Osteoarthritis ( OA) is a chronic joint disease characterized by degeneration of articular cartilage and changes of subchondral bone play an important role in the occurrence and development of OA .Recent studies have found that change in the struc-ture and mechanical properties of subchondral bone is one of the main pathological processes in OA .To confirm the role of subchondral bone in OA process can provide not only more details about the pathogenesis of OA , but also new targets for treatment .Early diagnosis and treatment of OA may be possible by detecting radiographic and genomics of subchondral bone .We review subchondral bone chan-ges andits role in OA process in aspects of biomechanics , biology, radiological and genomics .

OBJECTIVE:To compare the effects of strontium ranelate and PTH(1-34)on bone quality of ovariectomized rats. METHODS:80 SD rats were randomly divided into sham operation group(group A,n=10)and dual ovariectomy(group B,n=70). 3 months after operation,group B were randomly divided into 7 groups,with 10 rats in each group. B0 group were given nor-mal saline [0.9 g/(kg·d)] subcutaneously;B1-B3 groups were given low-dose,medium-dose and high-dose of strontium ranelate [0.45,0.9,1.35 g/(kg·d)] intragastrically;B4-B6 groups were given low-dose,medium-dose and high-dose of PTH(1-34)[30, 60,90 μg/(kg·d),treated for 5 days,rested for 2 days] subcutaneously. Group A was same to group B0 in therapy regimen. All rats were sacrificed 8 weeks later. The contents of P1NP and CTX-1 in serum of rats were determined by ELISA assay;bone densi-ty of 4th lumbar vertebrae was detected by bone densitometer;BV/TV,Tb.Th,Tb.N and Tb.Sp were detected by CT;maximal load and elastic modulus of 5th lumbar vertebrae were measured by compression test. RESULTS:Compared with group A,the se-rum levels of P1NP and CTX-1 in B0-B6 groups increased significantly,while bone density of 4th lumbar vertebrae,maximal load and elastic modulus of 5th lumbar vertebrae decreased significantly in B0-B3 groups(P<0.05);BV/TV level of 4th lumbar verte-brae decreased significantly,while Tb.Sp level increased significantly in B0 group(P<0.05). Compared with B0 group,bone den-sity of 4th lumbar vertebrae,maximal load and elastic modulus of 5th lumbar vertebrae increased significantly in B1-B3 groups (P<0.05);P1NP content,BV/TV,Tb.N level,bone density of 4th lumbar vertebrae,maximal load and elastic modulus of 5th lumbar vertebrae increased significantly in B4-B6 groups,and were higher than in B1-B3 groups(P<0.05). Tb.Sp level of B1-B6 groups decreased significantly and were lower than those of B1-B3 groups(P<0.05). There was no statistical significance in Tb.Th level among 8 groups and CTX-1 content among B0-B6 groups (P>0.05). CONCLUSIONS:PTH(1-34) is better than strontium ranelate in inhibiting bone loss,improving vertebral bone micro-structure and biomechanical properties of ovariectomized rats.

Objective To investigate the preventive effect of Strontium ranelate on stress-absence induced osteoporo?sis in tail-suspended rat. Methods A total of 30 SD rats with average age of 6 month were randomly divided into 3 groups (n=10 in each group):Group A was normal control group while rats in group B and C were subjected to tail suspension test to establish stress absence models. Rats in group C were administered with Strontium ranelate [1 g/(kg·d)]. All rats were sacri?ficed 4 weeks later. Left femurs were harvested for bone mineral density (BMD) test and prepared for undecalcified tissue sec?tion and thereby bone histomorphometry assessment. Bone marrow from right femurs and tibias were cultured and induced to?wards osteogenic-differentiation. The expression levels of osteocalcin in the fourth-passage cultured bone marrow cells and in blood serum were detected separately. Results Rats in group B showed markedly decreased BMD comparing to those in group A and C(P<0.05). Trabecular volume (BV/TV), number (Tb.N) and thickness (Tb.Th) in group B were lower than those in group A and C;erosion percentage (Er.Pm) and osteoclast number (Oc.N) in group B and C were higher than those in group A;comparing to those in group B, bone formation rate (BFR/BV), labeled percentage (L.Pm), were higher in group C, coupled with decreased Er.Pm and Oc.N(P<0.05). mRNA expression levels of OCN in group B and C were higher than those of group A. But its level in plasma were lower in group B than those in group A and C(P<0.05). Conclusion Tail suspension could induce osteosporosis. Strontium ranelate prevent bone loss in stress-absence osteoporosis in rat induced by tail-suspension for 4 weeks, which might be partially through upregulating the expression of OCN, thereby promoting bone formation.

