3D Printing of Calcium Phosphate Ceramics for Bone Tissue Engineering and Drug Delivery

Additive manufacturing, also known as 3D printing, has emerged over the past 3 decades as a disruptive technology for rapid prototyping and manufacturing. Vat polymerization, powder bed fusion, material extrusion, and binder jetting are distinct technologies of additive manufacturing, which have been used in a wide variety of fields, including biomedical research and tissue engineering. The ability to print biocompatible, patient-specific geometries with controlled macro- and micro-pores, and to incorporate cells, drugs and proteins has made 3D-printing ideal for orthopaedic applications, such as bone grafting. Herein, we performed a systematic review examining the fabrication of calcium phosphate (CaP) ceramics by 3D printing, their biocompatibility in vitro, and their bone regenerative potential in vivo, as well as their use in localized delivery of bioactive molecules or cells. Understanding the advantages and limitations of the different 3D printing approaches, CaP materials, and bioactive additives through critical evaluation of in vitro and in vivo evidence of efficacy is essential for developing new classes of bone graft substitutes that can perform as well as autografts and allografts or even surpass the performance of these clinical standards.

Increased numbers of CD23(+) CD21(hi) Bin-like B cells in human reactive and rheumatoid arthritis lymph nodes

A unique population of CD23(+) CD21(high) B cells in inflamed nodes (Bin) has been shown to accumulate in lymph nodes (LNs) draining inflamed joints of TNF-transgenic (TNF-tg) mice. Bin cells contribute to arthritis flare in mice by distorting node architecture and hampering lymphatic flow, but their existence in human inflamed LNs has not yet been described. Here, we report the characterization of resident B-cell populations in fresh popliteal lymph nodes (PLNs) from patients with severe lower limb diseases (non-RA) and rheumatoid arthritis (RA) patients, and from banked, cryopreserved reactive and normal human LN single cell suspension samples. Bin-like B cells were shown to be significantly increased in reactive LNs, and strikingly elevated (>30% of total) in RA samples. Histopathology and immunofluorescence analyses were consistent with B follicular hyperplasia and histological alterations in RA vs. non-RA PLNs. This is the first description of Bin-like B cells in human inflamed LNs. Consistent with published mouse data, this population appears to be associated with inflammatory arthritis and distortion of LN architecture. Further analyses are necessary to assess the role of CD23(+) CD21(hi) Bin-like B cells in RA pathogenesis and arthritic flare.

Antioxidant impregnated ultra-high molecular weight polyethylene wear debris particles display increased bone remodeling and a superior osteogenic:osteolytic profile vs. conventional UHMWPE particles in a murine calvaria model

Periprosthetic osteolysis remains a major limitation of long-term successful total hip replacements with ultra-high molecular weight polyethylene (UHMWPE) bearings. As intra and extracellular reactive oxygen species are know to contribute to wear debris-induced osteoclastic bone resorption and decreased osteoblastic bone formation, antioxidant doped UHMWPE has emerged as an approach to reduce the osteolytic potential of wear debris and maintain coupled bone remodeling. To test this hypothesis in vivo, we evaluated the effects of crosslinked UHMWPE wear debris particles (AltrX(™) ), versus similar wear particles made from COVERNOX(™) containing UHMWPE (AOX(™) ), in an established murine calvaria model. Eight-week-old female C57B/6 mice (n = 10/Group) received a pre-op micro-CT scan prior to surgical implantation of the UHMWPE particles (2mg), or surgery without particles (sham). Dynamic labeling was performed by intraperitoneal injection of calcein on day 7 and alizarin on day 9, and the calvaria were harvested for micro-CT and histology on day 10. Surprisingly, we found that AOX particles induced significantly more bone resorption (1.72-fold) and osteoclast numbers (1.99-fold) vs. AltrX (p < 0.001). However, AOX also significantly induced 1.64-fold more new bone formation vs. AltrX (p < 0.01). Moreover, while the osteolytic:osteogenic ratio of both particles was very close to 1.0, which is indicative of coupled remodeling, AOX was more osteogenic (Slope = 1.13 ± 0.10 vs. 0.97 ± 0.10). Histomorphometry of the metabolically labeled undecalcified calvaria revealed a consistent trend of greater MAR in AOX vs. AltrX. Collectively, these results demonstrate that anti-oxidant impregnated UHMWPE particles have decreased osteolytic potential due to their increased osteogenic properties that support coupled bone remodeling. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:845-851, 2016.

