Connective tissue response to fractionated thermo-ablative Erbium: YAG skin laser treatment

Synopsis Indications for and prevalence of laser therapies with a fractionated laser beam have risen significantly. However, as of yet, little is known about the underlying molecular changes, especially with respect to dermal extracellular‐matrix remodelling, wound healing and inflammation. This study aimed at the investigation of the connective tissue response of sun‐damaged skin following fractionated laser treatment. Seven patients received a laser therapy on the lateral side of the neck of wrinkles grade III–IV (Glogau scale) using a fractionated thermo‐ablative erbium yttrium aluminium garnet (Er:YAG) laser (2940 nm, BURANE XL; Quantel Derma, Erlangen, Germany). Skin biopsies were taken at baseline from untreated skin, 1 and 6 weeks after laser intervention to investigate hyaluronan (HA), collagen‐I (Coll‐I) and collagen‐III (Coll‐III) remodelling as well as alteration of matrix metalloproteinase 1 expression (MMP‐1). To address this issue, HA synthesizing (HA synthetases, HAS) and degrading (hyaluronidases, HYAL) enzymes were measured at mRNA‐level using a real‐time PCR. Furthermore, immunohistochemical staining for HA was performed by using the HA binding protein (HAbP) and for Coll‐I, Coll‐III and MMP‐1 by using monoclonal antibodies. The degree of inflammation was correlated descriptively. Our findings were that at the two examined read out points, HAS and HYAL showed a slight response alluding to HA synthesis under minimal signs of inflammatory reaction. Concordantly, although to a varying degree, an increase in the HA content of the skin after laser treatment could be detected by immunhistochemistry. During remodelling, Coll‐I, Coll‐III and MMP‐1 showed a cyclic course with a peak after 1 week. Conclusively, our results indicate a light alteration of the HA metabolism towards synthesis and a transient collagen neogenesis caused by a single fractionated thermo‐ablative laser skin intervention. Clinical improvement might be attributed to synergistic effects between collagen neogenesis and the water binding capacities of HA and its influence on skin contraction and remodelling. Résumé Les indications et les traitements réalisés avec des lasers fractionnés sont en phase croissante significative. Cependant, à ce jour, on connaît peu les modifications induites au niveau moléculaire, notamment pendant les phases d’inflammation, de guérison et de remodelage du derme. Cette étude a pour but d’examiner la réaction des tissus conjonctifs à un traitement pa