R. Geoff Richards

Nanotopographical modification: a regulator of cellular function through focal adhesions

UNLABELLED As materials technology and the field of biomedical engineering advances, the role of cellular mechanisms, in particular adhesive interactions with implantable devices, becomes more relevant in both research and clinical practice. A key tenet of medical device design has evolved from the exquisite ability of biological systems to respond to topographical features or chemical stimuli, a process that has led to the development of next-generation biomaterials for a wide variety of clinical disorders. In vitro studies have identified nanoscale features as potent modulators of cellular behavior through the onset of focal adhesion formation. The focus of this review is on the recent developments concerning the role of nanoscale structures on integrin-mediated adhesion and cellular function with an emphasis on the generation of medical constructs with regenerative applications. FROM THE CLINICAL EDITOR In this review, recent developments related to the role of nanoscale structures on integrin-mediated adhesion and cellular function is discussed, with an emphasis on regenerative applications.

Concise review: Bone marrow-derived mesenchymal stem cells change phenotype following in vitro culture: implications for basic research and the clinic.

Mesenchymal stem cells (MSCs) are increasingly being used in tissue engineering and cell‐based therapies in all fields ranging from orthopedic to cardiovascular medicine. Despite years of research and numerous clinical trials, MSC therapies are still very much in development and not considered mainstream treatments. The majority of approaches rely on an in vitro cell expansion phase in monolayer to produce large cell numbers prior to implantation. It is clear from the literature that this in vitro expansion phase causes dramatic changes in MSC phenotype which has very significant implications for the development of effective therapies. Previous reviews have sought to better characterize these cells in their native and in vitro environments, described known stem cell interactions within the bone marrow, and discussed the use of innovative culture systems aiming to model the bone marrow stem cell niche. The purpose of this review is to provide an update on our knowledge of MSCs in their native environment, focusing on bone marrow‐derived MSCs. We provide a detailed description of the differences between naive cells and those that have been cultured in vitro and examine the effect of isolation and culture parameters on these phenotypic changes. We explore the concept of “one step” MSC therapy and discuss the potential cellular and clinical benefits. Finally, we describe recent work attempting to model the MSC bone marrow niche, with focus on both basic research and clinical applications and consider the challenges associated with these new generation culture systems. Stem Cells 2014;32:1713–1723

Analysis of Ebh, a 1.1-Megadalton Cell Wall-Associated Fibronectin-Binding Protein of Staphylococcus aureus

ABSTRACT In order for Staphylococcus aureus to adhere to host extracellular matrix (ECM) substrates, it elicits a wide range of surface proteins. We have characterized a novel ∼1.1-MDa protein in S. aureus, termed Ebh (for ECM-binding protein homologue), which has homology to other ECM-binding proteins. Ebh consists of several domains, including a large central region with 44 imperfect repeats of 126 amino acids. Expression analysis revealed ebh to be growth phase regulated and repressed by agr. A fragment of the central repeat region of Ebh was cloned, overexpressed, and used in ligand-binding studies to determine Ebh function. The recombinant protein was found to specifically bind human fibronectin. Ebh is produced during human infection since serum samples taken from patients with confirmed S. aureus infections were found to contain anti-Ebh antibodies. Localization studies revealed Ebh to be cell envelope associated and is proposed to form a specialized surface structure involved in cellular adhesion.

Surfaces to control tissue adhesion for osteosynthesis with metal implants: in vitro and in vivo studies to bring solutions to the patient

For internal fracture-fixation, metal currently remains the material of choice, since it provides strength for bone fragment support, good ductility for presurgical contouring and has been shown extensively to be biopassive. For decades, the application of metal internal fixators has proven undoubtedly successful and is deemed by many as the greatest advance in orthopedic medicine to date. However, based on this unrivalled success, newer and more challenging applications for metal internal fixators have emerged. For instance, given the large increase in the occurrence of these procedures in children and the different mechanical and biological requirements based on anatomical site of implantation, the functional requirements of metal implants have become increasingly more demanding. Given this changing demand for metal internal fixators, a more pragmatic application approach is necessary. Therefore, current metal internal fixator-related orthopedic research is based on defining specific cell and tissue responses to materials both in vitro and in vivo, as well as methods to empirically facilitate implantation site-specific tissue responses. This review discusses current knowledge from both the author’s as well as others’ laboratories pertaining to cell- and tissue-specific responses to metal internal-fixation materials, with specific emphasis on a surface microtopographical approach to alleviating removal-related morbidity. The review also describes the ‘effective roughness spectrum’ hypothesis for control of cell surface integration.

