ARTICLE | PHOTOTHERAPY | The first phase is inflammation involving key cells:
mast cells and macrophages, which interact with each other and with the fibroblast, releasing degradative enzymes. This is the phase of cell activation. The second phase involves the inhibition of synthesis of glycol conjugated macromolecules and expression of genes encoding fibronectin and collagen I and III. The third phase is optional and is carried out by the myofibroblast resulting from a change of cellular phenotype of fibroblasts under the action of mechanical distension, with probable involvement of interferon and a possible increase in apoptosis. The outcome leads to a (atrophic dermal) scar through the dermis. Stretch marks are, therefore, not
exclusively a disease of elastic tissue (which represent only 10% of the dermis, whereas collagen accounts for 70–80%) and are not solely caused by excessive tension on the skin. Consequently, the Ôcollagen theoryÕ appears to be
the most dominant owing to the effect of fibroblast cells, the glycol conjugated macromolecules, and the microfibrils that form collagen bridges between the elastic fibres, and that have the same composition as the structure of glycoproteins. It might therefore be a degeneration of elastic fibres of collagen tissue13–19
.
Histology Clinically and histologically (i.e. during visual observation), stretch marks appear in the form of linear streaks or spindle-shaped, their length varying from 1 cm to several centimeters, and 1–2.5 cm wide. They are almost always multiple in appearance, and very often symmetrical. Recent stretch marks often vary in colour from bright
red to purple ® hence the name striae rubra ® but some will never be coloured. This colour is the result of an increase in blood vessels within the scar. Its original surface is often swollen, reflecting an inflammatory state. With age, they will gradually become visible and palpable skin depressions, becoming pearly white in colour (striae alba) and very often wrinkled in appearance. The skin of a stretch mark is weak, thin and rough, as
well as atrophied. A lack of hair and an absence of sweat and sebaceous secretions on the stretch-marked skin can also be observed, similar to those changes occurring in scar tissue. The impairment is primarily dermal, with a visible impact in the epidermis, and in cases of broad and deep stretch marks, can even reach the hypodermis. When examining stretch marks with an optical
microscope, one may find a greater positivity for collagen type I than type III. The reticular dermis, in contrast, shows no significant difference in the quantity of collagen. The collagen is strongly bridged and the fibre diameter is larger compared with healthy tissue. Its organisation is horizontal to the surface of the skin. In electron microscopy, the epithelium is thinner, but the basal membrane has no morphological alteration.
42 ❚ March 2012 |
prime-journal.com
The papillary dermis shows a partial disposition of the dermal papillae. It should be noted that the areas with thin collagen fibres and large interfibrillar spaces are completely replaced by coarse fibre bridges divided into dense bundles, which are arranged parallel to the surface of the skin. There is a difference in the amount of elastic fibres; fibres appear fragmented, less translucent and surrounded by a large number of small granules corresponding to glycoproteins. The reticular dermis is marked by a small amount of fibroblasts, the appearance of which is rather globular. An increase is observed with compound collagen fibres, showing a rearrangement of large bridges. The percentage of elastic material is higher and the elastic fibres appear less translucent and less responsive, with more material
the dermis3, 15, 20–22
condensed around. To summarise and simplify, therefore, stretch marks result from a degeneration of collagen tissue, leading to atrophic scarring in the middle of .
Stretch marks on dark skin Dermatological studies of stretch marks in dark skin are still generally poor, with serious publications rare. Histologically, the distinction is not a significant quantitative difference at the cellular level, but results from a difference in melanisation (formation of pigment granules or elementary melanosomes in melanocytes) and pigmentation (pigment transfer to the keratinocytes). Skin pigmentation is therefore the major component
Recent
stretch marks often vary in colour from bright red to purple ® hence the name striae rubra ® but some will never be coloured. This colour is the result of an increase in blood vessels within the scar.
of clinical differentiation between dark and bright skin, with all the intermediary shades of skins of ethnic origin. With regard to those patients with ethnic or darker skin tones treated during this study, the authorsÕ analysis of stretch marks is that they are wider in approximately 60% of subjects. Furthermore, as well as ÔclassicÕ areas, the authors frequently found stretch marks in more unusual areas, such as on the shoulders (top, front, back), the interiors of the arms, and sometimes on the inside of the forearms and lower calves. Finally, it seems that there are more adolescent girls affected in this population cohort, which may be a result of earlier puberty, changes in weight caused by nourishment, and especially, the different anatomical figures24
.
Materials and methods used in this study Two devices were used in this study: an LED light generator and radiofrequency (RF).
LED phototherapy The light generating device used was Chromospace M.U.S.T. Leds , which benefits from five wavelengths ® blue 465 nm, green 522 nm, yellow 595 nm, red 645 nm and infrared 855 nm ® through 24000 monochromatic LEDs, guaranteeing the quality of flow, and thus the light output and accuracy of wavelength.
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