Pericytes synthesize renin

Abstract

Aim: To investigate renin expression in pericytes during normal kidney development and after deletion of angiotensinogen, the precursor for all angiotensins.

Methods: We examined the distribution of renin expressing cells by immunoshistochemistry in the interstitial compartment of wild type (WT) and angiotensinogen deficient (AGT -/-) mice at different developmental stages from embryonic day 18 (E18: WT, n = 4; AGT -/-, n = 5) and at day 1 (P1: WT, n = 5; AGT -/-, n = 5), 5 (P5: WT, n = 7; AGT -/-, n = 8), 10 (P10: WT, n = 3; AGT -/-, n = 5), 21 (P21: WT, n = 7; AGT -/-, n = 5), 45 (P45: WT, n = 3; AGT -/-, n = 3), and 70 (P70: WT, n = 2; AGT -/-, n = 2) of postnatal life. We quantified the number of pericytes positive for renin at all the developmental stages mentioned above and compared the results of AGT -/- mice to their WT counterparts.

Results: In WT mice, renal interstitial pericytes synthesize renin in early life supporting a lineage relationship with renin cells in the vasculature. The number of pericytes positive for renin per area of 0.32 mm(2) (density) in WT mice was maintained from fetal life till weaning age (E18 = 4.25 ± 0.63, P1 = 3.75 ± 0.48, P5 = 3.75 ± 0.48, P10 = 4 ± 0.71, P21 = 3.8 ± 0.58) and markedly decreased in adult life (P45 = 1.2 ± 0.37, P70 = 0.8 ± 0.20). On the other hand, in AGT -/- mice the density of pericytes expressing renin was not significantly different from WT mice at E18 and P1: E18 = 5.75 ± 0.50 vs 4.25 ± 0.63 (P = 0.106), P1 = 9.25 ± 3.50 vs 3.75 ± 0.48 (P = 0.175) but significantly increased from P5 till P70: P5 = 38.25 ± 5 vs 3.75 ± 0.48 (P = 0.0004), P10 = 173 ± 7.50 vs 4 ± 0.70 (P = 5.24567 × 10(-7)), P21 = 83 ± 6.70 vs 3.8 ± 0.58 (P = 2.97358 × 10(-6)), P45 = 49 ± 3.50 vs 1.2 ± 0.37 (P = 8.18274 x 10(-7)) and P70 = 17.8 ± 2.30 vs 0.8 ± 0.20 (P = 3.51151 × 10(-5)). The AGT -/- mice showed a marked increase in the number of pericytes per field studied starting from P5, reaching its peak at P10, and then a gradually decreasing until P70.

Conclusion: Interstitial pericytes synthesize renin during development and the number of renin-expressing pericytes increases in response to a homeostatic threat imposed early in life such as lack of angiotensinogen.

Keywords: Angiotensin deficiency; Angiotensinogen; Development; Gene deletion; Homeostasis; Interstitium; Kidney; Renin angiotensin system.

Figure 1

Immunostaining for renin (brown) showing the overall distribution at low magnification in wild type and angiotensinogen deficient mice during embryonic (E18, A and H) and postnatal life (P1, P5, P10, P21, P45 and P70, B-G and I-N). A: Renin expression in large arteries and arterioles and in pericytes (arrowheads); B: Renin expression in large arteries, arterioles and in the glomerular mesangium; C: Renin expression is still extended in arterioles beyond the juxtaglomerular areas (JGAs); D: Renin expression is mostly restricted to the JGAs; E: Renin expression in JGAs and occasionally in few pericytes (arrowheads); F and G: Renin expression in JGAs; H: Renin expression in large arteries and arterioles and in pericytes (arrowheads) similar to A; I: Renin expression in large arteries and arterioles similar to B; J, L: Renin expression in thickened arteries, arterioles, pericytes (arrowheads) and tubules (arrows); M, N: Renin expression in thickened arteries and arterioles and in fewer pericytes (arrowheads). WT: Wild type; AGT: Angiotensinogen deficient. Bars: 100 μm.

Figure 2

Immunostaining for renin (brown) in wild type (A-D) and angiotensinogen deficient mice (E-H) during postnatal life (P1, P5, P10 and P45) Higher magnification. A: Renin expression in a transversal section of an arteriole and in isolated pericytes (arrowheads); B: Renin expression in a transversal section of a branching arteriole and in isolated pericytes (arrowheads); C: Renin expression is still present in arterioles beyond the juxtaglomerular areas (JGAs) and in isolated pericytes (arrowheads); D: Renin expression is restricted to the JGAs; E: Renin expression in arterioles and isolated pericytes (arrowheads) similar to A; F: Renin expression in an arteriole beyond the JGA similar to B but with a clear increase in the density of pericytes expressing renin (some marked with arrowheads); G: Peritubular pericytes (some marked with arrowheads) show a marked increase in renin expression; H: Renin expression in enlarged arterioles and in peritubular pericytes (arrowheads). WT: Wild type; AGT: Angiotensinogen deficient. Bars: 50 μm.

Figure 3

Quantification and comparison of pericytes positive for renin in wild type and angiotensinogen deficient mice. A: In wild type (WT) mice the density of renin positive pericytes was not significantly different from E18 to P21, but significantly decreased at P45 (P = 0.0052 vs E18) and P70 (P = 0.0007 vs E18); B: Angiotensinogen deficient (AGT) -/- mice showed a significant increase at P5 with a maximum at P10 and a progressive decrease towards P70 (^bP ≤ 0.01 vs E18); C: Comparison at each individual age showing a significant increase in the number of renin-positive pericytes in AGT -/- from P5 till P70 (^dP ≤ 0.001 vs WT).