In the same animal described above, a 1.4 mm diameter, 2 mm deep microdrill hole was created in the left knee trochlea and further treated by press- ﬁtting a presolidiﬁed chitosan-blood implant into the hole. 80 Relative to the con- tralateral untreated drill hole, after 2.5 months of repair, a delayed and altered EO process is seen in the treated defect ( ►Fig. 7). HyC repair tissue containing low levels of collagen type II and no collagen type I is observed above the minerali- zation front ( ►Fig. 7B, C). The hyaline-like repair is overlaid with undifferentiated mesenchyme surrounded by collagen type I (►Fig. 7C). In this implant-treated defect, the minerali- zation front has a more irregular appearance and consists in bony vascular invasion of hyaline tissue ( ►Fig. 7F). One can appreciate that in this osteochondral defect, the implant has delayed osteochondral ossi ﬁcation because the mineralized GAG is only beginning to form at the repair cartilage-bone interface (EO, ►Fig. 7A, D, E). Unlike the endochondral bone formed during spontaneous repair, hypertrophic chondro- cytes are scarcely present at the advancing interface of new bone and blood vessels ( ►Fig. 8). Collagen type I of newly formed bone is being deposited from inside the invading bone marrow channels. Given that the chondrocytes present in the collagen type II repair matrix are not yet terminally differen- tiated to hypertrophic cells, the proximity of repair cells and invading blood vasculature can still drive cell proliferation and appositional growth of more collagen type II hyaline-like matrix. At one edge of the drill hole, the bone has regenerated to the native tidemark level, and a new tidemark can be observed ( ►Fig. 9).
In order to explain the difference in behaviour between isolated cartilage and the cartilage-bone-system system, Edelsten et al.  suggested that cartilage at- tached to subchondral bone is more constrained in its deformation, and this may lead to it appearing stiffer and more elastic than when in isolation. Experimentally, this result has been verified as k” becomes frequency- independent under load [12, 13]. However, the trends in E’ and E” in isolated bone identified in this study (Fig. 3) may infer an additional explanation. Bone was found to be positively frequency-dependent for storage and nega- tively frequency-dependent for loss moduli. Therefore, the constraining effects of the bone could not be the sole reason for the frequency independence of k” for the cartilage-bone-system. A decrease in loss stiffness indicates a decrease in the energy dissipated, suggesting that bone does not dissipate as much energy to the sur- rounding tissue at higher frequencies. This may prevent the load energy being returned to the cartilage, which could be a further mechanism to prevent cartilage dam- age. While observing equine osteochondral cores under high-impact, Malekipour et al. identified that bone can absorb a much higher amount of impact energy than cartilage . Furthermore, it is often bone that breaks during high-impact loading, as the main mechanism by which it absorbs energy is through trabeculae fracture . Although this may be desirable, as bone has a greater propensity to heal than cartilage, this may put the joint at risk of long-term damage. Clearly, the inter- face between the two tissues plays an essential role in transferring the load energy through the cartilage and into the bone.
with deletion of the Ihh co-receptor Smo in the perichondral lineage leading to loss of endochondral bone (Long et al., 2004). Notably, hypertrophic chondrocytes themselves appear to be unresponsive to Ihh, which may explain the lack of high levels of osteoblast genes (e.g. Runx2, Col1a1, Spp1, Bglap) in growth plate chondrocytes (Long et al., 2001). However, elevation of Hh signaling in zebrafish, either by loss of the negative regulators ptc1 and ptc2 or treatment with the Hh pathway agonist purmorphamine, can induce osteoblast gene expression in chondrocytes, suggesting plasticity in the ability of developmental chondrocytes to express osteoblast-associated genes (Hammond and Schulte-Merker, 2009). In mice, stimulation of the Hh pathway can also promote the formation of bone in several skeletal injury contexts, although the mechanism by which Hh does so is not well understood (Baht et al., 2014; Huang et al., 2014; Zou et al., 2014). Specifically, none of these studies examined whether the increase in bone production is due to an effect on osteoprogenitor differentiation, an effect on chondrocytes, or both. By analyzing an adult viable Indian hedgehog homolog a (ihha) mutant in zebrafish, we find an unexpected role for Ihha in inducing the differentiation of periosteal cells into bone-producing chondrocytes during jawbone regeneration.
