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Cellular basis of urothelial squamous metaplasia: roles of lineage heterogeneity and cell replacement.

Liang FX, Bosland MC, Huang H, Romih R, Baptiste S, Deng FM, Wu XR, Shapiro E, Sun TT - J. Cell Biol. (2005)

Bottom Line: Although the epithelial lining of much of the mammalian urinary tract is known simply as the urothelium, this epithelium can be divided into at least three lineages of renal pelvis/ureter, bladder/trigone, and proximal urethra based on their embryonic origin, uroplakin content, keratin expression pattern, in vitro growth potential, and propensity to keratinize during vitamin A deficiency.During vitamin A deficiency, mouse urothelium form multiple keratinized foci in proximal urethra probably originating from scattered K14-positive basal cells, and the keratinized epithelium expands horizontally to replace the surrounding normal urothelium.These data suggest that the urothelium consists of multiple cell lineages, that trigone urothelium is closely related to the urothelium covering the rest of the bladder, and that lineage heterogeneity coupled with cell migration/replacement form the cellular basis for urothelial squamous metaplasia.

View Article: PubMed Central - PubMed

Affiliation: Epithelial Biology Unit, The Ronald O. Perelman Department of Dermatology.

ABSTRACT
Although the epithelial lining of much of the mammalian urinary tract is known simply as the urothelium, this epithelium can be divided into at least three lineages of renal pelvis/ureter, bladder/trigone, and proximal urethra based on their embryonic origin, uroplakin content, keratin expression pattern, in vitro growth potential, and propensity to keratinize during vitamin A deficiency. Moreover, these cells remain phenotypically distinct even after they have been serially passaged under identical culture conditions, thus ruling out local mesenchymal influence as the sole cause of their in vivo differences. During vitamin A deficiency, mouse urothelium form multiple keratinized foci in proximal urethra probably originating from scattered K14-positive basal cells, and the keratinized epithelium expands horizontally to replace the surrounding normal urothelium. These data suggest that the urothelium consists of multiple cell lineages, that trigone urothelium is closely related to the urothelium covering the rest of the bladder, and that lineage heterogeneity coupled with cell migration/replacement form the cellular basis for urothelial squamous metaplasia.

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Bovine urothelium is morphologically and biochemically heterogeneous. (a) The lower bovine urinary tract around the trigone area (male). B, bladder; MU, membranous urethra; PU, prostatic urethra; UO, ureteral orifices; TG, trigone. (b) Electron microscopy immunolocalization of UP IIIa in bovine urothelial umbrella cells. (c–f) Double immunofluorescent staining of the bovine bladder (c and d) and ureter (UR; e and f) using antibodies to UP IIIa (c and e; monoclonal antibody AU1; green) and keratins (d and f; a rabbit antiserum against total keratins; red; double exposure) showing more uniform cytoplasmic staining of bladder urothelial umbrella cells than the ureteral cells. (g and h) Transmission electron microscopy of the umbrella cells of bovine bladder (g) and ureteral (h) urothelium showing more abundant cytoplasmic UP-delivering vesicles (V) in bladder urothelial cells than ureteral cells. L, lumen; Nu, nucleus. (i) Immunoblot analysis of the total proteins of bovine urothelia that were isolated by scraping from the renal pelvis (RP), ureter, trigone, bladder, prostatic urethra, and membranous urethra using antibodies to UPs Ia, Ib, II, IIIa, and IIIb. Actin (Act) and the total UPs of bovine urothelial plaques (AUM) were used as a loading control and reference, respectively. (j) Semiquantification of UPs. Various amounts of total proteins (as indicated) from purified bovine AUM (lanes 1–4), scraped bovine bladder urothelium (5–8), and ureteral urothelium (9–12) were immunoblotted using antibodies to individual UPs as indicated. The immunoblot experiments were performed twice with similar results. Note that UPs in 10–20 μg of bladder urothelium were equivalent to those present in 100–200 μg of ureteral cells, suggesting that bladder epithelium contained ∼10 times more UPs than ureteral urothelium on a per total cellular protein basis. Bars (b), 1 μm; (c–f) 50 μm; (g and h) 1 μm.
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fig1: Bovine urothelium is morphologically and biochemically heterogeneous. (a) The lower bovine urinary tract around the trigone area (male). B, bladder; MU, membranous urethra; PU, prostatic urethra; UO, ureteral orifices; TG, trigone. (b) Electron microscopy immunolocalization of UP IIIa in bovine urothelial umbrella cells. (c–f) Double immunofluorescent staining of the bovine bladder (c and d) and ureter (UR; e and f) using antibodies to UP IIIa (c and e; monoclonal antibody AU1; green) and keratins (d and f; a rabbit antiserum against total keratins; red; double exposure) showing more uniform cytoplasmic staining of bladder urothelial umbrella cells than the ureteral cells. (g and h) Transmission electron microscopy of the umbrella cells of bovine bladder (g) and ureteral (h) urothelium showing more abundant cytoplasmic UP-delivering vesicles (V) in bladder urothelial cells than ureteral cells. L, lumen; Nu, nucleus. (i) Immunoblot analysis of the total proteins of bovine urothelia that were isolated by scraping from the renal pelvis (RP), ureter, trigone, bladder, prostatic urethra, and membranous urethra using antibodies to UPs Ia, Ib, II, IIIa, and IIIb. Actin (Act) and the total UPs of bovine urothelial plaques (AUM) were used as a loading control and reference, respectively. (j) Semiquantification of UPs. Various amounts of total proteins (as indicated) from purified bovine AUM (lanes 1–4), scraped bovine bladder urothelium (5–8), and ureteral urothelium (9–12) were immunoblotted using antibodies to individual UPs as indicated. The immunoblot experiments were performed twice with similar results. Note that UPs in 10–20 μg of bladder urothelium were equivalent to those present in 100–200 μg of ureteral cells, suggesting that bladder epithelium contained ∼10 times more UPs than ureteral urothelium on a per total cellular protein basis. Bars (b), 1 μm; (c–f) 50 μm; (g and h) 1 μm.

