Wnt pathway inhibition with the porcupine inhibitor LGK974 decreases trabecular bone but not fibrosis in a murine model with fibrotic bone

G protein-coupled receptors (GPCRs) mediate a wide spectrum of physiological functions, including the development, remodeling, and repair of the skeleton. Fibrous dysplasia (FD) of the bone is characterized by fibrotic, expansile bone lesions caused by activating mutations in GNAS. There are no effective therapies for FD. We previously showed that ColI(2.3)+/Rs1+ mice, in which Gs-GPCR signaling was hyper-activated in osteoblastic cell lineages using an engineered receptor strategy, developed a fibrotic bone phenotype with trabecularization that could be reversed by normalizing Gs-GPCR signaling, suggesting that targeting the Gs-GPCR or components of the downstream signaling pathway could serve as a promising therapeutic strategy for FD. The Wnt signaling pathway has been implicated in the pathogenesis of FD-like bone, but the specific Wnts and which cells produce them remain largely unknown. Single-cell RNA sequencing on long-bone stromal cells of 9-wk-old male ColI(2.3)+/Rs1+ mice and littermate controls showed that fibroblastic stromal cells in ColI(2.3)+/Rs1+ mice were expanded. Multiple Wnt ligands were up- or downregulated in different cellular populations, including in non-osteoblastic cells. Treatment with the porcupine inhibitor LGK974, which blocks Wnt signaling broadly, induced partial resorption of the trabecular bone in the femurs of ColI(2.3)+/Rs1+ mice, but no significant changes in the craniofacial skeleton. Bone fibrosis remained evident after treatment. Notably, LGK974 caused significant bone loss in control mice. These results provide new insights into the role of Wnt and Gs-signaling in fibrosis and bone formation in a mouse model of Gs-GPCR pathway overactivation.

Integrative Co-Registration of Elemental Imaging and Histopathology for Enhanced Spatial Multimodal Analysis of Tissue Sections through TRACE

Summary

Elemental imaging provides detailed profiling of metal bioaccumulation, offering more precision than bulk analysis by targeting specific tissue areas. However, accurately identifying comparable tissue regions from elemental maps is challenging, requiring the integration of hematoxylin and eosin (H&E) slides for effective comparison. Facilitating the streamlined co-registration of Whole Slide Images (WSI) and elemental maps, TRACE enhances the analysis of tissue regions and elemental abundance in various pathological conditions. Through an interactive containerized web application, TRACE features real-time annotation editing, advanced statistical tools, and data export, supporting comprehensive spatial analysis. Notably, it allows for comparison of elemental abundances across annotated tissue structures and enables integration with other spatial data types through WSI co-registration.

Availability and Implementation

Available on the following platforms- GitHub: jlevy44/trace_app , PyPI: trace_app , Docker: joshualevy44/trace_app , Singularity: joshualevy44/trace_app .

Contact

joshua.levy@cshs.org.

Supplementary information

Supplementary data are available.

Voided volume may not impact stone outcomes: Review of a large institutional nephrolithiasis cohort

Background

Urologic guidelines universally recommend increasing fluid intake for kidney stone prevention. Increased voided volume is thought to help reduce stone recurrence and severity, but supporting evidence is limited.

Patients and Methods

Nephrolithiasis outcomes and 24-h urine data for patients from the Registry for Stones of the Kidney and Ureter (ReSKU), a registry of nephrolithiasis patients collected between 2015 and 2020, were retrospectively analysed. Outcome was stone events, either an office visit where a patient reports symptomatic passage of stones or surgery for stone removal.

Results

We identified 450 stone patients with 24-h urine and kidney stone outcome data. There was no significant difference in 24-h voided volume between patients with one stone event and patients with two or more stone events. On multivariable logistic regression, after controlling for age, gender, BMI, and 24-h sodium and creatinine per kilogram, no significant associations were found between voided volume and stone events. There was a statistically significant negative correlation noted between voided volume and stone events in calcium oxalate dihydrate stone formers (Spearman R = -0.42, p = 0.04), but not others.