Understanding Haemonchus contortus Better Through Genomics and Transcriptomics

Parasitic roundworms (nematodes) cause substantial mortality and morbidity in animals globally. The barber's pole worm, Haemonchus contortus, is one of the most economically significant parasitic nematodes of small ruminants worldwide. Although this and related nematodes can be controlled relatively well using anthelmintics, resistance against most drugs in common use has become a major problem. Until recently, almost nothing was known about the molecular biology of H. contortus on a global scale. This chapter gives a brief background on H. contortus and haemonchosis, immune responses, vaccine research, chemotherapeutics and current problems associated with drug resistance. It also describes progress in transcriptomics before the availability of H. contortus genomes and the challenges associated with such work. It then reviews major progress on the two draft genomes and developmental transcriptomes of H. contortus, and summarizes their implications for the molecular biology of this worm in both the free-living and the parasitic stages of its life cycle. The chapter concludes by considering how genomics and transcriptomics can accelerate research on Haemonchus and related parasites, and can enable the development of new interventions against haemonchosis.

Orthopaedic device-related infection: current and future interventions for improved prevention and treatment

Orthopaedic and trauma device-related infection (ODRI) remains one of the major complications in modern trauma and orthopaedic surgery.Despite best practice in medical and surgical management, neither prophylaxis nor treatment of ODRI is effective in all cases, leading to infections that negatively impact clinical outcome and significantly increase healthcare expenditure.The following review summarises the microbiological profile of modern ODRI, the impact antibiotic resistance has on treatment outcomes, and some of the principles and weaknesses of the current systemic and local antibiotic delivery strategies.The emerging novel strategies aimed at preventing or treating ODRI will be reviewed. Particular attention will be paid to the potential for clinical impact in the coming decades, when such interventions are likely to be critically important.The review focuses on this problem from an interdisciplinary perspective, including basic science innovations and best practice in infectious disease. Cite this article: Moriarty TF, Kuehl R, Coenye T, et al. Orthopaedic device related infection: current and future interventions for improved prevention and treatment. EFORT Open Rev 2016;1:89-99. DOI: 10.1302/2058-5241.1.000037.

Lymphatic endothelial cells efferent to inflamed joints produce iNOS and inhibit lymphatic vessel contraction and drainage in TNF-induced arthritis in mice

Background

In this study, we sought to determine the cellular source of inducible nitric oxide synthase (iNOS) induced in lymphatic endothelial cells (LECs) in response to tumor necrosis factor (TNF), the effects of iNOS on lymphatic smooth muscle cell (LSMC) function and on the development of arthritis in TNF-transgenic (TNF-Tg) mice, and whether iNOS inhibitors improve lymphatic function and reduce joint destruction in inflammatory erosive arthritis.

Methods

We used quantitative polymerase chain reactions, immunohistochemistry, histology, and near-infrared imaging to examine (1) iNOS expression in podoplanin + LECs and lymphatic vessels from wild-type (WT) and TNF-Tg mice, (2) iNOS induction by TNF in WT LECs, (3) the effects of iNOS inhibitors on expression of functional muscle genes in LSMCs, and (4) the effects of iNOS inhibitors on lymphatic vessel contraction and drainage, as well as the severity of arthritis, in TNF-Tg mice.

Results

LECs from TNF-Tg mice had eight fold higher iNOS messenger RNA levels than WT cells, and iNOS expression was confirmed immunohistochemically in podoplanin + LECs in lymphatic vessels from inflamed joints. TNF (0.1 ng/ml) increased iNOS levels 40-fold in LECs. LSMCs cocultured with LECs pretreated with TNF had reduced expression of functional muscle genes. This reduction was prevented by ferulic acid, which blocked nitric oxide production. Local injection of L-N⁶-(1-iminoethyl)lysine 5-tetrazole-amide into inflamed paws of TNF-Tg mice resulted in recovery of lymphatic vessel contractions and drainage. Treatment of TNF-Tg mice with ferulic acid reduced synovial inflammation as well as cartilage and bone erosion, and it also restored lymphatic contraction and drainage.

Conclusions

iNOS is produced primarily by LECs in lymphatic vessel efferent from inflamed joints of TNF-Tg mice in response to TNF and inhibits LSMC contraction and lymph drainage. Ferulic acid represents a potential new therapy to restore lymphatic function and thus improve inflammatory arthritis by inhibiting local production of nitric oxide by LSMCs.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-016-0963-8) contains supplementary material, which is available to authorized users.

