VAPB-mediated ER-targeting stabilizes IRS-1 signalosomes to regulate insulin/IGF signaling.

The scaffold protein IRS-1 is an essential node in insulin/IGF signaling. It has long been recognized that the stability of IRS-1 is dependent on its endomembrane targeting. However, how IRS-1 targets the intracellular membrane, and what type of intracellular membrane is actually targeted, remains poorly understood. Here, we found that the phase separation-mediated IRS-1 puncta attached to endoplasmic reticulum (ER). VAPB, an ER-anchored protein that mediates tethers between ER and membranes of other organelles, was identified as a direct interacting partner of IRS-1. VAPB mainly binds active IRS-1 because IGF-1 enhanced the VAPB-IRS-1 association and replacing of the nine tyrosine residues of YXXM motifs disrupted the VAPB-IRS-1 association. We further delineated that the Y745 and Y746 residues in the FFAT-like motif of IRS-1 mediated the association with VAPB. Notably, VAPB targeted IRS-1 to the ER and subsequently maintained its stability. Consistently, ablation of VAPB in mice led to downregulation of IRS-1, suppression of insulin signaling, and glucose intolerance. The amyotrophic lateral sclerosis (ALS)-derived VAPB P56S mutant also impaired IRS-1 stability by interfering with the ER-tethering of IRS-1. Our findings thus revealed a previously unappreciated condensate-membrane contact (CMC), by which VAPB stabilizes the membraneless IRS-1 signalosome through targeting it to ER membrane.

Phase separation of insulin receptor substrate 1 drives the formation of insulin/IGF-1 signalosomes.

As a critical node for insulin/IGF signaling, insulin receptor substrate 1 (IRS-1) is essential for metabolic regulation. A long and unstructured C-terminal region of IRS-1 recruits downstream effectors for promoting insulin/IGF signals. However, the underlying molecular basis for this remains elusive. Here, we found that the C-terminus of IRS-1 undergoes liquid-liquid phase separation (LLPS). Both electrostatic and hydrophobic interactions were seen to drive IRS-1 LLPS. Self-association of IRS-1, which was mainly mediated by the 301-600 region, drives IRS-1 LLPS to form insulin/IGF-1 signalosomes. Moreover, tyrosine residues of YXXM motifs, which recruit downstream effectors, also contributed to IRS-1 self-association and LLPS. Impairment of IRS-1 LLPS attenuated its positive effects on insulin/IGF-1 signaling. The metabolic disease-associated G972R mutation impaired the self-association and LLPS of IRS-1. Our findings delineate a mechanism in which LLPS of IRS-1-mediated signalosomes serves as an organizing center for insulin/IGF-1 signaling and implicate the role of aberrant IRS-1 LLPS in metabolic diseases.

MAKO robotic assisted total hip replacement (THR) for patients with fused hips.

BACKGROUND: Previous articles about MAKO robotic-assisted total hip replacement (THR) were mainly in patients with comparatively normal anatomy. METHODS: From July 2020 to June 2021, we performed MAKO robotic-assisted THR in three hip-fused patients. We assessed the accuracy of prostheses implantation, collected clinical data, and discussed the value of this technique in this kind of patients. RESULT: All three patients achieved good leg length and prostheses position. A patient got femoral artery injury during the surgery. Moreover, she developed a thrombus. All three patients got acceptable Visual Analogue Scale scores and function recovery 6 months later. CONCLUSION: MAKO robotic-assisted THR achieved excellent prosthesis position in hip fused patients. More cases are needed to confirm this advantage. The function recovery was acceptable. Caution should be paid to protect the surrounding abnormal arteries, especially in a limited surgical field.

[Double plating through different approaches for periprosthetic femoral fracture following total knee arthroplasty].

