“Age Reversing Drugs and Devices in Dermatology”
Retinol, retinol derivatives, tazarotene and adapalene discussion
Retinol is also known as vitamin A and is widely available in the U.S. in over the counter
preparations. In an in vivo study of retinol, tretinoin, and vehicle applied to human buttock skin,
retinol 1.6% was found to significantly increase epidermal thickening comparable to tretinoin
0.025% but without the erythema associated with tretinoin . Subsequent studies demonstrated
that retinol inhibits UV induction of collagen degrading enzymes and stimulates collagen
production in photoaged skin . Low dose retinol 0.1% was found to promote keratinocyte
proliferation in vivo and improve clinical photoaging of fine lines and skin tone evenness in the
lateral periorbital regions when applied for a nine month period with minimal irritation . In
addition to the effects on photoaged skin, retinol has been shown to improve naturally aged skin.
This is important because the degree of collagen damage in naturally aged skin tends to be less
pronounced than in photoaged skin, and so the prospect of an irritating regimen becomes even
less desirable when treating subtle changes. Retinol 0.04% applied to sun protected skin of the
upper arms in an elderly population was demonstrated to significantly increase
glycosaminoglycan expression and procollagen I immunostaining compared with vehicle and
only mild irritation was noted in subjects .
Retinol derivatives such as retinyl acetate, retinyl proprionate and retinyl palmitate are
widely used in over the counter anti aging treatments. Retinyl retinoate applied twice daily was
shown to induce significant improvement of lateral periorbital rhytides and improved texture
measured by subject self-assessment, investigator assessment and image analysis when
compared to vehicle or retinol without significant side effects . This novel retinol derivative
has also been associated with upregulation of hyaluronan synthase 2 gene in human
keratinocytes . Hyaluronan is a glycosaminoglycan in the dermal extracellular space which
retains water; an increase in hyaluronan and resulting water retention is associated with
improved appearance and clinical reduction in wrinkling.
Tazarotene is another retinoid which is metabolized to tazarotenic acid, and it selectively
binds to RARs but does not bind RXRs. In a prospective, multicenter, randomized study of
varying strengths of tazarotene cream (0.01%, 0.025%, 0.05%, and 0.1%) for moderate facial
photodamage, tazarotene was found to significantly improve mottled hyperpigmentation and fine
wrinkles at week 24. The higher concentration demonstrated the best efficacy, and it was found
to be comparable to tretinoin. Tazarotene was fairly well tolerated though mild to moderate local
adverse events were seen at the higher concentrations . It should be noted that tazarotene
carries a Pregnancy category X rating in contrast to tretinoin which is pregnancy category C.
Only one study has been performed of adapalene, a synthetic retinoid widely used in acne
therapy, for photoaging. Subjects with actinic keratoses and photoaging applied two strengths of
adapalene or vehicle for up to nine months and actinic keratoses were reduced in the adapalene
groups compared to the vehicle. In addition lentigines were lightened in the adapalene groups
and retrospective photographic review revealed significant wrinkle improvement in adapalene
compared to vehicle .
Estrogen exerts its actions on skin through estrogen receptors. The effects of estrogen on
skin are derived from studies of post-menopausal women. Estrogens have been reported to have
effects on both the epidermis and the dermis. In the epidermis, they have been associated with
increased thickness, hydration and an increase in surface lipid content. In the dermis they have
been associated with increased hydration through an increase in glycosaminoglycan content as
well as through increased collagen . Menopause is associated with an increase in skin
dryness, decreased elasticity, and decreased dermal thickness [11, 12]. Estrogen based
treatments are believed to be beneficial for improving the appearance of photoaged skin, but the
scientific evidence is scanty. Women who take estrogen replacement are observed to have better
skin hydration, elasticity and fewer fine lines  . Other studies, however, have not
demonstrated beneficial effects of estrogen therapy on photoaged skin .
In a study of menopausal women assigned to receive transdermal estrogen only,
transdermal estrogen and progesterone, or oral estrogen and progesterone for 6 months, mean
levels of epidermal skin moisture, elasticity and skin thickness were significantly improved
compared to a no treatment group . Another study of low-dose hormone therapy
(norethindrone acetate and ethinyl estradiol) in postmenopausal women with mild to moderate
photoaging for 48 weeks demonstrated no significant change in global assessment in wrinkling
and sagging .
NAC is an amino acid derivative that is converted to glutathione, an endogenous antioxidant. In
clinical practice, it is used to treat acetaminophen toxicity, intravenous contrast-induced
nephropathy, and as a mucolytic. In a study of topical NAC 20% applied under occlusion to
human skin, reduced glutathione, the form of glutathione with potent ROS scavenging ability
was increased and the oxidized form was eliminated. Additionally, pre-treatment with NAC
prevented UV induced extracellular signal-regulated protein kinase (ERK) activation and
subsequent upregulation of AP-1 and MMPs which prevent collagen breakdown. NAC did not
function as a sunscreen nor did it reduce UV induced erythema . The unpleasant odor
associated with NAC imparts a major barrier to its use in cosmetic preparations.