Analysis of new bone, cartilage, and fibrosis tissue in healing murine allografts using whole slide imaging and a new automated histomorphometric algorithm

Histomorphometric analysis of histologic sections of normal and diseased bone samples, such as healing allografts and fractures, is widely used in bone research. However, the utility of traditional semi-automated methods is limited because they are labor-intensive and can have high interobserver variability depending upon the parameters being assessed, and primary data cannot be re-analyzed automatically. Automated histomorphometry has long been recognized as a solution for these issues, and recently has become more feasible with the development of digital whole slide imaging and computerized image analysis systems that can interact with digital slides. Here, we describe the development and validation of an automated application (algorithm) using Visiopharm’s image analysis system to quantify newly formed bone, cartilage, and fibrous tissue in healing murine femoral allografts in high-quality digital images of H&E/alcian blue-stained decalcified histologic sections. To validate this algorithm, we compared the results obtained independently using OsteoMeasure^TM and Visiopharm image analysis systems. The intraclass correlation coefficient between Visiopharm and OsteoMeasure was very close to one for all tissue elements tested, indicating nearly perfect reproducibility across methods. This new algorithm represents an accurate and labor-efficient method to quantify bone, cartilage, and fibrous tissue in healing mouse allografts.

Controlling Arteriogenesis and Mast Cells Are Central to Bioengineering Solutions for Critical Bone Defect Repair Using Allografts

Although most fractures heal, critical defects in bone fail due to aberrant differentiation of mesenchymal stem cells towards fibrosis rather than osteogenesis. While conventional bioengineering solutions to this problem have focused on enhancing angiogenesis, which is required for bone formation, recent studies have shown that fibrotic non-unions are associated with arteriogenesis in the center of the defect and accumulation of mast cells around large blood vessels. Recently, recombinant parathyroid hormone (rPTH; teriparatide; Forteo) therapy have shown to have anti-fibrotic effects on non-unions and critical bone defects due to inhibition of arteriogenesis and mast cell numbers within the healing bone. As this new direction holds great promise towards a solution for significant clinical hurdles in craniofacial reconstruction and limb salvage procedures, this work reviews the current state of the field, and provides insights as to how teriparatide therapy could be used as an adjuvant for healing critical defects in bone. Finally, as teriparatide therapy is contraindicated in the setting of cancer, which constitutes a large subset of these patients, we describe early findings of adjuvant therapies that may present future promise by directly inhibiting arteriogenesis and mast cell accumulation at the defect site.

Biomaterials approaches to treating implant-associated osteomyelitis

Orthopaedic devices are the most common surgical devices associated with implant-related infections and Staphylococcus aureus (S. aureus) is the most common causative pathogen in chronic bone infections (osteomyelitis). Treatment of these chronic bone infections often involves combinations of antibiotics given systemically and locally to the affected site via a biomaterial spacer. The gold standard biomaterial for local antibiotic delivery against osteomyelitis, poly(methyl methacrylate) (PMMA) bone cement, bears many limitations. Such shortcomings include limited antibiotic release, incompatibility with many antimicrobial agents, and the need for follow-up surgeries to remove the non-biodegradable cement before surgical reconstruction of the lost bone. Therefore, extensive research pursuits are targeting alternative, biodegradable materials to replace PMMA in osteomyelitis applications. Herein, we provide an overview of the primary clinical treatment strategies and emerging biodegradable materials that may be employed for management of implant-related osteomyelitis. We performed a systematic review of experimental biomaterials systems that have been evaluated for treating established S. aureus osteomyelitis in an animal model. Many experimental biomaterials were not decisively more efficacious for infection management than PMMA when delivering the same antibiotic. However, alternative biomaterials have reduced the number of follow-up surgeries, enhanced the antimicrobial efficacy by delivering agents that are incompatible with PMMA, and regenerated bone in an infected defect. Understanding the advantages, limitations, and potential for clinical translation of each biomaterial, along with the conditions under which it was evaluated (e.g. animal model), is critical for surgeons and researchers to navigate the plethora of options for local antibiotic delivery.