RT PCR and qPCR: RNA from ATDC5 cell cultures and cell cultures of rat calvaria was prepared using an RNeasy mini kit (Invitrogen) according to the manufacturer's instructions. The RNA from different skeletal elements was prepared following the removal of muscle, and the cartilaginous ends of the bones and centrifugation of the bone shafts for 5000rpm for 2 minutes to remove the marrow before snap-freezing in liquid nitrogen. Such frozen tissues were pulverized under liquid nitrogen using a mortar and pestle and lysed in Qiazol lysis reagent (Qiagen Ltd., Crawley, UK). Total RNA was extracted from lysed samples using RNeasy mini kit (QIAGEN, Crawley, UK). RNA integrity of samples was assessed by electrophoresis using ethidium bromide staining and by OD260/OD280 nm absorption ratio (>1.95). Total RNA was reverse transcribed with SuperScript II RNase reverse transcriptase (Invitrogen), using random primers (Invitrogen, Paisley, UK) for RT PCR and qPCR analysis. Real-time qPCR was carried out as previously described (Zaman G 2012) using QuantiTect SYBR green PCR kit and Opticon 2 LightCycler (MJ Research, Waltham, MA, USA). The expression levels of Sulf1 and Sulf2 were normalised to the reference gene 18s rRNA. RT PCR was carried out using Sigma PCR kit. PCR Primers used in this study were:
In addition, they give rise to melanocytes (Sommer, 2011) and endocrine cells (Le Douarin and Dupin, 2012). Cranial neural crest cells (CNCCs) emigrate from the caudal forebrain, midbrain and hindbrain to the level of the first somite and give rise to additional cell fates in comparison to trunk NCCs, contributing to cartilage, bone and connective tissue (Le Douarin et al., 2007; Santagati and Rijli, 2003). CNCCs migrate into the branchial arches (BAs), becoming NC-derived mesenchymal progenitor cells (MPCs), which produce cartilage and skeletogenic elements of the craniofacial region. Specific cell fates of CNCCs are controlled by positional cues that determine intrinsic gene expression patterns that are partially specified already at emigration from the neural tube. Central players in this process are the Hox genes that are differentially expressed in migratory CNCCs and BAs according to the axial position. In particular, cells in BA1 and anterior domains are devoid of Hox gene expression, which allows formation of the chondrogenic and skeletal elements of the facial region (Creuzet et al., 2002; Kanzler et al., 1998; Minoux and Rijli, 2010). In addition to these intrinsic cues, CNCC fates are regulated by environmental signals, such as Tgfβ (Wurdak et al., 2006) and Fgf8 expressed from the facial and BA ectoderm (Le Douarin et al., 2007; Santagati and Rijli, 2003). As a consequence of such signaling, expression of the transcription factor Sox9 is upregulated in MPCs, while expression levels of the NC specifier gene and NC stem cell (NCSC) marker Sox10 decrease (John et al., 2011). This switch in Sox transcription factor expression leads to suppression of neural fates and allows CNCCs to differentiate into mesectodermal NC derivatives, including bone, cartilage and smooth muscle.
7.1. MAPK Signalling Pathways Mediate an Osteochondral Crosstalk through Metabolism Regulatory Factors. Increasing evidence shows that the activation of MAPK, particularly ERK1/2, contributes to the expression of MMPs in chondro- cytes  and osteoblasts . MMPs, such as MMP-1, MMP-2, MMP-8, MMP-9, and MMP-13, play a crucial role in OA cartilage degradation due to their abnormal expres- sion, which can cleave the collagen triple helix domain, including COL-II . Majumdar et al.  showed that the double knockout of ADAMTS-4 and ADAMTS-5 pre- vented the progression of OA. Signals from OA subchondral osteoblasts in vitro stimulate the expression of ADAMTS-4, ADAMTS-5, MMP-2, MMP-3, and MMP-9 in chondrocytes, whereas OA chondrocytes increase the activities of MMP-1 and MMP-2 in osteoblasts, which is mediated by phosphor- ylating the ERK1/2 signalling pathway , indicating that there may be a catabolism-related bidirectional crosstalk in the osteochondral junction during OA progression. Sanchez et al.  designed a coculture model demonstrating that OA subchondral osteoblasts inhibited a normal chondrocyte anabolism, as evidenced by a reduced aggrecan synthesis followed by matrix mineralisation, which may be mediated through both phosphorylation of ERK1/2 signalling and inactivation of p38 phosphorylation . In brief, OA sub- chondral osteoblasts simultaneously inhibit chondrocyte anabolism and promote chondrocyte catabolism through the ERK1/2 signalling pathway. Therefore, it can be con- cluded that the MAPK signalling pathways contribute to car- tilage and SB damage through the metabolism of regulatory factor crosstalk in the cartilagebone unit.
