Effects of Structural Changes in Subchondral Bone on Articular Cartilage in a Beagle Dog Model

Objective Using MR T2-mapping and histopathologic score for articular cartilage to evaluate the effect of structural changes in subchondral bone on articular cartilage. Methods Twenty-four male Beagle dogs were randomly divided into a subchondral bone defect group （n = 12） and a bone cement group （n = 12）. Models of subchondral bone defectin the medial tibial plateau and subchondral bone filled with bone cement were constructed. In all dogs, the left knee joint was used as the experimental sideand the right knee as the sham side. The T2 value for articular cartilage at the medial tibial plateau was measured at postoperative weeks 4, 8, 16, and 24. The articular cartilage specimens were stained with hematoxylin and eosin, and evaluated using the Mankin score. Results There was a statistically significant difference （P 〈 0.05） in Mankin score between the bone defect group and the cement group at postoperative weeks 16 and 24. There was a statistically significant difference in the T2 values between the bone defect group and its sham group （P 〈 0.05） from week 8, and between the cement group and its sham group （P 〈 0.05） from week 16. There was significant difference in T2 values between the two experimental groups at postoperative week 24 （P 〈 0.01）. The T2 value for articular cartilage was positively correlated with the Mankin score （ρ = 0.758, P 〈 0.01）. Conclusion Structural changes in subchondral bone can lead to degeneration of the adjacent articular cartilage. Defects in subchondral bone cause more severe degeneration of cartilage than subchondral bone filled with cement. The T2 value for articular cartilage increases with the extent of degeneration. MR T2-mapping images and the T2 value for articular cartilage can indicate earlycartilage degeneration.

Abnormal subchondral bone remodeling and its association with articular cartilage degradation in knees of type 2 diabetes patients

Type 2 diabetes （T2D） is associated with systemic abnormal bone remodeling and bone loss. Meanwhile, abnormal subchondral bone remodeling induces cartilage degradation, resulting in osteoarthritis （OA）. Accordingly, we investigated alterations in subchondral bone remodeling, microstructure and strength in knees from T2D patients and their association with cartilage degradation. Tibial plateaus were collected from knee OA patients undergoing total knee arthroplasty and divided into non-diabetic （n---70） and diabetes （n = 51） groups. Tibial plateaus were also collected from cadaver donors （n = 20） and used as controls. Subchondral bone microstructure was assessed using micro-computed tomography. Bone strength was evaluated by micro-finite-element analysis. Cartilage degradation was estimated using histology. The expression of tartrate-resistant acidic phosphatase （TRAP）, osterix, and osteocalcin were calculated using immunohistochemistry. Osteoarthritis Research Society International （OARSI） scores of lateral tibial plateau did not differ between non-diabetic and diabetes groups, while higher OARSI scores on medial side were detected in diabetes group. Lower bone volume fraction and trabecular number and higher structure model index were found on both sides in diabetes group. These microstructural alterations translated into lower elastic modulus in diabetes group. Moreover, diabetes group had a larger number of TRAP~ osteoclasts and lower number of Osterix~ osteoprogenitors and Osteocalcin~ osteoblasts. T2D knees are characterized by abnormal subchondral bone remodeling and microstructural and mechanical impairments, which were associated with exacerbated cartilage degradation. In regions with intact cartilage the underlying bone still had abnormal remodeling in diabetes group, suggesting that abnormal bone remodeling may contribute to the early pathogenesis of T2D-associated knee OA.

Association Between Knee Alignment,Disease Severity and Subchondral Trabecular Bone Microarchitecture in Patients with Knee Osteoarthritis

