title: Automicroneedle therapy system combined with topical tretinoin shows better regenerative effects compared with each individual treatment.
abstract: BACKGROUND
  Regenerative therapy is a relatively new dermatological field. However, the currently available topical agents are unsuitable for transdermal drug delivery because of their high molecular weight and low liposolubility. Therefore, a more effective transdermal drug delivery system is needed in order to achieve better therapeutic effects with these agents. A recently introduced microneedle therapy system (MTS), which is a mechanical method for making minute holes in the skin, improves transdermal delivery. A recently developed refinement of this technique, the automicroneedle therapy system (AMTS), has several advantages over the traditional MTS, as it can achieve consistent results because of its automatic punching method.
  
  
  OBJECTIVE
  To evaluate the cutaneous effects of an AMTS in combination with topical tretinoin.
  
  
  METHODS
  Twelve hairless mice were divided into two groups, and the dorsal skin of each mouse was marked down the centre. The first group was treated with the AMTS plus 0.025% tretinoin on one side of the back, and with 0.025% tretinoin only on the other side. The other group was treated with the AMTS and vehicle on one side, while the other side was left untreated. The effects on cutaneous regeneration and the treatment side-effects were evaluated by functional assessment including transepidermal water loss and skin hydration, and by histopathology including epidermal and dermal thickness, and density of collagen fibres. Western blotting and real-time reverse transcriptase PCR were also performed to determine protein and mRNA expression of procollagen type 1 and matrix metalloproteinase-13.
  
  
  RESULTS
  Compared with the individual treatments (the AMTS alone or tretinoin alone) the combination of tretinoin plus the AMTS produced greater dermal regeneration as a result of increased proliferation of collagen fibres. This combination therapy did not result in treatment-related adverse effects.
  
  
  CONCLUSIONS
  An AMTS combined with topical tretinoin is a safe and effective method for skin regeneration, which works by increasing collagen production, and might be a new therapeutic option for regenerative therapy.
authors.affiliation: Department of Dermatology, Yonsei University Wonju College of Medicine, Korea.
authors.forename: J H
authors.initials: JH
authors.lastname: Kim
authors.forename: H Y
authors.initials: HY
authors.lastname: Park
authors.forename: M
authors.initials: M
authors.lastname: Jung
authors.forename: E H
authors.initials: EH
authors.lastname: Choi
mesh_terms: D000279:Administration, Cutaneous; D000818:Animals; D015153:Blotting, Western; D003094:Collagen / Q000187:drug effects; D024042:Collagen Type I / Q000378:metabolism; D016503:Drug Delivery Systems / Q000295:instrumentation; D005260:Female; D007641:Keratolytic Agents / Q000008:administration & dosage*; D053509:Matrix Metalloproteinase 13 / Q000378:metabolism; D051379:Mice; D008812:Mice, Hairless; D009339:Needles; D060888:Real-Time Polymerase Chain Reaction; D012867:Skin / Q000187:drug effects* / Q000378:metabolism; D014212:Tretinoin / Q000008:administration & dosage*
chemical_list: D024042:Collagen Type I; D007641:Keratolytic Agents; D014212:Tretinoin; D003094:Collagen; D053509:Matrix Metalloproteinase 13