Post operatively we have assessed all the patients with pure tone audiometry at 1 month, 6 months and 12 months. Table 4 shows the result of hearing in different months post operatively. It shows maximum number of patients were having normal hearing i.e. 0-25 dB and the result is better with bone ossiculoplasty. Few patients in cartilage ossiculoplasty showed hearing deterioration progressively i.e. in 40–55 dB category, 1 st month 4 patients, 6 th month 8 patients and 12 th month 9 patients. In these 9 patients, we have opened the middle ear again to find out the causes of hearing deterioration. It was found that in 5 cases cartilage was displaced and in 4 cases size of the cartilage decreased and detached from the ossicle. No such thing happened in bone ossiculoplasty.
A sinusoidally varying compressive force of between 16 N and 36 N (giving a maximum nominal stress of 1.7 MPa) was applied during the testing. The resulting displacement was also sinusoidally varying with the amplitude of the displacement in the range 0.012 to 0.093 mm. At the beginning of each test specimens were subjected to 1500 cycles of loading at 25 Hz and 3000 cycles at 50 Hz (with a rest period of 60 s between frequencies) to allow the specimens to stabilise before data collection. These values were determined during preliminary experiments, but are similar to the conditions of 1200 cycles previously used to reach a steady state . During the testing, where data were collected for measuring the viscoelastic properties of the cartilage, the sinusoidally varying compressive force was applied for 2 s at each frequency tested in the range 1– 92 Hz. The frequency of 1 Hz simulated a heel strike force rise time of 500 ms, while 92 Hz simulated a rise time of 5.4 ms. At the end of each frequency tested, the applied force returned to the mean value of 26 N and was main- tained for a dwell time of 2 s before the testing at the next frequency was undertaken. The testing involved starting at 1 Hz and increasing the frequency; preliminary tests showed that increasing the frequency from 1 Hz to 92 Hz t
An increasing amount of attention has been devoted to the role of the bone in the pathogenesis of osteoarthritis. Subchondral bone sclerosis, alterations in the trabecular structure, lesions (previously called development of bone marrow edema) and osteophytes are important features of the pathology of OA [2,10,29,37-39]. The present under- standing remains on an observational level, in which an increasing range of experimental evidence is emerging. In support of the important role of bone turnover in the pathogenesis of OA, several independent lines of experi- mental evidence are found [3,29-32]. In brief, examina- tions of peri-articular bone in knees and hips with OA have confirmed that the subchondral bone is abnormal in OA joints, which altered trabecular structure, sclerosis of the subchondral plate , as well increased bone turno- ver [41,42]. Cross-sectional studies have also established that women with advanced knee or hip OA have a higher bone mineral density (BMD) near or at the site of joint OA . Plausible proof of a link between bone and cartilage recently came from an animal model of OA, where exten- sive inhibition of bone resorption resulted in a 50% decrease in cartilage pathology score assessed by Mankin score [29,38]. In addition, accelerated bone turnover has in both traumatic and estrogen deficiency models (ova- riectomy (OVX)) been shown to augment articular carti- lage erosion [7,11,12,44,45], in which increased bone
Loss of estradiol did not cause changes in patellar tra- becular bone, and compared to the metaphysis, caused only mild changes in epiphyseal trabecular bone. How- ever, at all three sites, supplementation with estradiol strongly increased bone volume fraction, suggesting that these sites are sensitive but that patellar and epiphyseal bone are less dependent on circulating estradiol than metaphyseal bone. This may be due to differences in oes- trogen receptor levels or in local estradiol production. These as yet unknown differences between epiphyseal and patellar bone on one side and metaphyseal bone on the other side could be important for understanding the functional link between estradiol loss, bone turnover and development of osteoarthritis.
