Endochondral ossification of the mouse nasal septum

Abstract

Endochondral ossification at the caudal junctions of the cartilaginous nasal septum, in combination with interstitial expansion of the septum, is thought to displace the facial skeleton away from the neurocranium. However, the rate of endochondral ossification has not been measured or related to rates of septal enlargement. This study examined endochondral ossification at these junctions in mice from postnatal days 0-15, in the context of known cranial growth sites, the synchondroses. BrdU labeling was used to compare cell division at the septoethmoidal and septopresphenoidal junctions with cell division at the synchondroses, and double-fluorochrome labeling was used to measure mineralization rate. The results showed that the septoethmoidal and septopresphenoidal junctions develop the characteristic morphology of growth plates postnatally, and that the pattern of cell division is similar to that of synchondroses. Mineralization at these junctions occurred at rates that were not statistically different from those of the synchondroses. However, the cartilaginous septum increased in length much more rapidly than could be explained by caudal growth, implying that interstitial expansion is the more important contributor to septal growth.

Nasal Septal and Premaxillary Developmental Integration: Implications for Facial Reduction in Homo

“…Although the nasal septal cartilage in humans attains its adult size early in development, the perpendicular plate of the ethmoid continues to grow through endrochondral ossification of the septal cartilage into adulthood (Van Loosen et al, 1996). This pattern is similar to that seen in mice (Wealthall and Herring, 2006) and is thus likely similar to that in other hominins. Thus, as one aspect of craniofacial development, a continued assessment and more precise understanding of the growth and integration of the nasal septum and premaxilla is likely to help elucidate the complex developmental mechanisms that underlie facial reduction in genus Homo evolution.…”

“…The results of our analysis indicate that the developmental relationship between the nasal septum and premaxilla, as one component of midfacial growth, contributes to variation in adult facial length (e.g., Wexler and Sarnat, 1961;Sarnat and Wexler, 1966;Mooney et al, 1989;Wealthall and Herring, 2006). Our first hypothesis that facial growth restriction has no effect on the length of the nasal septum was indirectly supported by this analysis.…”

“…There are, however, exceptions to these studies (e.g., Strenström and Thilander, 1970;Freng, 1981;Cuparo et al, 2001), leading some to minimize the importance of the nasal septum as a craniofacial growth center. The negative results reported by these authors, however, are potentially due to the variation among animals in the regions of the cartilage that are most proliferative during growth (e.g., Long et al, 1968;Strenström and Thilander, 1970;Searls and Kinser, 1972;Copray, 1986;Van Loosen et al, 1996;Ma and Lozanoff, 1999;Wealthall and Herring, 2006). As such, partial resection of the septum may not include these proliferative regions.…”

“…Thus, as the nasal septum increases in length, tension is placed on the premaxilla via the septo-premaxillary ligament (Latham, 1970;Gange and Johnston, 1974;Siegel, 1986, 1991;Siegel et al, 1990). This dynamic results from the nasal septal cartilage acting as a growth plate, which develops through a combination of interstitial cellular division, chondrocyte hypertrophy, and endochondral ossification along its caudal border (Scott, 1953;Baume, 1961;Catala and Johnston, 1980;Copray, 1986;Wealthall and Herring, 2006).…”

Dlx5 and Dlx6 expression in the anterior neural fold is essential for patterning the dorsal nasal capsule

“…The midline position of the cartilaginous rod ( Fig. 1E-H) and the absence of cavity renders this structure similar to the nasal septum, which also derives from the midline juxtaposition of two hemisepta (Wealthall and Herring, 2006). Thus, in Dlx5/6 -/-mouse embryos, the dorsal nasal capsule (ectethmoid) is absent, while the ventral, mesethmoidderived, nasal septum is still present.…”