title: Dynamic compression of single cells.
abstract: OBJECTIVE
  The objective of this study was to measure the effects of dynamic compression on single chondrocyte gene expression using a single cell approach, combining single cell biomechanics with single cell gene expression.
  
  
  METHODS
  Articular chondrocytes from the middle and deep zones of bovine distal metatarsal cartilage were statically or dynamically compressed (at a frequency of approximately 1Hz) using a custom creep cytocompression apparatus, and their gene expression levels for type II collagen, aggrecan, tissue inhibitor of metalloproteinase-1, and matrix metalloproteinase-1 were subsequently measured using single cell real-time reverse transcriptase-polymerase chain reaction.
  
  
  RESULTS
  Single chondrocyte gene expression was lognormally distributed, suggesting that studies of populations of cells may be biased by a minority of cells with very high levels of gene expression, and would not accurately describe the behavior of most chondrocytes. Chondrocytes exposed to dynamic loading did, in general, have higher levels of type II collagen and aggrecan gene expression than statically loaded cells. Specifically, compressive forces of 50 and 100 nN suppressed type II collagen expression when applied statically, but the equivalent dynamic loads increased expression to control levels. Tissue inhibitor of metalloproteinase-1 was not affected by the mechanical loading regimens examined.
  
  
  CONCLUSIONS
  We have demonstrated that a single cell approach is a viable methodology for studying the responses of cells to mechanical forces. Furthermore, examining the effects of mechanical loading on a cell-by-cell basis allows us to capture behaviors and details that would otherwise elude studies performed on a larger scale.
authors.affiliation: Department of Bioengineering, Rice University, 6100 Main Street, Houston, TX 77005, USA.
authors.forename: A C
authors.initials: AC
authors.lastname: Shieh
authors.forename: K A
authors.initials: KA
authors.lastname: Athanasiou
mesh_terms: D053674:Aggrecans / Q000235:genetics*; D000818:Animals; D001696:Biomechanical Phenomena; D002358:Cartilage, Articular / Q000166:cytology / Q000502:physiology*; D002417:Cattle; D019902:Chondrocytes / Q000166:cytology / Q000502:physiology*; D024043:Collagen Type II / Q000235:genetics*; D015870:Gene Expression; D020781:Matrix Metalloproteinase 1 / Q000235:genetics*; D053504:Matrix Metalloproteinases, Membrane-Associated; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019714:Tissue Inhibitor of Metalloproteinases / Q000235:genetics*; D016474:Weight-Bearing
chemical_list: D053674:Aggrecans; D024043:Collagen Type II; D019714:Tissue Inhibitor of Metalloproteinases; D053504:Matrix Metalloproteinases, Membrane-Associated; D020781:Matrix Metalloproteinase 1