Abstract
The upper lamina propria (ULP) area of interstitial cells (IC) has been studied extensively in bladder, but is rather unexplored in the rest of the urinary tract. This cell layer is intriguing because of the localization directly underneath the urothelium, the intercellular contacts and the close relationship with nerve endings and capillaries. In this study, we examine the ULP layer of IC in human renal pelvis, ureter and urethra, and we make a comparison with ULP IC in bladder. Tissue was obtained from normal areas in nephrectomy, cystectomy and prostatectomy specimens, and processed for morphology, immunohistochemistry and electron microscopy. A morphological and immunohistochemical phenotype for the ULP IC was assessed and region-dependent differences were looked for. The ULP IC in renal pelvis, ureter and urethra had a similar ultrastructural phenotype, which differed somehow from that of bladder IC, that is, thinner and longer cytoplasmic processes, no peripheral actin filaments and presence of dense core granules and microtubules. Together with their immunohistochemical profile, these features are most compatible with the phenotype of telocytes, a recently discovered group of stromal cells. Based on their global ultrastructural and immunohistochemical phenotype, ULP IC in human bladder should also be classified as telocytes. The most striking immunohistochemical finding was the variable expression of oestrogen receptor (ER) and progesterone receptor (PR). The functional relevance of ULP telocytes in the urinary tract remains to be elucidated, and ER and PR might therefore be promising pharmacological research targets.
Highlights
The urinary tract extends from the renal pelvis towards the urethra, and is integrally lined by urothelium, which is a specialized transitional type of epithelium
The cell body was rather small: the cytoplasm presented a moderate amount of organelles as rough endoplasmic reticulum cisternae and Phenotype of upper lamina propria (ULP) interstitial cells (IC) in ureter
Immunohistochemical characterization of ureter ULP IC revealed the expression of vimentin (Fig. 5)
Summary
The urinary tract extends from the renal pelvis towards the urethra, and is integrally lined by urothelium, which is a specialized transitional type of epithelium. The area between urothelium and detrusor is called lamina propria. Several authors have reported on the presence of IC in this area, especially in the bladder [1,2,3,4]. A particular and dense layer of IC has been described in bladder ULP, which was found in both humans [3,4,5,6] and animals [2, 7] These ULP IC have been categorized heterogeneously as interstitial cells of Cajal (ICC) [1], interstitial Cajal-like cells (ICLC) [2, 5] or myofibroblasts [3, 8, 9]. Reasons for this diverse nomenclature might be the use of different experimental methods
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