Recent studies are showing that hyaluronic acid fillers (like Juvederm and Restylane) may possibly provide longer lasting results than we initially thought. Studies by Wang et al and Turlier et al have demonstrated neocollagenesis in patients injected with HA fillers. Fillers were shown to increase production in collagen types I and III in the areas they were injected.
Collagen, one of the strongest natural proteins and the most abundant one in humans as well as in skin, imparts durability and resilience to the skin. Collagen is synthesized in fibroblasts. Type I collagen comprises 80% to 85% of the dermal matrix and is responsible for th tensile strength of the dermis. Collagen I has been shown to be lower in photaged skin, and is likely most important in regard to skin aging. Type III is the second most important form of collagen in the dermis, making up anywhere from 10% to 15% of the matrix. This collagen type is of smaller diameter allowing for more pliability.
Intrinsic (internal causes) aging is the natural aging process that takes place over the years regardless of outside influences. After the age of 20, a person produces about 1 percent less collagen in the skin each year. As a result, the skin becomes thinner and more fragile with age.
Extrinsic aging (external causes) occurs in addition to intrinsic aging as a result of sun and environmental damage (tobacco use and exposure to pollution, for example). Extrinsic aging shows up as thickening of the cornified layer, precancerous changes such as lesions called actinic keratosis, skin cancer (including basal cell carcinoma, squamous cell carcinoma, lentigo maligna melanoma), freckle and sun spot formation, and exaggerated loss of collagen and elastin.. These processes give the skin the appearance of roughness, uneven tone, brown patches, thin skin and deep wrinkles.
So each year after you turn 20, your collagen will decrease by 1%. This would mean by age 40 you would experience a 20% decline in collagen, that is if you haven't been tanning, smoking or living in a polluted environment. If you have been partaking in any of the above mentioned activities, your collagen decrease will be greater than the expected 20%, as these cause collagen to decline more rapidly.
Where you see the most evident damage, often times, is where you have hyaluronic acid fillers injected, which coincidentally is where you would have more collagen loss. Therefore, the collagen production stimulated by the filler would provide even more long lasting results!