Peng Xia

Background: Knee osteoarthritis (KOA) lacks disease-modifying treatment, making early identification of modifiable risk factors in asymptomatic older adults a priority. Patellar tendon stiffness (PTS) and knee extensor strength (KESt) may independently influence KOA development, yet their prognostic value in individuals free of knee symptoms is unestablished. Objective: This study aimed to determine whether baseline extensor mechanism mechanical properties predict 2-year incident clinical KOA in community-dwelling older adults who were asymptomatic at enrollment, and to quantify the relative contribution of each parameter. Methods: This 2-year prospective cohort study enrolled 116 community-dwelling older adults (220 knees) free of knee pain at baseline. Incident clinical KOA was diagnosed according to the American College of Rheumatology criteria. Prognostic performance was evaluated across 7 survival algorithms using 5-fold nested cross-validation with the Harrell C-index. Predictor importance was quantified using Shapley Additive Explanations (SHAP) values from the best-performing model, and absolute KOA risk was estimated across tertiles of the linear predictor score. Results: Over 2 years, 55 (25%) knees developed incident clinical KOA. PTS and KESt were consistently selected across all cross-validation folds, whereas quadriceps muscle passive stiffness was not selected in any fold. The gradient boosted survival model achieved the highest discrimination (C-index=0.720, 95% CI 0.686-0.754), significantly exceeding chance ( P <.05). SHAP analysis identified KESt as the dominant predictor (mean |SHAP| 0.314, 95% CI 0.251-0.388), with PTS as the second most important predictor (0.166, 95% CI 0.128-0.200). Knees in the highest-risk tertile showed a 24-month KOA incidence of 38.4% (28/73), which was more than twice that in the lowest-risk tertile (13/74, 17.6%). Conclusions: PTS and KESt independently and consistently predicted 2-year incident clinical KOA in asymptomatic community-dwelling older adults. Extensor mechanism mechanical profiling may identify individuals at elevated KOA risk prior to symptom onset, although these exploratory findings require confirmation in larger cohorts before KESt and PTS can be considered for screening or preventive intervention.

Background: Photobiomodulation using light-emitting diode (LED) therapy is a promising and safe non-invasive approach for treating knee osteoarthritis (KOA), yet the most effective wavelength and energy density to prevent cartilage matrix degradation remain unclear. This study aimed to determine the optimal LED parameters for suppressing chondrocyte extracellular matrix (ECM) degradation in vitro, and for alleviating ECM degradation and pain-related behaviours in a murine KOA model. Methods: TNF-α-stimulated RCJ 3.1.C5.18 chondrocytes were irradiated with LEDs (625/810/940/1050 nm; 13–78 J/cm ² at 44 mW/cm ² ). Chondrocyte ECM-related markers ( mmp3, mmp13, col2a1, aggrecan ) were quantified via RT-qPCR. In vivo, destabilization of the medial meniscus (DMM)-induced KOA mice (n = 5–6/group) received 810 nm (39/52 J/cm ² ) or 940 nm (39/52 J/cm ² ) LED therapy thrice weekly for 6 weeks. Pain-like behaviors (Von Frey, incapacitance tests) and histopathology (OARSI scoring, mmp3/collagen II immunofluorescence) were assessed. Results: In vitro, 940 nm LED at 52 J/cm ² most effectively suppressed mmp3/mmp13 mRNA (P < 0.05) and upregulated col2a1/aggrecan ( P < 0.05), while 810 nm at 39 J/cm ² only inhibited mmp3 and mmp13 . The LED with 625 nm and 1050 nm showed no significant effect on chondrocyte ECM degradation markers. In vivo, 940 nm at 52 J/cm ² improved weight-bearing asymmetry by 31% at 6 weeks (vs. DMM controls, P = 0.03) and reduced cartilage degradation by 50% (OARSI score, P = 0.03). Immunofluorescence indicated that 940 nm at 52 J/cm ² LED therapy significantly inhibited the expression of mmp3 and increased collagen II protein levels in cartilage tissues. Conclusion: LED therapy at 940 nm with 52 J/cm ² attenuates ECM degradation and pain in KOA, defining a target LED parameter set for potential clinical translation.

Mesenchymal stem cells (MSCs) are stem cells that exhibit self-renewal capacity and multi-directional differentiation potential. They can be extracted from the bone marrow and umbilical cord, as well as adipose, amnion, and other tissues. They are widely used in tissue engineering and are currently considered an important source of cells in the field of regenerative medicine. Since certain limitations, such as an insufficient cell source, mature differentiation, and low transplantation efficiency, are still associated with MSCs, researchers have currently focused on improving the efficacy of MSCs. Low-intensity pulsed ultrasound (LIPUS) has mechanical, cavitation, and thermal effects that can produce different biological effects on organs, tissues, and cells. It can be used for fracture treatment, cartilage repair, and stem cell applications. An in-depth study of the role and mechanism of action of LIPUS in MSC treatment would promote our understanding of LIPUS and promote research in this field. In this article, we have reviewed the progress in research on the use of LIPUS with various MSCs and comprehensively discussed the progress in the use of LIPUS for promoting the proliferation, differentiation, and migration of MSCs, as well as its future prospects.

