metanephric mesenchyme morphogenesis

Definition

Target type: biologicalprocess

The process in which the anatomical structures of a metanephric mesenchymal tissue are generated and organized. Metanephric mesenchyme is the tissue made up of loosely connected mesenchymal cells in the metanephros. [GOC:mtg_kidney_jan10]

Metanephric mesenchyme morphogenesis is a complex and tightly regulated process that involves the formation of the metanephric kidney, the primary excretory organ in mammals. This process begins with the reciprocal interaction between the metanephric mesenchyme, a population of mesenchymal cells derived from the intermediate mesoderm, and the ureteric bud, an outgrowth from the Wolffian duct.

The ureteric bud, a tubular epithelial structure, invades the metanephric mesenchyme, inducing the mesenchymal cells to condense and differentiate into epithelial cells. This process, known as epithelialization, is essential for the formation of nephrons, the functional units of the kidney.

As the ureteric bud branches and extends into the metanephric mesenchyme, it secretes signaling molecules, such as glial cell line-derived neurotrophic factor (GDNF), that activate receptors, such as RET and GFRα1, on the mesenchymal cells. This signaling pathway triggers a cascade of events that ultimately leads to the formation of nephrons.

The mesenchymal cells respond to these signals by undergoing a series of morphological changes, including:

* **Condensation:** Mesenchymal cells aggregate and condense around the branching ureteric bud.
* **Epithelialization:** The condensed mesenchymal cells differentiate into epithelial cells, forming the renal vesicles.
* **Tubularization:** The renal vesicles elongate and differentiate into proximal and distal tubules.
* **Loop of Henle formation:** The tubules extend and form the loop of Henle, which is responsible for concentrating urine.
* **Glomerular formation:** The capillaries of the glomerulus, the filtering unit of the nephron, develop from the surrounding mesenchyme.

In addition to GDNF, other signaling molecules, such as Wnt, BMP, and FGF, play crucial roles in regulating metanephric mesenchyme morphogenesis. These signaling pathways interact and cross-talk with each other to ensure proper development of the kidney.

Throughout this process, the metanephric mesenchyme exhibits dynamic changes in gene expression and cellular behavior, regulated by intricate interactions between the mesenchyme and the ureteric bud. These interactions are essential for the formation of a functional kidney, capable of filtering waste products and maintaining fluid and electrolyte balance.'
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