Wiley: Journal of Orthopaedic Research: Table of Contents

Relaxation Time Mapping of Early‐Stage Osteonecrosis of the Femoral Head: An In Vivo Piglet Model Study

Thu, 04 Jun 2026 00:00:00 -0700

T2, T1ρ, adiabatic T1ρ, and adiabatic T2ρ relaxation time mapping techniques are sensitive in detecting ischemic injury to bone marrow of the femoral head in vivo in a piglet model at 3 T MRI. T2 and adiabatic T2ρ relaxation times have the most pronounced increase in ischemic versus perfused, contralateral-control femoral heads 1 week after induction of ischemia. These quantitative MRI techniques may aid in quantitative evaluation and monitoring of early-stage ischemic injury in patients with osteonecrosis of the femoral head.

ABSTRACT

Quantitative magnetic resonance imaging (MRI) relaxation time mapping techniques may be useful to evaluate early-stage osteonecrosis of the femoral head, particularly in children with Legg–Calvé–Perthes disease (LCPD). The purpose of this study was to assess the sensitivities of T2, T1ρ, adiabatic T1ρ (aT1ρ), and adiabatic T2ρ (aT2ρ) relaxation time mapping to detect early-stage ischemic injury to the secondary ossification center (SOC) of the femoral head in vivo in a piglet model of LCPD. We hypothesized that relaxation times would be increased in the SOCs of ischemic versus contralateral-control femoral heads 1 week following onset of ischemia. Bilateral hips of n = 13 piglets with confirmed, surgically-induced complete ischemia of the SOC were imaged 1 week post-operatively using a clinical 3 T MRI scanner. Median T2 (n = 13), T1ρ (n = 13), aT1ρ (n = 10), and aT2ρ (n = 10) relaxation times were measured for the total SOC, as well as its central and peripheral subregions, and were compared between the ischemic versus control femoral heads using paired t-tests (p < 0.05). All four relaxation times were significantly increased in the ischemic versus control femoral heads, with a more pronounced increase in the peripheral versus central subregion of the SOC. T2 and aT2ρ had the greatest percent increases and effect sizes of the four relaxation times. In conclusion, T2, T1ρ, aT1ρ, and aT2ρ relaxation time mapping techniques are sensitive in detecting ischemic injury to bone marrow of the femoral head in vivo in a piglet model of LCPD at clinical 3 T MRI field strength.

Inhibition of Sclerostin Protected Against Particle‐Induced Osteolysis via Activation of Wnt Signaling and Suppression of Osteoclast Function

Thu, 04 Jun 2026 00:00:00 -0700

ABSTRACT

Periprosthetic osteolysis induced by wear debris remains a leading cause of aseptic loosening after joint arthroplasty, with no established pharmacological treatment. We investigated an anti-sclerostin antibody (Ab-Scl) and elucidated its mechanism of action in cobalt-chromium (CoCr) particle-induced osteolysis. Tartrate-resistant acid phosphatase (TRAP)-tdTomato mice with labeled mature osteoclasts (mOCs) were used. CoCr particles were applied to the calvarial bone, with or without Ab-Scl administration. Intravital two-photon bone imaging, microcomputed tomography (μCT), and histological and immunohistochemical analyses were performed to evaluate osteolysis, osteoclast activity, and β-catenin expression. In vitro assays using RAW264.7-derived osteoclast-like cells were conducted to investigate downstream signaling pathways. μCT analysis revealed that CoCr particles reduced the bone volume–to–tissue volume fraction and trabecular thickness while increasing trabecular separation and the structural model index; conversely, Ab-Scl significantly attenuated osteolytic changes. Histological analysis showed that CoCr exposure increased the eroded surface area and number of TRAP-positive osteoclasts, both of which were significantly decreased by Ab-Scl. Immunohistochemistry demonstrated that CoCr exposure suppressed β-catenin expression on the bone surface, which was restored by Ab-Scl. Intravital two-photon microscopy revealed that CoCr particles reduced mOC motility and increased the acidic resorptive area, whereas Ab-Scl reversed these changes, enhancing motility and suppressing bone resorption. In vitro, RSPO2 enhanced osteoclastic bone resorption, pit formation, and Pyk2 phosphorylation, which were suppressed by PF-562271. Ab-Scl modulated osteoclast function through Wnt/β-catenin-related mechanisms, potentially involving Pyk2-related pathways, thereby suppressing CoCr particle-induced osteolysis. These findings suggest that Ab-Scl is a promising pharmacological strategy for preventing aseptic loosening following joint arthroplasty.