Aims: To evaluate the effect of ultrasound-targeted simvastatin-loaded microbubble destruction (UTMD_SV) for alleviation of the progression of osteoarthritis (OA) in rabbits through modulation of the peroxisome proliferator-activated receptor (PPARγ).Methods: In vitro, OA chondrocytes were treated with ultrasound (US), US-targeted microbubble destruction (UTMD), simvastatin (SV), and UTMD_SVon alternate days for four weeks. Chondrocytes were also treated with PPARγ inhibitor, PPARγ inhibitor+ UTMD_SV, and UTMD_SV. The cholesterol efflux rate and triglyceride levels were measured using an assay kit and oil red O staining, respectively. In vivo, the OA rabbits were treated with a single intra-articular injection of UTMD, SV, and UTMD_SVevery seven days for four weeks. Cartilage histopathology was assessed by safranin-O staining and the Mankin score. Total cholesterol (TC) and high-density lipoprotein-cholesterol (HDL-C) in rabbit knee synovial fluid were detected by enzyme-marker assay. Aggrecan, collagen II, and PPARγ expression levels were analyzed by Western blotting (WB).Results: In vitro, UTMD_SVsignificantly increased the cholesterol efflux rate and aggrecan, collagen II, and PPARγ levels in OA chondrocytes; these effects were blocked by the PPARγ inhibitor. In vivo, UTMD_SVsignificantly increased aggrecan, collagen II, PPARγ, and HDL-C levels, while TC levels and Mankin scores were decreased compared with the UTMD, SV, OA, and control groups.Conclusion: UTMD_SVpromotes cartilage extracellular matrix synthesis by modulating the PPARγ-mediated cholesterol efflux pathway in OA rabbits. Cite this article: Bone Joint Res 2021;10(10):693–703.

Objective: To evaluate ultrasound-targeted simvastatin-loaded microbubble destruction (UTMD_SV) attenuation of osteoarthritis (OA) progression in rabbits through modulation of the peroxisome proliferator-activated receptor (PPARγ)-mediated cholesterol efflux pathway.Methods: In vitro, chondrocytes were treated with ultrasound (US), US-targeted microbubble destruction (UTMD), simvastatin (SV) and UTMDsv on alternate days for 4 weeks. Chondrocytes were also treated with PPARγ inhibitor, PPARγ inhibitor+UTMDsv and UTMDsv. The cholesterol efflux rate and triglyceride were measured respectively by assay kit and oil red O staining. In vivo, the OA rabbits were treated with a single intra-articular injection of UTMD, SV and UTMD_SV every 7 days for 4 weeks. Cartilage histopathology was assessed by safranin-O staining and the Mankin score. Total cholesterol (TC) and high-density lipoprotein-cholesterol (HDL-C) in rabbit knee synovial fluid were detected by enzyme-marker assay. Aggrecan, collagen II and PPARγ expression levels were analyzed western blotting (WB).Results: OA models exhibited primarily by a loss of aggrecan and collagen II, changes to subchondral bone architecture and cartilage degradation. In vitro, UTMD_SV significantly increased the cholesterol efflux rate and aggrecan, collagen II and PPARγ levels in OA chondrocytes; these effects were blocked by the PPARγ inhibitor. In vivo, UTMD_SV significantly increased aggrecan, collagen II, PPARγ and HDL-C levels, while TC levels and Mankin scores were decreased compared with the UTMD, SV, OA and control groups (95% CI: 0.069 to 6.671).Conclusion: UTMD_SV promotes the expression of aggrecan and collagen II and relieve cartilage degradation by modulating the PPARγ-mediated cholesterol efflux pathway in rabbits.

Mesenchymal stem cell (MSC) migration is promoted by low-intensity pulsed ultrasound (LIPUS), but its mechanism is unclear. Since autophagy is known to regulate cell migration, our study aimed to investigate if LIPUS promotes the migration of MSCs via autophagy regulation. We also aimed to investigate the effects of intra-articular injection of MSCs following LIPUS stimulation on osteoarthritis (OA) cartilage. For the in vitro study, rat bone marrow-derived MSCs were treated with an autophagy inhibitor or agonist, and then they were stimulated by LIPUS. Migration of MSCs was detected by transwell migration assays, and stromal cell-derived factor-1 (SDF-1) and C-X-C chemokine receptor type 4 (CXCR4) protein levels were quantified. For the in vivo study, a rat knee OA model was generated and treated with LIPUS after an intra-articular injection of MSCs with autophagy inhibitor added. The cartilage repair was assessed by histopathological analysis and extracellular matrix protein expression. The in vitro results suggest that LIPUS increased the expression of SDF-1 and CXCR4, and it promoted MSC migration. These effects were inhibited and enhanced by autophagy inhibitor and agonist, respectively. The in vivo results demonstrate that LIPUS significantly enhanced the cartilage repair effects of MSCs on OA, but these effects were blocked by autophagy inhibitor. Our results suggest that the migration of MSCs was enhanced by LIPUS through the activation autophagy, and LIPUS improved the protective effect of MSCs on OA cartilage via autophagy regulation.