OBJECTIVE: To study clinical effects of double plating through different approaches for communicated and obvious osteoporosis periprosthetic femoral fracture following total knee arthroplasty(TKA). METHODS: From July 2010 to June 2017, 21 patients with periprosthetic femoral fracture following TKA were divided into two groups according to operative approach. Fifteen patients in medial and lateral double approaches group, including 5 males and 10 females aged from 63 to 79 years old with an average of (67.2±5.9) years old; 11 patients were type 33-A2 and 4 patients were type 33-A3 according to AO-OTA classification; 12 patients injured by falling down and 3 patients by traffic accident; treated with double plating. Six patients in medial parapatellar approach group, including 3 males and 3 females, aged from 61 to 74 years old with an average of (64.6±6.0) years old; 3 patients were type 33-A2 and 3 patients were type 33-A3 according to AO-OTA classification; 5 patients injured by falling down and 1 patient by traffic accident; treated with double plating. Operative time, blood loss, postoperative drainage, fracture healing time were compared between two groups; HSS score and radiology at 3 and 12 months were compared between two groups. RESULTS: All patients were followed up, and the follow-up time of bilateral approaches group ranged from 12 to 18 months with an average of (14.2±2.6 ) months, while the follow-up time of single approach group ranged from 12 to 16 months with an average of (12.6±2.5) months, and there was no statistical difference between two groups. The operative time and postoperative drainage in bilateral approaches group were (107.2±10.4) min and (213.9±30.4) ml, while in sigle approach group was (95.4±12.8) min and (256.8±34.2) ml, and the differences were significant(P<0.05). There were no significant difference in blood loss and fracture healing time(P>0.05). HHS score at 3 and 12 months after operation in bilateral approach were 82.9±5.7 and 84.8±7.1, while in single approach group were 83.6±6.1 and 86.3±6.8; there was no statistical difference in HSS score between two groups(P>0.05). According to HSS score at 12 months after operation, 2 cases got excellent results and 13 good in bilateral approaches group; 1 case got excellent result and 4 good and 1 moderate in single approach group; but there was no statistical difference between two groups (χ²=2.625, P=0.105). There wase no significant differences in complications between bilateral approaches group(2 cases) and single approach group (1 case)(P>0.05). CONCLUSIONS: Double plating technique for communicated and obvious osteoporosis periprosthetic femoral fracture following TKA could obtain good function of knee joint. The medial parapatellar approach has shorter operative time, while the bilateral approaches had less drainage.

Cepharanthine Prevents Estrogen Deficiency-Induced Bone Loss by Inhibiting Bone Resorption.

Osteoporosis is a common health problem worldwide caused by an imbalance of bone formation vs. bone resorption. However, current therapeutic approaches aimed at enhancing bone formation or suppressing bone resorption still have some limitations. In this study, we demonstrated for the first time that cepharanthine (CEP, derived from Stephania cepharantha Hayata) exerted a protective effect on estrogen deficiency-induced bone loss. This protective effect was confirmed to be achieved through inhibition of bone resorption in vivo, rather than through enhancement of bone formation in vivo. Furthermore, the in vitro study revealed that CEP attenuated receptor activator of nuclear factor κB ligand (RANKL)-induced osteoclast formation, and suppressed bone resorption by impairing the c-Jun N-terminal kinase (JNK) and phosphatidylinositol 3-kinase (PI3K)-AKT signaling pathways. The inhibitory effect of CEP could be partly reversed by treatment with anisomycin (a JNK and p38 agonist) and/or SC79 (an AKT agonist) in vitro. Our results thus indicated that CEP could prevent estrogen deficiency-induced bone loss by inhibiting osteoclastogenesis. Hence, CEP might be a novel therapeutic agent for anti-osteoporosis therapy.

Sophocarpine attenuates wear particle-induced implant loosening by inhibiting osteoclastogenesis and bone resorption via suppression of the NF-κB signalling pathway in a rat model.