Conclusions

Twenty-four-hour voided volume was not associated with stone events in a large institutional cohort, and subset analysis reveals that some stone formers may benefit more from increased voided volume than others; identifying such patients represents a novel precision medicine opportunity.

Evaluation of prognostic risk models for postoperative pulmonary complications in adult patients undergoing major abdominal surgery: a systematic review and international external validation cohort study

BACKGROUND

Stratifying risk of postoperative pulmonary complications after major abdominal surgery allows clinicians to modify risk through targeted interventions and enhanced monitoring. In this study, we aimed to identify and validate prognostic models against a new consensus definition of postoperative pulmonary complications.

METHODS

We did a systematic review and international external validation cohort study. The systematic review was done in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. We searched MEDLINE and Embase on March 1, 2020, for articles published in English that reported on risk prediction models for postoperative pulmonary complications following abdominal surgery. External validation of existing models was done within a prospective international cohort study of adult patients (≥18 years) undergoing major abdominal surgery. Data were collected between Jan 1, 2019, and April 30, 2019, in the UK, Ireland, and Australia. Discriminative ability and prognostic accuracy summary statistics were compared between models for the 30-day postoperative pulmonary complication rate as defined by the Standardised Endpoints in Perioperative Medicine Core Outcome Measures in Perioperative and Anaesthetic Care (StEP-COMPAC). Model performance was compared using the area under the receiver operating characteristic curve (AUROCC).

FINDINGS

In total, we identified 2903 records from our literature search; of which, 2514 (86·6%) unique records were screened, 121 (4·8%) of 2514 full texts were assessed for eligibility, and 29 unique prognostic models were identified. Nine (31·0%) of 29 models had score development reported only, 19 (65·5%) had undergone internal validation, and only four (13·8%) had been externally validated. Data to validate six eligible models were collected in the international external validation cohort study. Data from 11 591 patients were available, with an overall postoperative pulmonary complication rate of 7·8% (n=903). None of the six models showed good discrimination (defined as AUROCC ≥0·70) for identifying postoperative pulmonary complications, with the Assess Respiratory Risk in Surgical Patients in Catalonia score showing the best discrimination (AUROCC 0·700 [95% CI 0·683-0·717]).

INTERPRETATION

In the pre-COVID-19 pandemic data, variability in the risk of pulmonary complications (StEP-COMPAC definition) following major abdominal surgery was poorly described by existing prognostication tools. To improve surgical safety during the COVID-19 pandemic recovery and beyond, novel risk stratification tools are required.

FUNDING

British Journal of Surgery Society.

Global Wnt Inhibition With a Porcupine Inhibitor Decreases Established Trabecular Bone in a Mouse Model of Fibrous Dysplasia

Background: G protein-coupled receptors (GPCRs) mediate a wide spectrum of physiological functions, including bone development and remodeling. Fibrous dysplasia (FD) is a common skeletal dysplasia caused by increased G_s-GPCR signaling and characterized by fibrotic expansile bone lesions. FD has no effective medical treatments. Our prior studies used the ColI(2.3)⁺/Rs1⁺ mouse model where osteoblastic-cell G_s signaling induced a dramatic FD-like phenotype and increased Wnt signaling, which we hypothesized is a major driver of the phenotype. Furthermore, we previously showed that blocking Rs1 expression could reverse the abnormal bone phenotype, providing proof-of-concept for finding therapies for FD.

Methods: Long bone stromal cells from wildtype and ColI(2.3)⁺/Rs1⁺ 9-week-old male mice were analyzed by single-cell RNAseq to identify potential cellular sources of Wnt ligands. We compared these findings with global inhibition of Wnt activity by oral administration of the porcupine inhibitor LGK974 to ColI(2.3)⁺/Rs1⁺ mice. These mice were analyzed by histology and micro-computed tomography (micro-CT).

