Development, In-Vitro Characterization and In-Vivo Osteoinductive Efficacy of a Novel Biomimetically-Precipitated Nanocrystalline Calcium Phosphate With Internally-Incorporated Bone Morphogenetic Protein-2.

The repair of large-volume bone defects (LVBDs) remains a great challenge in the fields of orthopedics and maxillofacial surgery. Most clinically available bone-defect-filling materials lack proper degradability and efficient osteoinductivity. In this study, we synthesized a novel biomimetically-precipitated nanocrystalline calcium phosphate (BpNcCaP) with internally incorporated bone morphogenetic protein-2 (BpNcCaP + BMP-2) with an aim to develop properly degradable and highly osteoinductive granules to repair LVBDs. We first characterized the physicochemical properties of the granules with different incorporation amounts of BMP-2 using scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. We evaluated the cytotoxicity and cytocompatibility of BpNcCaP by assessing the viability and adhesion of MC3T3-E1 pre-osteoblasts using PrestoBlue assay, Rhodamine-Phalloidin and DAPI staining, respectively. We further assessed the in-vivo osteoinductive efficacy in a subcutaneous bone induction model in rats. In-vitro characterization data showed that the BpNcCaP + BMP-2 granules were comprised of hexagonal hydroxyapatite with an average crystallite size ranging from 19.7 to 25.1 nm and a grain size at 84.13 ± 28.46 nm. The vickers hardness of BpNcCaP was 32.50 ± 3.58 HV 0.025. BpNcCaP showed no obvious cytotoxicity and was favorable for the adhesion of pre-osteoblasts. BMP-2 incorporation rate could be as high as 65.04 ± 6.01%. In-vivo histomorphometric analysis showed that the volume of new bone induced by BpNcCaP exhibited a BMP-2 amount-dependent increasing manner. The BpNcCaP+50 µg BMP-2 exhibited significantly more degradation and fewer foreign body giant cells in comparison with BpNcCaP. These data suggested a promising application potential of BpNcCaP + BMP-2 in repairing LVBDs.

Role of endoplasmic reticulum stress pathway in hydrostatic pressure-induced apoptosis in rat mandibular condylar chondrocytes.

Excessive mechanical loads induce chondrocyte apoptosis and irreversible cartilage degeneration, but the underlying molecular mechanism is poorly understood. The aim of this study was to investigate the possible role of endoplasmic reticulum (ER) stress pathway in hydrostatic pressure (HP)-induced apoptosis in rat mandibular condylar chondrocytes. Chondrocytes were isolated from rat mandibular condylar cartilage and subjected to HP. Cell viability and apoptosis were assessed by Cell Counting Kit-8 and flow cytometry assay. Expression of ER stress-associated molecules was detected by quantitative real-time PCR and western blot analysis. In addition, expression of apoptosis-related proteins (bax, bcl-2, and cleaved-caspase-3) was assessed by western blot. To explore ER stress function, chondrocytes were pretreated with salubrinal before exposure to HP. Expression of type II collagen, aggrecan, MMP-13, and ADAMTS-5 was evaluated by real-time PCR. The results indicated that HP reduced cell viability in a magnitude- and time-dependent manner. HP-induced activation of ER stress pathway by increasing expression of GRP78, CHOP, caspase-12, PERK, and peIF2α in chondrocytes. Moreover, the expression of bax and cleaved-caspase-3 was increased, while the expression of bcl-2 was decreased in response to HP as the stress time prolonged. In addition, salubrinal suppressed HP-induced apoptosis, upregulated type II collagen and aggrecan mRNA expression, and downregulated MMP-13 and ADAMTS-5 mRNA expression in response to HP. These results demonstrate that HP induces apoptosis in mandibular condylar chondrocytes through ER stress-mediated apoptotic pathway. Suppression of ER stress by salubrinal prevents chondrocytes from undergoing apoptosis and matrix degradation induced by HP.

Hedgehog signal expression in articular cartilage of rat temporomandibular joint and association with adjuvant-induced osteoarthritis.

