The February 2025 Knee Roundup³⁶⁰ looks at: Once-weekly semaglutide in patients with obesity and knee osteoarthritis; How many patients should have a unicompartmental knee arthroplasty?; Staged revision of the infected knee arthroplasty and endoprosthesis; The metal allergy argument and knee arthroplasty; Is kinematic alignment all it’s cracked up to be?; Is bone-patella-bone the gold standard for revision?; Blood flow restriction and the dissatisfied knee arthroplasty.

Aims

Worldwide controversy exists on the optimal treatment of stable dysplastic hips. The most common treatment options are abduction brace treatment and active surveillance. The primary aim of this study was to assess the effect of active surveillance in stable hip dysplasia, by investigating the percentage of Graf IIb stable dysplastic hips that recover spontaneously without abduction brace treatment. The second aim was to identify prognostic factors for spontaneous recovery of stable dysplastic hips.

Aims

The aims of this study, using a porcine model of multiple trauma, were to investigate the expression of microRNAs at the fracture site, in the fracture haematoma (fxH) and in the fractured bone, compared with a remote unfractured long bone, to characterize the patterns of expression of circulating microRNAs in plasma, and identify and validate messenger RNA (mRNA) targets of the microRNAs.

Aims

Trauma & Orthopaedic (T&O) surgery has come under scrutiny for lagging behind other medical specialties in promoting gender and cultural equity and diversity within their workforce. The proportions of female, ethnic minority, and sexual and gender minority individuals within orthopaedic membership bodies are disproportionate to the populations they serve. The aim of this study is to report the findings of a national workforce survey of demographics and working patterns within T&O in Scotland.

Aims

Magnesium ions (Mg²⁺) play an important role in promoting cartilage repair in cartilage lesions. However, no research has focused on the role of Mg²⁺ combined with microfracture (MFX) in hyaline-like cartilage repair mediated by cartilage injury. This study aimed to investigate the beneficial effects of the combination of MFX and Mg²⁺ in cartilage repair.

Aims

The “2 to 10% strain rule” for fracture healing has been widely interpreted to mean that interfragmentary strain greater than 10% predisposes a fracture to nonunion. This interpretation focuses on the gap-closing strain (axial micromotion divided by gap size), ignoring the region around the gap where osteogenesis typically initiates. The aim of this study was to measure gap-closing and 3D interfragmentary strains in plated ovine osteotomies and associate local strain conditions with callus mineralization.

Aims

The involvement of long non-coding RNA (lncRNA) in bone marrow mesenchymal stem cell (MSC) osteogenic differentiation during osteoporosis (OP) development has attracted much attention. In this study, we aimed to disclose how LINC01089 functions in human mesenchymal stem cell (hMSC) osteogenic differentiation, and to study the mechanism by which LINC01089 regulates MSC osteogenesis.

Aims

Mesenchymal stem cells (MSCs) are usually cultured in a normoxic atmosphere (21%) in vitro, while the oxygen concentrations in human tissues and organs are 1% to 10% when the cells are transplanted in vivo. However, the impact of hypoxia on MSCs has not been deeply studied, especially its translational application.

Addressing bone defects is a complex medical challenge that involves dealing with various skeletal conditions, including fractures, osteoporosis (OP), bone tumours, and bone infection defects. Despite the availability of multiple conventional treatments for these skeletal conditions, numerous limitations and unresolved issues persist. As a solution, advancements in biomedical materials have recently resulted in novel therapeutic concepts. As an emerging biomaterial for bone defect treatment, graphene oxide (GO) in particular has gained substantial attention from researchers due to its potential applications and prospects. In other words, GO scaffolds have demonstrated remarkable potential for bone defect treatment. Furthermore, GO-loaded biomaterials can promote osteoblast adhesion, proliferation, and differentiation while stimulating bone matrix deposition and formation. Given their favourable biocompatibility and osteoinductive capabilities, these materials offer a novel therapeutic avenue for bone tissue regeneration and repair. This comprehensive review systematically outlines GO scaffolds’ diverse roles and potential applications in bone defect treatment. Cite this article: Bone Joint Res 2024;13(12):725–740

