Human miRNAs: an antiviral defense mechanism

Background miRNAs are short 21-24 nt RNAs that mediate post transcriptional repression of target genes. Various reports have shown that miRNAs are capable of repressing the gene expression levels of different viruses, leading to the suggestion that miRNAs are key mediators of host-virus interaction [1]. HIV-1 is a retrovirus known to cause AIDS, one of the major diseases in humans. The nef gene of the HIV-1 has been shown to be important for virus repression of CD4+ cells and virus progression. It has also been shown earlier that patients infected with nef deleted HIV-1 do not progress from infected to diseased state for longer periods of time, resulting in the Long Term Non-Progressor phenotype [2]. Materials and methods We computationally predicted five endogenously expressed human miRNAs to target the nef gene of HIV-1 retrovirus. On applying other stringency parameters we could focus on two of the five miRNAs viz. hsa-mir-29a and hsa-mir-29b as they were predicted to target the nef gene, at sites highly conserved amongst other clades of HIV-1 [3]. We then created reporter carrying the nef gene inserted downstream of a luciferase reporter. miRNA expression vectors were also made which would express the pri-miRNA when processed and thereby lead to high levels of the miRNA inside the cells. We then identified various cell lines for validating nef as a target for hsa-mir-29a and hsa-mir-29b. Results and discussion Gene reporter assays and ectopic over-expression of miRNAs conclusively showed that human cellular miRNAs hsa-mir-29a and hsa-mir-29b could bring down the nef protein levels and also affect viral replication [4]. These results would provide a better understanding of the mechanisms that could regulate the viral gene expression and human cellular antiviral defense mechanisms whereby miRNAs could serve as potential therapeutics to treat various viral diseases

Human cellular microRNA hsa-miR-29a interferes with viral nef protein expression and HIV-1 replication

protein expression and HIV-1 replicatio

Minimally Invasive Dorsal Cheilectomy of the first metatarsal

Category: Other Introduction/Purpose: Traditionally, a dorsal cheilectomy of the first metatarsophalangeal (MTP) joint is performed with an open approach through a dorsomedial or midmedial incision. It is now possible to perform minimally invasive dorsal cheilectomy (MIDC) of the first metatarsal with a wedge burr. The stab incision for MIDC needs to be dorsomedial to allow an ergonomic sweeping movement of the burr. This potentially puts the dorsomedial cutaneous nerve (DMCN) to the hallux at risk. There have been no clinical or cadaveric studies to date quantifying the risk to the DMCN and the surrounding structures when a Wedge burr was used for MIDC. We aim to determine this by using fresh-frozen cadaveric specimens in a “high-risk” situation in which most of the surgeons were novices to the technique. Methods: A total of 13 fresh-frozen cadaveric specimens (7 right, 6 left) amputated below the knee were obtained for this study. 13 foot and ankle surgeons (2 left handed, 11 right handed) who had no or minimal experience in MI surgery participated in this study. After a demonstration by an experienced MI surgeon and a practice on sawbones by participants, each surgeon performed a MIDC over the first metatarsal. Fluoroscopic guidance was available throughout the procedure. After the procedure, the specimens were dissected and the DMCN and the extensor hallucis longus (EHL) were inspected for damage. The same dissection steps were used for each specimen. The relationship of the DMCN to landmarks were measured. All measurements were made to the nearest millimetre. Results: Dissection of the specimens revealed that the DMCN to the hallux was cut completely in two specimens (15%). All the EHL tendon were intact, although in one specimen, the tendon showed some fraying on the underside of the tendon, estimated to be 15%. The average distance of the stab incision from the first MTP joint was 17.7 (range: 10 – 23) mm. In terms of the relationship of the DMCN to the stab incision in specimens where the DMCN was not cut, the DMCN was superior in five specimens and inferior in six specimens. The distance of the DMCN to the incision was 3.8 (range: 0 -7) mm. Conclusion: The DMCN to the hallux has been well studied by several authors and has a variable course. This nerve is at high risk of being damaged with open surgery and is a commonly reported complication of surgery to the hallux with rates reportedly as high as 45%. This nerve was damaged in 15% of our specimens following MIDC in a “high-risk” situation. Patients need to be specifically made aware of this risk when being consented for surgery. A carefully made working capsular pocket for the burr and marking this nerve before placing the incision if palpable could mitigate this risk