Phenotypic and genotypic characterisation of Staphylococcus aureus causing musculoskeletal infections.

One of the most common pathogens causing musculoskeletal infections remains Staphylococcus aureus. The aim of this multicentre study was to perform a phenotypic and genotypic characterisation of clinical S. aureus isolates recovered from musculoskeletal infections and to investigate differences between isolates cultured from Orthopaedic Implant Related Infections (OIRI) and those from Non-Implant Related Infections (NIRI). OIRI were further differentiated in two groups: Fracture Fixation-Device Infections (FFI) and Prosthetic Joint Infections (PJI). Three-hundred and five S. aureus strains were collected from 4 different Swiss and 2 French hospitals (FFI, n=112; PJI, n=105; NIRI, n=88). NIRI cases were composed of 27 Osteomyelitis (OM), 23 Diabetic Foot Infections (DFI), 27 Soft Tissue Infections (STI) and 11 postoperative Spinal Infections (SI). All isolates were tested for their ability to form biofilm, to produce staphyloxanthin and their haemolytic activity. They were typed by agr (accessory gene regulator) group, spa type and screened by PCR for the presence of genes of the most relevant virulence factors such as MSCRAMMs, Panton Valentine Leukotoxin (PVL), enterotoxins, exotoxins and toxic shock syndrome toxin. Overall, methicillin susceptible S. aureus (MSSA) was more prevalent than methicillin resistant S. aureus (MRSA) in this collection. The OIRI group trended towards a higher incidence of MRSA, gentamicin resistance and haemolysis activity than the NIRI group. Within the OIRI group, PJI isolates were more frequently strong biofilm formers than isolates from the FFI group. A statistically significant difference was observed between OIRI and NIRI isolates for the sdrE gene, the cna gene, the clfA gene and the bbp gene. Certain spa types (t230 and t041) with a specific genetic virulence pattern were only found in isolates cultured from OIRI. In conclusion, our study highlights significant trends regarding the virulence requirements displayed by S. aureus isolates associated with implant related infections in comparison to non-implant related infections. However, future studies including whole genome sequencing will be required to further examine genomic differences among the different infection cases.

Infection in fracture fixation: Can we influence infection rates through implant design?

Musculoskeletal infection is one of the most common complications associated with surgical fixation of bones fractured during trauma. These infections usually involve bacterial colonisation and biofilm formation on the fracture fixation device itself, as well as infection of the surrounding tissues. Antibiotic prophylaxis, wound debridement and postsurgical care can reduce the incidence of, but do not prevent, these infections. Much research and development has been focussed on ways to further reduce the incidence of infection and in the following short review we describe our experiences investigating the contribution of the basic design of fracture fixation devices on the susceptibility to infection. It has been shown in animal studies that device size, shape, mode of action and material and topography play an interrelated role in the susceptibility to infection. Although direct extrapolation from animal studies to the clinical setting is difficult, close consideration of the design factors that can reduce the incidence of infection in animal models is expected to help minimise the incidence of infection associated with any clinically implemented fracture fixation device.

A doxycycline-loaded polymer-lipid encapsulation matrix coating for the prevention of implant-related osteomyelitis due to doxycycline-resistant methicillin-resistant Staphylococcus aureus.