BACKGROUND:Osteoporosis and its complications severely threaten the elder’s health. Simvastatin, widely accepted as a lipid-lowering drug, is reported to potentialy promote bone formation, but it is in debate when oraly administered, and there is no evidence to support whether this is due to the region difference.
OBJECTIVE:To investigate the effect of oraly administered simvastatin on bone mass and biomechanical properties of the femur and vertebrae in osteopenia rats induced by ovariectomy (OVX).
METHODS: Twenty-four 6-month-old female Sprague-Dawley rats were subjected to OVX+oraly administered saline vehicle (OVX group,n=8), OVX+oraly administered simvastatin (5 mg/kg/d; intervention group,n=8) or sham surgery (sham group,n=8). After 8 weeks of treatment, al rats were sacrificed and the level of procolagen type I N-terminal propeptide in blood serum was assessed by ELISA. Bone mineral density was determined in the L5 vertebra and left femur using dual-energy X-rays. Furthermore, the biomechanical properties of the L4 vertebra and right femur, including maximum load and elastic modulus, were detected by compression testing and three-point bending test, respectively.
RESULTS AND CONCLUSION: The serum level of procolagen type I N-terminal propeptide in the sham group was significantly lower than that in the other two groups. OVX rats showed significantly lower bone mineral density in both the L5 vertebra and left femur than sham rats (P < 0.05). Rats in the intervention group showed higher bone mineral density than those in the OVX group, with statisticaly significant difference in the L5 vertebra (P < 0.05), but insignificant difference in the femur. Maximum load and elastic modulus of the L4 vertebra in the OVX group were significantly lower than those in the sham and intervention group. Markedly lower elastic modulus of the femur was found in the OVX group than the sham and intervention groups. These findings demonstrate that simvastatin treatment can partialy prevent bone loss in OVX rats with more notable effect on the vertebrae than the femur, and for this model, the vertebra is superior to the femur used in biomechanical test.

BACKGROUND:Tissue inhibitor of matrix metaloproteinase 1 (TIMP-1) is the corresponding antagonist of matrix metaloproteinase 13 (MMP-13), and their balance between expression and functional activity exerts an important role in the metabolic state of the extracelular matrix. During the development of osteoarthritis, however, TIMP-1 and MMP-13 expressions and their expression ratio show unclear changes in DH guinea pigs.
OBJECTIVE:To explore the expression levels of MMP-13 and TIMP-1 in DH guinea pigs with different ages, and to analyze the relationship between the ratio of MMP-13 to TIMP-1 and the age-dependent degenerative changes in the articular cartilage.
METHODS:Twenty-four female Dunkin Hartley guinea pigs were sacrificed at age of 2, 4, 8, 12 months separately, with six animals at each time point. The knee joints were colected and gross visual appearance of the articular cartilage was observed, then were decalcified and prepared for paraffin sections. VG staining and Mankin score were used to analyze the histological changes. Immunohistochemistry was conducted to assess the expression levels of MMP-13 and TIMP-1 in the cartilage. Integrated absorbance values were used as the quantitive analysis calculated by Image pro-Plus 6.0. Linear regression analysis was done to analysis the relationship between Mankin score and the ratio of MMP-13/TIMP-1. RESULTS AND CONCLUSION:Normal appearance in the articular cartilage was observed in 2-month-old DH guinea pigs, while degenerative changes in the articular cartilage were shown in 4-month-old animals, which became severer with age. Significant difference was found in Mankin score between any two groups (P < 0.05). The ratio of MMP-13 to TIMP-1 increased with age, and the ratio was positively correlated to the Mankin score (P < 0.05). Age-related articular cartilage degeneration occurred in Dunkin Hartley guinea pigs at 4 months of age, and devoloped with age, which is related with the imbanlance of the expression ratio of MMP-13 to TIMP-1.

