title: Characterization of mesenchymal stem cells and fibrochondrocytes in three-dimensional co-culture: analysis of cell shape, matrix production, and mechanical performance.
abstract: BACKGROUND
  Bone marrow mesenchymal stem cells (MSCs) have shown positive therapeutic effects for meniscus regeneration and repair. Preliminary in vitro work has indicated positive results for MSC applications for meniscus tissue engineering; however, more information is needed on how to direct MSC behavior. The objective of this study was to examine the effect of MSC co-culture with primary meniscal fibrochondrocytes (FCCs) in a three-dimensional collagen scaffold in fibrochondrogenic media. Co-culture of MSCs and FCCs was hypothesized to facilitate the transition of MSCs to a FCC cell phenotype as measured by matrix secretion and morphology.
  
  
  METHODS
  MSCs and FCCs were isolated from bovine bone marrow and meniscus, respectively. Cells were seeded in a 20 mg/mL high-density type I collagen gel at MSC:FCC ratios of 0:100, 25:75, 50:50, 75:25, and 100:0. Constructs were cultured for up to 2 weeks and then analyzed for cell morphology, glycosaminoglycan content, collagen content, and production of collagen type I, II, and X.
  
  
  RESULTS
  Cells were homogeneously mixed throughout the scaffold and cells had limited direct cell-cell contact. After 2 weeks in culture, MSCs transitioned from a spindle-like morphology toward a rounded phenotype, while FCCs remained rounded throughout culture. Although MSC shape changed with culture, the overall size was significantly larger than FCCs throughout culture. While 75:25 and 100:0 (MSC mono-culture) culture groups produced significantly more glycosaminoglycan (GAG)/DNA than FCCs in mono-culture, GAG retention was highest in 50:50 co-cultures. Similarly, the aggregate modulus was highest in 100:0 and 50:50 co-cultures. All samples contained both collagen types I and II after 2 weeks, and collagen type X expression was evident only in MSC mono-culture gels.
  
  
  CONCLUSIONS
  MSCs shift to a FCC morphology in both mono- and co-culture. Co-culture reduced hypertrophy by MSCs, indicated by collagen type X. This study shows that MSC phenotype can be influenced by indirect homogeneous cell culture in a three-dimensional gel, demonstrating the applicability of MSCs in meniscus tissue engineering applications.
authors.affiliation: Meinig School of Biomedical Engineering, Cornell University, Ithaca, NY, USA.
authors.forename: Mary Clare
authors.initials: MC
authors.lastname: McCorry
authors.affiliation: Meinig School of Biomedical Engineering, Cornell University, Ithaca, NY, USA.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Puetzer
authors.affiliation: Meinig School of Biomedical Engineering, Cornell University, Ithaca, NY, USA. lb244@cornell.edu.|Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, NY, USA. lb244@cornell.edu.
authors.forename: Lawrence J
authors.initials: LJ
authors.lastname: Bonassar
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D002417:Cattle; D018929:Cell Culture Techniques; D048430:Cell Shape; D002478:Cells, Cultured; D019902:Chondrocytes / Q000502:physiology*; D018920:Coculture Techniques; D005109:Extracellular Matrix / Q000378:metabolism*; D059630:Mesenchymal Stem Cells / Q000502:physiology*; D010539:Permeability; D044968:Regenerative Medicine; D023822:Tissue Engineering
keywords: Collagen; Meniscus; Regeneration; Repair; Tissue engineering