Patients and methods: This is a prospective, cross sectional study and was carried out on 36 patients (27 females and 9 males) with chronic suppurative otitis media, their age ranged from 12 to 38 years. Patient were subjected to complete history taking, complete ENT examination, preoperative audiological evaluation, high resolution computed tomography "HRCT" and complete laboratory investigations. All patients were operated by tympanomastoidectomy for eradication of middle ear pathology (21 cases underwent canal wall up technique while 15 cases underwent canal wall down technique), Then reconstruction of the ossicular chain was done by cartilage strip and bone cement (30cases between malleus to stapes while 6 cases between incus to stapes). Postoperative assessment done by pure tone audiometry & tympanometry 3 & 6 months postoperatively.
The transition of cartilage to bone in the healthy individual is under tight regulation so as to prevent disturbed development and/or longitudinal bone growth. Observations from disorders such as hypothyroidism, rickets and dwarfism may provide insights into the mechanisms underpinning defective hypertrophic differ- entiation and ossification (Combs et al. 2011, Santos et al. 2013). Regulation is also observed in repair of fractured bone tissue, in which there is a deliberate re-initiation of the endochondral processes (see above) previously dis- cussed in this review. There has been much recent focus upon the WNT signalling pathway in fracture repair and, in particular, the recent discovery of enhanced repair through the administration of neutralizing antibodies against sclerostin, a known WNT inhibitor (Secreto et al. 2009, Ominsky et al. 2011, Virk et al. 2013). In contrast to this desired acceleration in endochondral ossification processes, in certain diseases the ectopic redeployment of these processes is detrimental and considered to be at least contributory to the observed disease pathology. Herein we discuss conditions in which this occurs and touch upon current understanding regarding the role of these processes in their aetiology.
Data were analysed using STATA V.12 (StataCorp, College Station, TX, USA). Normal distribution of the data was investigated with Q-Q plots and histograms. Normally distributed data were presented as arithmetic mean (95% CI). Data not being normally distributed were log-trans- formed, checked for normality and presented as geometric mean (95% CI). The geometric mean difference between patients with OA and healthy subjects was found using bootstrapping with bias corrected and accelerated intervals to get 95% CI. Student’s t-test was used to test for statistical significance between the patients with OA and the healthy subjects. The difference of thickness measurement was made for the complete femoral head (OARSI grades 0–6), for areas without loss of cartilage thickness (OARSI≤3)
The DAN gene was isolated as a candidate tumor sup- pressor gene in a differential hybridization screen . Secreted DAN suppressed DNA synthesis in transformed cells. The head inducer gene Cereberus codes for a secreted protein and can induce heads in Xenopus embryos, and it is related to DAN in the cysteine rich domain . Gremlin is a Xenopus homolog related to DAN that inhibits BMP 2 action and was identified by screening an ovarian cDNA library for activities inducing the secondary axis . DAN family members are thus newly identified BMP antagonists [23–25]. It is not yet clear if they play a role in articular cartilage and in arthritis. BMP potentiating agonist: twisted
Mechanical loading plays an important role in the onset and development of OA. Musculoskeletal tissues are highly sensitive to mechanical stimulation. However, conflicting results regarding the ability of mechanical stimulation to alter cartilage, or trabecular bone struc- ture, in animal models and clinical studies, have recently been reported. Previous in vitro studies suggest that mid-term intermittent mechanical stimulation (cycles of 1-h sinusoidal stimulation [1 Hz] and a 4-h break; max- imum compression, 2.5%) in vitro has the potential to improve the quality of cellular matrix constructs pre- pared from dedifferentiated osteoarthritic chondrocytes . Tsuang Y-H et.al proved that mechanical stimula- tion (10% scaffold thickness 1-Hz amplitude lasting for 24 h) could enhance matrix protein accumulation in cul- tured chondrocytes . However, other studies found that long-term repetitive mechanical loading (20% of the maximum isometric force of the knee joint at 0.5 Hz for 50 min/day, 3 days/week, for 4 weeks) also accelerated cartilage degeneration and increased chondrocyte death in rabbits . Some other researchers have suggested that 18-week low-magnitude 35-Hz WBV accelerated
concentrations of cartilage oligomeric matrix protein (COMP) were found in all patients who developed rapid hip joint destruction. In contrast, levels of a putative marker of cartilage aggrecan synthesis, the chondroitin sulfate epitope 846, were increased only in patients with slow joint destruction. Levels of bone sialoprotein (BSP) were increased in both
Numerous studies have shown that cellular responses of skeletal tissues to TGF- β treatment occur in a dose-dependent manner including, for example, (1) the proliferation and collagen synthesis of rabbit PC cells (Dounchis et al., 1997), (2) the production of uronic acid by chicken PO cells (Iwasaki et al., 1995) and (3) the proliferation and differentiation of chondrocytes (Pateder et al., 2000; Qi and Scully, 2003). Similarly, we have observed that PC cells respond to treatment with exogenous TGF- β 1 by their production of active TGF- β - with a threshold level of ~300 pg/ml reached when treated with 2 ng/ml or greater TGF- β 1. This threshold level of TGF- β was reached after the TGF- β 1 treated PC cell cultures had been maintained for 18 hours in serum-free medium. Although we cannot rule out the possibility that the amount of active TGF- β would increase with time beyond 18 hours, we chose to study this time point as it was the time found previously (Di Nino et al., 2001) to be the most critical for collecting conditioned medium from cell cultures that resulted in the precise regulation of cartilage growth in the tibiotarsal organ culture system.