Implant-associated bone infections caused by antibiotic-resistant pathogens pose significant clinical challenges to treating physicians. Prophylactic strategies that act against resistant organisms, such as methicillin-resistant Staphylococcus aureus (MRSA), are urgently required. In the present study, we investigated the efficacy of a biodegradable Polymer-Lipid Encapsulation MatriX (PLEX) loaded with the antibiotic doxycycline as a local prophylactic strategy against implant-associated osteomyelitis. Activity was tested against both a doxycycline-susceptible (doxy(S)) methicillin-susceptible S. aureus (MSSA) as well as a doxycycline-resistant (doxy(R)) methicillin-resistant S. aureus (MRSA). In vitro elution studies revealed that 25% of the doxycycline was released from the PLEX-coated implants within the first day, followed by a 3% release per day up to day 28. The released doxycycline was highly effective against doxy(S) MSSA for at least 14days in vitro. A bolus injection of doxycycline mimicking a one day release from the PLEX-coating reduced, but did not eliminate, mouse subcutaneous implant-associated infection (doxy(S) MSSA). In a rabbit intramedullary nail-related infection model, all rabbits receiving a PLEX-doxycycline-coated nail were culture negative in the doxy(S) MSSA-group and the surrounding bone displayed a normal physiological appearance in both histological sections and radiographs. In the doxy(R) MRSA inoculated rabbits, a statistically significant reduction in the number of culture-positive samples was observed for the PLEX-doxycycline-coated group when compared to the animals that had received an uncoated nail, although the reduction in bacterial burden did not reach statistical significance. In conclusion, the PLEX-doxycycline coating on titanium alloy implants provided complete protection against implant-associated MSSA osteomyelitis, and resulted in a significant reduction in the number of culture positive samples when challenged with a doxycycline-resistant MRSA.

Advances in biomaterials and surface technologies

Summary: Tremendous advances in quality, reliability, performance, and versatility of surgical instrumentation and devices have been achieved over the past 50 years using biomaterials. The global orthopaedic implant industry is expected to grow to

Sacral Bone Mass Distribution Assessed by Averaged Three-Dimensional CT Models: Implications for Pathogenesis and Treatment of Fragility Fractures of the Sacrum.

41.8 billion by 2016, driven primarily by advancements in implant designs, including materials that provide improved biocompatibility, durability, and expanded clinical applications. Biomaterials have evolved through 3 clinical “generations”: (1) “bio-inert materials,” (2) materials with intrinsic bioactivity and degradability, and (3) biomaterials that stimulate specific biological host responses. In all cases, surface modifications, including coatings, represent a key strategy for improvements in tissue-contacting properties. Surfaces continue to be a focus for many device improvements and for tissue interfacing, especially for many orthopaedic structural implants comprising metal and metal alloys. Progress in implant materials processing, coating technologies, and coating combinations with therapeutic agents provide new properties and functionalities to improve device-tissue integration and reduce foreign body reactions and infections. Performance criteria for these surface modifications success in clinical practice are daunting, and translation of several technologies from in vitro proof-of-concept to in vivo applications has proven challenging.

Anti-infective efficacy, cytocompatibility and biocompatibility of a 3D-printed osteoconductive composite scaffold functionalized with quaternized chitosan

BACKGROUND Fragility fractures of the sacrum are increasing in prevalence due to osteoporosis and epidemiological changes and are challenging in their treatment. They exhibit specific fracture patterns with unilateral or bilateral fractures lateral to the sacral foramina, and sometimes an additional transverse fracture leads to spinopelvic dissociation. The goal of this study was to assess sacral bone mass distribution and corresponding changes with decreased general bone mass. METHODS Clinical computed tomography (CT) scans of intact pelves in ninety-one individuals (mean age and standard deviation, 61.5 ± 11.3 years) were used to generate three-dimensional (3D) models of the sacrum averaging bone mass in Hounsfield units (HU). Individuals with decreased general bone mass were identified by measuring bone mass in L5 (group 1 with <100 HU; in contrast to group 2 with ≥100 HU). RESULTS In group 1, a large zone of negative Hounsfield units was located in the paraforaminal lateral region from S1 to S3. Along the trans-sacral corridors, a Hounsfield unit peak was observed laterally, corresponding to cortical bone of the auricular surface. The lowest Hounsfield unit values were found in the paraforaminal lateral region in the sacral ala. An intermediate level of bone mass was observed in the area of the vertebral bodies, which also demonstrated the largest difference between groups 1 and 2. Overall, the Hounsfield units were lower at S2 than S1. CONCLUSIONS The models of averaged bone mass in the sacrum revealed a distinct 3D distribution pattern. CLINICAL RELEVANCE The negative values in the paraforaminal lateral region may explain the specific fracture patterns in fragility fractures of the sacrum involving the lateral areas of the sacrum. Transverse fractures located between S1 and S2 leading to spinopelvic dissociation may occur because of decreased bone mass in S2. The largest difference between the studied groups was found in the vertebral bodies and might support the use of transsacral or cement-augmented implants.