Results: Control and ColI(2.3)⁺/Rs1⁺ bones showed similar scRNAseq results, except for a large expansion of osteoblastic lineage cells and increased differential expression (DE) genes in this cluster. Expression of G_i-GPCRs was increased, potentially as compensation for the strong G_s-GPCR pathway activation induced by Rs1 expression. We also found increased GH/IGF1 pathway activation in the osteoblastic cluster, and expression of multiple Wnt ligands within multiple cell clusters. We also identified a cell population unique to the ColI(2.3)⁺/Rs1⁺ FD-like bone lesions. Broad Wnt production inhibition of porcupine by LGK974 induced dose-dependent resorption of the abnormal FD bone shown by decreased bone volume and trabecular thickness; however, the fibrocellular infiltrate in the ColI(2.3)⁺/Rs1⁺ mice was still present.

Conclusions: FD-like bones of ColI(2.3)⁺/Rs1⁺ mice showed broad activation of Wnt signaling in multiple cell types, suggesting both cell autonomous and non-cell autonomous activity. Broad Wnt inhibition decreased established FD-like trabecular bone, but the fibrocellular infiltrate did not fully reverse. These results suggest distinct roles of G_s-GPCR and Wnt signaling in FD pathogenesis.

The nature effect in motion: visual exposure to environmental scenes impacts cognitive load and human gait kinematics

Prolonged exposure to urban environments requires higher cognitive processing resources than exposure to nature environments, even if only visual cues are available. Here, we explored the moment-to-moment impact of environment type on visual cognitive processing load, measuring gait kinematics and reaction times. In Experiment 1, participants (n = 20) walked toward nature and urban images projected in front of them, one image per walk, and rated each image for visual discomfort. Gait speed and step length decreased for exposure to urban as compared with nature scenes in line with gait changes observed during verbal cognitive load tasks. We teased apart factors that might contribute to cognitive load: image statistics and visual discomfort. Gait changes correlated with subjective ratings of visual discomfort and their interaction with the environment but not with low-level image statistics. In Experiment 2, participants (n = 45) performed a classic shape discrimination task with the same environmental scenes serving as task-irrelevant distractors. Shape discrimination was slower when urban scenes were presented, suggesting that it is harder to disengage attention from urban than from nature scenes. This provides converging evidence that increased cognitive demands posed by exposure to urban scenes can be measured with gait kinematics and reaction times even for short exposure times.

Ablation of Ephrin B2 in Col2 Expressing Cells Delays Fracture Repair

Ephrin B2 is critical for endochondral bone development. In this study, we investigated its role in fracture repair by deleting ephrin B2 in type II collagen (Col.2) expressing cells. We used a nonstable tibia fracture model to evaluate fracture repair at 3 sites: intramembranous bone formation, endochondral bone formation, and intramedullary bone formation. We observed that during fracture repair, deletion of ephrin B2 impaired periosteal stem cell activation, inhibited their proliferation, decreased their survival, and blocked their differentiation into osteoblasts and chondrocytes. In addition, deletion of ephrin B2 decreased vascular endothelial growth factor production as well as vascular invasion into the fracture site. These changes led to reduced cartilage to bone conversion in the callus with decreased new bone formation, resulting in impaired fracture repair. Our data indicate that ephrin B2 in Col2-expressing cells is a critical regulator of fracture repair, pointing to a new and potentially targetable mechanism to enhance fracture repair.

A rare presentation of hepatolithiasis in an adolescent patient: A case report

INTRODUCTION

Hepatolithiasis (intrahepatic stones) is rare in adolescent patients and requires complex management strategies to prevent recurrent infections and progression to hepatic fibrosis. Surgical management is often required. In cases of unclear etiology, further work-up is indicated to provide insight into future management. In this report we describe an extensive stone analysis.

PRESENTATION OF CASE

A 20-year-old Caucasian female presented with known hepatolithiasis and multiple prior recurrent bouts of abdominal pain requiring hospitalization. Magnetic resonance cholangiopancreatography (MRCP) demonstrated an abnormal left-sided hepatic biliary ductal system dilatation. She was treated surgically with a formal left hepatectomy and preservation of the caudate lobe. The right ductal system had no stones or evidence of inflammation, and her bile and stones cultures were negative for organism growth. An extensive analysis demonstrated stone composition primarily of cholesterol.

