title: Three types of dermal grafts in rats: the importance of mechanical property and structural design.
abstract: BACKGROUND
  To determine how the mechanical property and micro structure affect tissue regeneration and angiogenesis, three types of scaffolds were studied. Acellular dermal matrices (ADM), produced from human skin by removing the epidermis and cells, has been widely used in wound healing because of its high mechanical strength. Collagen scaffolds (CS) incorporated with poly(glycolide-co-L-lactide) (PLGA) mesh forms a well-supported hybrid dermal equivalent poly(glycolide-co-L-lactide) mesh/collagen scaffolds (PMCS). We designed this scaffold to enhance the CS mechanical property. These three different dermal substitutes-ADM, CS and PMCSs are different in the tensile properties and microstructure.
  
  
  METHODS
  Several basic physical characteristics of dermal substitutes were investigated in vitro. To characterize the angiogenesis and tissue regeneration, the materials were embedded subcutaneously in Sprague-Dawley (SD) rats. At weeks 1, 2, 4 and 8 post-surgery, the tissue specimens were harvested for histology, immunohistochemistry and real-time quantitative PCR (RT-qPCR).
  
  
  RESULTS
  In vitro studies demonstrated ADM had a higher Young's modulus (6.94 MPa) rather than CS (0.19 MPa) and PMCS (3.33 MPa) groups in the wet state. Compared with ADMs and CSs, PMCSs with three-dimensional porous structures resembling skin and moderate mechanical properties can promote tissue ingrowth more quickly after implantation. In addition, the vascularization of the PMCS group is more obvious than that of the other two groups. The incorporation of a PLGA knitted mesh in CSs can improve the mechanical properties with little influence on the three-dimensional porous microstructure. After implantation, PMCSs can resist the contraction and promote cell infiltration, neotissue formation and blood vessel ingrowth, especially from the mesh side. Although ADM has high mechanical strength, its vascularization is poor because the pore size is too small. In conclusion, the mechanical properties of scaffolds are important for maintaining the three-dimensional microarchitecture of constructs used to induce tissue regeneration and vascularization.
  
  
  CONCLUSIONS
  The results illustrated that tissue regeneration requires the proper pore size and an appropriate mechanical property like PMCS which could satisfy these conditions to sustain growth.
authors.forename: Chuangang
authors.initials: C
authors.lastname: You
authors.forename: Xingang
authors.initials: X
authors.lastname: Wang
authors.forename: Yurong
authors.initials: Y
authors.lastname: Zheng
authors.affiliation: Department of Burn, the Second Affiliated Hospital of Zhejiang University, Hangzhou 310009, China. hanchunmao1@126.com.
authors.forename: Chunmao
authors.initials: C
authors.lastname: Han
mesh_terms: D062088:Acellular Dermis; D000818:Animals; D001672:Biocompatible Materials / Q000737:chemistry / Q000494:pharmacology*; D024042:Collagen Type I / Q000737:chemistry; D006801:Humans; D019344:Lactic Acid / Q000737:chemistry; D008297:Male; D055595:Mechanical Phenomena; D018919:Neovascularization, Physiologic / Q000187:drug effects; D011100:Polyglycolic Acid / Q000737:chemistry; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D051381:Rats; D017207:Rats, Sprague-Dawley; D012038:Regeneration / Q000187:drug effects; D016038:Skin Transplantation / Q000379:methods*; D013718:Tensile Strength; D054457:Tissue Scaffolds
chemical_list: D001672:Biocompatible Materials; D024042:Collagen Type I; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011100:Polyglycolic Acid; D019344:Lactic Acid