3D printed bioceramics for dual antibiotic delivery to treat implant-associated bone infection

Surgical implant-associated bone infections (osteomyelitis) have severe clinical and socioeconomic consequences. Treatment of chronic bone infections often involves antibiotics given systemically and locally to the affected site in poly (methyl methacrylate) (PMMA) bone cement. Given the high antibiotic concentrations required to affect bacteria in biofilm, local delivery is important to achieve high doses at the infection site. PMMA is not suitable to locally-deliver some biofilm-specific antibiotics, including rifampin, due to interference with PMMA polymerisation. To examine the efficacy of localised, combinational antibiotic delivery compared to PMMA standards, we fabricated rifampin- and vancomycin-laden calcium phosphate scaffolds (CPS) by three-dimensional (3D) printing to treat an implant-associated Staphylococcus aureus bone infection in a murine model. All vancomycin- and rifampin-laden CPS treatments significantly reduced the bacterial burden compared with vancomycin-laden PMMA. The bones were bacteria culture negative in 50 % of the mice that received sustained release vancomycin- and rifampin-laden CPS. In contrast, 100 % of the bones treated with vancomycin monotherapy using PMMA or CPS were culture positive. Yet, the monotherapy CPS significantly reduced the bacterial metabolic load following revision compared to PMMA. Biofilm persisted on the fixation hardware, but the infection-induced bone destruction was significantly reduced by local rifampin delivery. These data demonstrate that, despite the challenging implant-retaining infection model, co-delivery of rifampin and vancomycin from 3D printed CPS, which is not possible with PMMA, significantly improved the outcomes of implant-associated osteomyelitis. However, biofilm persistence on the fixation hardware reaffirms the importance of implant exchange or other biofilm eradication strategies to complement local antibiotics.

TGF-β1 Suppresses Plasmin and MMP Activity in Flexor Tendon Cells via PAI-1: Implications for Scarless Flexor Tendon Repair

Flexor tendon injuries caused by deep lacerations to the hands are a challenging problem as they often result in debilitating adhesions that prevent the movement of the afflicted fingers. Evidence exists that tendon adhesions as well as scarring throughout the body are largely precipitated by the pleiotropic growth factor, Transforming Growth Factor Beta 1(TGF-β1), but the effects of TGF-β1 are poorly understood in tendon healing. Using an in vitro model of tendon healing, we previously found that TGF-β1 causes gene expression changes in tenocytes that are consistent with scar tissue and adhesion formation, including upregulation of the anti-fibrinolytic protein, PAI-1. Therefore, we hypothesized that TGF-β1 contributes to scarring and adhesions by reducing the activity of proteases responsible for ECM degradation and remodeling, such as plasmin and MMPs, via upregulation of PAI-1. To test our hypothesis, we examined the effects of TGF-β1 on the protease activity of tendon cells. We found that flexor tendon tenocytes treated with TGF-β1 had significantly reduced levels of active MMP-2 and plasmin. Interestingly, the effects of TGF-β1 on protease activity were completely abolished in tendon cells from homozygous plasminogen activator inhibitor 1 (PAI-1) knockout (KO) mice, which are unable to express PAI-1. Our findings support the hypothesis that TGF-β1 induces PAI-1, which suppresses plasmin and plasmin-mediated MMP activity, and provide evidence that PAI-1 may be a novel therapeutic target for preventing adhesions and promoting a scarless, regenerative repair of flexor tendon injuries.

Increased Insulin mRNA Binding Protein-3 Expression Correlates with Vascular Enhancement of Renal Cell Carcinoma by Intravenous Contrast-CT and is Associated with Bone Metastasis

Purpose

To: 1) assess the correlation between CT vascularity and a candidate molecular marker of RCC metastasis (insulin-like mRNA binding protein-3 (IMP3)); and 2) demonstrate the differential expression of IMP3 in high vs. low vascular tumors.

Experimental design

Retrospectively obtained contrast CT from 72 patients with primary RCC were used to establish threshold values for Low, Intermediate and High tumor vascularity. Paired histopathology specimens from 33 of these patients were used for immunohistochemistry (IHC) to correlate CT with IMP-3 expression. IMP-3 gene expression studies were performed on RCC and poorly vascular prostate cancer (PC) human bone metastases samples to confirm presence of IMP3 in metastatic samples from RCC. Gene expression studies were performed on RCC 786-O and PC3 cell lines to confirm the presence of high expression of IMP3 in the RCC cell line.

Results

IMP-3 expression positively correlated with CT vascular enhancement (p<0.01). IMP3 expression by IHC was strongly positive in all RCC, but weak in PC bone metastases. Real time RT-PCR demonstrated a significant 4-fold increase in imp-3 expression in RCC 786-O vs. PC3 cells in vitro (p<0.001).

Conclusion

Quantitation of pre-operative CT is a feasible method to phenotype primary RCC vascularity, which correlates with IMP-3 expression. In situ and cell line studies demonstrate an association between high IMP-3 expression and RCC bone metastasis. Studies aimed at defining the diagnostic potential of biomarkers for RCC bone metastasis, and functional significance of IMP-3 in RCC vascularity and tumor progression are warranted.