Objective Most patients with knee osteoarthritis(OA)have alignment deformity with the change of Hip-knee-ankle(HKA)angle.The knee alignment influences load distribution at the tibial plateau.Meanwhile,change of subchondral trabecular bone microstructure is related to load bearing and OA progression.However,the relationship between knee alignment on the changes of subchondral trabecular bone microstructure and OA severity have been poorly investigated.The main goal of this work was to investigate variation in tibial plateaus subchondral trabecular bone microstructure in knee OA patients and their association with the severity of OA with the change of knee alignment.Methods Seventy-one knee OA patients planning to undergo total knee arthroplasty were enrolled in this study.The HKA angle and OA disease severity(OARSI score,compartment-specific Kellgren-Lawrence(K-L)grade and OARSI Atlas grade)based on full-leg standing posteroanterior radiographs were evaluated preoperatively in all patients.The tibial plateau collected during surgery was first used for micro-computed tomography(μCT)to analyze the subchondral trabecular bone microstructures,and then used for pathological sections to analyze cartilage degeneration(OARSI score).Pearson and spearman correlations were used to examine linear relationships between knee alignment,OA disease severity and subchondral trabecular bone microstructure.Patients were then divided into group I(HKA angle exceeds 0°in the valgus direction),group II(varus angle<10°)and group III(varus angle≥10°).The differences in subchondral trabecular bone microstructural parameters between the three groups were analyzed by the one-way ANOVA with a post hoc Tukey test.Results HKA angle was significantly correlated with all tibial plateau subchondral trabecular bone microstructure parameters.Regardless of the medial or lateral tibia,HKA angle was most strongly correlated with bone volume fraction(BV/TV),M:(r=0. 613,P<0.01);L:(r=-0.490,P<0.01).In addition,for the media-to-lateral ratios(M:L)of the subchondral trabecular bone microstructure parameters,the HKA angle is positively correlated with M:L BV/TV(r=0.658,P<0.01),M:L trabecular number(Tb.N)(r=0.525,,P<0.01),M:L trabecular thickness(Tb.Th)(r=0.636,P<0.01),and negatively correlated with M:L trabecular separation(Tb.Sp)(r=-0.636,P<0.01)and M:L Specific Bone Surface(BS/BV)(r=-0.792,P<0.01).The BV/TV,Tb.N,and Tb.Th of the medial tibia were sequentially incremented in the order of groupⅠ,Ⅱ,Ⅲof knee alignment,while the Tb.Sp and BS/BV were decreased in this order.The lateral tibia is the opposite.In addition,most of the severity indices of OA are associated with subchondral trabecular bone microstructures,of which OARSI score and BV/TV in medial tibia are the most relevant(r=0.787,P<0.01).HKA angle is significantly correlated with all OA severity grades in medial compartment,but only with OARSI score and Bone sclerosis grade in lateral compartment.Conclusions Tibial plateau subchondral trabecular bone microarchitecture is associated with the HKA angle and OA severity.With the increase of varus angle and the severity of OA,the subchondral trabecular bone in medial tibia has more obvious sclerosis changes and vice versa,suggesting that knee malalignment may promote abnormal subchondral trabecular bone remodeling by altering joint load distribution,thereby affecting the progression of OA.

Effects of Early Weightbearing on Microfracture Treatment of Osteochondral Lesions of Talus with Subchondral Bone Defects

When subchondral bone defects are present in osteochondral lesions of the talus(OCLT),it is inconclusive whether to allow early weightbearing after microfracture treatment because of the lack of effective support of the newly-formed fibrocartilage.After performing arthroscopic debridement and microfracture treatment on OCLT patients with subchondral bone defects,we allowed patients to have an early postoperative weightbearing exercise to observe their clinical outcome.Forty-two OCLT patients with subchondral bone defects were analyzed.Patients were randomly divided into two groups with 21 patients in each group.After arthroscopic debridement and microfracture treatment,group A was allowed to have early partial weightbearing while weightbearing was delayed in group B.Visual analogue scale(VAS)was used to evaluate joint pain before and after surgery.American Orthopaedic Foot and Ankle Society(AOFAS)anklc-hindfoot score was used to evaluate joint function.Tegner activity scale was used to assess patient's exercise level.The AOFAS ankle-hindfoot score in group A increased from 54.4 to 87.6,and that in group B increased from 54.9 to 87.3.The VAS score in group A decreased from 6.5 to 2.2,and that in group B decreased from 6.4 to 2.3.The Tegner activity scale increased from 2.6 to 4.4 in group A,and that in group B increased from 2.6 to 3.9.There was significant difference in the Tegner activity scale between group A and group B(P<0.05).It was suggested that when performing microfracture treatmenf on OCLT patients with subchondral bone defects,early postoperative weightbearing may achieve similar clinical outcomes as delayed weightbearing,and patients may be better able to return to sports.