Objective To investigate the effects of lovastatin alone or combined with calcitonin on fracture repair in osteoporotic rats. Methods Forty 4-month-old female SD rats were randomized into 5 groups(8 rats in each group):normal fractured group (A), osteoporotic fractured group (B), lovastatin treatment group(C), calcitonin treatment group (D) and lovastatin combined with calcitonin treatment group. All rats except group A received bilateral ovariectomy. The midshaft femur fracture model was established in all rats 8 weeks after operation. The serum level of procollagen amino-terminal propeptide (PINP) was assessed by ELISA. X-ray and bone mineral density detection was used to observe the fracture healing process. The maximal loading of femoral fractures was analyzed by biomechanical method. Results (1) The serum level of PINP was significantly lower in group A than that of other groups. There was a significantly higher level of PINP in group C and group E than that of group B, and the level of PINP was significantly lower in group D than that of group C. (2) The X-ray showed more progressed fracture healing in group A and group E. The accordingly score indicated that there was a markedly higher score in groups A and group E compared to that of other three groups. (3) There was a highest bone mineral density in the full-length and in the middle of femur bone in group A, followed by group E, group D and group C. The lowest bone mineral density was found in group B. (4) The biomechanical test showed that the maximal loading in femur fracture side was significantly higher in group A than that of other four groups, in which it was higher in group E than that of group B. Conclusion The osteoporosis decreased bone mass and delayed fracture healing process in rat model. The treatment of lovastatin combined with calcitonin showed more positive effect on preventing bone loss and promoting fracture repair than lovastatin alone.

Objective To study the effect of calcitonin on the expression of vascular endothelial growth factor in femoral fracture healing in ovariectomized rats .Methods 80 female rats of 3 months old were randomly divided into four groups :Sham operation group(Sham ,10 cases);Ovariectomized operation group(OVX ,10 cases);Ovariectomy+ fracture+ salinegroup(Control ,30 cases) and Ovariectomy+ fracture +calcitonin group(Experimental ,30 cases) .Rats in Sham group and OVX group were performed ovari-otomy and killed after 4 weeks ,femoral bone mineral density was measured .For rats in Control group and Experimental group ,right middle femoral facture was performed 4 weeks later after ovariectomy .Calcitonin(16 IU/kg)were injected subcutaneously once per 2 days in Experimental group ,while those in Control group were given equal volume of normal saline .Rods in these two groups were killed after 3 ,6 ,9 weeks(10 at a time) ,femoral bone mineral density(BMD)was measured;hematoxylin-eosin staining and im-munohisto-chemical staining were performed at the 3th ,6th and 9th week after fracture ,respectively .Results Compared with Sham group ,rats weight in OVX group gained more(P< 0 .05) ,and BMD in OVX group significantly decreased more(P< 0 .05) .HE staining ,at the 3th week after fracture ,endochondral ossification domained in fracture healing ,and no significant difference existed (P>0 .05)in BMD .At the 6th week after fracture ,bone trabecula in both groups arranged in order ,compared with the control group ,BMD in experimental group increased significantly(P<0 .05) .At the 9th week after fracture ,bone trabecula in both groups arranged closely ,BMD in both groups showed significant difference(P<0 .05) .There was no significant difference of vascular endo-thelial growth factor(VEGF)between experimental group and control group at the 3th ,6th ,9th week after fracture(P>0 .05) .Con-clusion The results suggest that calcitonin treatment could enhance the bone mineral density significantly after fracture ,but it has no impact on the expression of VEGF in osteoporotic fracture healing .

BACKGROUND:Simvastatin enhanced the expression of bone morphogenetic protein-2(BMP-2),which plays an anabolic role in bone metabolism and osteoblastic lineage differentiation.However,little is known about the molecular mechanism of simvastatin on regulation of bone marrow stromal cells differentiation.OBJECTIVE:To investigated the effect of simvastatin on osteoblastic differentiation of bone marrow stromal cells based on genetics level.METHODS:Bone marrow stromal cells derived from femur and tibia were cultured in different mediums with simvastatin or Vehicle for 7 days Following extraction and purification,mRNA was reverse-transcripted into cDNA.Fluorescence labelina was employed and the samples were then hybridized with oligonucleotide chip to screen the different genes,which were utillzed to analyze osteogenesis-related factors.Alkaline phosphatase and Von Kossa staining were performed at days 14 and 21,respectively.RESULTS AND CONCLUSIONS:At day 14,alkaline phosphatase-positive cells were more in the experimental group than control group.Von Kossa staining demonstrated that simvastatin could promote BMSCs osteoblastic differentiation and mineralization.Comparative analysis showed that 103 genes out of 22 575 rat genes had differential expression (≥2 fold or≤ 0.5 fold),and some genes were related to cell proliferation and ostoeblastic differentiation,including C/EBP δ,Cited,Ascl2,Ptpnl6,Wisp2,Tieg,etc.Simvastatin could induce osteoblastic differentiation of bone marrow stromal cells,involving in many osteogenetic-related genes.

