patients. Eur J Orthod. 29(3):232–237.

Chen

Guo

Itoh

Moreno

Rosenthal

Zappitelli

Zirngibl

Flenniken

Cole

Grynpas

. 2014. First mouse model for combined osteogenesis imperfecta and Ehlers-Danlos syndrome. J Bone Miner Res. 29(6):1412–1423.

Corruccini

Beecher

. 1982. Occlusal variation related to soft diet in a nonhuman primate. Science. 218(4567):74–76.

Dacic

Kalajzic

Visnjic

Lichtler

Rowe

. 2001. Col1a1-driven transgenic markers of osteoblast lineage progression. J Bone Miner Res. 16(7):1228–1236.

de Carlos

Varela

Germanà

Montalbano

Freije

Vega

López-Otin

Cobo

. 2008. Microcephalia with mandibular and dental dysplasia in adult zmpste24-deficient mice. J Anat. 213(5):509–519.

De Coster

Cornelissen

De Paepe

Martens

Vral

. 2007. Abnormal dentin structure in two novel gene mutations [COL1a1, Arg134Cys] and [ADAMTS2, Trp795-to-ter] causing rare type I collagen disorders. Arch Oral Biol. 52(2):101–109.

10.

Gonzalez

Kristensen

Morck

Boyd

Hallgrimsson

. 2013. Effects of growth hormone on the ontogenic allometry of craniofacial bones. Evol Dev. 15(2):133–145.

11.

Hallgrimsson

Lieberman

Liu

Ford-Hutchinson

Jirik

. 2007. Epigenetic interactions and the structure of phenotypic variation in the cranium. Evol Dev. 9(1):76–91.

12.

Homan

Rauch

Grafe

Lietman

Doll

Dawson

Bertin

Napierala

Morello

Gibbs

. 2011. Mutations in SERPINF1 cause osteogenesis imperfecta type VI. J Bone Miner Res. 26(12):2798–2803.

13.

Ierardo

Calcagnile

Luzzi

Ladniak

Bossu

Celli

Zambrano

Franchi

Polimeni

. 2015. Osteogenesis imperfecta and rapid maxillary expansion: report of 3 patients. Am J Orthod Dentofacial Orthop. 148(1):130–137.

14.

Kelley

Malfait

Bonafe

Baldridge

Homan

Symoens

Willaert

Elcioglu

Van Maldergem

Verellen-Dumoulin

. 2011. Mutations in FKBP10 cause recessive osteogenesis imperfecta and Bruck syndrome. J Bone Miner Res. 26(3):666–672.

15.

Koreeda-Miura

Onishi

Ooshima

. 2003. Significance of histopathologic examination in the diagnosis of dentin defects associated with type iv osteogenesis imperfecta: two case reports. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 95(1):85–89.

16.

Laurita

Koyama

Chin

Taylor

Lakin

Hankenson

Bartlett

Nah

H-D

. 2011. The muenke syndrome mutation (FGFR3p244r) causes cranial base shortening associated with growth plate dysfunction and premature perichondrial ossification in murine basicranial synchondroses. Dev Dyn. 240(11):2584–2596.

17.

Létourneau

Pérusse

Buithieu

. 2001. Oral manifestations of Ehlers-Danlos syndrome. J Can Dent Assoc. 67(6):330–334.

18.

Lukinmaa

. 1988. Immunofluorescent localization of type III collagen and the N-terminal propeptide of type III procollagen in dentin matrix in osteogenesis imperfecta. J Craniofac Genet Dev Biol. 8(3):235–243.

19.

Nakamura

Zeredo

Utsumi

Fujishita

Koga

Yoshida

. 2013. Influence of malocclusion on the development of masticatory function and mandibular growth. Angle Orthod. 83(5):749–757.

20.

Newmann

Takei

Carranza

editors. 2003. Clinical periodontology. Philadelphia: WB Saunders Co.

21.

Norton

Assael

. 1997. Orthodontic and temporomandibular joint considerations in treatment of patients with Ehlers-Danlos syndrome. Am J Orthod Dentofacial Orthop. 111(1):75–84.

22.

Paradis

Raj

Boughner

. 2013. Jaw growth in the absence of teeth: the developmental morphology of edentulous mandibles using the p63 mouse mutant. Evol Dev. 15(4):268–279.

23.