BACKGROUND AND PURPOSE: Aseptic prosthesis loosening, caused by wear particles, is one of the most common causes of arthroplasty failure. Extensive and over-activated osteoclast formation and physiological functioning are regarded as the mechanism of prosthesis loosening. Therapeutic modalities based on inhibiting osteoclast formation and bone resorption have been confirmed to be an effective way of preventing aseptic prosthesis loosening. In this study, we have investigated the effects of sophocarpine (SPC, derived from Sophora flavescens) on preventing implant loosening and further explored the underlying mechanisms. EXPERIMENTAL APPROACH: The effects of SPC in inhibiting osteoclastogenesis and bone resorption were evaluated in osteoclast formation, induced in vitro by the receptor activator of NF-κB ligand (RANKL). A rat femoral particle-induced peri-implant osteolysis model was established. Subsequently, micro-CT, histology, mechanical testing and bone turnover were used to assess the effects of SPC in preventing implant loosening. KEY RESULTS: In vitro, we found that SPC suppressed osteoclast formation, bone resorption, F-actin ring formation and osteoclast-associated gene expression by inhibiting NF-κB signalling, specifically by targeting IκB kinases. Our in vivo study showed that SPC prevented particle-induced prosthesis loosening by inhibiting osteoclast formation, resulting in reduced periprosthetic bone loss, diminished pseudomembrane formation, improved bone-implant contact, reduced bone resorption-related turnover and enhanced stability of implants. Inhibition of NF-κB signalling by SPC was confirmed in vivo. CONCLUSION AND IMPLICATIONS: SPC can prevent implant loosening through inhibiting osteoclast formation and bone resorption. Thus, SPC might be a novel therapeutic agent to prevent prosthesis loosening and for osteolytic diseases.

Gambogic acid inhibits invasion of osteosarcoma via upregulation of TIMP-1.

Gambogic acid (GA), the natural product, has been demonstrated to be a promising chemotherapeutic drug for osteosarcoma (OS) due to its ability to induce apoptosis and cell cycle arrest. To date, no studies have examined the role of GA in metastatic bone disease. Matrix metalloproteinases (MMPs) play critical roles in invasion and metastasis, and the tissue inhibitors of metalloproteinase (TIMP) family regulates the activity of multifunctional metalloproteinases. In this study, we investigated the gene expression of matrix metalloproteinase-9 (MMP-9) and tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) in OS cell lines treated by the GA. The expression of MMP-9 and TIMP-1 were studied by reverse transcription-polymerase chain reaction (RT-PCR) and western blotting. In vitro invasion of OS cell lines (Saos-2, MG-63) were investigated by the Matrigel invasion assay. Mean MMP-9 protein and mRNA expression was significantly suppressed; in addition, mean TIMP-1 protein mRNA expression were upregulated by increasing GA concentrations. GA reduced the invasiveness of OS cell lines dose-dependently. Furthermore, specific inhibition of TIMP-1 secretion with siRNA against TIMP-1 significantly reduced the effect of GA on OS cell lines. Overall, our findings suggest that GA reduces the invasive potential of OS cells via attenuation of MMP-9 and upregulation of TIMP-1. Moreover, TIMP-1 played an important role in the reduction of invasive potential of the OS cells which were treated by GA.

[Medium-term follow-up outcomes of total hip arthroplasty for patients with ankylosing spondylitis].

OBJECTIVE: To retrospectively study medium-term follow-up outcomes of total hip arthroplasty (THA) for patients with ankylosing spondylitis (AS). METHODS: From January 2000 to December 2008, 67 patients (88 hip joints) with AS were treated with all ceramic interface THA. And 55 patients (74 hips) were finally followed up. Among them, there were 30 males and 25 females, with an average age of 32.6 (ranged 19 to 58) years old. Sixty-one hips were treated with biological prosthesis and 13 hips were treated with hybrid prosthesis. Fifty-five patients were followed up at least 5 years, with an average of (75.2 +/- 8.6) months. Clinical symptoms and radiography information were evaluated after follow-up. RESULTS: Harris hip score were significantly improved from 30.8 +/- 7.0 preoperatively to 85.2 +/- 5.5 at the last follow-up (P<0.01). The hip movement range increased from (21.2 +/- 8.5) degrees preoperatively to (142.0 +/- 10.2) degrees postoperatively (P<0.01). The 5-year survival of prosthesis was 95.9%. One patient were renovated because of internal wall broken caused by injury, 1 was renovated for infection, 1 was renovated for fracture arround femoral stem prostheses, and 1 was treated with conservative treatment by dislocation. Three cases with abnormal sound were cured with non-operation. 7 cases with heterotopic ossification were not treated, 2 cases with thigh pain received conservative treatment. Bone dissolve around prosthesis, loose and sink of femur and acetabulum prosthesis were occurred in other cases. CONCLUSION: THA for the treatment of AS is a reliable method, which has a satisfied medium-term follow-up outcomes.

