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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Osteochondral tissue repair in osteoarthritic joints： clinical challenges and opportunities in tissue engineering

Osteoarthritis （OA）, identified as one of the priorities for the Bone and Joint Decade, is one of the most prevalent joint diseases, which causes pain and disability of joints in the adult population. Secondary OA usually stems from repetitive overloading to the osteochondral （OC） unit, which could result in cartilage damage and changes in the subchondral bone, leading to mechanical instability of the joint and loss of joint function. Tissue engineering approaches have emerged for the repair of cartilage defects and damages to the subchondral bone in the early stages of OA and have shown potential in restoring the joint＇s function. In this approach, the use of three-dimensional scaffolds （with or without cells） provides support for tissue growth. Commercially available OC scaffolds have been studied in OA patients for repair and regeneration of OC defects. However, none of these scaffolds has shown satisfactory clinical results. This article reviews the OC tissue structure and the design, manufacturing and performance of current OC scaffolds in treatment of OA. The findings demonstrate the importance of biological and biomechanical fixations of OC scaffolds to the host tissue in achieving an improved cartilage fill and a hyaline-like tissue formation. Achieving a strong and stable subchondral bone support that helps the regeneration of overlying cartilage seems to be still a grand challenge for the early treatment of OA.