Effects of acupotomy on the activity of osteoclasts and osteoblasts in the subchondral bone of rabbits with early and mid-stage knee osteoarthritis models

Objective:To investigate whether acupotomy could inhibit subchondral bone remodeling in knee osteoarthritis(KOA)rabbits by regulating the activity of osteoblasts and osteoclasts.Methods:KOA rabbits were prepared by immobilization for 6 and 9 weeks by Videman method.Nine groups of rabbits(control,6 weeks and 9 weeks model,6 weeks and 9 weeks acupotomy,6 weeks and 9 weeks electroacupuncture,and 6 weeks and 9 weeks drug groups)received acupotomy,electroacupuncture and risedronate sodium intervention,respectively,for 3 weeks.Results:Acupotomy can inhibit the activity of osteoclasts and osteoblasts in subchondral bone by reducing the proteins expression of cathepsin K(CK)and tartrate-resistant acid phosphatase(TRAP)and decreasing the proteins expression of osteocalcin(OCN)and alkaline phosphatase(ALP),to intercept the abnormal bone resorption and bone formation of subchondral bone in 6-week and 9-week immobilization-induced KOA rabbits.Conclusion:These findings indicated that acupotomy may be more advantageous than risedronate sodium intervention in modulating subchondral bone remodeling in KOA rabbits,especially in 9-week immobilization-induced KOA rabbits.

Subchondral bone as a novel target for regenerative therapy of osteochondritis dissecans:A case report

BACKGROUND Osteochondritis dissecans(OCD)is a rare disease of unclear cause characterized by subchondral bone damage and overlying cartilage defects.The current report presents the results of subchondral bone as a novel target for implantation of peripheral blood stem cells(PBSCs)in the treatment of OCD.CASE SUMMARY A 16-year-old patient diagnosed with OCD underwent subchondral bone implantation of PBSCs.Four months later,the patient's visual analog scale scores,Western Ontario and McMaster University osteoarthritis index,and whole-organ magnetic resonance imaging score improved significantly,and regeneration of cartilage and subchondral bone was observed on magnetic resonance imaging.CONCLUSION This is the first case of OCD treated with subchondral bone as an implantation target of PBSCs,which highlights the importance of subchondral bone for cartilage repair.This treatment could be a potential option for articular cartilage and subchondral bone recovery in OCD.

A TETRACYCLINE LABELING STUDY OF SUBCHONDRAL BONE TISSUES IN OSTEOARTHRITIC HIP JOINT

Seven female patients (mean age of 56 years) with advanced hip joint osteoarthritis underwent total hip replacement. Four days before operation they were given oral tetracycline for two days. During operation specimens were taken from the white articular cartilage, the yellowish articular cartilage and the ivory bone together with their subchondral bone tissues. The undecalcified specimens were cut into 10 μm sections and observed under the fluorescence microscope. In all the specimens the following findings could be observed. 1. The osteoarthritic articular cartilage became thinner, with uneven surface and fissures. 2. The superficial and deep surfaces and the central part of the subchondral bone plate showed bright golden yellow fluorescence. It reflected extensive new bone formation. 3. The subchondral bone trabeculae also revealed bright golden yellow fluorescence on their peripheral borders, so trabeculae turned thicker obviously. 4. The marrow tissues between the bone trabeculae exhibited particulate or spherical bright golden yellow fluorescence, reflecting new bone formation in the marrow. The particulate and spherical bright golden yellow fluorescent materials might aggregate, enlarge and merge into large piece of new bone and they also fused with the neighbouring bone trabeculae. The aforementioned changes in the structure of the subchondral bone tissues increased greatly the mass in the osteoarthritic femoral head.