Minimally invasive calcaneal osteotomy

Category: Hindfoot Introduction/Purpose: A calcaneal osteotomy can be used to treat a variety of pathologic entities in which the hindfoot needs realignment. Minimally invasive calcaneal osteotomy (MICO) is becoming increasingly popular due to being soft tissue friendly, its ability to place other incisions nearby and high union rate. Previous studies have look specifically at medialising MICO or comparing open calcaneal osteotomy versus MICO. The purpose of our study was to compare 3 different types of commonly used MICO in our centre. Methods: Sixty-two MICO which fit the criteria were included in this study. They were performed in our unit from 2010 and 2016 and all patients had at least one year follow up data. The type of osteotomies was as follows: Medialising, n = 34, Lateralising, n =15 and Zadek (Dorsal closing wedge), n =13. Clinical and radiographic data were recorded. The diagnosis for 31/34 of the medialising MICO was Stage 2 PTTD, the diagnosis for 12/15 of the lateralising MICO was cavus foot, while the diagnosis for all Zadek MICO was for insertional Achilles tendinopathy. Apart from the Zadek MICO, the other MICO were all associated with other procedures. The average age (years) were as follows: Medialising, 58 (30 – 74); Lateralising, 33 (14 – 67) and Zadek, 47 (42-62). Results: The average calcaneal displacement was 10.2 (range: 8 – 12) mm for medialising MICO, and 6.6 (4 – 8) mm for lateralising MICO(p=0.021). Average time to union was 7.8 (5.4 – 11.6) weeks for medialising MICO, 6.2 (4.6 to 7.9) weeks for lateralising MICO, and 6.1 (4.1 – 7.6) weeks for Zadek MICO. All the MICO healed radiologically and clinically. Five (8%) patients (Medialising, n = 2; Lateralising n =2; Zadek, n =1) reported transient sural nerve paraesthesia following surgery. Wound problems developed in 5 patients (Lateralising, n =3; Zadek, n =2). The number of total complications were as follow: Medialising, n = 5, Lateralising, n = 7 and Zadek, n =5. Average length of stay was as follows: Medialising, 2(0-8) days; Lateralising, 1(0-3) day and Zadek, 1(0-3) day. Conclusion: Minimally invasive calcaneal osteotomy was safe with a high union rate and low complication rates and length of stay across all 3 common osteotomies. The average calcaneal displacement was significantly less for lateralising than medialising which is similar to reported figures for open osteotomy. Wound problems were more likely for lateralising and Zadek MICO compared to medialising and this could be because of how the osteotomies are shifted

Does nerve injury following minimally invasive calcaneal osteotomy clinically correlate to Talusan’s Zone?

Category: Hindfoot Introduction/Purpose: Talusan et al (FAI, 2005) described a safe zone for neural structures in medial displacement calcaneal osteotomy following a cadaveric and radiographic investigation. The safe zone was determined to be within the area 11.2 ± 2.7 mm anterior to the landmark line which is from the plantar fascia origin through the center of the posterosuperior aspect of the calcaneal tuberosity. Minimally invasive calcaneal osteotomies been gaining in popularity as it minimises soft tissue disruption and surgical morbidity. However, neural structures are at risk on both the medial and lateral side of the foot during this procedure. We aim to correlate our clinical results with Talusan’s Radiographic Zone (TRZ) following minimally invasive calcaneal osteotomies. Methods: Sixty-three calcaneal osteotomies were performed in our unit from 2010 and 2016. The type of osteotomies was as follows: Medialising, n = 34; Lateralising n =15; Zadek (Dorsal closing wedge), n =13; and Dwyer (lateral closing wedge), n = 1. Clinical data were recorded with any nerve injury noted. The calcaneal osteotomies were graded into whether they fell into TRZ. We also evaluated Talusan’s alternative method which he described and is based on alternative line 60% of the distance from the angle of Gissane to the tip of most posterior aspect of the calcaneal tuberosity where the safe zone is a window 5.6 mm anterior to this. Results: Five (8%) patients (Medialising, n = 2; Lateralising n =2; Zadek, n =1) reported sural nerve paraesthesia following surgery in our series. However, this was transient and they recovered fully. In total, seven patients (Medialising, n = 4; Lateralising n =1; Zadek, n =1; Dwyer, n=1) fell outside TRZ in our series, of which 2 reported transient sural nerve paraesthesia. Based on our results, TRZ clinically correlated with nerve injury (Chi square test, p=0.032). The other three patients who reported sural nerve paraesthesia but fell inside TRZ measured on average 10.4 mm from the landmark line (10.2, 10.4, 10.7 mm). However when we used the alternative method, they all fell outside the safe zone of this alternative line. Conclusion: Our results suggest that TRZ clinically correlated with nerve injury. However, the alternative line (where the safe zone is a window 5.6 mm anterior to this line) might be more accurate than the landmark line (where the safe zone is 11.2 ± 2.7 mm anterior to this line). More clinical studies with larger numbers might be required to confirm this

