title: Lamellar spacing in cuboid hydroxyapatite scaffolds regulates bone formation by human bone marrow stromal cells.
abstract: BACKGROUND
  A major goal in bone engineering is the creation of large volume constructs (scaffolds and stem cells) that bear load. The scaffolds must satisfy two competing requirements--they need be sufficiently porous to allow nutrient flow to maintain cell viability, yet sufficiently dense to bear load. We studied the effect of scaffold macroporosity on bone formation and scaffold strength, for bone formed by human bone marrow stromal cells.
  
  
  METHODS
  Rigid cubical hydroxyapatite/tricalcium phosphate scaffolds were produced by robo-casting. The ceramic line thickness was held constant, but the distance between adjacent lines was either 50, 100, 200, 500, or 1000 μm. Cultured human bone marrow stromal cells were combined with the scaffolds in vitro; transplants were placed into the subcutis of immunodeficient mice. Transplants were harvested 9, 18, 23, 38, or 50 weeks later. Bone formation and scaffold strength were analyzed using histology and compression testing.
  
  
  RESULTS
  Sixty transplants were evaluated. Cortical bone increased with transplant age, and was greatest among 500 μm transplants. In contrast, maximum transplant strength was greatest among 200 μm transplants.
  
  
  CONCLUSIONS
  Lamellar spacing within scaffolds regulates the extent of bone formation; 500 μm yields the most new bone, whereas 200 μm yields the strongest transplants.
authors.affiliation: Department of Surgery, University of California-San Francisco, San Francisco, California 94143-0807, USA. mahesh.mankani@ucsf.edu
authors.forename: Mahesh H
authors.initials: MH
authors.lastname: Mankani
authors.forename: Shahrzad
authors.initials: S
authors.lastname: Afghani
authors.forename: Jaime
authors.initials: J
authors.lastname: Franco
authors.forename: Max
authors.initials: M
authors.lastname: Launey
authors.forename: Sally
authors.initials: S
authors.lastname: Marshall
authors.forename: Grayson W
authors.initials: GW
authors.lastname: Marshall
authors.forename: Robert
authors.initials: R
authors.lastname: Nissenson
authors.forename: Janice
authors.initials: J
authors.lastname: Lee
authors.forename: Antoni P
authors.initials: AP
authors.lastname: Tomsia
authors.forename: Eduardo
authors.initials: E
authors.lastname: Saiz
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena / Q000187:drug effects; D001854:Bone Marrow Cells / Q000166:cytology* / Q000187:drug effects; D016026:Bone Marrow Transplantation; D019245:Compressive Strength / Q000187:drug effects; D017886:Durapatite / Q000494:pharmacology*; D006801:Humans; D008297:Male; D051379:Mice; D008855:Microscopy, Electron, Scanning; D010012:Osteogenesis / Q000187:drug effects*; D017154:Stromal Cells / Q000166:cytology / Q000187:drug effects / Q000637:transplantation; D054457:Tissue Scaffolds / Q000737:chemistry*; D055815:Young Adult
chemical_list: D017886:Durapatite