Pure alumina bearings with cementless stems versus sandwich bearings with cemented stems in total hip arthroplasty.

BACKGROUND: Ceramic bearing surfaces have been introduced to prevent osteolysis after total hip arthroplasty (THA), but little is known about the difference in clinical and radiological results between pure alumina and sandwich alumina bearings. The purpose of this study was to analyze the results obtained with third-generation alumina-on-alumina THA with two different designs both in liner and femoral stem fixation after a minimum follow-up of 4.2 years. METHODS: The results of 195 primary alumina-on-alumina THAs in 167 patients were evaluated. The procedures were performed between January 1998 and October 2006. Three patients died and 11 patients were lost to follow-up, leaving a total of 153 patients (181 hips) available for study. In the 88 group A patients, 107 hips were implanted using pure alumina bearings with cementless femoral stems. These patients were followed for (6.84 ± 1.49) years. In the 65 group B patients, 74 hips were implanted using sandwich alumina ceramic bearings with cemented femoral stems. These patients had a follow-up period of (7.73 ± 1.60) years. Patients in both groups were evaluated clinically and radiographically. RESULTS: One ceramic liner fracture occurred in group A and five took place in group B (P < 0.05), four of them revised for liner fracture. In each group, one acetabular shell migration happened without liner breakage and two hips developed deep infections, and all these six hips received revisions. Nine femoral components loosened in group B, with seven undergoing revisions. Kaplan-Meier survivorship at 5 years for revision of any component for any reason in group A was 96.26% compared to 90.54% in group B (P < 0.05). Better function was determined in group A (average Harris hip scores: 92.13 ± 2.85) than in group B (average Harris hip scores: 86.03 ± 4.21) and the difference was significant (P < 0.05). Squeaking was not recorded in either group. CONCLUSIONS: The sandwich design of the acetabular bearings can not reduce the migration rate in ceramic bearings but increase the liner fracture rate compared to pure ceramic liners. The high loosening rate in fluted and taped designed cemented stems with sandwich liners warrant caution to their use.

Short reconstruction nail for intertrochanteric fracture: does it really fit Asian feature?

BACKGROUND: The Trigen short reconstruction trochanteric antegrade nail (TAN) is considered most suitable for the small skeletons of Asian patients. We have evaluated the results of TAN for intertrochanteric fractures in Asian patients. METHODS: Between January 2006 and March 2009, 174 fractures in 164 patients were treated by TAN in our department. Epidemiological data, radiological changes, fracture types, cortical bone indices, clinical outcomes, and complications over a mean of 26 months were analyzed retrospectively. RESULTS: We observed a 17.0% fracture rate at the tip of the nail, a poor reduction rate of 15.9%, and a 41.4% cracking rate of the lateral trochanter for type 31-A3 fracture. Review of these cracking cases showed that they were all type 31-A3 unstable fractures combined with comminuted lateral trochanter fractures. Two shaft fractures required revision, with other fractures showing no delayed union, nonunion or infection. No screw breakage but one cut-out occurred, which received total hip arthroplasty revision. All other fractures healed at last. Risk of distal shaft fractures was not associated with patient age, gender, fracture type or cortical bone index. CONCLUSION: Despite the theoretically better design of TAN and the healing of most fractures and good activity at last follow-up, poor reduction and coxa vara caused by insertion of the nail could not be completely avoided, and the design of the distal part of the nail had the potential to cause femoral shaft fracture. Future improvements are necessary to enable the use of this system in Asians.

Comparison of percutaneous compression plating and short reconstruction nail for treatment of intertrochanteric fracture.