Subchondral fatigue fracture of the femoral head in young military recruits:Potential risk factors

BACKGROUND Subchondral fatigue fracture of the femoral head(SFFFH)mainly occurs in young military recruits and might be confused with osteonecrosis of the femoral head.However,less research focuses on the risk factor for SFFFH.AIM To evaluate the intrinsic risk factors for SFFFH in young military recruits.METHODS X-ray and magnetic resonance imaging data were used for analysis.Acetabular anteversion of the superior acetabulum,acetabular anteversion of the center of the acetabulum(AVcen),anterior acetabular sector angle(AASA),posterior acetabular sector angle,superior acetabular sector angle,neck-shaft angle(NSA),inferior iliac angle(IIA),and ischiopubic angle were calculated.Then,logistic regression,receiver operating characteristic curve analysis,and independent samples t-test were performed to identify the risk factors for SFFFH.RESULTS Based on the results of logistic regression,age[odds ratio(OR):1.33;95%confidence interval(95%CI):1.12-1.65;P=0.0031]and treatment timing(OR:0.86;95%CI:0.75-0.96;P=0.015)could be considered as the indicators for SFFFH.AVcen(P=0.0334),AASA(P=0.0002),NSA(P=0.0007),and IIA(P=0.0316)were considered to have statistical significance.Further,AVcen(OR:1.41;95%CI:1.04-1.95)and AASA(OR:1.44;95%CI:1.21-1.77),especially AASA(area under curve:66.6%),should be paid much more attention due to the higher OR than other indicators.CONCLUSION We have for the first time unveiled that AASA and age could be key risk factors for SFFFH,which further verifies that deficient anterior coverage of the acetabulum might be the main cause of SFFFH.

Subchondral Bone and Its Role in Osteoarthritis

Osteoarthritis (OA) is the most prevalent form of arthritis and one of the leading causes of chronic disability which is becoming more pronounced as the population ages. Various genetic, biologic and mechanical factors contribute to disease process in OA. A large cascade of events leads to breakdown and degeneration of cartilage in a progressive manner ultimately resulting in the damage of the joint including the subchondral bone. Although majority of attention was given to chondral surface of the joint in the past, recently subchondral bone has been taken more and more attention during the investigation of degenerative phase in osteoarthritis. In our review we aimed to review the processes that were taken place during the osteoarthrosis especially in the sub-chondral bone and to give a new point of view for the further investigations.

Observation on the Clinical Effect of Needle Knife Release Combined with Microporous Decompression in Subchondral Bone Marrow Edema Area for Treatment of Knee Osteoarthritis

Objective:To observe the curative effect of release with needle knife combined with microporous decompression in bone marrow edema area of subchndral bone for treatment of knee osteoarthritis.Method:From March 2019 to March 2020,66 patients with knee osteoarthritis were selected as the research objects,and divided into treatment group and control group according to random nuber table.The treatment group was treated with release with needle knife combined with microporous decompression in bone marrow edema area,while the control group was treated with release with needle knife.Visual analogue scale(VAS),the Western Ontario and Mc Master University composite index(WOMCA)and inflammatory factors were used to evaluate the curative effect of patients before treatment and after treatment.Results:The VAS scores of knee pain in both groups decreased after treatment.The treatment group was lower than the control group.The WOMAC scores of both groups were decreased significantly after treatment,and then gradually decreased with time.The WOMAC scroes of the treatment group were lower than those of the control group after treatment,and there was an interactive effect on time factor.Conclusion:Release with needle knife combined with microporous decompression in bone marrow edema area of subchondral bone has good curative effect in the treatment of knee osteoarthritis;it can relieve the pain of patients,improve the function of joint,reduce inlfammatory reaction,and then delay the pathological progress of KOA,which is worthy of clinical promotion.