DISCUSSION

Adolescent presentations of hepatolithiasis are rare and considerations in the differential diagnosis include primary sclerosing cholangitis, bile acid transporter defects, and other known genetic diseases. This case is unique because only the left half of the intrahepatic ductal system had evidence of stone disease and the bile was sterile. A detailed stone analysis demonstrating cholesterol supersaturation provides additional context though the etiology remains unclear in this case and will require lifelong follow-up.

CONCLUSION

Early-onset hepatolithiasis is rare and requires expert management, and in some cases definitive surgical management with life-long follow-up. Extensive stone analysis and genetic testing can be performed to help identify disease etiology in unique cases.

SAT0445 TRABECULAR BONE SCORE IMPROVES FRACTURE RISK STRATIFICATION IN PATIENTS WITH REDUCED BONE MINERAL DENSITY

Background:

Trabecular bone score (TBS) is a textural index of bone microarchitecture and has been found to be related to 3D bone structure. A number of cohort studies have demonstrated the value of TBS as an independent fracture risk in clinical trials. Yet, very little is known about the performance and clinical value of TBS in real life practice.

Objectives:

To investigate the sensitivity and specificity of TBS in identifying prevalent fractures when compared with bone mineral density (BMD) measured by DXA. To evaluate the added value of TBS in fracture risk prediction above that obtained from DXA.

Methods:

Consecutive patients aged ≥ 18 with BMI 15-37 attnding a DXA plus TBS assessment were considered eligible. Sensitivity, specificity, and area under the curve (AUC) for prevalent major osteoporotic fracture (MOF) and clinical vertebral fractures (VF) were assessed for the following parameters: BMD lowest T-score ≤-2.5 (neck of femur, total hip, or spine), TBS T-score ≤-2.5, and either TBS or BMD T-score ≤-2.5. BMD categories (normal, osteopenia, and osteoporosis) were stratified by TBS T-score: normal (T-score ≥-1), moderate (-1≥T-score≥-2.5), and degraded TBS (T-score ≤-2.5) resulting in 9 risk groups. Odds ratios were calculated for all risk categories and fracture prevalence was compared between the best and worst TBS strata at each BMD level using chi-square test.

Results:

540 patients (87% females, 68.1 ± 11.6 years) were included. 238 (44%) had MOF including 81 (15%) clinical VF. For MOF, BMD had higher sensitivity (49.6% vs 30.7%), lower specificity (68.2% vs 82.1%), and similar AUC (0.59 vs 0.56) versus TBS. For VF, the sensitivity, specificity and AUC for BMD were 60%, 64%, and 0.62 respectively versus 42%, 79.7%, and 0.61 for TBS. Combining TBS and BMD (either T-score ≤ -2.5) increased the sensitivity to 63% for MOF and 75.3% for VF without affecting AUC (0.6 and 0.64 respectively). Patients with osteoporosis and degraded TBS had the highest OR of 2.65 for MOF and 3.8 for VF. The fracture risk increased at the same level of BMD when TBS was degraded. Numerically, the risk of MOF increased steadily from strata 1 to 9 and was statistically significant for osteoporosis with degraded TBS and osteoporosis with moderate TBS. When both TBS and BMD were normal, the risk of fracture was significantly reduced. In the osteopenia and osteoporosis BMD categories, patients with degraded TBS had significantly higher prevalence of fracture compared to those with normal TBS in the same BMD category.

Conclusion:

Fracture risk stratification can be improved when TBS is added to BMD. The sensitivity of predicting fracture may also improve when TBS and BMD are combined. Patients with both normal TBS and BMD have the lowest fracture risk, whereas those with degraded TBS and osteoporosis have the highest risk of fracture and should be targeted for early or more aggressive treatment.

References:

[1]Hans D et al. J Bone Miner Res. 2011;26(11).

[2]McCloskey EV et al. Calcif Tissue Int. 2015;96(6).

Table 1.

