Balancing mechanical strength with bioactivity in chitosan–calcium phosphate 3D microsphere scaffolds for bone tissue engineering: air- vs. freeze-drying processes

Authors

D.T. Nguyen, J.D. McCanless, M.M. Mecwan, A.P. Noblett, W.O. Haggard, R.A. Smith & J.D. Bumgardner

Abstract

The objective of this study was to evaluate the potential benefit of 3D composite scaffolds composed of chitosan and calcium phosphate for bone tissue engineering. Additionally, incorporation of mechanically weak lyophilized microspheres within those air-dried (AD) was considered for enhanced bioactivity. AD microsphere, alone, and air- and freeze-dried microsphere (FDAD) 3D scaffolds were evaluated in vitro using a 28-day osteogenic culture model with the Saos-2 cell line. Mechanical testing, quantitative microscopy, and lysozyme-driven enzymatic degradation of the scaffolds were also studied. FDAD scaffold showed a higher concentration (p < 0.01) in cells per scaffold mass vs. AD constructs. Collagen was 31% greater (p < 0.01) on FDAD compared to AD scaffolds not evident in microscopy of microsphere surfaces. Alternatively, AD scaffolds demonstrated a superior threefold increase in compressive strength over FDAD (12 vs. 4 MPa) with minimal degradation. Inclusion of FD spheres within the FDAD scaffolds allowed increased cellular activity through improved seeding, proliferation, and extracellular matrix production (as collagen), although mechanical strength was sacrificed through introduction of the less stiff, porous FD spheres.

Link to Article

http://dx.doi.org/10.1080/09205063.2012.735099

Inflammatory arthritis increases mouse osteoclast precursors with myeloid suppressor function

Authors

Julia F. Charles, Lih-Yun Hsu, Erene C. Niemi, Arthur Weiss, Antonios O. Alipranti and Mary C. Nakamura

Abstract

Increased osteoclastic bone resorption leads to periarticular erosions and systemic osteoporosis in RA patients. Although a great deal is known about how osteoclasts differentiate from precursors and resorb bone, the identity of an osteoclast precursor (OCP) population in vivo and its regulatory role in RA remains elusive. Here, we report the identification of a CD11b–/loLy6Chi BM population with OCP activity in vitro and in vivo. These cells, which can be distinguished from previously characterized precursors in the myeloid lineage, display features of both M1 and M2 monocytes and expand in inflammatory arthritis models. Surprisingly, in one mouse model of RA (adoptive transfer of SKG arthritis), cotransfer of OCP with SKG CD4+ T cells diminished inflammatory arthritis. Similar to monocytic myeloid-derived suppressor cells (M-MDSCs), OCPs suppressed CD4+ and CD8+ T cell proliferation in vitro through the production of NO. This study identifies a BM myeloid precursor population with osteoclastic and T cell–suppressive activity that is expanded in inflammatory arthritis. Therapeutic strategies that prevent the development of OCPs into mature bone-resorbing cells could simultaneously prevent bone resorption and generate an antiinflammatory milieu in the RA joint.

Link to Article

http://dx.doi.org/10.1172/JCI60920

Hydrogen water consumption prevents osteopenia in ovariectomized rats

Authors

Ji-Dong Guo, Li Li, Ya-Min Shi, Hua-Dong Wang, Shu-Xun Hou

Abstract

Accumulating evidence indicates an important role of oxidative stress in the progression of osteoporosis. Recently, it was demonstrated that hydrogen gas, as a novel antioxidant, could selectively reduce hydroxyl radicals and peroxynitrite anion to exert potent therapeutic antioxidant activity. The aim of the present work was to investigate the effect of hydrogen water (HW) consumption on ovariectomy-induced osteoporosis. Ovariectomized rats were fed with HW (1.3 ± 0.2 mg·L−1) for 3 months. Then, blood was collected and femur and vertebrae were removed for evaluation of the effect of HW on bone. HW consumption in ovariectomized rats had no significant effect on oestrogen production, but prevented the reduction of bone mass including bone mineral content and bone mineral density in femur and vertebrae, and preserved mechanical strength including ultimate load, stiffness, and energy, and bone structure including trabecular bone volume fraction, trabecular number, and trabecular thickness in femur, and preserved mechanical strength including ultimate load and stiffness, and bone structure including trabecular bone volume fraction and trabecular number in vertebrae. In addition, treatment with HW abated oxidative stress and suppressed IL-6 and TNF-α mRNA expressions in femur of ovariectomized rats; treatment with HW increased femur endothelial NOS activity and enhanced circulating NO level in ovariectomized rats. HW consumption prevents osteopenia in ovariectomized rats possibly through the ablation of oxidative stress induced by oestrogen withdrawal.