Quantifying the natural history of biofilm formation in vivo during the establishment of chronic implant-associated Staphylococcus aureus osteomyelitis in mice to identify critical pathogen and host factors

While it is well known that Staphylococcus aureus establishes chronic implant-associated osteomyelitis by generating and persisting in biofilm, research to elucidate pathogen, and host specific factors controlling this process has been limited due to the absence of a quantitative in vivo model. To address this, we developed a murine tibia implant model with ex vivo region of interest (ROI) imaging analysis by scanning electron microscopy (SEM). Implants were coated with Staphylococcus aureus strains (SH1000, UAMS-1, USA300LAC) with distinct in vitro biofilm phenotypes, were used to infect C57BL/6 or Balb/c mice. In contrast to their in vitro biofilm phenotype, results from all bacteria strains in vivo were similar, and demonstrated that biofilm on the implant is established within the first day, followed by a robust proliferation phase peaking on Day 3 in Balb/c mice, and persisting until Day 7 in C57BL/6 mice, as detected by SEM and bioluminescent imaging. Biofilm formation peaked at Day 14, covering ∼40% of the ROI coincident with massive agr-dependent bacterial emigration, as evidenced by large numbers of empty lacunae with few residual bacteria, which were largely culture negative (80%) and PCR positive (87.5%), supporting the clinical relevance of this implant model.

TNF signals are dispensable for the generation of CD23+ CD21/35-high CD1d-high B cells in inflamed lymph nodes

Tumor necrosis factor (TNF) is a key cytokine in rheumatoid arthritis (RA) pathogenesis, as underscored by the clinical effectiveness of TNF antagonists. While several of TNF's key targets in RA are well understood, its many pleiotropic effects remain to be elucidated. TNF-transgenic mice develop inflammatory-erosive arthritis associated with disruption of draining lymph node histology and function, and accumulation of B cells with unique phenotypic and functional features consistent with contribution to pathogenesis (B cells in inflamed nodes, Bin). Bin cell induction depends on the inflamed microenvironment, but the specific signals are unknown. Using anti-TNF treatment and TNF-receptor-deficient mice, here we show that Bin cells are induced and maintained independently of B cell-intrinsic TNF signals.

Validation of power Doppler versus contrast-enhanced magnetic resonance imaging quantification of joint inflammation in murine inflammatory arthritis

Contrast-enhancement magnetic resonance imaging (CE-MRI) of synovial volume is the radiographic gold standard to quantify joint inflammation; however, cost limits its use. Therefore, we examined if power Doppler-ultrasound (PD-US) outcomes of synovitis in tumor necrosis factor transgenic (TNF-Tg) mice correlate with CE-MRI. TNF-Tg mice underwent PD-US of their knees to measure the joint space volume (JSV) and power Doppler volume (PDV), and the results were correlated with synovial volume determined by CE-MRI. Immunohistochemistry for CD31 was performed to corroborate the PD signal. Synovial volume strongly correlated with both JSV and PDV (p < 0.01). CD31(+) blood vessels were observed in inflamed synovium proximal to the joint surface, which corresponded to areas of intense PD signals. JSV and PDV are valid measures of joint inflammation that correlate with synovial volume determined by CE-MRI and are associated with vascularity. Given the emergence of PD-US as a nonquantitative outcome of joint inflammation, we find JSV and PDV to be feasible and highly cost-effective for longitudinal studies in animal models. Furthermore, given the increasing use of PD-US in standard clinical practice, JSV and PDV could be translated to better quantify joint flare and response to therapy in patients with rheumatoid arthritis (RA).

Loss of the PGE2 receptor EP1 enhances bone acquisition, which protects against age and ovariectomy-induced impairments in bone strength

PGE2 exerts anabolic and catabolic effects on bone through the discrete actions of four prostanoid receptors (EP1-4). We have previously demonstrated that loss EP1 accelerates fracture repair by enhancing bone formation. In the present study we defined the role of EP1 in bone maintenance and homeostasis during aging and in response to ovariectomy. The femur and L4 vertebrae of wild type (WT) and EP1(-/-) mice were examined at 2-months, 6-months, and 1-year of age, and in WT and EP1(-/-) mice following ovariectomy (OVX) or sham surgery. Bone volume fraction, trabecular architecture and mechanical properties were maintained during aging in EP1(-/-) mice to a greater degree than age-matched WT mice. Moreover, significant increases in bone formation rate (BFR) (+60%) and mineral apposition rate (MAR) (+50%) were observed in EP1(-/-), relative to WT, while no change in osteoclast number and osteoclast surface were observed. Following OVX, loss of EP1 was protective against bone loss in both femur and L4 vertebrae, with increased bone volume/total volume (BV/TV) (+32% in femur) and max load at failure (+10% in femur) relative to WT OVX, likely resulting from the increased bone formation rate that was observed in these mice. Taken together these studies identify inhibition of EP1 as a potential therapeutic approach to suppress bone loss in aged or post-menopausal patients.

