Buds of new bone formation within the Femoral Head of Hip Fracture Patients Coincide with Zones of Low Osteocyte Sclerostin.

Romosozumab treatment reduces the rate of hip fractures and increases hip bone density, increasing bone formation by inhibiting sclerostin protein. We studied the normal pattern of bone formation and osteocyte expression in the human proximal femur because it is relevant to both antisclerostin treatment effects and fracture. Having visualized and quantified buds of new bone formation in trabeculae, we hypothesized that they would coincide with areas of (a) higher mechanical stress and (b) low sclerostin expression by osteocytes. In patients with hip fracture, we visualized each bud of active modeling-based formation (forming minimodeling structure [FMiS]) in trabecular cores taken from different parts of the femoral head. Trabecular bone structure was also measured with high-resolution imaging. More buds of new bone formation (by volume) were present in the higher stress superomedial zone (FMiS density, N.FMiS/T.Ar) than lower stress superolateral (p < 0.05), and inferomedial (p < 0.001) regions. There were fewer sclerostin expressing osteocytes close to or within FMiS. FMiS density correlated with greater amount, thickness, number, and connectivity of trabeculae (bone volume BV/TV, r = 0.65, p < 0.0001; bone surface BS/TV, r = 0.47, p < 0.01; trabecular thickness Tb.Th, r = 0.55, p < 0.001; trabecular number Tb.N, r = 0.47, p < 0.01; and connectivity density Conn.D, r = 0.40, p < 0.05) and lower trabecular separation (Tb.Sp, r = -0.56, p < 0.001). These results demonstrate modeling-based bone formation in femoral trabeculae from patients with hip fracture as a potential therapeutic target to enhance bone structure. © 2023 American Society for Bone and Mineral Research (ASBMR).

Radiographic Cortical Thickness Index Predicts Fragility Fracture in Gaucher Disease.

Background Patients with Gaucher disease (GD) have a high risk of fragility fractures. Routine evaluation of bone involvement in these patients includes radiography and repeated dual-energy x-ray absorptiometry (DXA). However, osteonecrosis and bone fracture may affect the accuracy of DXA. Purpose To assess the utility of DXA and radiographic femoral cortical thickness measurements as predictors of fragility fracture in patients with GD with long-term follow-up (up to 30 years). Materials and Methods Patients with GD age 16 years and older with a detailed medical history, at least one bone image (DXA and/or radiographs), and minimum 2 years follow-up were retrospectively identified using three merged UK-based registries (Gaucherite study, enrollment 2015-2017; Clinical Bone Registry, enrollment 2003-2006; and Mortality Registry, enrollment 1993-2019). Cortical thickness index (CTI) and canal-to-calcar ratio (CCR) were measured by two independent observers, and inter- and intraobserver reliability was calculated. The fracture-predictive value of DXA, CTI, CCR, and cutoff values were calculated using receiver operating characteristic curves. Statistical differences were assessed using univariable and multivariable analysis. Results Bone imaging in 247 patients (123 men, 124 women; baseline median age, 39 years; IQR, 27-50 years) was reviewed. The median follow-up period was 11 years (IQR, 7-19 years; range, 2-30 years). Thirty-five patients had fractures before or at first bone imaging, 23 patients had fractures after first bone imaging, and 189 patients remained fracture-free. Inter- and intraobserver reproducibility for CTI/CCR measurements was substantial (range, 0.96-0.98). In the 212 patients with no baseline fracture, CTI (cutoff, ≤0.50) predicted future fractures with higher sensitivity and specificity (area under the receiver operating characteristic curve [AUC], 0.96; 95% CI: 0.84, 0.99; sensitivity, 92%; specificity, 96%) than DXA T-score at total hip (AUC, 0.78; 95% CI: 0.51, 0.91; sensitivity, 64%; specificity, 93%), femoral neck (AUC, 0.73; 95% CI: 0.50, 0.86; sensitivity, 64%; specificity, 73%), lumbar spine (AUC, 0.69; 95% CI: 0.49, 0.82; sensitivity, 57%; specificity, 63%), and forearm (AUC, 0.78; 95% CI: 0.59, 0.89; sensitivity, 70%; specificity, 70%). Conclusion Radiographic cortical thickness index of 0.50 or less was a reliable independent predictor of fracture risk in Gaucher disease. Clinical trial registration no. NCT03240653 © RSNA, 2022 Supplemental material is available for this article.