Phenylboronic-tannin nanocolloids that scavenge subchondral reactive oxygen microenvironment and inhibit RANKL induced osteoclastogenesis for osteoarthritis treatment

The excessive reactive oxygen species (ROS) accumulation and overactivated osteoclastogenesis in subchondral bone has proved to be a major cause of osteoarthritis (OA). Scavenging of ROS microenvironment to inhibit the osteoclastogenesis is highly valued in the therapeutic process of osteoarthritis. Despite the excellent ability of polyphenolic colloidal to scavenge reactive oxygen species and its affinity for macrophages, the preparation of polyphenolic colloidal nanoparticles is limited by the complex intermolecular forces between phenol molecules and the lack of understanding of polymerization/sol-gel chemistry. Herein, our work introduces a novel poly-tannin-phenylboronic colloidal nanoparticle (PTA) exclusively linked by ROS-responsive bondings. Nanocolloidal PTA has a uniform particle size, is easy and scalable to synthesize, has excellent scavenging of ROS, and can be slowly degraded. For in vitro experiments, we demonstrated that, PTA could eliminate ROS within RAW264.7 cells and impede osteoclastogenesis and bone resorption. RNA sequencing results of PTA-treated RAW264.7 cells further reveal the promotion of antioxidant activity and inhibition of osteoclastogenesis. For in vivo experiments, PTA could eliminate the ROS environment and reduce the number of osteoclasts in the subchondral bone, thereby alleviating the damage of subchondral bone and symptoms of osteoarthritis. Our research, by delving into the formation of polyphenol colloidal nanoparticles and validating their role in ROS scavenging to inhibit osteoclastogenesis in subchondral bone, may open new avenues for OA treatment in the future.

Pathological progression of osteoarthritis:a perspective on subchondral bone

Osteoarthritis(OA)is a degenerative bone disease associated with aging.The rising global aging population has led to a surge in OA cases,thereby imposing a significant socioeconomic burden.Researchers have been keenly investigating the mechanisms underlying OA.Previous studies have suggested that the disease starts with synovial inflammation and hyperplasia,advancing toward cartilage degradation.Ultimately,subchondral-bone collapse,sclerosis,and osteophyte formation occur.This progression is deemed as“top to bottom.”However,recent research is challenging this perspective by indicating that initial changes occur in subchondral bone,precipitating cartilage breakdown.In this review,we elucidate the epidemiology of OA and present an in-depth overview of the subchondral bone’s physiological state,functions,and the varied pathological shifts during OA progression.We also introduce the role of multifunctional signal pathways(including osteoprotegerin(OPG)/receptor activator of nuclear factor-kappa B ligand(RANKL)/receptor activator of nuclear factor-kappa B(RANK),and chemokine(CXC motif)ligand 12(CXCL12)/CXC motif chemokine receptor 4(CXCR4))in the pathology of subchondral bone and their role in the“bottom-up”progression of OA.Using vivid pattern maps and clinical images,this review highlights the crucial role of subchondral bone in driving OA progression,illuminating its interplay with the condition.

Microarray analysis of signalling interactions between inflammation and angiogenesis in subchondral bone in temporomandibular joint osteoarthritis

Inflammation and angiogenesis,the major pathological changes of osteoarthritis(OA),are closely associated with joint pain;however,pertinent signalling interactions within subchondral bone of osteoarthritic joints and potential contribution to the peripheral origin of OA pain remain to be elucidated.Herein we developed a unilateral anterior crossbite mouse model with osteoarthritic changes in the temporomandibular joint.Microarray-based transcriptome analysis,besides quantitative real-time polymerase chain reaction,was performed to identify differentially expressed genes(DEGs).Overall,182 DEGs(fold change≥2,P<0.05)were identified between the control and unilateral anterior crossbite groups:168 were upregulated and 14 were downregulated.On subjecting significant DEGs to enrichment analyses,inflammation and angiogenesis were identified as the most affected.Inflammation-related DEGs were mainly enriched in T cell activation and differentiation and in the mammalian target of rapamycin/nuclear factor-κB/tumour necrosis factor signalling.Furthermore,angiogenesis-related DEGs were mainly enriched in the Gene Ontology terms angiogenesis regulation and vasculature development and in the KEGG pathways of phosphoinositide 3-kinase-protein kinase B/vascular endothelial growth factor/hypoxia-inducible factor 1 signalling.Protein-protein interaction analysis revealed a close interaction between inflammation-and angiogenesis-related DEGs,suggesting that phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit delta(Pi3kcd),cathelicidin antimicrobial peptide(Camp),C-X-C motif chemokine receptor 4(Cxcr4),and MYB proto-oncogene transcription factor(Myb)play a central role in their interaction.To summarize,our findings reveal that in subchondral bone of osteoarthritic joints,signal interaction is interrelated between inflammation and angiogenesis and associated with the peripheral origin of OA pain;moreover,our data highlight potential targets for the inhibition of OA pain.

