A recent study of skin tightening mechanisms suggests that although the role of immediate skin tightening achieved by collagen denaturation is likely minimal, any skin tightening thereby achieved appears highly directional.
"It's fair to say there are two different factors that could cause contraction of skin" after various skin- tightening procedures, says Dieter Manstein, M.D., the study's lead researcher and instructor in dermatology at Harvard Medical School and Massachusetts General Hospital.
"First, it's known that if one heats collagen above a certain temperature, around 60 degrees Celsius, then it melts and contracts. This would cause an immediate skin tightening" based on passive heat-induced contraction rather than any biological response, Dr. Manstein tells Dermatology Times.
Therefore, Dr. Manstein says, "Our conclusion is that this immediate skin tightening is most likely not the major mechanism involved" in results delivered by available skin-tightening modalities.
Because study results showed only very limited epidermal contraction, even at very high temperatures, Dr. Manstein says one shouldn't neglect the role of the various skin layers other than the dermis, such as the epidermis and subcutaneous fat.
"It's fairly obvious," Dr. Manstein says, "but nobody talks about the fact that the epidermis virtually does not contract immediately. It's something one should be aware of."
In the study, Dr. Manstein and his colleagues immersed about 100 full-thickness abdominal skin samples (measuring approximately 3 cm by 1 mm, taken from two donors of skin types II and IV after abdominoplasty) in water at temperatures ranging from 37 C to 97 C for one minute. At this duration, they found that shrinkage occurred with a sharp onset at about 60 C, with minimal further shrinkage above about 70 C, he says.
"The extent of shrinkage exhibited was highly variable and related to orientation of the samples," Dr. Manstein says.
Furthermore, he says, "The epidermis appeared not to shrink" at any temperature, while the deep reticular dermis generally exhibited more shrinkage than the papillary dermis.
Additionally, skin shrinkage appeared highly directional and occurred parallel to modified Langer's Lines, he says. Researchers observed a maximum shrinkage of 47 percent parallel to these lines and 29 percent perpendicular.
"For the immediate skin contraction based on collagen denaturation," Dr. Manstein says, "there is a highly directional component which is intrinsic and can't be changed."
Though immediate skin tightening probably plays a minimal role in clinical results, Dr. Manstein says, "It's a very interesting question. If immediate skin tightening is highly directional, this may also affect the direction of contraction during wound healing. And which factors can influence its direction?"
At press time, Dr. Manstein and his colleagues were beginning to explore this question in animal and clinical models.
"Our study lays the groundwork for future work," says Henry H. Chan, M.D., honorary clinical associate professor of dermatology, University of Hong Kong, and a study co-author. Dr. Chan says, "Perhaps one can optimize the clinical outcome by taking into consideration this direction of contraction."
Scars, for example, can result from excess collagen and inappropriate tightening. "A better understanding of this whole process hopefully will be beneficial in both cosmetic and wound healing applications," he says.
Additional issues the researchers plan to explore include how immediate skin tightening relates to delayed remodeling and where excess epidermis goes if dermal tightening is achieved.
Disclosure: Drs. Manstein and Chan report no financial interests relevant to this article.
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