Aim. Biomaterial-associated infections (BAI) present a formidable clinical challenge. Bioactive glasses (BG) have proven highly successful in diverse clinical applications, especially in dentistry and orthopaedics. In this study, we aimed to determine the effect of three commonly used BG composition and particle sizes on cell and bacterial attachment and growth. Our focus is on understanding the changes in pH and osmotic pressure in the surrounding environment during glass degradation. Method. First, three different melt-derived glasses were characterized by analyzing particle size and glass network structure using Raman and NMR. The different glasses were then tested in vitro by seeding 4x 10. 4. cells/well (SaOS Cell line) in a 48 well plate. After a pre-incubation period of 72 hours, the different BGs and particle sizes were added to the cells and the pH value, ion release and live/dead staining was measured every hour. The effect of BG against bacteria (S. epidermidis) was analyzed after 24 and 72 hours of treatment by using XTT viability assay and CFU counting by plating out the treated aliquot agar to estimate the viable bacteria cells. Results. All three BG compositions tested showed a significant increase in pH, which was highest in BG composition 45S5 with a value of 11 compared to the other BG compositions 10 and 9 in S53P4 and 13-93 respectively. This strong increase in the pH in all BG samples tested results in a strongly reduced cell viability rate of more than 75% compared to the untreated control and 6-fold reduction in bacterial viability compared to the untreated control. The live/ dead assay also showed an increased cell viability with increasing glass particle size (i. e smallest glass particle < 25% viable cell and largest glass particle> 65% viable cell). The ion release concentration over 50 h showed an increase in sodium ions to 0.25 mol/L, calcium to 0.003 mol/L and a decrease in phosphorus. Conclusions. These results show that the composition of the bioactive glass and the choice of particle size have a major influence on subsequent applications. In addition to the different compositions of the BG, particle size and additional medium change also influence the pH and ion release, and therefore also on cells or bacteria viability. The sizes of the bioactive glass particle are inversely proportional to it. Further tests are necessary to develop custom design BG compositions, which simultaneously stimulate osteoblasts proliferation and prevent microbial adhesion

Aims

Osteoarthritis (OA) is a common degenerative disease. PA28γ is a member of the 11S proteasome activator and is involved in the regulation of several important cellular processes, including cell proliferation, apoptosis, and inflammation. This study aimed to explore the role of PA28γ in the occurrence and development of OA and its potential mechanism.

Introduction. Homogenous and consistent preparations of mesenchymal stem cells (MSCs) can be acquired by selecting them for integrin α10β1 (integrin a10-MSCs). Safety and efficacy of intra-articular injection of allogeneic integrin a10-MSCs were shown in two post-traumatic osteoarthritis horse studies. The current study investigated immunomodulatory capacities of human integrin a10-MSCs in vitro and their cell fait after intra-articular injection in rabbits. Method. The concentration of produced immunomodulatory factors was measured after licensing integrin a10-MSCs with pro-inflammatory cytokines. Suppression of T-cell proliferation was determined in co-cultures with carboxyfluorescein N-succinimidyl ester (CFSE) labelled human peripheral blood mononuclear cells (PBMCs) stimulated with anti-CD3/CD28 and measuring the CFSE intensity of CD4+ cells. Macrophage polarization was assessed in co-cultures with differentiated THP-1 cells stimulated with lipopolysaccharide and analysing the M2 macrophage cell surface markers CD163 and CD206. In vivo homing and regeneration were investigated by injecting superparamagnetic iron oxide nanoparticles conjugated with Rhodamine B-labeled human integrin a10-MSCs in rabbits with experimental osteochondral defects. MSC distribution in the joint was followed by MRI and fluorescence microscopy. Result. The production of the immunomodulatory factors indoleamine 2,3-dioxygenase and prostaglandin E2 was increased after inflammatory licensing integrin a10-MSCs. Co-cultures with integrin a10-MSCs suppressed T-cell proliferation and increased the frequency of M2 macrophages. In vivo injected integrin a10-MSCs homed to osteochondral defects and were detected in the repair tissue of the defects up to 10 days after injection, colocalized with aggrecan and type II collagen. Conclusion. This study showed that human integrin a10-MSCs have immunomodulatory capacities and in vivo can home to the site of osteochondral damage and directly participate in cartilage regeneration. This suggests that human integrin α10β1-selected MSCs may be a promising therapy for osteoarthritis with dual mechanisms of action consisting of immunomodulation and homing to damage followed by early engraftment and differentiation into chondrocyte-like cells that deposit hyaline cartilage matrix molecules