Disturbance of osteonal bone remodeling and high tensile stresses on the lateral cortex in atypical femoral fracture after long-term treatment with Risedronate and Alfacalcidol for osteoporosis.

An 83 year-old Japanese woman complained of left lateral thigh pain following a low-energy fall 4 months prior to admission. She had been treated for osteoporosis with Risedronate and Alfacalcidol for the previous five years. She was diagnosed with an atypical femoral fracture (AFF) according to the American Society for Bone and Mineral Research (ASBMR) Task Force revised criteria. Radiographs revealed cortical thickening and a transverse radiolucent fracture line in the lateral cortex of the shaft. MRI showed a high intensity signal on the T2WI image 1 cm long in the lateral cortex. The patient had normal levels of bone resorption and formation biomarkers except for low 25(OH) Vitamin D. Double fluorescent labeling was done preoperatively. Due to significant bowing, a corrective osteotomy and intramedullary nailing were performed, and the resected bone wedge was analyzed by bone histomorphometry. Three ground sections of the lateral cortex at the fracture site showed many and large pores, with or without tetracycline labeling. Histomorphometric assessment was done on intracortical pores, classified by a novel criteria, only to assess size of the pores to know prolonged osteoclastic activity and its characteristics of inner surfaces to assess whether bone formation has been occurring or not in labeling period in remodeling cycle, and coalition of multi-pores. Increased size with widespread variation of pores suggested prolonged osteoclastic activity in the reversal/resorptive phase. Bone labeling showed lamellar bone on the endocortical surface. We hypothesize that the case had developed from a regional disturbance of osteonal remodeling in the lateral cortex, in which accumulated microcracks might have initiated a resorption process resulting in resorption cavities, i.e., pores, which became larger due to prolonged activity of secondary osteoclasts. Various sized pores could form lamellar bone, still forming at the time of biopsy, some had formed lamellar bone, but stopped to form before labeling and not to start to form at all, probably due to incomplete coupling. Endocortical lamellar bone might had started to resorbed to smooth off endocortical surface, followed by formation of lamellar bone. The endocortical bone formation was assessed and its formation period is about 2.7 years. A finite element analysis using preoperative CT data revealed high tensile stresses on the lateral aspect of the femur. Histomorphometric results suggest that there might be more pores in the tensile area than the compressive area. These findings may subsequently connect accumulation of microcracks, an increase of size and number of pores and coalition and subsequent fracture in the lateral cortex.

The JNK pathway represents a novel target in the treatment of rheumatoid arthritis through the suppression of MMP-3.

BACKGROUND AND AIM: The pathophysiology of rheumatoid arthritis (RA) is characterized by excess production of pro-inflammatory cytokines, including tumor necrosis factor-α (TNF-α), interleukin-1ß (IL-1ß), and interleukin-6 (IL-6) by neutrophils and macrophages in synovium. Additionally, these cytokines promote the production of reactive oxygen species (ROS), and increased production of matrix metalloproteinases (MMPs), including MMP-3, in synoviocytes that result in joint destruction. There is limited information on how proteolytic enzymes such as MMP-3 can be regulated. We evaluated the effect of the antioxidant N-acetylcysteine (NAC) on RA and identified the relationship between the c-Jun N terminal kinase (JNK) pathway and MMP-3. We hypothesized that elucidating this relationship would lead to novel therapeutic approaches to RA treatment and management. METHODS: We investigated the effect of administering a low dose (1000 µM or less) of an antioxidant (NAC) to human rheumatoid fibroblast-like synoviocytes (MH7A cells). We also investigated the response of antioxidant genes such as nuclear factor erythroid -derived 2-related factor 2 (Nrf2) and Sequestosome 1 (p62). The influence of MMP-3 expression on the JNK pathway leading to joint destruction and the mechanisms underlying this relationship were investigated through primary dispersion culture cells collected from the synovial membranes of RA patients, consisting of rheumatoid arthritis-fibroblast-like synoviocytes (RA-FLS). RESULTS: Low-dose NAC (1000 µM) increased the expression of Nrf2 and phospho-p62 in MH7A cells, activating antioxidant genes, suppressing the expression of MMP-3, and inhibiting the phosphorylation of JNK. ROS, MMP-3 expression, and IL-6 was suppressed by administering 30 µM of SP600125 (a JNK inhibitor) in MH7A cells. Furthermore, the administration of SP600125 (30 µM) to RA-FLS suppressed MMP-3. CONCLUSIONS: We demonstrated the existence of an MMP-3 suppression mechanism that utilizes the JNK pathway in RA-FLS. We consider that the JNK pathway could be a target for future RA therapies.