Link to Article

http://dx.doi.org/10.1111/bph.12036

A histomorphometric study of cellular layers after hemiepiphyseal stapling on the physeal plate in rabbits

Authors

Su-Min Son, Il-Hyung Park, Chang-Wug Oh, Hyun-Joo Lee, Byung-Chul Park, Je-Yong Choi

Abstract

Epiphyseal stapling has been widely used to correct angular deformity. The mechanism, however, has not been well determined. To determine the effect of temporary hemiepiphyseal stapling on the cellular layers of the physis, a histomorphometric study was performed using immature rabbits. Distal lateral epiphyseal stapling of the right femur was performed on 6-week-old New Zealand white rabbits. Thirty rabbits were randomly assigned to five groups, and six rabbits in each group were analyzed weekly for up to 5 weeks. The distal femur was deformed into the valgus, and the anatomical lateral distal femoral angle decreased with the passage of time. In the sequential histomorphometry of the operated physeal plate, the area ratio of each layer, compared to the control side, decreased every week. The total area of the physeal plate had decreased up to 60 % at the 5th week compared to the area of the 1st week, and the area of the proliferative layer decreased by the greatest amount among the three layers. Our findings suggest that the proliferation of chondrocytes seemed to be more suppressed by the compression of the stapling, thereby slowing the growth rate, although hypertrophy of the chondrocytes was also suppressed.

Link to Article

http://dx.doi.org/10.1007/s00776-012-0317-6

Deferoxamine Enhances the Vascular Response of Bone Regeneration in Mandibular Distraction Osteogenesis

Authors

Alexis Donneys, Aaron Farberg, Catherine Tchanque-Fossuo, Sagar Deshpande, Steven R. Buchman

Abstract

Bone regeneration during distraction osteogenesis is intricately associated with an enhanced vascular response. Augmenting this response may offer considerable clinical advantages such as optimizing the quality of regenerate formation, decreasing lengthy consolidation periods, or increasing regenerate size and distance. Using deferoxamine, an angiogenic transcriptional activator, the authors posit that substantial increases in vascular volume beyond the normal response to mechanical distraction can be quantified with micro–computed tomography after vessel perfusion during mandibular distraction osteogenesis. Two groups of Sprague-Dawley rats (n = 12) underwent external fixator placement, mandibular osteotomy, and 5.1-mm distraction. During distraction, the experimental group (n = 6) was treated with deferoxamine injections into the distraction gap. After consolidation, the animals were perfused and imaged with micro–computed tomography. Vascular radiomorphometrics were calculated and statistical comparison was conducted with the independent samples t test. A value of p ≤ 0.05 was considered statistically significant. A 40 percent statistically significant increase in the number of vessels (0.82 vessels/mm versus 1.15 vessels/mm; p < 0.012) and a complementary decrease in the space between vessels (1.18 mm versus 0.86 mm; p < 0.012) were calculated in the experimental regenerate when compared with controls. This robust increase in vascularity could also be readily observed with micro–computed tomographic image reconstruction. Gross examination revealed a denser regenerate in the deferoxamine-injected group that is clearly illustrated with Faxitron radiography. The authors' study quantifies the ability of deferoxamine to augment the vascular response of mandibular distraction osteogenesis and establishes correlations between this therapeutic enrichment and enhanced regenerate formation.

Link to Article

http://dx.doi.org/10.1097/PRS.0b013e31824422f2

Prolonged alendronate treatment prevents the decline in serum TGF-β1 levels and reduces cortical bone strength in long-term estrogen deficiency rat model

Authors

Junjing Jia, Wei Yao, Sarah Amugongo, Mohammad Shahnazari, Weiwei Dai, Yu-An E. Lay, Diana Olvera, Elizabeth A. Zimmermann, Robert O. Ritchie, Chin-Shang Li, Tamara Alliston, Nancy E. Lane

Abstract

While the anti-resorptive effects of the bisphosphonates (BPs) are well documented, many questions remain about their mechanisms of action, particularly following long-term use. This study evaluated the effects of alendronate (Ale) treatment on TGF-β1 signaling in mesenchymal stem cells (MSCs) and osteocytes, and the relationship between prolonged alendronate treatment on systemic TGF-β1 levels and bone strength. TGF-β1 expression and signaling were evaluated in MSCs and osteocytic MLO-Y4 cells following Ale treatment. Serum total TGF-β1 levels, a bone resorption marker (DPD/Cr), three-dimensional microCT scans and biomechanical tests from both the trabecular and cortical bone were measured in ovariectomized rats that either received continuous Ale treatment for 360days or Ale treatment for 120days followed by 240days of vehicle. Linear regression tests were performed to determine the association of serum total TGF-β1 levels and both the trabecular (vertebrae) and cortical (tibiae) bone strength. Ale increased TGF-β1 signaling in the MSCs but not in the MLO-Y4 cells. Ale treatment increased serum TGF-β1 levels and the numbers of TGF-β1-positive osteocytes and periosteal cells in cortical bone. Serum TGF-β1 levels were not associated with vertebral maximum load and strength but was negatively associated with cortical bone maximum load and ultimate strength. The increase of serum TGF-β1 levels during acute phase of estrogen deficiency is likely due to increased osteoclast-mediated release of matrix-derived latent TGF-β1. Long-term estrogen-deficiency generally results in a decline in serum TGF-β1 levels that are maintained by Ale treatment. Measuring serum total TGF-β1 levels may help to determine cortical bone quality following alendronate treatment.

Link to Article

http://dx.doi.org/10.1016/j.bone.2012.10.017