Introduction. Osteoarthritis (OA) is a prevalent joint disorder characterized by cartilage degeneration, inflammation, and pain. Current treatments provide only symptomatic relief, necessitating novel molecular targets. The caspase family, known for its roles in apoptosis and inflammation regulation, may additionally influence crucial processes for cartilage homeostasis such as differentiation and proliferation. However, the specific roles of individual caspases in OA pathogenesis remain unclear. This study aims to investigate the involvement of the caspase family in OA and as potential targets for therapy, with a focus on caspase-1 and -8. Method. Chondrocytes from both healthy and OA donors were cultured in 2D and 3D culture models and stimulated with TNF-α or IL-1β. The expression and activation of caspase-1 and -8 was assessed using RT-PCR, ELISA. Transcriptome analysis of OA and healthy cartilage samples, along with Mendelian randomization (MR) analysis were conducted to explore the involvement of caspase family in OA and to assess its potential as therapeutic targets. Result. Higher expression levels of caspase-1, -8 were observed in OA cartilage compared to healthy cartilage. TNF-α stimulation increased their expression in both healthy and OA chondrocytes, while IL-1β had limited impact. Caspase-8 expression was causally associated with knee OA in MR analysis, suggesting a potential therapeutic target. The caspase-1 inhibitor VX-765 mildly reduced chondrocyte viability, with no significant effect in the presence of TNF-α. While the caspase-8 inhibitor Z-IETD-FMK exhibited slight enhancements in cell viability, these improvements were not statistically significant. Nevertheless, its effectiveness significantly increased in the presence of TNF-α. Conclusion. This study highlights the involvement of caspase-1 and caspase-8 in OA pathology, with caspase-8 emerging as a potential therapeutic target for knee OA treatment. Further investigation into the roles of caspase-1 and -8 in OA pathophysiology, including the efficacy and potential side effects of their corresponding inhibitors, is warranted. Acknowledgements. Funding Inter-Action/Inter-Excellence project (BTHA-JC-2022-36/LUABA22019)

Introduction. Recent studies suggested that the progression of osteoarthritis (OA), a chronic degenerative joint disease, may be affected by the autonomic nervous system (ANS). Under healthy conditions, the sympathetic (SNS) and parasympathetic (PNS) branches of the ANS are well coordinated to maintain homeostasis. However, pathological conditions are frequently associated with a disturbance of this fine-tuned balance. Therefore, we analyzed whether an autonomic dysfunction occurs in OA patients. Method. 225 participants with early- or late-stage knee OA as well as 40 healthy age-matched probands were included in this study. Autonomic activity was investigated by analyzing heart rate variability (HRV), which decreases under chronic sympathetic overactivity. Time- and frequency-domain HRV indices SDRR, RMSSD, pRR50 and LF were examined. Linear regression analysis was performed to adjust for clinical characteristics, such as age, sex, BMI, or medication. Moreover, perceived chronic stress (PSQ) and pain (WOMAC) were assessed via questionnaires. In addition, the serum stress hormones cortisol, DHEA-S and IL-6 were analyzed via ELISA. Result. SDRR, RMSSD, and pRR50 were slightly reduced in the early stage of OA and showed significant decrease in the later stage of the disease. Also LF decreased significantly with OA progression. HRV was significantly influenced by the grade of OA, but not other patient characteristics. Moreover, late-stage OA patients demonstrated significantly higher PSQ and WOMAC levels compared to healthy controls. In addition, cortisol/DHEA-S ratio and IL-6 serum concentrations were significantly higher in late-stage than in early-stage OA patients and healthy controls. Conclusion. Reduced HRV, increased cortisol/DHEA-S ratio and PSQ level as well as elevated systemic IL-6 concentration indicated an autonomic shift towards a more pronounced SNS activity due to PNS deficiency in OA patients, particularly in the late-stage of the disease. Therefore, modulation of the ANS, for example by vagus nerve stimulation, might be a potential treatment strategy for of knee OA patients