Low-intensity pulsed ultrasound (LIPUS) can induce mesenchymal stem cell (MSC) differentiation, although the mechanism of its potential effects on chondrogenic differentiation is unknown. Since autophagy is known to regulate the differentiation of MSCs, the aim of our study was to determine whether LIPUS induced chondrogenesis via autophagy regulation. MSCs were isolated from the rat bone marrow, cultured in either standard or chondrogenic medium, and stimulated with 3 MHz of LIPUS given in 20% on–off cycles, with or without prior addition of an autophagy inhibitor or agonist. Chondrogenesis was evaluated on the basis of aggrecan (AGG) organization and the amount of type II collagen (COL2) and the mRNA expression of AGG, COL2, and SRY-related high mobility group-box gene 9 (SOX9) genes. LIPUS promoted the chondrogenic differentiation of MSCs, as shown by the changes in the extracellular matrix (ECM) proteins and upregulation of chondrogenic genes, and these effects were respectively augmented and inhibited by the autophagy inhibitor and agonist. Taken together, these results indicate that LIPUS promotes MSC chondrogenesis by inhibiting autophagy.

Low-intensity pulsed ultrasound (LIPUS) is a mechanical stimulus that plays a key role in regulating the differentiation of bone marrow mesenchymal stem cells (BMSCs). However, the way in which it affects the chondrogenic differentiation of BMSCs remains unknown. In this study, we aimed to investigate whether LIPUS is able to influence TGF-β1-induced chondrogenesis of BMSCs through the integrin-mechanistic target of the Rapamycin (mTOR) signaling pathway. BMSCs were isolated from rat bone marrow and cultured in either standard or TGF-β1-treated culture medium. BMSCs were then subjected to LIPUS at a frequency of 3 MHz and a duty cycle of 20%, and integrin and mTOR inhibitors added in order to analyze their influence on cell differentiation. BMSCs were phenotypically analyzed by flow cytometry and the degree of chondrogenesis evaluated through toluidine blue staining, immunofluorescence, and immunocytochemistry. Furthermore, expression of COL2, aggrecan, SOX9, and COL1 was assessed by qRT-PCR and western blot analysis. We found that LIPUS promoted TGF-β1-induced chondrogenesis of BMSCs, represented by increased expression of COL2, aggrecan and SOX9 genes, and decreased expression of COL1. Notably, these effects were prevented following addition of integrin and mTOR inhibitors. Taken together, these results indicate that mechanical stimulation combined with LIPUS promotes TGF-β1-induced chondrogenesis of BMSCs through the integrin-mTOR signaling pathway.

We established a rabbit osteoarthritis model by anterior cruciate ligament transaction and observed the articular cartilage repair effect of low-intensity pulsed ultrasound irradiation. Thirty-six healthy New Zealand rabbits were randomized into early control group, early osteoarthritis group, early treatment group, medium-term control group, medium-term osteoarthritis group and medium-term treatment group. Animals in early control group and medium-term control group underwent articular capsulotomy surgery, and those in other four groups underwent anterior cruciate ligament transaction. In early osteoarthritis group and early treatment group, rabbits received low-intensity pulsed ultrasound irradiation 3 days after surgery, while in medium-term osteoarthritis group and medium-term treatment group irradiation received at the beginning of the fifth week after surgery. However, ultrasound irradiation of early osteoarthritis group and medium-term osteoarthritis group was no output. Six weeks after irradiation, the rabbits were sacrificed and pathologic changes in the articular surface of femoral condyle were assessed. Also, expression of type II collagen, proteoglycan, phophorylated extracellular signalregulated kinase1/2 and p38 of the articular cartilage was measured by Western blot. The result shows that low-intensity pulsed ultrasound intervention is beneficial to articular cartilage repair by abating damage of extracellular matrix in early term of osteoarthritis and extracellular signal-regulated kinase1/2 and p38 signaling pathway was involved.

We established a rabbit OA model by ACLT surgery, and observed the articular cartilage repair effect of LIPUS irradiation. Thirty-six healthy New Zealand rabbits equally randomized to six groups: early control group (EC group), early OA group (EO group), early treatment group (ET group), medium-term control group (MC group), medium-term OA group (MO group) and medium-term treatment group (MT group). Animals in ET group received LIPUS irradiation 3 days after surgery, and those in MT group received LIPUS irradiation at the fifth week after surgery. Six weeks after irradiation, the rabbits were sacrificed respectively and observed for modified Mankin score, proliferating cell nuclear antigen (PCNA) and phosphatidylinositol-3-kinase (PI3K). The result shows that early LIPUS intervention is beneficial to articular cartilage repair through promotion of chondrocytes proliferation in OA. The mechanism of action is closely associated with the role of LIPUS in PI3K signal transduction pathway.