Acupotomy inhibits aberrant formation of subchondral bone through regulating osteoprotegerin/receptor activator of nuclear factor-κB ligand pathway in rabbits with knee osteoarthritis induced by modified Videman method

OBJECTIVE:To investigate the effects of acupotomy on inhibiting abnormal formation of subchondral bone in rabbits with knee osteoarthritis(KOA).METHODS:A total of 24 New Zealand rabbits were randomly divided into four groups of 6 rabbits each[control,model,electroacupuncture(EA)and acupotomy].Eighteen KOA model rabbits were established using a modified Videman method.Rabbits in EA and acupotomy groups received the intervention for 3 weeks.Then,the cartilage and subchondral bone unit were obtained and the histomorphological changes were recorded.Osteoprotegerin(OPG)and receptor activator of nuclear factor-κB ligand(RANKL)in subchondral bone were evaluated by Western blotting,real-time polymerase chain reaction and immunohistochemistry.RESULTS:Compared with the model group,both the acupotomy and EA groups showed a significant decrease in the Lequesne index(both P<0.01)and Mankin score(P<0.01,<0.05).In addition,both EA and acupotomy groups had a higher expression of total articular cartilage(TAC)(P<0.05,<0.01)and lower expression of articular calcified cartilage(ACC)/TAC(P<0.05,<0.05)compared with the model group.The thickness of the subchondral bone plate in EA and acupotomy groups were decreased(both P<0.01)compared to the model group.Moreover,trabecular bone volume(BV/TV),protein and relative expression of OPG and the ratio of OPG/RANKL in the subchondral bone of acupotomy group were decreased statistically significant,while these parameters were not significantly changed in the EA group compared with the model group.CONCLUSIONS:In the rabbit model of KOA,acupotomy inhibits aberrant formation of subchondral bone by suppressing OPG/RANKL ratio as a potential therapy for KOA.

Dynamic Alterations in Microarchitecture, Mineralization and Mechanical Property of Subchondral Bone in Rat Medial Meniscal Tear Model of Osteoarthritis

Background： The properties of subchondral bone influence the integrity of articular cartilage in the pathogenesis of osteoarthritis （OA）. However, the characteristics ofsubchondral bone alterations remain unresolved. The present study aimed to observe the dynamic alterations in the microarchitecture, mineralization, and mechanical properties of subchondral bone during the progression of OA. Methods： A medial meniscal tear （MMT） operation was pertbrmed in 128 adult Sprague Dawley rats to induce OA. At 2, 4, 8, and 12 weeks following the MMT operation, cartilage degeneration was evaluated using toluidine blue O staining, whereas changes in the microarchitecture indices and tissue mineral density （TMD）, mineral-to-collagen ratio, and intrinsic mechanical properties of subchondral bone plates （BPs） and trabecular bones （Tbs） were measured using micro-computed tomography scanning, conibcal Raman microspectroscopy and nanoindentation testing, respectively. Results： Cartilage degeneration occurred and worsened progressively from 2 to 12 weeks after OA induction. Microarchitecture analysis revealed that the subchondral bone shifted from bone resorption early （reduced trabecular BV/TV, trabecular number, connectivity density and trabecular thickness [Tb.Th], and increased trabecular spacing （Tb.Sp） at 2 and 4 weeks） to bone accretion late （increased BV/TV, Tb.Th and thickness of subchondral bone plate, and reduced Tb.Sp at 8 and 12 weeks）. The TMD of both the BP and Tb displayed no significant changes at 2 and 4 weeks but decreased at 8 and 12 weeks. The mineral-to-collagen ratio showed a significant decrease from 4 weeks for the Tb and from 8 weeks for the BP after OA induction. Both the elastic modulus and hardness of the Tb showed a significant decrease from 4 weeks after OA induction. The BP showed a significant decrease in its elastic modulus from 8 weeks and its hardness from 4 weeks. Conclusion： The microarchitecture, mineralization and mechanical properties of subchondral bone changed in a time-dependent manner as OA progressed.