BACKGROUND: Recently simvastatin has been shown to stimulate osteogenic differentiation and bone formation, but there is no report about the effect of simvastatin on the bone development of young rats.OBJECTIVE: To evaluate the effects of simvastatin on osteogenic relative genes of proximal tibia trabecular bone and osteogenic differentiation of bone marrow stromal cells (BMSCs).METHODS: Twenty 1-week-old Spragua-Dawley young rats were randomly and equally divided into simvastatin and control groups. Rats in the simvastatin group were treated with a subcutaneous injection of simvastatin[5 mg/(kg·d)] for 2 weeks, while rats in the control group were treated with placebo for 2 weeks. The expressions of bone morphogenetic protein-2 (BMP-2), matrix metalloproteinase-13 (MMP-13), and vascular endothelial growth factor (VEGF) of trabecular bone in the tibia were analyzed by mmunohistochemicel staining. BMSCs harvested from the rat femur were osteogenic-differentiation cultured. Alkaline phosphatase (ALP) staining was performed on day 14, real-time PCR analysis was applied to investigate the BMP2, RUNX2,Osterix, MSX2, DLX3, DLX5 mRNA expressions during osteogenic differentiation in vitro on day 21, and von Kossa staining was detected on day 28.RESULTS AND CONCLUSION: ① There was no significant difference in the expressions of BMP-2, MMP-13, and VEGF between simvastatin and control groups. ② The percentages of ALP positive-stained cells were about 30% and there was no significant difference between the two groups (P ＞ 0.05). ③There was no significant difference in the expressions of BMP-2,RUNX2, Osterix, MSX2, DLX3, DLX5 mRNA in osteoganic differentiation-induced BMSCs. ④ von Kossa staining demonstrated that dark brown calcified spots in various sizes were observed, but there was no significant difference in size and density between simvastatin and control groups. A subcutaneous injection of simvastatin[5 mg/(kg·d)] for 2 weeks could not remarkably affect osteogenic relative genes of bone trabecula and osteogenic differentiation of BMSCs.

BACKGROUND:As a lipid-lowering drug, simvastatin has been proved to be effective in promoting bone formation. Previous studies have demonstrated that local y applied simvastation accelerated fracture healing at middle phase in osteoporotic rats, while no study focuses on the influence of local y applied simvastatin on fracture healing at late period in an osteoporotic rat.
OBJECTIVE:To investigate the effect of simvastatin local y applied from a bioactive polymer coating of implants on osteoporotic fracture healing at late period.
METHODS:Female Sprague-Dawley rats were divided into sham group, osteoporotic fracture group and simvastatin group. In the sham group, the abdominal cavity was exposed without ovariectomy. Six weeks later, femur fracture models were established in normal or osteotoporotic Sprague-Dawley rats, and intramedul ary stabilization was achieved with uncoated titanium Kirschner wires in normal rats (sham group),with polylactic acid coated titanium Kirschner wires (osteoporotic fracture group) and with simvastatin/polylactic acid coated titanium Kirschner wires (simvastatin group). Femurs were harvested after 12 weeks, bone mineral density was determined with dual X-ray absorptiometry, and then radiographic and histological analysis was performed for analysis of fracture healing. Immunohistochemical evaluation was employed for bone morphogenetic protein 2 expression.
RESULTS AND CONCLUSION:The bone mineral densities of both the total fractured femur and fractured site 12 weeks after fracture in the osteoporotic fracture group and simvastatin group were markedly decreased compared to normal fractured rats. The bone mineral density of the fractured site was significantly higher in the simvastatin group than the osteoporotic fracture group. Radiographic results demonstrated completely finished cal us remodeling in the sham group;poor healing, pale cal us density and blurred fracture line were seen in the osteoporotic fracture group;disappearance of fracture line, bone defects fil ed with cal us, and deep periosteal reaction were found in the simvastatin group. X-ray scores in the sham and simvastatin groups were significantly higher than that in the osteoporotic group (P<0.05). Hematoxylin-eosin staining showed a delayed healing process in the osteoporotic group, and revealed a significantly processed cal us with regular-shaped newly formed bone trabeculae in the simvastatin group. Immunohistochemical evaluation showed no significant difference in the bone morphogenetic protein 2 expression between any two groups. These findings suggest an improved fracture healing under local application of simvastatin in osteoporotic rats.