METTL14‐Mediated RPL13A Expression Regulates Apoptosis and Invasion of Osteosarcoma via the PTEN/PI3K/AKT Signaling Pathway

Tue, 02 Jun 2026 00:00:00 -0700

ABSTRACT

Osteosarcoma (OS) is a highly aggressive mesenchymal bone tumor with a dismal prognosis, and its underlying molecular mechanisms remain elusive. Ribosomal protein L13a (RPL13a) contributes to tumorigenesis, while methyltransferase-like 14 (METTL14), a core m⁶A methyltransferase, modulates OS progression via epigenetic regulation. Our prior work identified the PTEN/PI3K/AKT pathway as a key OS regulator. This study aimed to clarify the regulatory interplay among METTL14, RPL13a and PTEN/PI3K/AKT in OS, and verify that METTL14 mediates RPL13a m⁶A modification to regulate PTEN/PI3K/AKT signaling, affecting OS cell proliferation, apoptosis, migration and invasion. METTL14, RPL13a and m⁶A levels were detected in OS cell lines (U2OS, HOS, MG-63) and normal osteoblast hFOB1.19 cells. RPL13a knockdown, PTEN overexpression and METTL14 overexpression models were established in U2OS/HOS cells. M⁶A-RIP-qPCR and MeRIP assays confirmed RPL13a m⁶A modification, with functional (CCK-8, flow cytometry, wound healing, Transwell) and molecular (RT-qPCR, Western blotting) assays performed in triplicate replicates. METTL14 and RPL13a were upregulated in U2OS/HOS cells versus hFOB1.19 (p < 0.05). METTL14 overexpression elevated RPL13a m⁶A modification by ~1.8-fold (p < 0.05); si-RPL13a reduced RPL13a mRNA by > 60% (p < 0.05). RPL13a knockdown promoted apoptosis, inhibited proliferation/migration/invasion, downregulated PTEN and activated PI3K/AKT signaling, partially reversed by PTEN overexpression. METTL14 overexpression upregulated RPL13a/PTEN and suppressed PI3K/AKT activation, abolished by RPL13a knockdown. METTL14 appears to mediate the m6A methylation modification of RPL13a mRNA. Downregulation of RPL13a is associated with reduced PTEN and activated PTEN/PI3K/AKT signaling, which may ultimately contribute to suppressed osteosarcoma cell proliferation, migration, and invasion while promoting apoptosis.

Collagen III Deficiency Following Injury in Female Murine Tendons Alters Matrix Composition, Structure, Organization and Function

J. A. Carlson, W. Yen, S. N. Weiss, S. W. Volk, L. J. Soslowsky — Tue, 26 May 2026 00:00:00 -0700

ABSTRACT

Tendons withstand large forces due to an aligned, dense collagen matrix. However, their low cellularity and relative inability to recruit reparative cells post-injury, coupled with a susceptibility to excessive scarring results in loss of tendon structure and function. Type III collagen (COL3) plays a key role in regulating matrix architecture and limiting scar formation following cutaneous injury; however, its role in tendon remains unclear. We examined the impact of reduced COL3 using an established murine Col3a1 knockdown model. Uninjured tendons in Col3a1 ^+/− mice had a broader distribution of fibrils compared to Col3a1 ^+/+ mice. Fibrils in injured tendons of Col3a1 ^+/− mice were larger than those in Col3a1 ^+/+ mice at 3-weeks post injury but were smaller than their littermates at 6-weeks. Injured Col3a1 ^+/− tendons had enhanced fiber alignment at 1- and 6-weeks post-injury and an increase in ɑSMA⁺ myofibroblasts at 3-weeks post-injury. Differential expression of matrix components, as well as markers of cells, cell-ECM interaction, and inflammation were discovered. Anti-inflammatory macrophages were decreased in Col3a1 ^+/− tendons 1-week following injury, with no differences between genotypes later in healing. Pro-inflammatory macrophages remained unchanged between genotypes early in healing, but were increased in Col3a1 ^+/+ tendons compared to Col3a1 ^+/− tendons at 3-weeks post-injury. Finally, altered quasistatic mechanical properties was noted in COL3-deficient injured tendons. Our data suggests COL3 plays a complex role in regulating cell phenotype, activity, and fate, as well as collagen matrix architecture in the tendon injury microenvironment, which impacts tendon structure-function post-injury.