Mentions: Bovine tissues are particularly suitable for analyses of possible urothelial heterogeneity because (1) we can readily isolate sufficient amounts of relatively pure urothelial cells from various parts of the urinary tract for UP analyses (Fig. 1 a); (2) we have generated antibodies that are monospecific to all bovine UPs (Wu et al., 1994; Liang et al., 2001); and (3) we can serially cultivate bovine urothelial cells (Surya et al., 1990; Sun et al., 1999). As shown previously, UP antibodies strongly labeled not only the apical surface-associated urothelial plaques (AUM) but also the cytoplasmic UP-delivering vesicles (Fig. 1 b; Wu et al., 1990; Wu and Sun, 1993; Liang et al., 2001). Immunofluorescent staining showed that although UPs were associated with the apical surface of both bladder (Fig. 1, c and d) and ureteral urothelia (Fig. 1, e and f), the cytoplasm of the bladder umbrella cells stained more uniformly and strongly than that of the ureter. This result was consistent with the electron microscopic data showing that the bladder umbrella cells had many more cytoplasmic UP-delivering vesicles (Fig. 1 g) than the corresponding ureteral cells (Fig. 1 h). To confirm that the bladder urothelial cells contained more UPs than ureteral cells, we analyzed the total proteins of these two epithelia as well as the bovine renal pelvis, trigone, prostatic urethra, and membranous urethra (of males) by immunoblotting. With the exception of the membranous urethra, which was UP negative, all of the urothelia were found to contain UPs Ia, Ib, II, IIIa, and IIIb (Fig. 1 i). The relative sizes of UPs of the various urothelia were identical to those of the bladder except renal pelvis, whose UPIIIa was slightly larger than that of the bladder (Fig. 1 i), possibly reflecting a different degree of glycosylation (Hu et al., 2005). The results indicated that ureteral and renal pelvis urothelia indeed contained less UPs than the bladder (including the trigone) and urethral urothelia (Fig. 1 i). To study this more carefully, we compared the immunoblot intensities of various urothelial UPs with known amounts of bovine AUM UPs (Chen et al., 2003). The results indicated that 10–20 μg of total bladder urothelial proteins contained about the same amount of UPs as in 100–200 μg of total ureteral urothelial proteins (Fig. 1 j), indicating that the UP content of the bladder urothelium was ∼10 times higher than that of the ureteral epithelium.