Survivorship and risk factors for revision of metal-on-metal hip resurfacing: a long-term follow-up study

Aims: Metal-on-metal hip resurfacing (MoM-HR) has seen decreased usage due to safety and longevity concerns. Joint registries have highlighted the risks in females, smaller hips, and hip dysplasia. This study aimed to identify if reported risk factors are linked to revision in a long-term follow-up of MoM-HR performed by a non-designer surgeon. Methods: A retrospective review of consecutive MoM hip arthroplasties (MoM-HRAs) using Birmingham Hip Resurfacing was conducted. Data on procedure side, indication, implant sizes and orientation, highest blood cobalt and chromium ion concentrations, and all-cause revision were collected from local and UK National Joint Registry records. Results: A total of 243 hips (205 patients (163 male, 80 female; mean age at surgery 55.3 years (range 25.7 to 75.3)) with MoM-HRA performed between April 2003 and October 2020 were included. Mean follow-up was 11.2 years (range 0.3 to 17.8). Osteoarthritis was the most common indication (93.8%), and 13 hips (5.3%; 7M:6F) showed dysplasia (lateral centre-edge angle < 25°). Acetabular cups were implanted at a median of 45.4° abduction (interquartile range 41.9° - 48.3°) and stems neutral or valgus to the native neck-shaft angle. In all, 11 hips (4.5%; one male, ten females) in ten patients underwent revision surgery at a mean of 7.4 years (range 2.8 to 14.2), giving a cumulative survival rate of 94.8% (95% confidence interval (CI) 91.6% to 98.0%) at ten years, and 93.4% (95% CI 89.3% to 97.6%) at 17 years. For aseptic revision, male survivorship was 100% at 17 years, and 89.6% (95% CI 83.1% to 96.7%) at ten and 17 years for females. Increased metal ion levels were implicated in 50% of female revisions, with the remaining being revised for unexplained pain or avascular necrosis. Conclusion: The Birmingham MoM-HR showed 100% survivorship in males, exceeding the National Institute for Health and Care Excellence ‘5% at ten years’ threshold. Female sex and small component sizes are independent risk factors. Dysplasia alone is not a contraindication to resurfacing. Cite this article: Bone Jt Open 2023;4(11):853–858

Endocytosis by Random Initiation and Stabilization of Clathrin-Coated Pits

Clathrin-coated vesicles carry traffic from the plasma membrane to endosomes. We report here the real-time visualization of cargo sorting and endocytosis by clathrin-coated pits in living cells. We have detected the formation of coats by monitoring incorporation of fluorescently tagged clathrin or its adaptor AP-2; we have also followed clathrin-mediated uptake of transferrin and of single LDL or reovirus particles. The intensity of a cargo-loaded clathrin cluster grows steadily during its lifetime, and the time required to complete assembly is proportional to the size of the cargo particle. These results are consistent with a nucleation-growth mechanism and an approximately constant growth rate. There are no strongly preferred nucleation sites. A proportion of the nucleation events are weak and short lived. Cargo incorporation occurs primarily or exclusively in a newly formed coated pit. Our data lead to a model in which coated pits initiate randomly but collapse unless stabilized, perhaps by cargo capture.