OBJECTIVE: The aim of this study was to investigate the changes in hedgehog (Hh) expression and its possible effects on cartilage degeneration in adjuvant-induced temporomandibular joint osteoarthritis (TMJOA) of rats. METHODS: Forty-eight male Sprague-Dawley rats were randomly divided into experimental osteoarthritis (OA) and sham control groups. The bilateral TMJs of six rats from each group were harvested at three, seven, 14, and 28 days. Histological changes in condylar cartilage were assessed by hematoxylin and eosin, toluidine blue, and safranin O staining. The expression of Hh signal-related proteins including Indian hedgehog (Ihh), patched-1 (Ptch1), smoothened (Smo), glioma-associated oncogene homologue1 (Gli1) in cartilage was assessed by immunohistochemistry and Western blot. The protein expression of matrix metalloproteinase-13 (MMP-13), type X collagen, and a disintegrin and metalloproteinase with thrombospondin motifs 5 (ADAMTS-5) in cartilage was evaluated by Western blot. RESULTS: The histological analysis showed marked cartilage degeneration in adjuvant-induced OA groups, including reduced cartilage cellular density, thinner and degraded cartilage, and decreased proteoglycan content in the extracellular matrix. Compared with matched control groups, the expression of Ihh, Ptch1, Smo, and Gli1 in the OA groups was higher in a time-dependent manner. The protein levels of MMP-13, type X collagen, and ADAMTS-5 were substantially increased in OA cartilage compared with those in matched control rats. CONCLUSION: These results indicate that the activation of Ihh signaling may be correlated with pathological changes of condylar cartilage in adjuvant-induced TMJOA.

Notoginsenoside R1 significantly promotes in vitro osteoblastogenesis.

Notoginsenoside R1 (NGR1), one of the main effective components of Panax notoginseng, appears to be effective in promoting osteogenesis and treating osteoporosis. However, hitherto, whether NGR1 can directly promote osteoblastogenesis remains to be elucidated. In the present study, we hereby examined the effects of NGR1 on the osteoblastogenesis of a pre-osteoblast cell line (MC3T3-E1) in in vitro time-course and dose-dependent experiments. Its efficacy was evaluated by assessing cell viability (indicator of proliferation), alkaline phosphatase (ALP) activity (a marker of early osteoblastic differentiation), levels of osteocalcin (OCN; a marker of late osteoblastic differentiation), calcium deposition (a marker of final mineralization) and the expression of a series of osteoblastogenic marker genes (such as collagen Iα, Runx2, ALP and OCN) at different time points. When examining the proliferation of and ALP activity in the pre-osteoblasts, a bell-shaped dose-response pattern was observed when the cells were treated with various concentrations of NGR1, with a peak being observed at the concentration of 50 µg/ml. NGR1 markedly increased the expression of OCN at the concentration of 1,000 µg/ml in a dose­dependent manner. Furthermore, treatment with 1,000 µg/ml NGR1 resulted in the highest mineralization by 4.3- and 5.9-fold on the 21st and 28th day, respectively compared with the control group (no treatment). On the whole, our findings indicate that NGR1 significantly promotes the osteoblastogenesis of pre-osteoblasts, which suggests that NGR1 has potential for use as a bone regeneration agent.

[The expression of VEGF-C in the condylar cartilage after anterior disc displacement and its clinical significance].

PURPOSE: To investigate the expression and significance of vascular endothelial growth factor-C in the condylar cartilage after anterior disc displacement of temporomandibular joint. METHODS: Sixty healthy adult Japanese rabbits were used in this study. Forty-eight rabbits were subjected to surgical anterior disc displacement in the right TMJs, every 12 rabbits were sacrificed 1, 2, 4, 8 weeks post-operation, 12 rabbits without operation were used as normal control.The gene expression and distribution of VEGF-C in condylar cartilage were studied by gene chip, real-time quantitative PCR and SP immunohistochemical methods. Paired t test was used for analysis with SPSS19.0 software package. RESULTS: After anterior disc displacement, the expression of VEGF-C in the 2nd week reached to a minimum level, there was a significant difference (P<0.05), and increased in the 8th week. VEGF-C was expressed by cells of articular cartilage in the proliferative zone, hypertrophic zone and calcified cartilage zone. The expression in 1-week group was mainly found in the deep proliferative zone and hypertrophic zone, while the expression mainly found in the hypertrophic zone in 2-and 4-week group; calcified cartilage gradually enhanced, and there was significant difference (P<0.05) between 8-week group and control group. CONCLUSIONS: VEGF-C gene transcription and expression may be involved in the remodeling of the condylar cartilage after anterior disc displacement.

Transcriptomic study on the impact of temporomandibular joint internal derangement in the condylar cartilage of rabbits.

Internal derangement (ID) in the temporomandibular joint (TMJ) compromises a group of clinical problems, and holds a relative high prevalence in populations. However, the temporal genomic change in gene expression of condylar cartilage during continuous ID remains unclear. Here we reported the differentially expressed gene pattern in condylar cartilage of rabbits with ID from 1 to 8 weeks by microarray analysis. The whole genome project was deposited at GenBank under the accession PRJNA278127. The microarray analysis showed that 6478 genes have more than two-fold changes among all the tested transcripts. Many inflammation gene increased rapidly in the early stage while decrease later. On the contrary, the bone construction related genes showed a low level at first and increased at later period in the ID progression. Besides, the current study found some genes such as HLA2G, which had never been reported, might be relevant with ID.