Issue Information

Sun, 24 May 2026 21:54:57 -0700

Journal of Orthopaedic Research, Volume 44, Issue 6, June 2026.

In Vivo Assessment of Distal Femur Fracture Motion via Weightbearing CT

Sun, 24 May 2026 00:00:00 -0700

ABSTRACT

Distal femur fractures have a significant risk of healing complications, with potentially suboptimal fracture motion. We developed an in vivo method of quantifying fracture motion to support translational research. Five men and one woman (age 48.3 ± 24.9 years; weight 79.8 ± 12.9 kg, mean ± SD) underwent non-weightbearing and weightbearing CT following plate (4) or nail (2) fixation of distal femur fractures (AO/OTA 33) while recording static ground reaction forces. Subject-specific models were generated, coordinate systems were established, and fragment poses were reconstructed to assess motion. Fracture motion was measurable and greater at the medial than the lateral aspects of fractures, with notable axial plane motion. Three-dimensional (3D) displacement (mean ± standard deviation [SD]) was greater at the medial than lateral fracture (4.4 ± 2.6 vs. 3.5 ± 2.6 mm, p = 0.047), including mean proximal-distal displacement at the medial fracture (2.0 ± 3.0 mm) versus lateral fracture (0.8 ± 3.2 mm, p = 0.030), and mean axial plane displacement at the medial (3.5 ± 1.6 mm) versus lateral (2.6 ± 1.6 mm, p = 0.009) fracture. Axial plane displacement was similar to proximal-distal displacement at the medial (p = 0.318) and lateral (p = 0.488) fracture. 3D and axial plane displacement were moderately associated with load, while proximal-distal displacement was minimally associated with load. Weightbearing magnitude only modestly explained intersubject differences in motion. This method allows exploration of relationships between fracture motion, fracture pattern, fixation, loading, and healing.

A Novel Surgical Approach to Induce an Ankle Joint Contracture in Rats

Sun, 24 May 2026 00:00:00 -0700

ABSTRACT

Our primary aim was to establish a novel surgical immobilization approach to induce a persistent ankle plantar-flexion contracture in the Wistar rat. A stainless steel suture was placed in experimental animals (n = 14) and pulled taut between the calcaneal bone and the knee joint, restricting dorsal-flexion while still allowing for limited ankle plantar-flexion, muscle activity, and loading. The immobilization method was well tolerated; adverse events were limited and manageable. After 4 weeks, immobilization was released by cutting the suture. After 4 weeks of immobilization, ankle angle at 5 Nmm passive torque shifted 48° towards plantar-flexion, plantar-flexion torque and stiffness at 55° ankle angle increased 4.5 and eightfold, respectively (n = 8). Exploratory tissue analyses ex-vivo revealed significant atrophy of the medial gastrocnemius muscle-belly (34% smaller mass than controls, n = 4). Ankle angle at 5 Nmm, torque, and stiffness at 55° angle showed no signs of recovery 4 weeks post-release of the immobilization (n = 3). Morphological and mechanical assessments at this timepoint revealed persistent medial-gastrocnemius atrophy (19% smaller mass and 30% lower distal-tendon length in experimental animals (n = 3) compared to controls, n = 4). Also, passive and active length-force relationships of medial gastrocnemius were shifted towards lower lengths (i.e., plantar-flexion) compared to controls. Taken together, our novel surgical approach elicits an ankle plantar-flexion contracture that appears to persist for at least 4 weeks, providing a window for an intervention study. This model may be used to improve our understanding of the biomechanical, morphological and neurological changes following joint contractures, and to evaluate therapeutic interventions.