Acupotomy ameliorates subchondral bone absorption and mechanical properties in rabbits with knee osteoarthritis by regulating bone morphogenetic protein 2-Smad1 pathway

OBJECTIVE:To investigate the effects of acupotomy on the subchondral bone absorption and mechanical properties in rabbits with knee osteoarthritis(KOA).METHODS:The rabbits were divided into blank control,model,acupotomy and electroacupuncture(EA)groups,with 12 rabbits in each.Modified Videman's method was used to prepare KOA model.The acupotomy and EA group were given indicated intervention for 3 weeks.The behavior of rabbits in each group was recorded.Subsequently,cartilage–subchondral bone units were obtained and morphological changes were observed by optical microscope and micro computed tomography.Compression test was used to detect the mechanical properties of subchondral bone,Western blot and real-time polymerase chain reaction(RT-PCR)were applied to detect the expression of bone morphogenetic protein 2-Smad1(BMP2-Smad1)pathway in subchondral bone.RESULTS:Compared with the control group,rabbits in the KOA group showed lameness,knee pain,and cartilage degradation;the subchondral bone showed active resorption,the mechanical properties decreased significantly and the BMP2-Smad1 pathway downregulated significantly.Both acupotomy and EA intervention could increase the thickness of trabecular bone(Tb.Th),the bone volume fraction(BV/TV)and the thickness of subchondral bone plate,reduce the separation of trabecular bone(Tb.Sp),improve the maximum load and elastic modulus of subchondral bone,and effectively delay cartilage degeneration in KOA rabbits.This process may be achieved through upregulation the related proteins of BMP2-Smad1 pathway.The maximum load and elastic modulus of subchondral bone in the acupotomy group were slightly better than those in the EA group.CONCLUSIONS:Acupotomy could effectively protect cartilage by inhibiting abnormal bone resorption and improving mechanical properties of subchondral bone thorough the related proteins of BMP2-Smad1 pathway in KOA rabbits.

3D printed-electrospun PCL/hydroxyapatite/MWCNTs scaffolds for the repair of subchondral bone

Osteochondral defect caused by trauma or osteoarthritis exhibits a major challenge in clinical treatment with limited symptomatic effects at present.The regeneration and remodeling of subchondral bone play a positive effect on cartilage regeneration and further promotes the repair of osteochondral defects.Making use of the strengths of each preparation method,the combination of 3D printing and electrospinning is a promising method for designing and constructing multi-scale scaffolds that mimic the complexity and hierarchical structure of subchondral bone at the microscale and nanoscale,respectively.In this study,the 3D printed-electrospun poly(ɛ-caprolactone)/nano-hydroxyapatites/multi-walled carbon nanotubes(PCL/nHA/MWCNTs)scaffolds were successfully constructed by the combination of electrospinning and layer-by-layer 3D printing.The resulting dual-scale scaffold consisted of a dense layer of disordered nanospun fibers and a porous microscale 3D scaffold layer to support and promote the ingrowth of subchondral bone.Herein,the biomimetic PCL/nHA/MWCNTs scaffolds enhanced cell seeding efficiency and allowed for higher cell-cell interactions that supported the adhesion,proliferation,activity,morphology and subsequently improved the osteogenic differentiation of bone marrow mesenchymal stem cells in vitro.Together,this study elucidates that the construction of 3D printed-electrospun PCL/nHA/MWCNTs scaffolds provides an alternative strategy for the regeneration of subchondral bone and lays a foundation for subsequent in vivo studies.