Prevalence and risk of MOF and VF according to BMD stratified by TBS T-score

Patients within categoryNumber of MOFOR for MOFNumber of VFOR for VFNormal BMD & TBS497 (14.3%)0.19(0.08-0.43)*00.83(0.80-.87)*Normal BMD moderate TBS195 (26.3%)0.44(0.16-1.24)2 (10.5%)0.66(0.15-2.9)Normal BMD degraded TBS72 (28.6%)0.50(0.1-2.6)1 (14.3%)0.94(0.11-7.9)Osteopenia normal TBS9633 (34.4%)0.61(0.39-0.97)7 (7.3%)0.39(0.18-0.88)*Osteopenia moderate TBS9843 (43.9%)0.99(0.64-1.54)11 (11.2%)0.67(0.34-1.32)Osteopenia degraded TBS5730 (52.6%)1.47(.085-2.55)11 (19.3%)1.41(0.7-2.86)Osteoporosis normal TBS3918 (46.2%)1.1(0.57-2.1)6 (15.4%)1(0.42-2.6)Osteoporosis moderate TBS11259 (52.7%)1.55(1.02-2.35)*21 (18.8%)1.42(0.82-2.45)Osteoporosis degraded TBS6341 (65.1%)2.65(1.53-4.59)*22 (34.9%)3.8(2.12-6.83)*Total54023881

Acknowledgments:

Bone density team, Robert Jones and Agnes Hunt Orthopaedic Hospital

Disclosure of Interests:

None declared

SAT0479 IMPACT OF TRABECULAR BONE SCORE ON INTERVENTION THRESHOLD FOR BONE SPARING THERAPY IN PATIENTS REFERRED FOR BONE MINERAL DENSITY

Background:

Trabecular bone score (TBS) is an index of skeletal quality that has been validated as an independent risk factor for fracture and incorporated into fracture risk assessment (FRAX). TBS provides information on bone microarchitecture not captured from standard bone mineral density (BMD) measured by dual energy X-ray absorptiometry (DXA). Nonetheless, the clinical implications of using TBS in routine practice are not yet fully understood and warrant further evaluation.

Objectives:

To determine whether lumbar TBS can have an impact on clinician’s treatment threshold derived from DXA and clinical risk factors: does the addition of TBS to DXA measurements make the clinician more or less likely to recommend bone sparing therapy?

Methods:

A cross-sectional study at a tertiary metabolic bone centre in the West Midlands region of England. Three expert metabolic bone physicians, two rheumatologists and one elderly care, assessed consecutive patients referred for a DXA scan ± clinic review and provided treatment recommendations with and without TBS. Patients ≥ 18 years old with BMI of 15-37 who were not on bone sparing therapy were considered eligible. TBS was defined according to T-score as normal (T-score ≥ -1), moderate (-1 > T-score ≥ -2.5) or degraded (T-score ≤ -2.5). TBS groups were stratified by BMD T-scores (normal, osteopenia, or osteoporosis) using minimum T-score of total hip, femoral neck, and spine to identify categories in which TBS may be of more clinical use. The main outcome measure was the proportion of change in clinician’s treatment threshold between BMD alone and BMD plus TBS. The difference was assessed for significance using Chi-square test. Additionally, the change in UK National Osteoporosis Guideline Group (NOGG) threshold was also assessed using TBS-adjusted FRAX scores. Correlations between BMD-TBS strata and the change in intervention threshold (yes/no) were carried out using Spearman test.

Results:

540 patients were analysed. The inclusion of TBS resulted in 8.2% change in clinician’s treatment threshold (p <0.001) shifting the outcome 6.5 % for and 1.7 % against treatment. More than half of the cases in which the clinical decision was changed were for patients with osteopenia and degraded TBS (significant correlation; P <0.001). NOGG intervention threshold was changed in 7.4% of the cases (P<0.001); 6.1% for and 1.3% against treatment. 37.5% of NOGG changed outcome was related to osteopenia with degraded TBS (p<0.001). Kappa agreement between the clinician and NOGG was fair at 0.42 (p<0.001).

Conclusion:

These results demonstrate that using TBS in routine clinical practice is most likely to impact treatment decision in patients with osteopenia who have compromised bone microarchitecture. Incorporating TBS in routine DXA scans may lead to a net increase in bone protective therapy of approximately 5%. It is unknown whether adopting such an approach universally can reduce future fracture risk, and prospective studies are needed to address this question.