Antiresorptive-associated spontaneous fractures of both tibiae, followed by an atypical femur fracture during the sequential treatment with alendronate, denosumab then teriparatide.

A 35-year-old man with juvenile idiopathic arthritis since childhood presented with bilateral atypical tibial fractures, followed by a later, single atypical fracture of the femur. The fractures were associated with 6 years of oral alendronate treatment immediately followed by subcutaneous denosumab therapy and later teriparatide therapy for osteoporosis. Atypical fractures are known to occur in the femur following bisphosphonate therapy; however, there are only a few documented cases of atypical fractures in the tibia. Our case highlights a rare but serious complication of a commonly prescribed antiresorptive agent. It also shows that teriparatide, while helpful in increasing bone mass, does not fully prevent the development of atypical fractures. Careful investigation should be considered in patients on long-term antiresorptive therapy presenting with bony tenderness to exclude an atypical fracture.

Evidence for Ongoing Modeling-Based Bone Formation in Human Femoral Head Trabeculae via Forming Minimodeling Structures: A Study in Patients with Fractures and Arthritis.

Bone modeling is a biological process of bone formation that adapts bone size and shape to mechanical loads, especially during childhood and adolescence. Bone modeling in cortical bone can be easily detected using sequential radiographic images, while its assessment in trabecular bone is challenging. Here, we performed histomorphometric analysis in 21 bone specimens from biopsies collected during hip arthroplasty, and we proposed the criteria for histologically identifying an active modeling-based bone formation, which we call a "forming minimodeling structure" (FMiS). Evidence of FMiSs was found in 9 of 20 specimens (45%). In histomorphometric analysis, bone volume was significant higher in specimens displaying FMiSs compared with the specimens without these structures (BV/TV, 31.7 ± 10.2 vs. 23.1 ± 3.9%; p < 0.05). Osteoid parameters were raised in FMiS-containing bone specimens (OV/BV, 2.1 ± 1.6 vs. 0.6 ± 0.3%; p < 0.001, OS/BS, 23.6 ± 15.5 vs. 7.6 ± 4.2%; p < 0.001, and O.Th, 7.4 µm ± 2.0 vs. 5.2 ± 1.0; p < 0.05). Our results showed that the modeling-based bone formation on trabecular bone surfaces occurs even during adulthood. As FMiSs can represent histological evidence of modeling-based bone formation, understanding of this physiology in relation to bone homeostasis is crucial.

[Intravital bone imaging ~Osteocyte.]

Osteocytes are the most abundant cellular component of bone and have been considered dormant until recent evidence has demonstrated their critical roles in bone homeostasis and endocrine regulation. Until now the location of osteocytes within mineralized bone has restricted experimental access, especially in vivo. Here, intravital bone imaging by two-photon excitation microscopy allowed us to directly visualize the osteocytic lacuno-canalicular system. We demonstrated that sciatic neurectomy causes significant acidification around osteocytic lacunae and enlargement of lacuno-canalicular areas. These results show that two-photon intravital microscopy is useful for analysis of osteocytes in vivo.

Intravital bone imaging by two-photon excitation microscopy to identify osteocytic osteolysis in vivo.