Distribution of mechanical strain in equine distal metacarpal subchondral bone:A microCT-based finite element model

Microdamage accumulation and adaptation of subchondral bone subjected to intensive cyclic loading are important processes associated with catastrophic bone failure,and joint degeneration in athletic humans and racehorses.At the tissue-level,they lead to a spatial variation in bone tissue mineral density(TMD)which affects the response of the bone to mechanical load.Quantifying the spatial distribution of mechanical load within the subchondral bone is critical for understanding the mechanism of the joint failure.Previously,a gradient of TMD and mechanical properties has been reported under unconfined compression in osteochondral plugs.In the present study,we used micro computed tomography(μCT)-based finite element(FE)models of cartilage-bone to investigate the gradient of strain in the subchondral bone(SCB)from the third metacarpal(MC3)condyle of racehorses under simulated in situ compression.Non-destructive mechanical testing of specimens under high-rate compression provided the apparent-level modulus of SCB.FE models were analysed using unconfined and confined boundary conditions.Unconfined FE-predicted apparent-level gradient of modulus across the SCB thickness correlated well with the experimental results(R^(2)=0.72,p<0.05).The highest strain occurred in the most superficial SCB(0.5–2.5 mm deep to the cartilage-bone interface)under the simulated in-situ compression through articular cartilage.The findings of this study provide an estimation for the spatial distribution of mechanical strain within SCB in-situ in the presence of heterogeneous bone tissue which is commonly observed in joints subjected to intensive cyclic loading.

Mechanotransduction in subchondral bone microenvironment and targeted interventions for osteoarthritis

Osteoarthritis(OA)is a progressive degenerative joint sickness related with mechanics,obesity,ageing,etc.,mainly characterized by cartilage degeneration,subchondral bone damage and synovium inflammation.Coordinated mechanical absorption and conduction of the joint play significant roles in the prevalence and development of OA.Subchondral bone is generally considered a load-burdening tissue where mechanosensitive cells are resident,including osteocytes,osteoblast lineage cells,and osteoclast lineage cells(especially less concerned in mechanical studies).Mechano-signaling imbalances affect complicated cellular events and disorders of subchondral bone homeostasis.This paper will focus on the significance of mechanical force as the pathogenesis,involvement of various mechanical force patterns in mechanosensitive cells,and mechanobiology research of loading devices in vitro and in vivo,which are further discussed.Additionally,various mechanosensing structures(e.g.,transient receptor potential channels,gap junctions,primary cilia,podosome-associated complexes,extracellular vesicles)and mechanotransduction signaling pathways(e.g.,Ca^(2+) signaling,Wnt/β-catenin,RhoA GTPase,focal adhesion kinase,cotranscriptional activators YAP/TAZ)in mechanosensitive bone cells.Finally,we highlight potential targets for improving mechanoprotection in the treatment of OA.These advances furnish an integration of mechanical regulation of subchondral bone homeostasis,as well as OA therapeutic approaches by modulating mechanical homeostasis.

Diagnosing, planning and evaluating osteochondral ankle defects with imaging modalities

This current concepts review outlines the role of diffe-rent imaging modalities in the diagnosis, preoperative planning, and follow-up of osteochondral ankle defects. An osteochondral ankle defect involves the articular cartilage and subchondral bone(usually of the talus) and is mostly caused by an ankle supination trauma. Conventional radiographs are useful as an initial imaging tool in the diagnostic process, but have only moderate sensitivity for the detection of osteochondral defects. Computed tomography(CT) and magnetic resonance imaging(MRI) are more accurate imaging modalities. Recently, ultrasonography and single photon emission CT have been described for the evaluation of osteochondral talar defects. CT is the most valuable modality for assessing the exact location and size of bony lesions. Cartilage and subchondral bone damage can be visualized using MRI, but the defect size tends to be overestimated due to bone edema. CT with the ankle in full plantar flexion has been shown a reliable tool for preoperative planning of the surgical approach. Postoperative imaging is useful for objective assessment of repair tissue or degenerative changes of the ankle joint. Plain radiography, CT and MRI have been used in outcome studies, and different scoring systems are available.