Microscope characterization of HE staining in different groups of rats confirmed the efficacy of bone setting in treating the disease. For the cartilage from naïve rats, the microscope observation of stained cartilage showed a com- plete, smooth structure. The cells within the cartilage tissue had a well-organized, layered structure (Figure 3A). On the contrast, the carti- lage from the diseased model group had a rough surface; additionally, and the cells had a disrupted structure and the cartilage had cer- tain degree of damage (Figure 3B). The treat- ment with the sticker improved the disease symptom: The cartilage had an improved sur- face smoothness and a more clear structure and an increased number of cartilage cells (Figure 3C). DS treatment also improved the disease symptom as well, although surface roughness and disorganized cells were still observable (Figure 3D). Markin score was employed to assess the treatment efficacy. The disease model group had a significantly higher score than naïve group (P < 0.05). The sticker and DS group had a significantly lower score than the disease model group (P < 0.05); There was also statistic difference between the stick- er and DS group (P < 0.05) (Table 2).
Processing of histological specimens
The distal femurs were ﬁxed in neutralized 4% para- formaldehyde for 11 weeks, demineralized in Calci-Clear Rapid (National Diagnostics, Atlanta, Georgia, USA) and embedded in Paraf ﬁn. Embedded specimens were stored at 20 C. Four repre- sentative 4 m m slides from the center of the defects (de ﬁned by a diameter >80% of the drill bit diameter, corresponding to >2.6 mm) were obtained. For each knee, one haematoxylin eosin (HE), one type II collagen (as a marker of hyaline cartilage 20 ) one type I collagen (as a marker of ﬁbrocartilage 20 ) and one type X collagen staining (as a marker of chondrocyte hypertrophy 6 ) was prepared ( Table I ). Negative controls with equally concentrated mouse serum replacing the antibodies were carried out along with each batch. For antibody detection, a streptavidin-biotin interaction based kit using alkaline phosphatase to catalyse fast red was used (Super- Sensitive TM Link-label IHC Detection System, BioGenex, Fremont CA, USA). Endogenous alkaline phosphatase was blocked by addi- tion of levamisole hydrochloride (Sigma, St. Louis MO, USA).
Our cell culture model comes with some limitations. The amount of matrix obtained from a single knee and the large number of osteoclasts required to perform the cultures with a suitable number of technical replicates limits the number of conditions that can be used, resulting in relatively low statistical power that is sensitive to vari- ation within conditions. Increased robustness could be achieved by investigating only the matrix and compound of interest in addition to reference matrices (cortical bone and/or articular cartilage) and reference inhibitors (diphyl- lin, E-64, and GM6001); this was, however, not suitable for the profiling approach of our study. Some experimen- tal outputs varied between experiments, as can be seen by comparing the data in this article (Figs. 2, 3 and 4) with the supplementary data (Additional files 1, 2, 3, 4, 5 and 6: Figures S1–S6). This could potentially be explained by dif- ferences in osteoclast quality between donors and varia- tions in matrix content between the knee joints, further necessitating strict use of reference matrices and inhibi- tors to validate each experiment. Finally, due to the in vitro design of our study, the findings cannot be directly extrapolated to the OA disease process.