Paschetta

de Azevedo

Castillo

Martinez-Abadias

Hernandez

Lieberman

Gonzalez-Jose

. 2010. The influence of masticatory loading on craniofacial morphology: a test case across technological transitions in the Ohio valley. Am J Phys Anthropol. 141(2):297–314.

24.

Perlyn

DeLeon

Babbs

Govier

Burell

Darvann

Kreiborg

Morriss-Kay

. 2006. The craniofacial phenotype of the crouzon mouse: analysis of a model for syndromic craniosynostosis using three-dimensional microct. Cleft Palate Craniofac J. 43(6):740–748.

25.

Plancke

Holder-Espinasse

Rigau

Manouvrier

Claustres

Van Kien

. 2009. Homozygosity for a null allele of COL3a1 results in recessive Ehlers-Danlos syndrome. Eur J Hum Genet. 17(11):1411–1416.

26.

Pyeritz

. 2000. Ehlers-Danlos syndrome. N Engl J Med. 342(10):730–732.

27.

Rauch

Glorieux

. 2004. Osteogenesis imperfecta. Lancet. 363(9418):1377–1385.

28.

Rauch

Travers

Parfitt

Glorieux

. 2000. Static and dynamic bone histomorphometry in children with osteogenesis imperfecta. Bone. 26(6):581–589.

29.

Renaud

Auffray

Porte

. 2010. Epigenetic effects on the mouse mandible: common features and discrepancies in remodeling due to muscular dystrophy and response to food consistency. BMC Evol Biol. 10:28.

30.

Richards

Martin

Nicholls

Harrison

Pope

Burrows

. 1998. A single base mutation in col5a2 causes Ehlers-Danlos syndrome type II. J Med Genet. 35(10):846–848.

31.

Rizkallah

Schwartz

Rauch

Glorieux

Muller

Retrouvey

. 2013. Evaluation of the severity of malocclusions in children affected by osteogenesis imperfecta with the peer assessment rating and discrepancy indexes. Am J Orthod Dentofacial Orthop. 143(3):336–341.

32.

Roschger

Keplingter

Klaushofer

Abdullah

Kneissel

Rauch

. 2014. Effect of sclerostin antibody treatment in a mouse model of severe osteogenesis imperfecta. Bone. 66:182–188.

33.

Roschger

Fratzl-Zelman

Misof

Glorieux

Klaushofer

Rauch

. 2008. Evidence that abnormal high bone mineralization in growing children with osteogenesis imperfecta is not associated with specific collagen mutations. Calcif Tissue Int. 82(4):263–270.

34.

Saito

Kajii

Sugawara-Kato

Tsukamoto

Arai

Hirabayashi

Fujimori

Iida

. 2011. Three-dimensional craniomaxillary characteristics of the mouse with spontaneous malocclusion using micro-computed tomography. Eur J Orthod. 33(1):43–49.

35.

Sillence

Senn

Danks

. 1979. Genetic heterogeneity in osteogenesis imperfecta. J Med Genet. 16(2):101–116.

36.

Simon

Marchadier

Riviere

Vandamme

Koenig

Lezot

Trouve

Benhamou

Saffar

Berdal

. 2014. Cephalometric assessment of craniofacial dysmorphologies in relation with msx2 mutations in mouse. Orthod Craniofac Res. 17(2):92–105.

37.

Swiderski

Zelditch

. 2013. The complex ontogenetic trajectory of mandibular shape in a laboratory mouse. J Anat. 223(6):568–580.

38.

van Dijk

Nesbitt

Zwikstra

Nikkels

Piersma

Fratantoni

Jimenez

Huizer

Morsman

Cobben

. 2009. PPIB mutations cause severe osteogenesis imperfecta. Am J Hum Genet. 85(4):521–527.

39.

von Cramon-Taubadel

2011. Global human mandibular variation reflects differences in agricultural and hunter-gatherer subsistence strategies. Proc Natl Acad Sci U S A. 108(49):19546–19551.

40.

Waltimo-Siren

Kolkka

Pynnonen

Kuurila

Kaitila

Kovero

. 2005. Craniofacial features in osteogenesis imperfecta: a cephalometric study. Am J Med Genet A. 133A(2):142–150.

41.

Wenstrup

Langland

Willing

D’Souza

Cole

. 1996. A splice-junction mutation in the region of col5a1 that codes for the carboxyl propeptide of pro alpha 1(v) chains results in the gravis form of the Ehlers-Danlos syndrome (type I). Hum Mol Genet. 5(11):1733–1736.

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