Expression of FGF-23 and FGFR1 is increased in uremic rat skin.

Purpose: Alterations in skin structure and function are very common in uremic patients, but still there is no unifying hypothesis for uremic skin disorders. Fibroblast growth factor-23 (FGF-23) deficiency has been linked to skin disorders in non-uremic animals. We aimed to study alterations in FGF-23 and fibroblast growth factor-23 receptor 1 (FGFR1) expression in uremic rat skins.

Material and methods: Wistar albino rats were divided into two groups: sham group (SG, n = 8) and uremic group (UG, n = 8). Uremia was induced by reduction of the total kidney mass in the UG. Animals were sacrificed after 14 weeks of the follow-up.

Results: Serum creatinine and blood urea nitrogen levels in the UG increased significantly, compared to the SG, at the end of the experiment (0.69 ± 0.08 vs. 0.3 ± 0.04 Mann-Whitney U test (MWU), p = 0,003 and 55.2 ± 8.9 vs. 29.6 ± 6.8 MWU, p = 0.002, respectively). Serum FGF-23 level in the UG was increased non-significantly, compared to the SG (53.5 ± 20.9 vs. 37.2 ± 9.7 MWU, p = 0.072), whereas serum 1,25(OH)₂D₃ level was significantly lower in the UG (149.4 ± 33.5 vs. 213.8 ± 43.8 MWU, p < 0.05). Expression of FGF-23 in UG skins, assessed by western blot, was significantly higher than that in the SG (186.3 ± 16.8 vs. 148.9 ± 25.9, MWU, p < 0.01). FGFR1 expression was increased in almost all parts of the uremic skin. Receptor expression was most dense at the epidermis and hair follicles. Normal skin appendages and cells either expressed no receptor, or expressed it very weakly.

Conclusion: This study shows increased FGF-23 levels and FGFR1 expression in uremic rat skins. It deserves further study to fully place this finding in the pathophysiology and clinical picture of uremic skin diseases.