This is the first such clinical study evaluating the efficacy of SP on ageing skin.
Substance P is a neuropeptide consisting of 11 amino acids and is mainly produced in wound areas as it exhibits skin regenerative activity.
The anti-ageing effects of SP are attributed to its anti-inflammatory activity and effects on collagen synthesis. However, there are currently limited applications of SP in cosmeceuticals, due to its low stability.
In order to expand the potential of SP in anti-ageing products, researchers developed a stable formulation known as SP-based hydrogel. The formulation contains sodium thiosulfate and polysorbate to prevent oxidation of SP, and a hydroxyethyl cellulose gelling agent to stabilise it in the hydrogel.
The SP-based hydrogel demonstrated superior in vitro stability and anti-ageing efficacy compared to SP alone.
The research was published in the journal Cosmetics.
A total of 23 women (average age: 59.5) were recruited and randomised to receive either a topical stable SP-based hydrogel or placebo on the right or left side of the face.
The SP-based hydrogel contained 1 μg/mL of SP, the placebo contained distilled water instead of SP-based hydrogel.
Participants applied twice daily for eight weeks.
Photographic scores of wrinkles were collected at week zero, four and eight (0, none; 1, none/mild; 2, mild; 3, mild/moderate; 4, moderate; 5, moderate/severe; 6, severe; and 7, very severe).
A skin-visiometer SV 600 measured skin roughness (R1), maximum roughness (R2), average roughness (R3), smoothness depth (R4), and arithmetic average roughness (R5) at week four and eight.
Wrinkle reducing effect
After eight weeks of treatment, the visiometer analysis revealed a statistically significant decrease in the five parameters (R1 to R5) between the placebo and SP-based hydrogel groups (p<0.05).
However, researchers reported no significant decrease at week four, indicating a longer period of treatment was needed.
Based on the photographic scores, the treatment group also had significantly lower wrinkle grades that of the placebo group after week eight.
These findings suggest that the SP-based hydrogel can be used in the cosmetic industry as a novel anti-wrinkle agent.
Researchers recommended further studies including extending the screening duration longer than eight weeks and even a follow-up period to clarify the anti-wrinkle efficacy of SP.
Researchers said they were working on a separate clinical study comparing the anti-wrinkle efficacy of SP-based hydrogel and retinol (control). The study will last 12 weeks.
“Anti-Wrinkle Efficacy of Neuropeptide Substance P-Based Hydrogel in Human Volunteers”
Authors: Da Jung Kim, et al.