References:

[1]Hans D et al. J Bone Miner Res. 2011;26(11):2762-9.

[2]McCloskey EV et al. Calcif Tissue Int. 2015;96(6):500-9.

Table 1.

Demographic and baseline characteristics (n = 540)

Female470 (87%)Age (years)68.1 ± 11.6Body mass index (BMI)26.2 ± 4.6Femoral neck T-score-1.80 ± 1.04Total hip T-score-1.32 ± 1.07Lumbar spine T-score-1.37 ± 1.42Lumbar spine TBS1.32 ± 0.13Major osteoporotic fractures238 (44%)Spinal fractures81 (15%)FRAX major osteoporotic fracture14.43 ± 9.03FRAX hip fracture4.60 ± 6.20TBS-adjusted FRAX major osteoporotic fracture13.82 ± 8.80TBS-adjusted FRAX hip fracture4.45 ± 5.73Figure 1.

Distribution of changed clinical treatment threshold in normal, moderate, and degraded TBS according to BMD T-score

Acknowledgments:

Bone density unit &Rheumatology team, Robert Jones and Agnes Hunt Orthopaedic Hospital

Disclosure of Interests:

None declared

SUN-368 Wnt Inhibition Decreases Trabecular Bone in a Mouse Model of Fibrous Dysplasia

Background: G protein-coupled receptor (GPCR) signaling mediates a wide spectrum of physiological functions, including bone development and remodeling. Fibrous dysplasia (FD) is a common skeletal dysplasia where normal bone and bone marrow are replaced by fibrous tissue and expansile trabecular bone lesions. The craniofacial bones are often involved, leading to pain and facial deformities. FD is a mosaic disease caused by a somatic mutation in the GNAS gene encoding the G-protein alpha subunit (Gsα) that leads to constitutive activation of the G_s signaling pathway. Unfortunately, FD has no effective medical treatments.

Major challenges have hampered the development of pharmacologic strategies that specifically target GNAS or the G_sα protein. We previously developed the Col1(2.3)/Rs1 mouse model (Rs1) in which the G_s signaling pathway is activated specifically in bone by an engineered GPCR protein. These mice showed increased trabecular bone formation with loss of marrow space and cortical bone, which strongly resembles human FD (1–4). There was also a dramatic increase in the number of immature osteoblasts present in the FD lesions, suggesting that activation of G_s signaling caused an accumulation of these cells. Our prior studies showed increased Wnt signaling, which may be a major driver of this effect. Furthermore, blocking the G_s signaling could reverse the bone phenotype, providing proof-of-concept for finding drugs that could reverse the phenotype. Therefore, we administered the Wnt inhibitor LGK974, currently used in human clinical trials, to the Rs1 mice to test if the FD lesions could be pharmacologically reversed.

Methods: We administered LGK974 in 4-week-old Rs1 and non-Rs1 mice. We used a low dose (5mg/kg) for 8 weeks or high dose (30mg/kg) for 4 weeks. The mice were evaluated by histology and micro computed tomography (micro-CT) for mineral density (mg/cm³), bone volume (mm³), and trabecular thickness (um).

Results: LGK974 decreased β-catenin levels in bone on western blots. In the low-dose group, the histology and micro-CT showed no statistically significant differences between drug and control groups. In the high-dose group, the micro-CT showed significantly decreased trabecular bone thickness (p=0.0364, n=3) in the drug-treated group (22±2µm) compared with controls (17±2µm). Furthermore, histology showed resorption of the abnormal bone; however, the fibrocellular infiltrate in the Rs1 mice was still present.

Conclusions: Wnt inhibition can lead to decreased fibrous dysplastic bone, but separates abnormal bone formation from the fibrocellular infiltrate. These results provide new insight into understanding interactions between the Wnt and G_s signaling pathways in FD pathogenesis and bone formation.

References: 1. Hsiao EC et al. PNAS. 2008. 2. Hsiao EC et al. JBMR. 2010. 3. Schepers, Hsiao EC et al. Blood. 2012. 4. Cain CJ et al. Endocrinology. 2016.

