For Retin-A I am seeing this interesting...
[Topical application 3x/week in elderly people, left arm vs right arm comparison, 0.4% retinol lotion for 24 weeks]...Topical retinol improves fine wrinkles associated with natural aging. Significant induction of glycosaminoglycan, which is known to retain substantial water, and increased collagen production are most likely responsible for wrinkle effacement. With greater skin matrix synthesis, retinol-treated aged skin is more likely to withstand skin injury and ulcer formation along with improved appearance.
DMAE study:
In a randomized clinical study, 3% DMAE facial gel applied daily for 16 weeks has been shown to be safe and efficacious (p < 0.05) in the mitigation of forehead lines and periorbital fine wrinkles, and in improving lip shape and fullness and the overall appearance of aging skin. These effects did not regress during a 2-week cessation of application. Beneficial trends (p > 0.05 but </= 0.1) were noted in the appearance of coarse wrinkles, under-eye dark circles, nasolabial folds, sagging neck skin, and neck firmness. Application was found to be well tolerated, with no differences in the incidence of erythema, peeling, dryness, itching, burning, or stinging between the DMAE and placebo groups. An open-label extension of the trial showed that the long-term application of DMAE gel for up to 1 year was associated with a good safety profile. The acute skin-firming effects of DMAE have been confirmed by quantitative measures of cutaneous tensile strength.
Palmitoyl Pentapeptide-3
The compound shows a dose-dependent effect of the peptide of type I collagen of in vitro cultured skin fibroblasts detected with an ELISA. In view of the excellent in vitro results, this sequence was developed as a cosmetic ingredient.
Four groups of 15 volunteers each applied a cream - on one half of the face twice a day during 84 days - containing 10 ppm of Palmitoyl Tripeptide-5, 25 ppm of Palmitoyl Tripeptide-5, 10 ppm competitor’s peptide or no active ingredient (placebo). It could be demonstrated that deep wrinkles are significantly reduced within 3 months and the overall skin appearance is improved. - Peptides for Youth The Proceedings of the 20th American Peptide Symposium, 2009 page 264