OBJECTIVE: To compare percutaneous compression plating (PCCP) with Trigen short reconstruction nail (Trigen SRN) for the treatment of intertrochanteric hip fracture. METHODS: Eighty-four patients with intertrochanteric hip fracture admitted to our hospital from January 2007 to June 2008 were included in this retrospective study. Thirty-six patients were treated with PCCP and 48 with Trigen SRN. Information regarding age, surgical time, blood loss, length of follow-up, mortality, fracture impaction, time to union, complications, Harris score and visual analog scale (VAS) were all recorded. RESULTS: The mean follow-up time was 16.3 ± 3.2 months (13-19 months). The mean time to achieve radiological fracture healing was 3.6 ± 0.8 and 4.1 ± 1.0 months for the PCCP and Trigen SRN groups, respectively (P= 0.020); the mean Harris hip scores were 78.1 ± 4.8 and 74.1 ± 5.2 (P= 0.001); and the mean fracture impaction was 3.6 ± 2.3 and 3.3 ± 2.6 mm (P= 0.023). There were no statistical differences between the two groups in duration of surgery (P= 0.131) and blood loss (P= 0.268). The amount of nail in the inferior-central quadrants was greater in the PCCP group than in the Trigen SRN group. CONCLUSION: PCCP achieves earlier pain release and better fracture reduction than Trigen SRN.

[Intermediate outcomes of alumina-on-alumina bearing total hip arthroplasty].

OBJECTIVE: To explore the intermediate outcomes of third-generation alumina-on-alumina total hip arthroplasty (THA). METHODS: A consecutive series of 165 primary alumina-on-alumina total hip arthroplasties were performed in 135 patients. Three patients died and 13 patients lost follow-up so that a total of 119 patients (146 hips) were available for study. The mean patient age was 53.4 ± 11.0 years old (range: 26 - 79). Hydroxyapatite. (HA)-coated press-fit acetabular cups were used in all cases. At femoral side, 123 cases were implanted with HA-coated uncemented stems and 23 cases implanted with high polished double taped cemented stems. All patients were evaluated clinically and radiographically after a minimal follow-up duration of 60 months. RESULTS: The preoperative mean Harris hip score of 49.6 ± 7.9 points improved to 91.7 ± 3.0 points at the last follow-up (P < 0.05). The 5-year survival for any reason lead to revision was 96.6%. Five hips were under revision, 1 for acetabular shell loosening and migration, 1 for Vancouver B2 periprosthetic fracture, 1 for fracture of pure alumina liner and 2 for infections. All other prostheses demonstrated no radiographic evidence of loosening. No periprosthetic osteolysis was found. There were 2 cases of dislocations and 2 patients presented postoperatively with "squeaking-like" hips. CONCLUSION: The clinical and radiographic outcomes after primary THA with third-generation ceramic-on-ceramic bearing surfaces are favorable after a minimal follow-up duration of 5 years. The modified alumina-on-alumina bearing implants offer a better option for younger and active patients.

Combined use of extensively porous coated femoral components with onlay cortical strut allografts in revision of Vancouver B2 and B3 periprosthetic femoral fractures.

BACKGROUND: Periprosthetic femoral fractures following total hip arthroplasty are getting more prevalent. The aim of this study was to evaluate the clinical results of combined use of uncemented extensively porous coated femoral components with onlay cortical strut allografts in revision of Vancouver type B2 and B3 periprosthetic femoral fractures. METHODS: Thirteen hips after total hip arthroplasty in 13 patients who suffered a Vancouver B2 or B3 periprosthetic fracture were treated with an uncemented extensively porous coated femoral component combined with onlay cortical strut allografts. Each patient was assigned a Harris hip score, and a visual analog scale (VAS) score for pain and satisfaction. Radiographs were examined for component stability, fracture site and allograft-host union and allograft reconstruction. RESULTS: At an average of 5.3-year follow-up, no patient required repeat revision. The average Harris hip score was (71.8 +/- 6.3) points, the pain VAS score was (16.6 +/- 4.3) points, and the patient satisfaction VAS score was (81.5 +/- 5.7) points. Radiographic examination showed no detectable loosening of the prostheses, and 12 cases were presented fixation by osseointegration and the other one was stable fibrous ingrown fixation. All fractures united for (5.2 +/- 1.4) months in average. And all onlay strut allografts united to host bone for about (11.5 +/- 2.6) months. CONCLUSIONS: Combined use of uncemented, long stemmed, extensively porous coated implant with cortical onlay strut allografts can achieve good clinic results and high rate of union for both fracture site and allograft-host bone junction. This technique could be used routinely to augment fixation and healing of Vancouver B2 and B3 periprosthetic fractures.