Advanced platelet-rich fibrin and freeze-dried bone allograft for ridge preservation: A randomized controlled clinical trial

BACKGROUND

Advanced platelet-rich fibrin (A-PRF) is an autogenous blood product with applications in dento-alveolar surgery. However, there is minimal information regarding its optimal clinical application or efficacy. The aim of this multi-arm parallel randomized controlled clinical trial was to evaluate the efficacy of A-PRF alone or with freeze-dried bone allograft (FDBA) in improving vital bone formation and alveolar dimensional stability during ridge preservation.

METHODS

Forty patients requiring extraction of non-molar teeth and replacement with dental implants were randomized into one of four ridge preservation approaches: A-PRF, A-PRF+FDBA, FDBA, or blood clot. A-PRF was prepared at 1,300 rpm for 8 minutes. Non-traumatic extractions and ridge preservation was performed. After an average of 15 weeks healing, bone core samples were harvested at the time of implant placement for micro-CT and histomorphometric analysis. Ridge dimensions were measured immediately after extraction and before implant placement.

RESULTS

Significantly greater loss of ridge height was noted in the blood clot group (3.8 ± 2.0 mm) compared to A-PRF (1.8 ± 2.1 mm) and A-PRF+FDBA (1.0 ± 2.3 mm) groups (P < 0.05). No significant differences in ridge width reduction were noted between groups. Significantly more vital bone was present in the A-PRF group (46% ± 18%) compared to the FDBA group (29% ± 14%) (P < 0.05). Bone mineral density was significantly greater in the FDBA group (551 ± 58 mg/cm³ ) compared to blood clot (487 ± 64 mg/cm³ ) (P < 0.05).

CONCLUSIONS

This study demonstrates A-PRF alone or augmented with FDBA is a suitable biomaterial for ridge preservation. This study represents the first randomized controlled clinical trial comparing A-PRF with and without FDBA to FDBA alone for ridge preservation.

The Fracture Callus Is Formed by Progenitors of Different Skeletal Origins in a Site-Specific Manner

We evaluated repair following a mid‐diaphyseal fracture of the tibia in 3‐month‐old mice. We observed differences in the repair process at three different sites of the callus. Site 1: bone developing from the outer layer of the periosteum of the cortex; site 2: bone developing within the bridge/central region of the fracture; and site 3: bone developing within the marrow of the ends of broken bones. We characterized these sites by correlating datasets from X‐ray CT and histology. Correlated data demonstrated the involvement of different cells and different rates of mineralization. The origin of the progenitors and mechanism of progenitor differentiation involved at these sites was then evaluated using lineage tracing of cells expressing Prx1 and Col.2. The Prx1 progeny contributed to intramembranous bone formation (IBF) at site 1 and endochondral bone formation (EndoBF) at site 2 but not to intramedullary bone formation (IMBF) at site 3. IBF at site 1 was confirmed without a chondrocyte intermediate unlike EndoBF at site 2. Additionally, the presence of Col.2 progeny contributed to EndoBF in site 2 and IMBF in site 3 but not to IBF in site 1. However, the Col.2 progeny in IMBF in site 3 appeared to come from Col.2‐expressing osteocytes originating in the cortices of the ends of the fractured bone. In conclusion we have identified three sites of bone fracture repair that differ in their origin of cells and their mechanisms of bone formation. © 2019 The Authors JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

Abstract P1-12-07: Prospective 36-month follow-up to determine changes in body mass index and weight among Chinese breast cancer survivors

Background:Anticancer treatment for breast cancer has been associated with weight gain but such observation has mainly been reported in western patients. More recent data in Asian patients have inconsistent findings. Factors including socio-demographic, clinical and lifestyle may be associated with post-diagnosis weight gain. In this prospective cohort study of women with breast cancer, the objectives were to determine the body mass index (BMI) and weight changes over 36 months after initial diagnosis and the factors associated with such changes.

