Prospero-related homeobox protein 1 (Prox1) enhances myelin sheath regeneration in injured sciatic nerve

Background

Peripheral nerve injury (PNI), such as sciatic nerve injury (SNI), often results in poor functional recovery due to myelin damage, which critically impairs nerve regeneration. Prox1, a homeobox transcription factor known to influence neurogenesis, has not been studied in peripheral myelin regeneration.

Objective

To investigate morphological changes in myelin sheaths and the expression of Prox1 and MBP proteins during sciatic nerve repair, and to determine the role of Prox1 in nerve regeneration.

Methods

Mice were divided into seven groups (n = 8): one control and six experimental groups based on sciatic nerve collection at Days 3, 4, 5, 6, 7, and 14 post-injury. H&E staining, electron microscopy, Luxol Fast Blue staining, Western Blot, and immunohistochemistry were used to assess myelin morphology and Prox1/MBP expression. Immunofluorescence analyzed colocalization of Prox1 and MBP. Prox1 was overexpressed in Schwann cells via plasmid transfection, and MBP levels were measured by Western blot.

Results

Control group myelin sheaths showed normal structure, while Day 7 nerves displayed disorganized sheaths with vacuolation and axonal spacing. By Day 14, myelin structure largely recovered. MBP levels decreased from Day 3, reached a minimum at Day 7, and increased significantly by Day 14. Prox1 expression rose on Day 3, peaked on Day 7, and declined by Day 14. Prox1 and MBP colocalized in injured nerves, and Prox1 overexpression significantly increased MBP levels in Schwann cells.

Conclusion

Prox1 protein level is upregulated in injured sciatic nerve, and Prox1 overexpression promotes the increase of MBP protein level, which positively correlates to myelin regeneration in morphology. This strongly suggests that Prox1 promotes myelin regeneration of injured peripheral nerves.