Aim:Extract of Hominis Placenta (HP) has been used in oriental medicine as anagent for improving physiological function.The present study was conducted toinvestigate whether HP treatment in an experimental sciatic nerve injury animalmodel produces growth-promoting effects on regenerating peripheral nerve fibersafter injury.Methods:After HP was injected into a sciatic nerve injury site,changesin protein levels were analyzed in the regenerating nerve area by Western blottingand immunofluorescence staining analyses.For quantitative assessment of ax-onal regeneration,a retrograde tracing technique was used to identify the neu-ronal cell bodies corresponding to regenerating axons,and the extent of neuriteoutgrowth in cultured dorsal root ganglia (DRG) sensory neurons prepared fromanimals that had experienced a sciatic nerve crush injury 7d before neuron collec-tion was analyzed.Results:Induction levels of axonal growth-associated protein(GAP-43) in the injured sciatic nerves were elevated by HP treatment.HP treat-ment also upregulated cell division cycle 2 (Cdc2) protein levels in the distalstump of the injured sciatic nerve.Induced Cdc2 protein was detected in Schwanncells,suggesting that Cdc2 kinase activity may be involved in the growth-promot-ing activity of regenerating axons via Schwann cell proliferation.Cell body mea-surement by retrograde tracing indicated that HP treatment produced significantincreases in regenerating motor axons.Finally,HP treatment of cultured DRGsensory neurons significantly increased neurite arborization and elongation.Conclusion:HP promotes the regeneration of injured sciatic axons by upregulatingthe synthesis of regeneration-related protein factors such as GAP-43 and Cdc2. Aim: Extract of Hominis Placenta (HP) has been used in oriental medicine as anagent for improving physiological function. The present study was conducted to investigate whether an HP treatment in an experimental sciatic nerve injury animal model produces growth-promoting effects on regenerating peripheral nerve fibers after injury. Methods: After HP was injected into a sciatic nerve injury site, changes in protein levels were analyzed in the regenerating nerve area by Western blotting and immunofluorescence staining analyzes. For quantitative assessment of ax-onal regeneration, a retrograde tracing technique was used to identify the neu- ronal cell bodies corresponding to regenerating axons, and the extent of neurite outgrowth in cultured dorsal root ganglia (DRG) sensory neurons prepared fromanimals that had experienced a sciatic nerve crush injury 7d before neuron collation was analyzed. Results: Induction levels of axonal growth- associated protein (GAP-43) in the injured sciatic nerves were elevated b suggests that Cdc2 kinase activity may be involved in the growth-promot-ment pathway. ing activity of regenerating axons via Schwann cell proliferation. Cell body mea-surement by retrograde tracing indicated that HP treatment produced significant enzymes in regenerating motor axons. Finaally, HP treatment of cultured DRGsensory neurons significantly increased neurite arborization and elongation. Conlusion: HP promotes the regeneration of injured sciatic axons by upregulating the synthesis of regeneration-related protein factors such as GAP-43 and Cdc2.