Study evaluates mechanisms of fractional CO2 laser on burn scars

Key Points

Grapevine, Texas - Preliminary results of a study evaluating biopsy specimens obtained from mature burn scars pre- and postfractional CO₂ laser resurfacing show histologic changes that are consistent with the clinical improvement achieved, but further data is needed to understand the mechanisms leading to normal skin regeneration, reported David M. Ozog, M.D., at the 2011 annual meeting of the American Society for Laser Medicine and Surgery.

Dr. Ozog, director of cosmetic dermatology, division of Mohs and dermatological surgery, Henry Ford Hospital, Detroit, conducted the clinical portion of the study while doing a Mohs and cosmetic surgery fellowship with Ron Moy, M.D., at the Moy-Fincher Medical Group in Beverly Hills, Calif. The study enrolled 18 patients with mature burn scars defined as more than one year elapsed since the injury.

Patients were recruited from Grossman Burn Center, and the laboratory work was conducted in the dermatology research lab at Henry Ford Hospital under the direction of Qing-sheng Mi, M.D., Ph.D.

Study results

Histologic information was available from 10 patients, and miRNA analysis was performed in 10 patients. The histologic review showed a shift toward more normal dermal architecture with normalization of collagen appearance and in the ratio of type I to type III collagen. Early immunological analysis showed fourfold decreases in miRNA for transforming growth factor beta-1 (TGF-B1), TGF-B2 and TGF-B3 at 48 hours after treatment.

"Treatment with fractional CO₂ lasers has been reported in various uncontrolled studies and case series to be effective for improving the appearance of hypertrophic burn scars. However, there are no good prospective studies describing the histologic and biochemical effects of these treatments," Dr. Ozog says. "Understanding the immunohistochemistry behind these effects can help us in optimizing treatment and potentially developing new drug targets."

Dr. Ozog says the observed reduction in TGF-B3 was unexpected.

"We hypothesized we should see a decrease in TGF-B isoforms 1 and 2, which are increased in hypertrophic scars," he says. "However, we expected TGF-B3 to increase as this cytokine is decreased in hypertrophic scars but known to be important in mediating scarless fetal wound healing. Perhaps TGF-B3 is initially suppressed and then rebounds, or maybe the response to fractional CO₂ laser treatment is mediated by other pathways and upregulation of TGF-B3 is not important.

"Additional results from immunological studies evaluating changes in other cytokines and from longer follow-up will be used to explore these hypotheses."

The patients included in the study had a mean age of 35 years and were ethnically diverse. Mean body surface area of scar involvement was 35 percent, and the average area of treatment was 280 cm².