Methods: Chinese women with newly diagnosed early-stage breast cancer were recruited. Individual woman had her weight measured at breast cancer diagnosis (W0), at study entry (W1) and at 36-month follow-up (W2). Body height was measured at W0. We evaluated change in weight and body mass index (BMI) before and after breast cancer diagnosis.Socio-demographic, clinical and lifestyle factors were assessed to identify potential associated factors with weight changes.

Results: A total of 1133 women with breast cancer had detailed weight measurements at the 3 time-points of assessment. The mean age at diagnosis was 52 years. Fifty-four percent were premenopausal at W1. The proportion of patients with stage 0-I, II and III diseases were 35%, 46% and 19%, respectively.

The proportions of patients who were overweight and obese at the three assessment time-points were 21.2% and 28.5% at W0, 19.7% and 26.6% at W1, and 21.7% and 30.9% at W2 assessment, respectively. When compared to W0, the proportions of women who gained weight within 2-5kg at W1 and W2 were 2.4% and 20.6% respectively, that with weight gain of &gt;5kg at W1 and W2 were 0.5% and 10.0% respectively; 6.1% and 19.6% of women had weight loss &gt;2kg at W1 and W2 respectively.

Compared to W0, the median value of weight change was -0.5 kg (range: -11.4, 18.3) at W1 and 0.6 kg (range: -19.6, 20.5) at W2. On multivariate analysis, only BMI at diagnosis were significantly associated with weight change betweenassessments at diagnosis and W2; the median (range) for weight changes for women who were underweight, normal, overweight and obese were respectively 0.9 (-4.8, 7.6), 0.6 (-13.2, 20.5), 0.5 (-11.5, 13.0) and 0.5 (-19.6, 12.6) kg, p &lt;0.001.

Conclusions: In this prospective study of Chinese women with a history of breast cancer who were followed-up over a 36-months' period, the proportions of women with overweight and obese statuses were relatively stable; weight gain was uncommon among Hong Kong women with breast cancer during the same period. These findings are in contrast with studies conducted in the West, where weight gains were more commonly reported.

Funding: World Cancer Research Fund International (Grant Number WCRF 2010/249 and WCRF 2014/1197)

Citation Format: Yeo W, Lei YY, Cheng AC, Kwok CC, Cheung KL, Lee R, Lee IC, He YQ, Ho S. Prospective 36-month follow-up to determine changes in body mass index and weight among Chinese breast cancer survivors [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P1-12-07.

Critical care usage after major gastrointestinal and liver surgery: a prospective, multicentre observational study

BACKGROUND

Patient selection for critical care admission must balance patient safety with optimal resource allocation. This study aimed to determine the relationship between critical care admission, and postoperative mortality after abdominal surgery.

METHODS

This prespecified secondary analysis of a multicentre, prospective, observational study included consecutive patients enrolled in the DISCOVER study from UK and Republic of Ireland undergoing major gastrointestinal and liver surgery between October and December 2014. The primary outcome was 30-day mortality. Multivariate logistic regression was used to explore associations between critical care admission (planned and unplanned) and mortality, and inter-centre variation in critical care admission after emergency laparotomy.

RESULTS

Of 4529 patients included, 37.8% (n=1713) underwent planned critical care admissions from theatre. Some 3.1% (n=86/2816) admitted to ward-level care subsequently underwent unplanned critical care admission. Overall 30-day mortality was 2.9% (n=133/4519), and the risk-adjusted association between 30-day mortality and critical care admission was higher in unplanned [odds ratio (OR): 8.65, 95% confidence interval (CI): 3.51-19.97) than planned admissions (OR: 2.32, 95% CI: 1.43-3.85). Some 26.7% of patients (n=1210/4529) underwent emergency laparotomies. After adjustment, 49.3% (95% CI: 46.8-51.9%, P<0.001) were predicted to have planned critical care admissions, with 7% (n=10/145) of centres outside the 95% CI.

CONCLUSIONS

After risk adjustment, no 30-day survival benefit was identified for either planned or unplanned postoperative admissions to critical care within this cohort. This likely represents appropriate admission of the highest-risk patients. Planned admissions in selected, intermediate-risk patients may present a strategy to mitigate the risk of unplanned admission. Substantial inter-centre variation exists in planned critical care admissions after emergency laparotomies.