Anti-EDAR Agonist Antibody Therapy Resolves Palate Defects in Pax9^-/- Mice

Abstract

To date, surgical interventions are the only means by which craniofacial anomalies can be corrected so that function, esthetics, and the sense of well-being are restored in affected individuals. Unfortunately, for patients with cleft palate-one of the most common of congenital birth defects-treatment following surgery is prolonged over a lifetime and often involves multidisciplinary regimens. Hence, there is a need to understand the molecular pathways that control palatogenesis and to translate such information for the development of noninvasive therapies that can either prevent or correct cleft palates in humans. Here, we use the well-characterized model of the Pax9 mouse, which displays a consistent phenotype of a secondary cleft palate, to test a novel therapeutic. Specifically, we demonstrate that the controlled intravenous delivery of a novel mouse monoclonal antibody replacement therapy, which acts as an agonist for the ectodysplasin (Eda) pathway, can resolve cleft palate defects in Pax9 embryos in utero. Such pharmacological interventions did not reverse the arrest in tooth, thymus, and parathyroid gland development, suggesting that the relationship of Pax9 to the Eda/Edar pathway is both unique and essential for palatogenesis. Expression analyses and unbiased gene expression profiling studies offer a molecular explanation for the resolution of palatal defects, showing that Eda and Edar-related genes are expressed in normal palatal tissues and that the Eda/Edar signaling pathway is downstream of Pax9 in palatogenesis. Taken together, our data uncover a unique relationship between Pax9 and the Eda/Edar signaling pathway that can be further exploited for the development of noninvasive, safe, and effective therapies for the treatment of cleft palate conditions and other single-gene disorders affecting the craniofacial complex.

Pax9's dual roles in modulating Wnt signaling during murine palatogenesis

“…One of the potential alternative approaches is targeting Eda/Edar signaling pathway, which is proven to be downstream of the Wnt signaling pathway. Our previous work has demonstrated that the treatments with Eda/Edar agonists mAbEDAR antibody or EDI200 rescued palatal defects in Pax9 −/− embryos 26 . The recent prenatal correction of X‐linked hypohidrotic ectodermal dysplasia (XLHED) through replacement therapies for ectodysplasin signaling has opened up a new dimension of research in the field.…”

Hoxa2 Inhibits Bone Morphogenetic Protein Signaling during Osteogenic Differentiation of the Palatal Mesenchyme

“…Hoxa2 peaks in its expression in the developing palate at E13.5 (Smith et al, 2009 ), a stage when the mesenchymal cells simultaneously proliferate and commit to form preosteoblasts of the prospective palatal process of the palatine bone. This suggests that the cleft palate phenotype in Hoxa2 −/− mice, due to the failure of palatal shelves to elevate and reorient horizontally above the tongue after E13.5 (Barrow and Capecchi, 1999 ), may be a consequence of abnormal cell proliferation (Smith et al, 2013 ) and osteogenic differentiation (Wu et al, 2008 ; Fu et al, 2017 ; Jia et al, 2017a , b ). To gain further insight into the role of Hoxa2 during this early stage of palate development, the rate of mesenchymal cell proliferation and the commitment of mesenchymal cells to osteoprogenitor fate was investigated in vivo at E13.5.…”

“…In the palatal mesenchyme, increased or decreased cell proliferation could result in failure of the palatal shelves to elevate and reorient above the tongue leading to cleft palate (Bush and Jiang, 2012 ; Smith et al, 2013 ). Recent studies show evidence for abnormal osteogenic signaling prior to the elevation of palatal shelves in several well-studied cleft palate mutant mice models including Pax9 −/− mice (Jia et al, 2017a , b ) and Osr2 −/− mice (Fu et al, 2017 ). Consistent with our findings here in the Hoxa2 −/− mice, Osr2 −/− exhibit increased osteogenic centers of the palatal process of the palatine bone prior to the elevation of the palatal shelves at E13.5 and in addition to defective cell proliferation, enhanced osteogenesis could contribute to cleft palate phenotype in Osr2 −/− mice (Fu et al, 2017 ).…”

“…Similarly, reduced expression of Bmp2 is associated with reduced cell proliferation in the palatal shelves of Hand2 hypomorphic mice ( Hand2 LoxP /− ) (Xiong et al, 2009 ). In addition, growing evidence highlight the importance of osteogenic differentiation in the elevation of palatal shelves and abnormal osteogenic differentiation could lead to cleft palate manifestations (Wu et al, 2008 ; Fu et al, 2017 ; Jia et al, 2017a , b ). BMP signaling is critical for osteogenic differentiation in the palatal mesenchyme (Wu et al, 2008 ; Baek et al, 2011 ; Hill et al, 2014 ), where it is required for the expression of osteoblast markers such as Runx2, Sp7 , and AlpI (Baek et al, 2011 ).…”

Understanding and prevention of orofacial clefting: A myth or possibility?

“…[ 1 ] The Journal of Dental Research recently published a special series of articles focusing on this area, especially on the recent scientific and technical advances in craniofacial development and genetics. [ 4 5 6 7 ]…”