Effect of delayed pulsed-wave ultrasound on local pharmacokinetics and pharmacodynamics of vancomycin-loaded acrylic bone cement in vivo.

This study sought to investigate the effect of delayed pulsed-wave ultrasound with low frequency on drug release from and the antimicrobial efficacy of vancomycin-loaded acrylic bone cement in vivo and the possible mechanism of this effect. After the implantation of cement and the inoculation of Staphylococcus aureus into the bilateral hips of rabbits, ultrasound (average intensity, 300 mW/cm(2); frequency, 46.5 kHz; on/off ratio, 20 min/10 min) was applied to animals in the normal ultrasound group (UG(0-12)) from 0 through 12 h after surgery and to those in the delayed-ultrasound group (UG(12-24)) from 12 through 24 h after surgery. The control group (CG) was not exposed to ultrasound. Based on vancomycin concentrations in left hip cavities at projected time intervals, the amount of time during which the local drug concentration exceeded the MIC (T(>MIC)) in UG(12-24) was significantly prolonged compared with that in either CG or UG(0-12), and the ratios between the areas under the concentration-time curves over 24 h and the MIC for UG(0-12) and UG(12-24) were both increased compared with that for CG. The greatest reductions in bacterial densities in both right hip aspirates and right femoral tissues at 48 h were achieved with UG(12-24). Local hemorrhage in rabbits of UG(0-12) during the 12-h insonation was more severe than that in rabbits of UG(12-24). Of four variables, the T(>MIC) and the bioacoustic effect were both identified as parameters predictive of the enhancement of the antimicrobial efficacy of cement by ultrasound. Sustained concentrations above the MIC replaced early high maximum concentrations and long-term subtherapeutic release of the drug, provided that ultrasound was not applied until local hemorrhage was relieved. The enhancement of the antimicrobial efficacy of cement by ultrasound may be attributed to the prolonged T(>MIC) and the bioacoustic effect caused by ultrasound.

[Tibial infected nonunion treated by internal bone transport using the mono-lateral external fixation].

OBJECTIVE: To evaluate the clinical and functional outcomes of infected nonunion of the tibia by internal bone transport using the LRS mono-lateral external fixation. METHODS: From June 2003 to October 2005, twenty-eight patients who underwent internal bone transport for infected nonunion in the tibia were reviewed. Twenty-three cases were open fractures: grade IIIA, 5 cases; grade IIIB, 11 cases; grade IIIC, 7 cases. The other five cases were infected nonunion after internal fixation. The results were evaluated by the classification of the Association for the Study and Application of the Method of Ilizarove (ASAMI) which divided into bone and functional categories. RESULTS: Mean follow-up was 16 months. All the cases got primary bone union, and infection was controlled. Bone results were 14 excellent, 9 good, 2 fair and 3 poor. And functional results were 10 excellent, 13 good, 2 fair and 3 poor. The mean length of time in healing for all patients were 9 months. The mean length of regenerate bone were 6.6 cm. The most common complication was pin infection, and 2 cases refractured at the docking site. CONCLUSIONS: Tibial infected nonunion can be successfully treated using the internal bone transport technique.

[Finite element analysis of changes in femoral stresses after elite total hip arthroplasty].

OBJECTIVE: To determine the variation in femoral stress after insertion of Elite cemented femoral prosthesis. METHODS: Three-dimentional finite element models of the normal human femur and Elite femoral prosthesis were developed through CT scan. With the application of hip joint loading, quantitatively measure stress changes of an intact femur with corresponding femur inserted with Elite implants were measured. RESULTS: Compared with intact femur, insertion of Elite implants into the femoral canal decreased the proximal femoral stresses level, especially in calcar femoral, femur wall and tuberositas. However, the stress in the prosthesis distal end. CONCLUSION: Insertion of Elite implants induced significant stress shielding in the proximal femur, especially at calcar femoral, femur wall and tuberositas. However, stress concentrates in the prosthesis distal end.