Secondary Palate Development in the Dog (Canis lupus familiaris)

Abstract

Objective: To investigate the gestational timing of morphologic events in normal canine secondary palate development as a baseline for studies in dog models of isolated cleft palate (CP). Methods: Beagle and beagle/cocker spaniel-hybrid fetal dogs were obtained by cesarean-section on various days of gestation, timed from the initial rise of serum progesterone concentration. Morphology of fetal heads was determined by examining serial coronal sections. Results: On gestational day 35 (d35), the palatal shelves pointed ventrally alongside the tongue. On d36, palatal shelves were elongated and elevated to a horizontal position above the tongue but were not touching. On d37, palatine shelves and vomer were touching, but the medial epithelial seam (MES) between the apposed shelves remained. Immunostaining with epithelial protein markers showed that the MES gradually dissolved and was replaced by mesenchyme during d37-d44, and palate fusion was complete by d44. Examination of remnant MES suggested that fusion of palatal shelves began in mid-palate and moved rostrally and caudally. Conclusion: Palate development occurs in dogs in the steps described in humans and mice, but palate closure occurs at an intermediate time in gestation. These normative data will form the basis of future studies to determine pathophysiologic mechanisms in dog models of CP. Added clinical significance is the enhancement of dogs as a large animal model to test new approaches for palate repair, with the obvious advantage of achieving full maturity within 2 years rather than 2 decades.

Non-Syndromic Cleft Palate and Transverse Limb Deficiency Segregating in a Family of Dogs

“…The immuno-staining for K17 and p63 appeared normal, showing that periderm and basal epithelial formation and function were not grossly affected. At gestational d39, the palate shelves are fusing in normal dog fetuses (Freiberger et al 2021), but while the palate shelves of affected pups had elevated over the tongue, they had failed to fuse. This could be failure of the palate shelves to grow and elongate horizontally so that the epithelia did not meet at midline.…”

“…Affected pups and littermate controls euthanized on the rst postnatal day were processed variously for histologic analysis or X-ray computed microtomography (µCT) of the head. Processing for light microscopic and immunohistochemical evaluation was as previously described (Freiberger et al 2021). In some matings, day 0 of gestation was determined by serial measurements of pre-ovulatory serum progesterone concentration, as previously described (Freiberger et al 2021), and fetal pups were removed by cesarean section on day 39 (d39).…”

“…Processing for light microscopic and immunohistochemical evaluation was as previously described (Freiberger et al 2021). In some matings, day 0 of gestation was determined by serial measurements of pre-ovulatory serum progesterone concentration, as previously described (Freiberger et al 2021), and fetal pups were removed by cesarean section on day 39 (d39). Immediately upon removal from the uterus, fetal pups were placed in ice-cold sterile saline, examined under a dissection microscope, and decapitated.…”

“…Serial coronal sections (7 µm) were collected from the rostral tip of the planum nasale through the back of the eyes. Hematoxylin and eosin (H&E) and immunostaining were performed as described previously (Freiberger et al 2021). For µCT, heads from 3 cleft-affected and 3 normal newborn littermates were xed overnight in formalin, skinned, and transferred to 50% ethanol.…”

“…To explore potential pathophysiological mechanisms, we performed histologic analyses on serial coronal sections of heads from fetuses with and without cleft palate. By cesarean section we interrupted backcross matings of each of the 3 surgically repaired affected females with their common sire on estimated d39, the previously de ned day of normal palate fusion (Freiberger et al 2021). Cleft palate was readily identi ed in 9 of 19 fetuses, 5 males and 4 females (Fig.…”