Local origins impart conserved bone type-related differences in human osteoblast behaviour

Abstract

Osteogenic behaviour of osteoblasts from trabecular, cortical and subchondral bone were examined to determine any bone type-selective differences in samples from both osteoarthritic (OA) and osteoporotic (OP) patients. Cell growth, differentiation; alkaline phosphatase (TNAP) mRNA and activity, Runt-related transcription factor-2 (RUNX2), SP7-transcription factor (SP7), bone sialoprotein-II (BSP-II), osteocalcin/bone gammacarboxyglutamate (BGLAP), osteoprotegerin (OPG, TNFRSF11B), receptor activator of nuclear factor-κβ ligand (RANKL, TNFSF11) mRNA levels and proangiogenic vascular endothelial growth factor-A (VEGF-A) mRNA and protein release were assessed in osteoblasts from paired humeral head samples from age-matched, human OA/OP (n = 5/4) patients. Initial outgrowth and increase in cell number were significantly faster (p < 0.01) in subchondral and cortical than trabecular osteoblasts, in OA and OP, and this bone type-related differences were conserved despite consistently faster growth in OA. RUNX2/SP7 levels and TNAP mRNA and protein activity were, however, greater in trabecular than subchondral and cortical osteoblasts in OA and OP. BSP-II levels were significantly greater in trabecular and lowest in cortical osteoblasts in both OA and OP. In contrast, BGLAP levels showed divergent bone type-selective behaviour; highest in osteoblasts from subchondral origins in OA and trabecular origins in OP. We found virtually identical bone type-related differences, however, in TNFRSF11B:TNFSF11 in OA and OP, consistent with greater potential for paracrine effects on osteoclasts in trabecular osteoblasts. Subchondral osteoblasts (OA) exhibited highest VEGF-A mRNA levels and release. Our data indicate that human osteoblasts in trabecular, subchondral and cortical bone have inherent, programmed diversity, with specific bone type-related differences in growth, differentiation and pro-angiogenic potential in vitro.

Detection of early osteogenic commitment in primary cells using Raman spectroscopy

“…Although bone exhibits some highly conserved factors in its development, remodelling and repair, it is also apparent that the response to many in vivo challenges is not always consistent in different regions of bone [1][2][3]. These observations suggest that osteoblast populations are inherently heterogeneous and support a current hypothesis that their identity is specific to their local environment [4]. In recent attempts to clinically improve the success of joint replacement much focus has been on the study of the bone cell-implant interface with the long term success of joint replacement relying on sufficient osteoblast adherence, proliferation and differentiation in promoting osseointegration in specific regions.…”

Spatial mapping of humeral head bone density

“…Power analysis indicated that a sample size of 8 humeri was required to achieve 80% power for each of the RM-ANOVA statistical analyses. For this power analysis, we chose our clinically meaningful difference in bone density to be 15%, which falls between the 10% and 20% values previously reported in the literature, 9 , 15 and our group standard deviations were ±0.037 g∙cm −3 as taken from pilot specimens.…”

“…This may be especially advantageous for patients who experience a marked decrease in bone density in the region of the greater tuberosity because of age while their bone density remains unchanged in the medial and posterior regions independent of age and sex as described by Barvencik et al. 1 In addition, Shah et al, 15 using osteoblasts derived from age-matched and paired humeral head samples with osteoarthritis and osteoporosis, showed that cortical and subchondral bone had greater proangiogenic (higher levels of vascular endothelial growth factor A messenger RNA and protein release) capacity and fracture healing characteristics compared with trabecular bone. Their trabecular bone sample taken from the central regions distal to the anatomic neck also consistently showed slower osteoblast proliferation.…”

Murine precision-cut lung slices exhibit acute responses following exposure to gasoline direct injection engine emissions

“…Total cellular RNA was isolated from the homogenates using the PureLink RNA Mini Kit (Life Technologies) according to the manufacturer's protocol. RNA purity was validated using UV-vis spectroscopy absorbance; acceptable samples were characterized by 260/ 280 ratios N2.0 and 260/230 N 1.8 (Shah et al, 2015). Purified RNA was stored at −80°C prior to complementary DNA (cDNA) synthesis.…”