Histomorphometry of the embryonic avian growth plate by proton nuclear magnetic resonance microscopy

Quantitative nuclear magnetic resonance (NMR) microscopy was used to charac terize the biochemical and morphological properties of the different zones within the growth plate of an embryonic chick femur. For precalcified tissu e, water proton transverse relaxation times (T-2) and magnetization transfe r values (MT) were directly and inversely dependent, respectively, on tissu e cellularity, defined as the intracellular area per unit area on histologi cal sections. T-2 values extrapolated for intra- and extracellular water we re 96 ms and 46 ms, respectively. The extracellular T-2 was comparable with that measured for mature cartilage. The MT values extrapolated for intra- and extracellular compartments were 0.32 and 0.85, respectively, These valu es were comparable with those values reported in the literature for cell pe llets and for mature cartilage tissue. Thus, cellularity dominated the NMR properties of this immature cartilage tissue. Mineral deposits within calci fied cartilage and periosteal bone invoked NMR relaxation processes that we re dependent on the inorganic mineral phase; Additionally, collagen molecul es present in mineralized zones gave rise to a significant MT effect. These results show the utility of water proton NMR microscopy for assessing both the organic and inorganic ph ases within mineralized tissues.