Cellular basis of urothelial squamous metaplasia: roles of lineage heterogeneity and cell replacement.

Liang FX, Bosland MC, Huang H, Romih R, Baptiste S, Deng FM, Wu XR, Shapiro E, Sun TT - J. Cell Biol. (2005)

Bovine urothelium is morphologically and biochemically heterogeneous. (a) The lower bovine urinary tract around the trigone area (male). B, bladder; MU, membranous urethra; PU, prostatic urethra; UO, ureteral orifices; TG, trigone. (b) Electron microscopy immunolocalization of UP IIIa in bovine urothelial umbrella cells. (c–f) Double immunofluorescent staining of the bovine bladder (c and d) and ureter (UR; e and f) using antibodies to UP IIIa (c and e; monoclonal antibody AU1; green) and keratins (d and f; a rabbit antiserum against total keratins; red; double exposure) showing more uniform cytoplasmic staining of bladder urothelial umbrella cells than the ureteral cells. (g and h) Transmission electron microscopy of the umbrella cells of bovine bladder (g) and ureteral (h) urothelium showing more abundant cytoplasmic UP-delivering vesicles (V) in bladder urothelial cells than ureteral cells. L, lumen; Nu, nucleus. (i) Immunoblot analysis of the total proteins of bovine urothelia that were isolated by scraping from the renal pelvis (RP), ureter, trigone, bladder, prostatic urethra, and membranous urethra using antibodies to UPs Ia, Ib, II, IIIa, and IIIb. Actin (Act) and the total UPs of bovine urothelial plaques (AUM) were used as a loading control and reference, respectively. (j) Semiquantification of UPs. Various amounts of total proteins (as indicated) from purified bovine AUM (lanes 1–4), scraped bovine bladder urothelium (5–8), and ureteral urothelium (9–12) were immunoblotted using antibodies to individual UPs as indicated. The immunoblot experiments were performed twice with similar results. Note that UPs in 10–20 μg of bladder urothelium were equivalent to those present in 100–200 μg of ureteral cells, suggesting that bladder epithelium contained ∼10 times more UPs than ureteral urothelium on a per total cellular protein basis. Bars (b), 1 μm; (c–f) 50 μm; (g and h) 1 μm.
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Related In: Results  -  Collection