Introduction. PIEZO mechanoreceptors are increasingly recognized to play critical roles in fundamental physiological processes like proprioception, touch, or tendon biomechanics. However, their gating mechanisms and downstream signaling are still not completely understood, mainly due to the lack of effective tools to probe these processes. Here, we developed new tailor-made nanoswitches enabling wireless targeted actuation on PIEZO1 by combining molecular imprinting concepts with magnetic systems. Method. Two epitopes from functionally relevant domains of PIEZO1 were rationally selected in silico and used as templates for synthesizing molecularly imprinted nanoparticles (MINPs). Highly-responsive superparamagnetic zinc-doped iron oxide nanoparticles were incorporated into MINPs to grant them magnetic responsiveness. Endothelial cells (ECs) and adipose tissue-derived stem cells (ASCs) incubated with each type of MINP were cultured under or without the application of cyclical magnetomechanical stimulation. Downstream effects of PIEZO1 actuation on cell mechanotransduction signaling and stem cell fate were screened by analyzing gene expression profiles. Result. Nanoswitches showed sub-nanomolar affinity for their respective epitope, binding PIEZO1-expressing ECs similarly to antibodies. Expression of genes downstream of PIEZO1 activity significantly changed after magnetomechanical stimulation, demonstrating that nanoswitches can transduce this stimulus directly to PIEZO1 mechanoreceptors. Moreover, this wireless actuation system proved effective for modulating the expression of genes related to musculoskeletal differentiation pathways in ASCs, with RNA-sequencing showing pronounced shifts in extracellular matrix organization, signal transduction, or collagen biosynthesis and modification. Importantly, targeting each epitope led to different signaling effects, implying distinct roles for each domain in the sophisticated function of these channels. Conclusion. This innovative wireless actuation technology provides a promising approach for dissecting PIEZO-mediated mechanobiology and suggests potential therapeutic applications targeting PIEZO1 in regenerative medicine for mechanosensitive tissues like tendon. Acknowledgements. EU's Horizon 2020 ERC under grant No. 772817 and Horizon Europe under grant No. 101069302; FCT/MCTES for PD/BD/143039/2018, COVID/BD/153025/2022, 10.54499/2020.03410.CEECIND/CP1600/CT0013, 10.54499/2022.05526.PTDC, 10.54499/UIDB/50026/2020, 10.54499/UIDP/50026/2020, and 10.54499/LA/P/0050/2020

Introduction. Supraspinatus tears comprise most rotator cuff injuries, the leading cause of shoulder pain and an increasing problem with ageing populations. Surgical repair of considerable or persistent damages is customary, although not invariably successful. Tissue engineering presents a promising alternative to generate functional tissue constructs with improved healing capacities. This study explores tendon tissue constructs’ culture in a platform providing physiological mechanical stimulation and reports on the effect of different loading regimes on the viability of human tendon cells. Method. Porcine decellularized tendon scaffolds were fixed into flexible, self-contained bioreactor chambers, seeded with human tenocytes, allocated in triplicates to either static control, low (15±0.8Newtons [N]), medium (26±0.5N), or high (49±2.1N)-force-regime groups, connected to a perfusion system and cultured under standard conditions. A humanoid robotic arm provided 30-minute adduction/abduction stimulation to chambers daily over a week. A metabolic activity assay served to assess cell viability at four time points. Statistical significance = p<0.05. Result. One day after beginning mechanical stimulation, chambers in the medium and high-force regimes displayed a rise in metabolic activity by 3% and 5%, respectively. By the last experimental day, all mechanical stimulation regimes had induced an augment in cell viability (15%, 57% and 39% with low, medium, and high loads, respectively) matched against the static controls. Compared to all other conditions, the medium-force regime prompted an increased relative change in metabolic activity for every time point set against day one (p<0.05). Conclusion. Human tenocytes’ viability reflected by metabolic activity in a physiologically relevant bioreactor system is enhanced by loading forces around 25N when mechanically stimulating using adduction/abduction motions. Knowing the most favourable load regime to stimulate tenocyte growth has informed the ongoing exploration of the distinctive effect of different motions on tendon regeneration towards engineering tissue grafts. This work was supported by the Engineering and Physical Sciences Research Council EP/S003509/1

Introduction. Herein, a tri-layered core-shell microfibrous scaffold with layer-specific growth factors (GFs) release is developed using coaxial electrohydrodynamic (EHD) printing for in situ cell recruitment and differentiation to facilitate gradient enthesis tissue repair. Our findings suggest that the microfibrous scaffolds with layer-specific GFs release may offer a promising clinical solution for enthesis regeneration. Method. Utilizing coaxial electrohydrodynamic (EHD) printing, we engineered tri-layered core-shell microfibrous scaffolds, each layer tailored with specific growth factors (GFs) for targeted enthesis tissue repair. This configuration aims to sequentially guide cell migration and differentiation, mirroring the natural enthesis’ gradient structure. SDF-1 was strategically loaded into the shell, while bFGF, TGF-β, and BMP-2 were encapsulated in the core, each selected for their roles in stimulating the regeneration of corresponding enthesis tissue layers. Result. The coaxial EHD-printed microfibrous scaffolds demonstrated a core-shell fiber width of 24.3 ± 6.3 μm, supporting distinct tenogenic, chondrogenic, and osteogenic layers with pore sizes of 81.5 ± 4.6 μm, 173.3 ± 6.9 μm, and 388.9 ± 6.9 μm, respectively. This structure facilitated a targeted and effective release of growth factors, optimizing stem cell recruitment and differentiation. In vivo assessments demonstrated that the scaffolds significantly enhanced biomechanical properties and facilitated the formation of gradient enthesis structures, with improved biomechanical strength approximately 2-3 times that of control groups. These results highlight the scaffold's capability to mimic the native enthesis structure, encouraging a conducive environment for cell-mediated repair and regeneration. Conclusion. The integration of layer-specific growth factors not only fostered a conducive environment for tissue regeneration but also exemplified a leap in the design of scaffolds that closely mimic the native tendon-to-bone interface. The findings illuminate the scaffold's capacity to direct cellular behavior and tissue formation, heralding a new era in regenerative strategies and offering a promising avenue for clinical translation in the treatment of rotator cuff injuries

