Differentiation of the anterior body wall and truncal epidermis and associated co‐migration of cutaneous nerves and mesenchyme

Abstract

The present study examines the relationship between the migration of mesenchyme and associated cutaneous nerves that are involved in the closure of the anterior body wall in embryonic mice and rats by light and electron microscopy. The sternum is formed by the migration of condensations of mesenchyme originating in the dorsolateral body wall known as sternal bands. In the course of analyzing this process in rodent embryos we have identified similar paired caudal extensions of the sternal bands that are responsible for the closure of the abdominal wall following resolution of the umbilical hernia, and we suggest these bands of mesoderm should be referred to as the abdominal bands. Both the sternal and abdominal bands are associated with the development of the segmental spinal nerves and their cutaneous terminal branches. The first cutaneous nerve to reach the skin surface in rats is the later cutaneous nerve (PCN and ACN) at E13.5 days. The ACN co-migrates with the sternal and abdominal bands, and terminal branches of axons from the ACN approach the epidermis during this migration. Differentiation of the epidermis could be recognized as a change in shape of epidermal cells from squamous to cuboidal, and this initial differentiation coincides with the onset of cutaneous innervation, beginning at the site of the LCN and following the extent of innervation of the PCN as well as the migration of the mesodermal bands and associated ACN. The paired ACN's meet in the ventral midline at E16.5 in rats as the sternal bands fuse, and terminal axons from both nerves densely innervate the midline skin.(ABSTRACT TRUNCATED AT 250 WORDS)

Finally, a sense of closure? Animal models of human ventral body wall defects

“…Sternal bands, originating in the dorsolateral body wall on either side of the embryo, migrate around to the ventral surface and fuse in the midline to form the mature sternum, thus contributing to the formation of the thoracic ventral body wall. (15,16) Abdominal bands are associated with the closure of the abdominal body wall following resolution of the umbilical hernia (17) (Fig. 5).…”

“…Following the disappearance of the physiological umbilical hernia, the abdominal bands will fuse at the ventral midline and form the rectus abdominus. (17) Defects of the ventral body wall in humans Ventral body wall defects, including such anomalies as gastroschisis and omphalocele, are observed in $1 in 2000 births. (18) There is no common system for the classification of defects concerning the ventral body wall.…”

Neuronal Activity in Ontogeny and Oncology

“…Innervation occurs very early in cutaneous morphogenesis and correlates closely with the development of epidermal structures [115,116]. For example, sensory innervation precedes hair follicle development [116]; with sensory nerves innervating the follicle secreting Shh ligand [117] and follicular stem cells responding to Hh signaling.…”

Tgfß2 -/- Tgfß3 -/- double knockout mice display severe midline fusion defects and early embryonic lethality

“…The etiology of ectopia cordis is unknown and, in general, the mechanisms involved in body wall closure have not yet been elucidated in detail. Obviously, cell migration and attachment do play a role (Munger and Munger 1991).…”