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fig1: Bovine urothelium is morphologically and biochemically heterogeneous. (a) The lower bovine urinary tract around the trigone area (male). B, bladder; MU, membranous urethra; PU, prostatic urethra; UO, ureteral orifices; TG, trigone. (b) Electron microscopy immunolocalization of UP IIIa in bovine urothelial umbrella cells. (c–f) Double immunofluorescent staining of the bovine bladder (c and d) and ureter (UR; e and f) using antibodies to UP IIIa (c and e; monoclonal antibody AU1; green) and keratins (d and f; a rabbit antiserum against total keratins; red; double exposure) showing more uniform cytoplasmic staining of bladder urothelial umbrella cells than the ureteral cells. (g and h) Transmission electron microscopy of the umbrella cells of bovine bladder (g) and ureteral (h) urothelium showing more abundant cytoplasmic UP-delivering vesicles (V) in bladder urothelial cells than ureteral cells. L, lumen; Nu, nucleus. (i) Immunoblot analysis of the total proteins of bovine urothelia that were isolated by scraping from the renal pelvis (RP), ureter, trigone, bladder, prostatic urethra, and membranous urethra using antibodies to UPs Ia, Ib, II, IIIa, and IIIb. Actin (Act) and the total UPs of bovine urothelial plaques (AUM) were used as a loading control and reference, respectively. (j) Semiquantification of UPs. Various amounts of total proteins (as indicated) from purified bovine AUM (lanes 1–4), scraped bovine bladder urothelium (5–8), and ureteral urothelium (9–12) were immunoblotted using antibodies to individual UPs as indicated. The immunoblot experiments were performed twice with similar results. Note that UPs in 10–20 μg of bladder urothelium were equivalent to those present in 100–200 μg of ureteral cells, suggesting that bladder epithelium contained ∼10 times more UPs than ureteral urothelium on a per total cellular protein basis. Bars (b), 1 μm; (c–f) 50 μm; (g and h) 1 μm.
Mentions: Bovine tissues are particularly suitable for analyses of possible urothelial heterogeneity because (1) we can readily isolate sufficient amounts of relatively pure urothelial cells from various parts of the urinary tract for UP analyses (Fig. 1 a); (2) we have generated antibodies that are monospecific to all bovine UPs (Wu et al., 1994; Liang et al., 2001); and (3) we can serially cultivate bovine urothelial cells (Surya et al., 1990; Sun et al., 1999). As shown previously, UP antibodies strongly labeled not only the apical surface-associated urothelial plaques (AUM) but also the cytoplasmic UP-delivering vesicles (Fig. 1 b; Wu et al., 1990; Wu and Sun, 1993; Liang et al., 2001). Immunofluorescent staining showed that although UPs were associated with the apical surface of both bladder (Fig. 1, c and d) and ureteral urothelia (Fig. 1, e and f), the cytoplasm of the bladder umbrella cells stained more uniformly and strongly than that of the ureter. This result was consistent with the electron microscopic data showing that the bladder umbrella cells had many more cytoplasmic UP-delivering vesicles (Fig. 1 g) than the corresponding ureteral cells (Fig. 1 h). To confirm that the bladder urothelial cells contained more UPs than ureteral cells, we analyzed the total proteins of these two epithelia as well as the bovine renal pelvis, trigone, prostatic urethra, and membranous urethra (of males) by immunoblotting. With the exception of the membranous urethra, which was UP negative, all of the urothelia were found to contain UPs Ia, Ib, II, IIIa, and IIIb (Fig. 1 i). The relative sizes of UPs of the various urothelia were identical to those of the bladder except renal pelvis, whose UPIIIa was slightly larger than that of the bladder (Fig. 1 i), possibly reflecting a different degree of glycosylation (Hu et al., 2005). The results indicated that ureteral and renal pelvis urothelia indeed contained less UPs than the bladder (including the trigone) and urethral urothelia (Fig. 1 i). To study this more carefully, we compared the immunoblot intensities of various urothelial UPs with known amounts of bovine AUM UPs (Chen et al., 2003). The results indicated that 10–20 μg of total bladder urothelial proteins contained about the same amount of UPs as in 100–200 μg of total ureteral urothelial proteins (Fig. 1 j), indicating that the UP content of the bladder urothelium was ∼10 times higher than that of the ureteral epithelium.

Bottom Line: Although the epithelial lining of much of the mammalian urinary tract is known simply as the urothelium, this epithelium can be divided into at least three lineages of renal pelvis/ureter, bladder/trigone, and proximal urethra based on their embryonic origin, uroplakin content, keratin expression pattern, in vitro growth potential, and propensity to keratinize during vitamin A deficiency.During vitamin A deficiency, mouse urothelium form multiple keratinized foci in proximal urethra probably originating from scattered K14-positive basal cells, and the keratinized epithelium expands horizontally to replace the surrounding normal urothelium.These data suggest that the urothelium consists of multiple cell lineages, that trigone urothelium is closely related to the urothelium covering the rest of the bladder, and that lineage heterogeneity coupled with cell migration/replacement form the cellular basis for urothelial squamous metaplasia.

View Article: PubMed Central - PubMed

Affiliation: Epithelial Biology Unit, The Ronald O. Perelman Department of Dermatology.

ABSTRACT
Although the epithelial lining of much of the mammalian urinary tract is known simply as the urothelium, this epithelium can be divided into at least three lineages of renal pelvis/ureter, bladder/trigone, and proximal urethra based on their embryonic origin, uroplakin content, keratin expression pattern, in vitro growth potential, and propensity to keratinize during vitamin A deficiency. Moreover, these cells remain phenotypically distinct even after they have been serially passaged under identical culture conditions, thus ruling out local mesenchymal influence as the sole cause of their in vivo differences. During vitamin A deficiency, mouse urothelium form multiple keratinized foci in proximal urethra probably originating from scattered K14-positive basal cells, and the keratinized epithelium expands horizontally to replace the surrounding normal urothelium. These data suggest that the urothelium consists of multiple cell lineages, that trigone urothelium is closely related to the urothelium covering the rest of the bladder, and that lineage heterogeneity coupled with cell migration/replacement form the cellular basis for urothelial squamous metaplasia.

Show MeSH
Related in: MedlinePlus