title: Cancellous bone properties and matrix content of TGF-beta2 and IGF-I in human tibia: a pilot study.
abstract: Transforming and insulin-like growth factors are important in regulating bone mass. Thus, one would anticipate correlations between matrix concentrations of growth factors and functional properties of bone. We therefore investigated the relationships of (1) TGF-beta2 and (2) IGF-I matrix concentrations with the trabecular microstructure, stress distribution, and mechanical properties of tibial cancellous bone from six male human cadavers. Trabecular stress amplification (VMExp/sigma(app)) and variability (VMCOV) were calculated using microcomputed tomography (muCT)-based finite element simulations. Bone volume fraction (BV/TV), surface/volume ratio (BS/BV), trabecular thickness (Tb.Th), number (Tb.N) and separation (Tb.Sp), connectivity (Eu.N), and anisotropy (DA) were measured using 3-D morphometry. Bone stiffness and strength were measured by mechanical testing. Matrix concentrations of TGF-beta2 and IGF-I were measured by ELISA. We found higher matrix concentrations of TGF-beta2 were associated with higher Tb.Sp and VMExp/sigma(app) for pooled data and within subjects. Similarly, a higher matrix concentration of IGF-I was associated with lower stiffness, strength, BV/TV and Tb.Th and with higher BS/BV, Tb.Sp, VMExp/sigma(app) and VMCOV for pooled data and within subjects. IGF-I and Tb.N were negatively associated within subjects. It appears variations of the stress distribution in cancellous bone correlate with the variation of the concentrations of TGF-beta2 and IGF-I in bone matrix: increased local matrix concentrations of growth factors are associated with poor biomechanical and architectural properties of tibial cancellous bone.
authors.affiliation: Department of Orthopaedics and Rehabilitation, Section of Biomechanics, Bone and Joint Center, Henry Ford Hospital, 2799 West Grand Boulevard, E&R 2015, Detroit, MI 48202, USA. yeni@bjc.hfh.edu
authors.forename: Yener N
authors.initials: YN
authors.lastname: Yeni
authors.forename: X Neil
authors.initials: XN
authors.lastname: Dong
authors.forename: Bingbing
authors.initials: B
authors.lastname: Zhang
authors.forename: Gary J
authors.initials: GJ
authors.lastname: Gibson
authors.forename: David P
authors.initials: DP
authors.lastname: Fyhrie
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D001857:Bone Matrix / Q000737:chemistry* / Q000000981:diagnostic imaging; D002102:Cadaver; D003198:Computer Simulation; D055119:Elastic Modulus; D004797:Enzyme-Linked Immunosorbent Assay; D020342:Finite Element Analysis; D006801:Humans; D021621:Imaging, Three-Dimensional; D007334:Insulin-Like Growth Factor I / Q000032:analysis*; D008297:Male; D008875:Middle Aged; D008953:Models, Anatomic; D010865:Pilot Projects; D013314:Stress, Mechanical; D013977:Tibia / Q000737:chemistry* / Q000000981:diagnostic imaging; D053781:Transforming Growth Factor beta2 / Q000032:analysis*; D055114:X-Ray Microtomography
chemical_list: D053781:Transforming Growth Factor beta2; D007334:Insulin-Like Growth Factor I