Genistein is an isoflavone characterized as a phytoestrogen and the major active
constituent in soybeans and has well documented potent antioxidant and chemopreventive
activitie  . Topical pre-treatment with genistein 5% prevents UV-induced activation of
the EGF receptor in human skin leading to the prevention of upregulation of AP-1 and MMPs
and subsequent collagen breakdown . In a study of women in their late 30s and early 40s, 40
mg of soy isoflavone aglycone was given to a treatment group and a placebo food to the control
group. The women who received the soy isoflavone aglycone were noted to have a statistically
significant improvement of fine wrinkles at week 12 and of malar skin elasticity at week 8
compared to the control group .
Vitamin C or ascorbic acid is a co-factor for several enzymes and importantly is a
scavenger of free radicals because it allows vitamin E to remain in its active form. In the dermis,
it is required for the formation of stable collagen . Topically applied vitamin C stimulates
the collagen producing activity of the dermis and applied for 6 months led to clinical
improvement in photoaged skin with respect to firmness, smoothness and dryness compared to
vehicle  .
Coenzyme Q10 or ubiquinone plays an important role in the mitochondrial respiratory
chain because it distributes electrons between various dehydrogenases. In its fully reduced state
(ubiquinol) it is a potent scavenger of superoxide . Idebenone is a synthetic analog of
Coenzyme Q10 with potent antioxidant activity. It is used in clinical practice for the treatment
of cardiac hypertrophy in Friedreich’s ataxia . Applied topically in 0.5% and 1%
formulations, it was noted to reduce skin roughness, increase hydration, reduce fine lines and
was associated with overall global improvement in photoaged skin .
The continuous wave carbon dioxide laser was the first ablative resurfacing device and
continues to be the gold standard against which all other resurfacing procedures are compared.
The CO2 laser emits a 10,500nm wavelength whose chromophore is water. CO2 laser light
penetrates 20-30 um into tissue. The CO2 laser generates heat which results in immediate
tightening due to the shrinkage and denaturation of type I collagen . Clinical improvement
and tissue remodeling occurs over a period of several months. Wrinkle improvement has been
reported to be on the order of 50-90% with fine wrinkles around the mouth and eyes being more
improved than the deep, coarse ones seen in the nasolabial creases  . The mechanisms of
CO2 laser resurfacing were quantified by Orringer et al. in photodamaged human forearm skin
and were found to proceed through a reproducible wound healing response leading to an
improved dermal structure. Cytokines involved in wound healing responses such as IL-1, TNF-
and TGF-1 were elevated and accompanied collagen production evidenced by elevated types
I and III procollagen mRNA levels at 21 days after treatment and remained so for at least 6
month. In addition, enzymes associated with breakdown of fragmented collagen known as
matrix metalloproteinases (MMPs) were noted to be elevated when mRNAs levels were
measured. The breakdown of old and damaged collagen coupled with new collagen formation
are known events in wound healing and are also associated with enhanced skin appearance .
The erbium:yttrium-aluminum-garnet (Er:YAG) laser is another ablative skin resurfacing
laser that emits a wavelength of 2940nm and is close to the absorption peak of water. Its
penetration depth is limited to 1-3 um of tissue so is thought to provide more precise skin
ablation than CO2 ablation. In comparative studies, however, of CO2 to Er:YAG, CO2 laser
ablation is considered to be superior likely due to the greater tissue tightening effect of CO2 
Q-switched lasers, intense pulsed light (IPL) and radiofrequency 
Short-pulsed lasers or Q-switched lasers deliver high-energy pulses to selectively target pigment
with minimal thermal damage to surrounding tissue . Examples of these laser sources
include the Q-switched 532nm, Q-switched 755nm alexandrite and the Q-switched 1064nm. The
QS 532nm targets melanin and red/orange and yellow tattoo pigments. The QS 755 alexandrite
targets melanin and green/blue tattoo pigments. The QS 1064nm targets melanin and black
tattoo pigments. Though the QS 1064nm is pigment specific, it has been shown to induce
nonablative dermal remodeling, new collagen formation, and an increase in fibroblasts and
Intense pulsed light (IPL) is a light based therapy comprised of several different
wavelengths. It is used to target both pigment and vascularity, and the term “photorejuvenation”
has been used to describe the global improvement seen with this technology . The
improvement seen in rhytides is much more modest with IPL than the improvement seen in
pigment and vascular issues. Pretreatment with the topical photosensitizer 5-ALA results in a
significantly greater improvement in global photodamage, mottled hyperpigmentation and fine
lines than treatment with IPL alone .
Radiofrequency wavelengths  produce electrical energy that heats the dermis using
relatively low temperatures. These wavelengths are employed to increase the depth of
penetration in an attempt to achieve skin tightening . RF has the advantage of minimal post
procedure erythema. The theory driving the technology is that uniform volumetric heating of the
reticular dermis occurs due to the tissue’s resistance to the current flow .
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