Department of Clinical Cell Biology, Lillebaelt/Vejle Hospital, Institute of Regional Health Science, University of Southern Denmark, Vejle.
Department of Clinical Cell Biology, Lillebaelt/Vejle Hospital, Institute of Regional Health Science, University of Southern Denmark, Vejle.
Am J Pathol. 2014 Mar;184(3):778-89. doi: 10.1016/j.ajpath.2013.11.022. Epub 2014 Jan 9.
It is commonly proposed that bone forming osteoblasts recruited during bone remodeling originate from bone marrow perivascular cells, bone remodeling compartment canopy cells, or bone lining cells. However, an assessment of osteoblast recruitment during adult human cancellous bone remodeling is lacking. We addressed this question by quantifying cell densities, cell proliferation, osteoblast differentiation markers, and capillaries in human iliac crest biopsy specimens. We found that recruitment occurs on both reversal and bone-forming surfaces, as shown by the cell density and osterix levels on these respective surfaces, and that bone formation occurs only above a given cell density. Canopies appeared an important source of osteoprogenitors, because (i) canopy cells proved to be more proliferative and less differentiated than bone surface cells, as shown by the inverse levels of Ki-67 and procollagen-3 N-terminal peptide versus osterix, and (ii) canopy cell densities, found to decline with age, and canopy-capillary contacts above eroded surfaces correlated positively with osteoblast density on bone-forming surfaces. Furthermore, we showed that bone remodeling compartment canopies arise from a mesenchymal envelope surrounding the red bone marrow, which is lifted and hypertrophied on initiation of bone resorption. This study, together with earlier reports, led to a model in which canopies and nearby capillaries are critical for reaching the osteoblast density required for bone formation.
人们普遍认为，骨重建过程中募集的成骨细胞源自骨髓血管周细胞、骨改建腔龛细胞或骨衬细胞。然而，目前缺乏对成人松质骨骨重建过程中成骨细胞募集的评估。我们通过定量分析人髂嵴活检标本中的细胞密度、细胞增殖、成骨细胞分化标志物和毛细血管来解决这个问题。我们发现，募集发生在反转和形成骨的表面，这可以通过这些表面的细胞密度和骨钙素水平来证明，并且只有在达到一定的细胞密度之上才会发生骨形成。腔龛似乎是成骨前体细胞的重要来源，因为（i）与骨表面细胞相比，腔龛细胞的增殖能力更强，分化程度更低，这可以通过 Ki-67 和前胶原 3 N 端肽与骨钙素的相反水平来证明，（ii）随着年龄的增长而降低的腔龛细胞密度，以及侵蚀表面上方的腔龛-毛细血管接触，与形成骨表面的成骨细胞密度呈正相关。此外，我们还表明，骨改建腔龛源自围绕红骨髓的间充质包膜，在骨吸收开始时，该包膜被抬起并肥大。这项研究与早期的报告一起，提出了一个模型，其中腔龛和附近的毛细血管对于达到形成骨所需的成骨细胞密度至关重要。
