Children with proximal hypospadias admitted to the Department of Urology of Shanghai Children's Hospital Inclusion criteria: 46, XY karyotype; treated with Byar staged surgery; and informed consent from guardians. Exclusion criteria: patients with sexual development disorders; those undergoing one-stage repair; patients or guardians refusing participation; and those lost to follow-up.

Use the sodium hyaluronate

200 ml of urine was collected by aseptic catheterization, after which it was centrifuged and expanded to the P6 generation using a gelatin-coated culture plate. Exosome extraction: USC-Exos was isolated via tangential flow filtration combined with ultrafiltration. Quality control was performed via nano-flow cytometry (particle size 72.27±21.90 nm), transmission electron microscopy (double-membrane structure), and Western blot (positive for CD9/CD63/TSG101).

First stage, the dorsal penile foreskin flap was transferred to the ventral side to reconstruct the urethral plate (Byar Stage Ⅰ). In the exosome group, USC-Exos (1-3×10^10^/ml) were applied topically.

Second-stage, urethral tubularization after 6-9 months, urethral plate tissues were taken for HE, CD31, α-SMA and VEGF immunohistochemical analysis during the surgery.

82 participants were average divided into Exosome and Control group. All the participants were treated with the Byar's staged surgery(including I and II stage).