Abstract
Tracheal anomalies are potentially catastrophic congenital defects. As a newborn begins to breathe, the trachea needs to maintain an appropriate balance of elasticity and rigidity. If the tracheal cartilages are disorganized or structurally weak, the airways can collapse, obstructing breathing. Cartilage rings that are too small or too rigid can also obstruct breathing. These anomalies are frequently associated with craniofacial syndromes, and, despite the importance, are poorly understood. In this review, we summarize the spectrum of pathological phenotypes of the trachea and correlate them with the molecular events uncovered in mouse models.
Highlights
We summarize the spectrum of pathological phenotypes of the trachea and correlate them with the molecular events uncovered in mouse models
In the absence of Sonic Hedgehog (SHH) function, BMP4 and Noggin can partially induce chondrogenesis, suggesting that chondrogenic induction is sensitive to relative levels of bone morphogenetic protein (BMP) activity. These results suggest that both Bmp4 and noggin genes are downstream of Shh, and they can promote cartilage formation in trachea through regulation of chondrogenic genes such as Sox9 (Figure 2B)
This review has highlighted how normal tracheal anatomy can be affected at many stages development
Summary
The high morbidity associated with upper airway defects is an increasingly recognised clinical problem. Congenital tracheal defects can be fatal due to intrinsic airway cartilage pathology, especially at birth when the neonate must take a first breath. These tracheal defects most commonly present as part of a syndrome, such as the tracheal stenosis associated with Apert or Crouzon syndromes [1]. With recent advances in regenerative medicine, tracheal transplants, though currently controversial, may provide treatment for some patients [4] Even though these tracheal transplants are groundbreaking, new and can claim to be ‘curative’, the fundamentals of embryological tracheal morphogenesis and aetiology of disease processes affecting the trachea remain obscure. The committed mesenchymal cells proliferate, aggregate, and condense into pre-cartilaginous nodules, which subsequently differentiate into chondrocytes forming the semi-circular cartilage rings of the trachea [7]
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