Single Local Application of TGF-β Promotes a Proregenerative State Throughout a Chronically Injured Nerve

Area of Science:

• Neuroscience
• Regenerative Medicine
• Biochemistry

Background:

• Nerve injuries, especially to large nerve trunks, often result in poor functional recovery due to limited axon regeneration and loss of neurotrophic support from Schwann cells (SCs).
• Overcoming these limitations is crucial for improving outcomes in peripheral nerve repair.

Purpose of the Study:

• To evaluate the efficacy of a single application of transforming growth factor-beta (TGF-β) combined with forskolin, or forskolin alone, in promoting axonal regeneration through the distal nerve stump.
• To assess the potential of these treatments to support regeneration in chronically injured nerves.

Main Methods:

• A delayed repair rat model of tibial nerve injury was utilized.
• Nerve repair was performed after 8 weeks, followed by treatment with saline, forskolin, or TGF-β plus forskolin at the repair site.
• Nerve tissues were analyzed for histology, axon counts, and expression of regeneration markers (S100, CD68, Ki67, p75NGFR, activated caspase-3) after 6 weeks.

Main Results:

• TGF-β plus forskolin significantly increased the number of regenerated axons distal to the repair site and in the furthest nerve sections.
• Both treatments (TGF-β plus forskolin and forskolin alone) showed a significant increase in distal axon regeneration compared to saline.
• Regeneration-associated marker proteins showed extended expression in the treated groups.

Conclusions:

• A single application of TGF-β plus forskolin effectively promotes axonal regeneration and increases regeneration-associated proteins beyond the repair site in chronically injured nerves.
• This approach may help overcome the reduction in regenerated axons over long distances, offering a potential therapeutic strategy for severe nerve injuries.