Bone is a highly dynamic organ in which several cell types function cooperatively. Among these, osteocytes have recently emerged as an important regulator of bone homeostasis, although their mechanism of regulation is unclear. Here, intravital bone imaging by two-photon excitation microscopy allowed us to directly visualize 'osteocytic osteolysis', or resorption of bone in the lacuno-canalicular system. Osteocyte lacunae and the canalicular network in the cortex of murine tibiae were imaged by in vivo calcein staining, and local acidification in these structures was monitored using a topically applied pH sensor. We also demonstrated that sciatic neurectomy causes significant acidification around osteocytic lacunae and enlargement of lacuno-canalicular areas. These results provide strong evidence for osteocytic osteolysis, and demonstrate that two-photon intravital microscopy is useful for analysis of this phenomenon.

Bilateral atypical femoral subtrochanteric fractures in a premenopausal patient receiving prolonged bisphosphonate therapy: evidence of severely suppressed bone turnover.

We report a case of bilateral atypical femoral fractures that occurred in a patient who had been taking bisphosphonate long-term. A 36-year-old premenopausal female diagnosed with systemic lupus erythematosus and dermatomyositis had been treated with glucocorticoid and alendronate (5 mg/day) to prevent glucocorticoid-induced osteoporosis. She was taken to our hospital because she could not walk immediately after falling down from the standing position. A plain radiograph showed a subtrochanteric fracture of the left femur. Four months later, she fell again and sustained a contralateral subtrochanteric fracture. For each fracture, a femoral intramedullary nail was inserted. Delayed union was detected in both sides, and revision surgery with an iliac bone graft was required for implant breakage in the right side. Histomorphometric findings for the ilium revealed remarkably decreased osteoid volume with no osteoclasts and a minimally eroded surface, suggesting that bone turnover was severely suppressed. However, histology of the delayed union site revealed callus formation and some osteoclast appearance, suggesting that fracture healing was occurring. In total, it took 29 months (left) and 24 months (right) until fracture healing was achieved, showing delayed union. This case is extremely rare in that patient who presented with atypical femoral fractures in spite of her premenopausal status. The bone histomorphometric findings from this case suggest that severely suppressed bone turnover is associated with atypical femoral subtrochanteric fracture and can cause delayed union in patients treated with alendronate long-term.

Tight control is important in patients with rheumatoid arthritis treated with an anti-tumor necrosis factor biological agent: prospective study of 91 cases who used a biological agent for more than 1 year.

The purpose of this study is to identify the factors that require arthroplasty due to the progression of joint destruction, even when an anti-tumor necrosis factor (TNF) biological agent is used for rheumatoid arthritis (RA). Among 91 cases that used the anti-TNF biological agent for more than 1 year, two groups of 21 cases that resulted in arthroplasty (surgery group) and 70 cases that did not result in arthroplasty (non-surgery group) were compared and examined. When the anti-TNF biological agent was first administered, disease activity and internal use of glucocorticoid (PSL) were not different in these two groups. The average DAS28-CRP(4) (disease activity score including a 28-joint count/C-reactive protein) (p < 0.001) and the amount of internal use of PSL (p < 0.05) were significantly decreased in the non-surgery group compared with the surgery group at the final survey. To inhibit the need for joint surgery in patients using the anti-TNF biological agent, it is important to maintain tight control over RA activity.

Proximal femoral fracture in patients with rheumatoid arthritis.

Hip fracture occurrence was examined cross-sectionally in Japanese patients with rheumatoid arthritis (RA). Between January 2005 and June 2006 we studied RA outpatients with a past history of hip fractures. Patients included 1 man and 25 women. As 3 women had bilateral hip fractures, the total number was 29. Age at the time of fracture was 72.1 +/- 4.5 years. Of the 29 fractures, 22 were cervical and 7 were trochanteric. Four fractures were spontaneous while the others occurred in falls. 24 fractures were associated with oral steroid administration. All 5 fractures unassociated with prednisolone were cervical. Of the 26 patients, 8 were taking bisphosphonate when fracture occurred. Cervical fracture was treated with total hip arthroplasty in 1 patient whose hip showed RA changes. In others whose hip joint lacked RA change, procedures included osteosynthesis in 2 patients with good function over 6 years; and hemiarthroplasty with a bipolar system in 19 displaced fractures, with good function over 4.1 years. Osteosynthesis was performed for all 7 trochanteric fractures. Trabeculae were thin, and fewer transverse trabeculae could be found in specimens from cervical fracture. Hip fracture in RA patients occurred 10 years earlier than in the general population, and many fractures were cervical.