Microbiota Alters Urinary Bladder Weight and Gene Expression

Abstract

We studied the effect of microbiota on the transcriptome and weight of the urinary bladder by comparing germ-free (GF) and specific pathogen-free (SPF) housed mice. In total, 97 genes were differently expressed (fold change > ±2; false discovery rate (FDR) p-value < 0.01) between the groups, including genes regulating circadian rhythm (Per1, Per2 and Per3), extracellular matrix (Spo1, Spon2), and neuromuscular synaptic transmission (Slc18a3, Slc5a7, Chrnb4, Chrna3, Snap25). The highest increase in expression was observed for immunoglobulin genes (Igkv1-122, Igkv4-68) of unknown function, but surprisingly the absence of microbiota did not change the expression of the genes responsible for recognizing microbes and their products. We found that urinary bladder weight was approximately 25% lighter in GF mice (p = 0.09 for males, p = 0.005 for females) and in mice treated with broad spectrum of antibiotics (p = 0.0002). In conclusion, our data indicate that microbiota is an important determinant of urinary bladder physiology controlling its gene expression and size.

Keywords: germ-free; microbiome; mouse; transcriptome; urinary bladder.

Figure 1

Comparison of bladder weight and size in germ-free and SPF animals. (A) Bladder weight of all groups of mice. (B) Bladder-to-body weight ratio of B6J 6-weeks-old mice shown in mg/g units. (C) Body weight of B6J 6-week-old mice. (D) Bladder size (length in mm) of B6N 9-week-old mice. Bars represent mean ± SEM. Student T-test (p-value without asterisk) and Mann-Whitney test were used to determine significance (p-value with asterisk). (E) Representative photographs of GF and SPF bladders. (ABX—antibiotics, ns—non-significant).

Figure 2

Bladder tissue of GF and SPF animals. Hematoxylin-eosin staining of GF and SPF mice at 100× and 600× magnification. Letters represent particular bladder layers: U—urothelium, LP—lamina propria, M—muscle layer.

Figure 3

Heat Map of differentially expressed genes. Comparison of urinary bladder gene expression between GF and SPF mice. Values represent log₂(fold change) with FDR less than 0.01, Euclidian distance, complete linkage.

Figure 4

KEGG pathway ‘ECM-receptor interaction’ with significant changes in gene expression.