title: Variation of mesenchymal cells in polylactic acid scaffold in an osteochondral repair model.
abstract: OBJECTIVE
  To achieve osteochondral regeneration utilizing transplantation of cartilage-lineage cells and adequate scaffolds, it is essential to characterize the behavior of transplanted cells in the repair process. The objectives of this study were to elucidate the survival of mesenchymal cells (MCs). In a polylactic acid (PLA) scaffold and assess the possibility of MC/PLA constructs for osteochondral repair.
  
  
  METHODS
  Bone marrow from mature male rabbits was cultured for 2 weeks, and fibroblast-like MCs, which contain mesenchymal stem cells (MSCs), were obtained. A cell/scaffold construct was prepared with one million MCs and a biodegradable PLA core using a rotator device. One week after culturing, the construct was transplanted into an osteochondral defect in the medial femoral condyle of female rabbits and the healing process examined histologically. To examine the survivability of transplanted MCs, the male-derived sex-determining region Y (SRY) gene was assessed as a marker of MCs in the defect by polymerase chain reaction (PCR).
  
  
  RESULTS
  In the groups of defects without any treatment, and the transplantation of PLA without cells, the defects were not repaired with hyaline cartilage. The cartilaginous matrix by safranin O staining and type II collagen by immunohistochemical staining were recognized, however the PLA matrix was still present in the defects at 24 weeks after transplantation of the construct. During the time passage, transplanted MCs numbers decreased from 7.8 x 105 at 1 week, to 3.5 x 105 at 4 weeks, and to 3.8 x 104 at 12 weeks. Transplanted MCs were not detectable at 24 weeks.
  
  
  CONCLUSIONS
  MCs contribute to the osteochondral repair expressing the cartilaginous matrix, however the number of MCs were decreasing with time (i.e. 24 weeks). These results could be essential for achieving cartilage regeneration by cell transplantation strategies with growth factors and/or gene therapy.
authors.affiliation: Department of Orthopaedic Surgery, University of California San Diego , La Jolla, CA 92093-0630, USA.
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Oshima
authors.forename: Frederick L
authors.initials: FL
authors.lastname: Harwood
authors.forename: Richard D
authors.initials: RD
authors.lastname: Coutts
authors.forename: Toshikazu
authors.initials: T
authors.lastname: Kubo
authors.forename: David
authors.initials: D
authors.lastname: Amiel
mesh_terms: D000818:Animals; D002452:Cell Count; D019902:Chondrocytes / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D005260:Female; D005269:Femur / Q000187:drug effects / Q000473:pathology*; D005786:Gene Expression Regulation / Q000187:drug effects; D007150:Immunohistochemistry; D019344:Lactic Acid / Q000494:pharmacology*; D008297:Male; D020781:Matrix Metalloproteinase 1 / Q000235:genetics / Q000378:metabolism; D045164:Mesenchymal Stem Cell Transplantation; D059630:Mesenchymal Stem Cells / Q000166:cytology* / Q000187:drug effects* / Q000378:metabolism; D011091:Polyesters; D016133:Polymerase Chain Reaction; D011108:Polymers / Q000494:pharmacology*; D011817:Rabbits; D051876:Sex-Determining Region Y Protein / Q000235:genetics / Q000378:metabolism; D013194:Staining and Labeling; D054457:Tissue Scaffolds / Q000737:chemistry*; D014945:Wound Healing / Q000187:drug effects*
chemical_list: D011091:Polyesters; D011108:Polymers; D051876:Sex-Determining Region Y Protein; D019344:Lactic Acid; C033616:poly(lactide); D020781:Matrix Metalloproteinase 1