INTRODUCTION
The lips and perioral area play a crucial role in facial aesthetics.1 Signs of aging, such as wrinkles, reduced muscle tone, and thinning skin, frequently appear first in this anatomical area and, subsequently, in other areas. The shape, color, and texture of the lips can be considered signifiers of beauty and youth. However, in older faces, the loss of volume, thinning skin and subcutaneous structures, lip inversion, and changes in teeth occlusion are associated with a loss of attractiveness and sex appeal, particularly in women. This is an important factor in the psychological comfort and self-confidence of many women, considering that perioral wrinkles (the most evident sign of aging) are associated with the female sex.2 This may explain why the lips and perioral area are frequently requested focus areas for aesthetic treatments that retain the client’s natural features.
Thinning skin (one of the elements of aging) depends on different factors (sun exposure, smoking, chrono-aging),3,4,5 which lead to collagen depletion. A decrease in collagen density, and its disorganization and fragmentation, has been reported as a cause of wrinkle development.6,7 Collagen is the most abundant (~30%) protein in the body and accounts for up to 70% of the skin protein content. It is the largest component of the extracellular matrix, providing essential structure to tissues and organs through its tensile strength. Collagen is characterized by a distinctive amino acid (AA) triplet repeat, Gly–X–Y, where Gly represents glycine, and positions X and Y can be any residue but are commonly proline and hydroxyproline, respectively. According to recent studies, collagen is biochemically composed of approximately one-third glycine, such that every third AA is a glycine molecule, according to the formula of the so-called collagen melody GLY–X–Y.8 The next most prevalent AA is proline or its derivative, hydroxyproline. Other AAs, such as leucine or lysine, can occupy the Y position. This distinctive AA repeat gives rise to a signature triple helical structure, which comprises 3 intertwined strands (α-chains).9
Over 20 types of collagen have been identified in different tissues. Collagen types I and III comprise 90% of the dry weight of the skin and are organized in 3D fiber bundles. This reticular structure determines the biomechanical properties of the skin.10 In addition, the presence of a structural cluster of AA is crucial
Thinning skin (one of the elements of aging) depends on different factors (sun exposure, smoking, chrono-aging),3,4,5 which lead to collagen depletion. A decrease in collagen density, and its disorganization and fragmentation, has been reported as a cause of wrinkle development.6,7 Collagen is the most abundant (~30%) protein in the body and accounts for up to 70% of the skin protein content. It is the largest component of the extracellular matrix, providing essential structure to tissues and organs through its tensile strength. Collagen is characterized by a distinctive amino acid (AA) triplet repeat, Gly–X–Y, where Gly represents glycine, and positions X and Y can be any residue but are commonly proline and hydroxyproline, respectively. According to recent studies, collagen is biochemically composed of approximately one-third glycine, such that every third AA is a glycine molecule, according to the formula of the so-called collagen melody GLY–X–Y.8 The next most prevalent AA is proline or its derivative, hydroxyproline. Other AAs, such as leucine or lysine, can occupy the Y position. This distinctive AA repeat gives rise to a signature triple helical structure, which comprises 3 intertwined strands (α-chains).9
Over 20 types of collagen have been identified in different tissues. Collagen types I and III comprise 90% of the dry weight of the skin and are organized in 3D fiber bundles. This reticular structure determines the biomechanical properties of the skin.10 In addition, the presence of a structural cluster of AA is crucial
