title: Clonal growth of human articular cartilage and the functional role of the periosteum in chondrogenesis.
abstract: OBJECTIVE
  Clinical cartilage repair with transplantation of cultured chondrocytes, the first described technique introduced in 1994, includes a periosteal membrane but today cells are also implanted without the periosteal combination. The aim of this study was to see if the periosteum had more than a biomechanical function and if the periosteum had a biological effect on the seeded cells tested in an agarose system in which the clonal growth in agarose and the external growth stimulation could be analysed.
  
  
  METHODS
  Four different experiments were used to study the growth of human chondrocytes in agarose and the periosteal influence. Human chondrocytes were isolated and transferred to either primary or secondary agarose culture. After 4 weeks, the total number of clones >50 microm was counted. Cocultures of chondrocytes and periosteal tissue, cultures of chondrocytes with conditioned medium from chondrocytes, periosteal cells and fibroblast were used to study a potential stimulatory effect on growth and different cytokines and growth factors were analysed.
  
  
  RESULTS
  It was found that the human chondrocytes had different growth properties in agarose with the formation of four different types of clones: a homogenous clone without matrix production, a homogenous clone with matrix production, a differentiated clone with matrix production and finally a differentiated clone without matrix production. The periosteum exerted a paracrine effect on cultured chondrocytes in agarose resulting in a higher degree of cloning. The chondrocytes produced significant amounts of interleukin (IL)-6, IL-8, granulocyte-macrophage colony-stimulating factor (GM-CSF) and transforming growth factor (TGF)-beta. The periosteum produced significant amounts of IL-6, IL-8 and TGF-beta. Cocultures of chondrocytes and periosteum demonstrated a potentiation of IL-6 and IL-8 release but not of TGF-beta and GM-CSF.
  
  
  CONCLUSIONS
  Articular chondrocytes are able to form clones of different properties in agarose and the periosteum has a capacity of stimulating chondrocyte clonal growth and differentiation and secretes significant amounts of IL-6, IL-8, GM-CSF and TGF-beta. It may be that the repair of cartilage defects with seeded chondrocytes could benefit from the combination with a periosteal graft. The production of TGF-beta by implanted chondrocytes could influence the chondrogenic cells in the periosteum to start a periosteal chondrogenesis and together with the matrix from implanted chondrocyte production, a repair of cartilaginous appearance may develop; a dual chondrogenic response is possible.
authors.affiliation: Department of Orthopaedics, Sahlgren's University Hospital, S-413 45 Göteborg, Sweden. mats.brittberg@telia.com
authors.forename: M
authors.initials: M
authors.lastname: Brittberg
authors.forename: E
authors.initials: E
authors.lastname: Sjögren-Jansson
authors.forename: M
authors.initials: M
authors.lastname: Thornemo
authors.forename: B
authors.initials: B
authors.lastname: Faber
authors.forename: A
authors.initials: A
authors.lastname: Tarkowski
authors.forename: L
authors.initials: L
authors.lastname: Peterson
authors.forename: A
authors.initials: A
authors.lastname: Lindahl
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002358:Cartilage, Articular / Q000254:growth & development* / Q000378:metabolism; D002455:Cell Division / Q000502:physiology; D002478:Cells, Cultured; D019902:Chondrocytes / Q000378:metabolism / Q000502:physiology; D020219:Chondrogenesis / Q000502:physiology*; D002999:Clone Cells / Q000502:physiology; D016207:Cytokines / Q000096:biosynthesis; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000502:physiology; D008297:Male; D008875:Middle Aged; D010521:Periosteum / Q000502:physiology*; D012685:Sepharose
chemical_list: D016207:Cytokines; D012685:Sepharose