title: Continuous cyclic compressive loading modulates biological and mechanical properties of collagen hydrogels seeded with human chondrocytes.
abstract: OBJECTIVE
  This study investigated the potential of cyclic compressive loading in the generation of in vitro engineered cartilaginous tissue with the aim of contributing to a better understanding of mechanical preconditioning and its possible role in further optimizing existing matrix-associated cartilage replacement procedures.
  
  
  METHODS
  Human chondrocytes were harvested from 12 osteoarthritic knee joints and seeded into a type I collagen (col-I) hydrogel at low density (2 × 10(5) cells/ml gel). The cell-seeded hydrogel was condensed and cultivated under continuous cyclic compressive loading (frequency: 0.3 Hz; strain: 10%) for 14 days under standardized conditions. After retrieval, specimens were subject to staining, histomorphometric evaluation, gene expression analysis and biomechanical testing.
  
  
  RESULTS
  Cellular morphology was altered by both stimulation and control conditions as was staining for collagen II (col-II). Gene expression measurements revealed a significant increase for col-II under either cultivation condition. No significant differences in col-I, aggrecan and MMP-13 gene expression profiles were found. The col-II/col-I mRNA ratio significantly increased under stimulation, whereas the biomechanical properties deteriorated under either cultivation method.
  
  
  CONCLUSIONS
  Although the effects observed are small, mechanical preconditioning has demonstrated its potential to modulate biological properties of collagen hydrogels seeded with human chondrocytes.
authors.affiliation: Department of Orthopaedics and Trauma Surgery, Aachen University Hospital, Aachen, Germany. Sven.Nebelung@rwth-aachen.de
authors.forename: Sven
authors.initials: S
authors.lastname: Nebelung
authors.forename: Karsten
authors.initials: K
authors.lastname: Gavenis
authors.forename: Björn
authors.initials: B
authors.lastname: Rath
authors.forename: Marcus
authors.initials: M
authors.lastname: Tingart
authors.forename: Andreas
authors.initials: A
authors.lastname: Ladenburger
authors.forename: Marcus
authors.initials: M
authors.lastname: Stoffel
authors.forename: Bei
authors.initials: B
authors.lastname: Zhou
authors.forename: Ralf
authors.initials: R
authors.lastname: Mueller-Rath
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D053674:Aggrecans / Q000378:metabolism; D019149:Bioreactors; D002358:Cartilage, Articular / Q000166:cytology; D002478:Cells, Cultured; D019902:Chondrocytes / Q000166:cytology* / Q000473:pathology; D024042:Collagen Type I / Q000235:genetics / Q000378:metabolism; D024043:Collagen Type II / Q000235:genetics / Q000378:metabolism; D005260:Female; D006801:Humans; D020100:Hydrogels / Q000737:chemistry*; D007150:Immunohistochemistry; D008297:Male; D053509:Matrix Metalloproteinase 13 / Q000378:metabolism; D008875:Middle Aged; D011312:Pressure; D023822:Tissue Engineering
chemical_list: D053674:Aggrecans; D024042:Collagen Type I; D024043:Collagen Type II; D020100:Hydrogels; D053509:Matrix Metalloproteinase 13