Age-related transversal changes in craniofacial sutures of the anterior viscerocranium in growing rats

Abstract

Objective: To evaluate the dimensional changes that occur in the internasal and nasopremaxillary sutures, and related transverse craniofacial dimensions, of rats from 4 to 38-weeks of age. Methods: Four groups of twelve male Wistar rats were sacrificed at different ages [4-weeks (immature), 16-weeks (adolescent), 26-weeks (young adult), 38-weeks (adult)]. The rats were scanned with a high-resolution micro-computed tomography imaging device with 90 µm voxel size and 45 mm × 45 mm field of view (FOV) to obtain images of the viscreocranium, and with 10 µm voxel size and 5 mm × 5 mm FOV to obtain images of the internasal and left nasopremaxillary sutures. The nasal bone width, transverse width between the nasopremaxillary sutures and interzygomatic width were measured as craniofacial measurements. The endocranial, ectocranial and mean suture widths (cross-sectional area between endocranial and ectocranial borders/suture height), and suture height were measured at 5 frontal planes with 1.2 mm intervals. Outcomes were compared at different ages, and correlation coefficients were used to assess the relationship between craniofacial and suture changes. Results: All transverse craniofacial dimensions increased significantly from 4-16 weeks of age (p < 0.001). After 16-weeks of age, the only significant increase was observed in interzygomatic width (p = 0.02), between 26 and 38 weeks. In both the internasal and nasopremaxillary sutures, the endocranial suture mean widths decreased from 4-16 weeks (p < 0.001 and p = 0.002, respectively), but did not show any significant change after 16-weeks of age. The ectocranial internasal suture width decreased from 4-16 weeks (p < 0.001), increased until 26-weeks (p = 0.035), and subsequently decreased (p < 0.001). The nasopremaxillary suture widths decreased from 4-38 weeks to varying degrees in different frontal planes. Except for the internasal ectocranial suture width, all suture measurements were found highly and negatively correlated with the transverse craniofacial dimensions. The height of the sutures increased with time, with the most significant changes occurring between 4 and 16 weeks of age (p < 0.001). Conclusion: Although the internasal and nasopremaxillary endocranial suture widths nearly reach their final widths during adolescence, the changes in the ectocranial and mean suture widths continue into early adulthood. These results may serve as a reference for future studies aiming to evaluate the effects of functional demands on suture development and dimensional changes of the viscerocranium.

Keywords: micro-CT; rat; skull; suture growth; suture height; suture width.

FIGURE 1

Measurements representing the nasal bone width and interzygomatic width.

FIGURE 2

Measurements representing the transverse width between nasopremaxillary sutures.

FIGURE 3

(A) The region of interest starting from the most anterior point of zygomatic arches and extending 5 mm anteriorly, and the placement of 5 frontal planes used for the measurements of anterior, 25%, middle, 75% and posterior regions; (B) the caudal view of the skull; (C) the three-dimensional image established with the scanning protocol.

FIGURE 4

Measurements representing: (A) Endocranial suture width of the internasal suture; (B) Height of the internasal suture; (C) Ectocranial suture width of the internasal suture (D) The area of internasal suture; (E) Endocranial suture width of nasopremaxillary suture; (F) Height of the nasopremaxillary suture; (G) Ectocranial suture width of the nasopremaxillary suture; (H); area of nasopremaxillary suture of a 26-week-old rat.

FIGURE 5

Box plots showing the changes in: (A) internasal endocranial suture width; (B) internasal ectocranial suture width; (C) internasal suture width (mean); (D) internasal suture height. Boxes represent the interquartile range, with whiskers representing the maximum and minimum values. The median is represented as the line within the box and the mean as the X within the box. Outliers are represented with individual data points.

FIGURE 6

Fusion seen in the ectocranial region of the internasal suture of a (A) 16-week-old rat; and (B) 38-week-old rat.

FIGURE 7

Box plots showing the changes in: (A) nasopremaxillary endocranial suture width; (B) nasopremaxillary ectocranial suture width; (C) nasopremaxillary suture width (mean); (D) nasopremaxillary suture height. Boxes represent the interquartile range, with whiskers representing the maximum and minimum values. The median is represented as the line within the box and the mean as the X within the box. Outliers are represented with individual data points.