Organ Culture of Intact Metanephric Kidneys
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This chapter describes the methodology for culture of the metanephros, the direct precursor of the adult mammalian kidney (
1
). The metanephros initially has two tissue compartments (Fig. 1
A,B
): i) the ureteric bud epithelium, a branch of the mesonephric (Wolffian) duct, which itself branches recurrently to form the renal collecting ducts; and ii) the renal mesenchyme, a caudal section of intermediate mesoderm, which undergoes an epithelial transformation via comma and S-shaped bodies to form nephron components including glomerular and proximal tubule epithelia (Fig. 1
C
). The metanephric mesenchyme also differentiates into interstitial cells and at least some renal capillaries. The ureteric bud also forms the urothelium of the renal pelvis and the ureter. The junction of the bud and the mesonephric duct becomes incorporated into the cloaca, forming the urinary bladder trigone. The remainder of the bladder epithelium is derived from endoderm, and both the ureter and bladder become enveloped in mesodermal-derived smooth muscle.
Fig. 1.
Differentiation of the metanephric kidney. (
A
) Histology of a rat metanephric kidney
in situ
at d 12.5 of gestation (the equivalent stage in mouse is 11 d of gestation). This is called the “utereric bud” stage. Note that the ureteric bud (ub) has branched once and is surrounded by condensing metanephric mesenchyme (mm). There are no glomeruli present at this stage. (
B
) This frame represents the ureteric bud stage diagrammatically. (
C
) This frame depicts a metanephric kidney after about 4 d of development, when the ureteric bud has branched recurrently. In the outer part of the organ, the ureteric bud branch tips are surrounded by condensed metanephric mesenchyme (cmm), and the first glomeruli (g) have appeared.