Introduction. Intervertebral disc degeneration (IDD) is a progressive process affecting all disc tissues, namely the nucleus pulposus (NP), annulus fibrosus (AF), and cartilaginous endplates (CEPs). Several cell-based therapies have been proposed to replenish the disc cell population and promote tissue regeneration. However, cell-free therapeutics have been increasingly explored due to potentially higher advantages and cost-effectiveness compared to cell transplantation. Recently, extracellular vesicles (EVs) isolated from healthy Tie2. +. -NP cells (NPCs) have shown promising regenerative outcomes on degenerative NPCs (dNPCs). The aim of this study was to assess the effect of such EVs on all disc cell types, including AF cells (AFCs) and CEP cells (CEPCs), compared to EVs isolated from bone-marrow derived mesenchymal stromal cells (BM-MSCs). Method. NPCs harvested from young donors underwent an optimized culture protocol to maximize Tie2 expression (NPCs. Tie2+. ). BM-MSCs were retrieved from a commercial cell line or harvested during spine surgery procedures. EV characterization was performed via particle size analysis (qNano), expression of EV markers (Western blot), and transmission electron microscopy. dNPCs, AFCs, and CEPCs were isolated from surgical specimens of patients affected by IDD, culture-expanded, and treated with NPCs. Tie2+. -EVs or BM-MSC-EVs ± 10 ng/mL IL-1b. EV uptake was assessed with PKH26 staining of EVs under confocal microscopy. Cell proliferation and viability were assessed with the CCK-8 assay. Result. Upon characterization, isolated EVs exhibited the typical exosomal characteristics. NPCs. Tie2+. -EVs and BM-MSC-EVs uptake was successfully observed in all dNPCs, AFCs, and CEPCs. Both EV products significantly increased dNPC, AFC, and CEPC viability, especially in samples treated with NPCs. Tie2+. -EVs. Conclusion. NPCs. Tie2+. -EVs demonstrated to significantly stimulate the proliferation and viability of degenerative cells isolated from all disc tissues. Rather than the sole NP, EVs isolated by committed progenitors physiologically residing within the disc may exert their regenerative effects on the whole organ, thus possibly constituting the basis for a new therapy for IDD

Introduction. Osteoarthritis (OA) is a chronic degenerative disease of the entire joint leading to joint stiffness and pain (PMID:33571663). Recent evidence suggests that the sympathetic nervous system (SNS) plays a role in the pathogenesis of OA (PMID:34864169). A typical cause for long-term hyperactivity of the SNS is chronic stress. To study the contribution of increased sympathetic activity, we analyzed the progression of OA in chronically stressed mice. Method. We induced OA in male C57BL/6J mice by destabilizing the medial meniscus (DMM)(PMID:17470400) and exposed half of these mice to chronic unpredictable mild stress (CUMS)(PMID:28808696). Control groups consisted of sham-operated mice with and without CUMS exposure. After 12 weeks, CUMS efficacy was determined by assessing changes in body weight gain and activity of mice, measuring splenic norepinephrine and serum corticosterone levels. OA progression was studied by histological analysis of cartilage degeneration and synovitis, and by μCT to evaluate changes in calcified cartilage and subchondral bone microarchitecture. A dynamic weight-bearing system was used to assess OA-related pain. Result. CUMS resulted in significantly decreased body weight gain and activity, as well as increased splenic norepinephrine and serum corticosterone concentrations compared to the respective controls. Surprisingly, already DMM alone resulted in elevated stress hormone levels. CUMS significantly exacerbated cartilage degeneration and synovial inflammation and increased OA pain in DMM mice. The underlying cellular and molecular mechanisms are currently being analyzed using FACS, single cell RNAseq, and spatial proteomics. Conclusion. Overall, chronic stress exacerbates OA severity and pain. Moreover, increased levels of stress hormones were observed in OA mice without CUMS induction, suggesting a complex bi-directional interaction between the SNS and OA. Targeting the autonomic nervous system, such as attenuating the SNS but also stimulating the activity of the parasympathetic nervous system, as a counterpart of the SNS, may therefore be promising for novel preventive or causal treatments of OA