A novel murine model of established Staphylococcal bone infection in the presence of a fracture fixation plate to study therapies utilizing antibiotic-laden spacers after revision surgery

Mice are the small animal model of choice in biomedical research due to the low cost and availability of genetically engineered lines. However, the devices utilized in current mouse models of implant-associated bone infection have been limited to intramedullary or trans-cortical pins, which are not amenable to treatments involving extensive debridement of a full-thickness bone loss and placement of a segmental antibiotic spacer. To overcome these limitations, we developed a clinically faithful model that utilizes a locking fracture fixation plate to enable debridement of an infected segmental bone defect (full-thickness osteotomy) during a revision surgery, and investigated the therapeutic effects of placing an antibiotic-laden spacer in the segmental bone defect. To first determine the ideal time point for revision following infection, a 0.7 mm osteotomy in the femoral mid-shaft was stabilized with a radiolucent PEEK fixation plate. The defect was inoculated with bioluminescent Staphylococcus aureus, and the infection was monitored over 14 days by bioluminescent imaging (BLI). Osteolysis and reactive bone formation were assessed by X-ray and micro-computed tomography (micro-CT). The active bacterial infection peaked by 5 days post-inoculation, however the stability of the implant fixation became compromised by 10-14 days post-inoculation due to osteolysis around the screws. Thus, day 7 was defined as the ideal time point to perform the revision surgery. During the revision surgery, the infected tissue was debrided and the osteotomy was widened to 3mm to place a poly-methyl methacrylate spacer, with or without vancomycin. Half of the groups also received systemic vancomycin for the remaining 21 days of the study. The viable bacteria remaining at the end of the study were measured using colony forming unit assays. Volumetric bone changes (osteolysis and reactive bone formation) were directly measured using micro-CT image analysis. Mice that were treated with local or systemic vancomycin did not display gross pathology at the end of the study. While localized vancomycin delivery alone tended to decrease the bacterial burden and osteolysis, these effects were only significant when combined with systemic antibiotic therapy. This novel mouse model replicates key features of implant-associated osteomyelitis that make treatment extremely difficult, such as biofilm formation and osteolysis, and imitates the clinical practice of placing an antibiotic-laden spacer after infected tissue debridement. In addition, the model demonstrates the limitations of current PMMA spacers and could be an invaluable tool for evaluating alternative antimicrobial treatments for implant-associated bone infection.

The role of the lymphatic system in inflammatory-erosive arthritis

Rheumatoid arthritis (RA) is a prevalent inflammatory joint disease with enigmatic flares, which causes swelling, pain, and irreversible connective tissue damage. Recently, it has been demonstrated in murine models of RA that the popliteal lymph node (PLN) is a biomarker of arthritic flare, as it "expands" in size and contrast enhancement during a prolonged asymptomatic phase, prior to when it "collapses" with accelerated synovitis and joint erosion. This PLN collapse is associated with adjacent knee flare, decreases in PLN volume and contrast enhancement, lymphatic pulse and pumping pressure, and an increase in PLN pressure. Currently, it is known that PLN collapse is accompanied by a translocation of B cells from the follicles to the sinuses, effectively clogging the lymphatic sinuses of the PLN, and that B cell depletion therapy ameliorates arthritic flare by eliminating these B cells and restoring passive lymphatic flow from inflamed joints. Here we review the technological advances that have launched this area of research, describe future directions to help elucidate the potential mechanism of PLN collapse, and speculate on clinical translation towards new diagnostics and therapies for RA.

Are biologic treatments a potential approach to wear- and corrosion-related problems?

WHERE ARE WE NOW?: Biological treatments, defined as any nonsurgical intervention whose primary mechanism of action is reducing the host response to wear and/or corrosion products, have long been postulated as solutions for osteolysis and aseptic loosening of total joint arthroplasties. Despite extensive research on drugs that target the inflammatory, osteoclastic, and osteogenic responses to wear debris, no biological treatment has emerged as an approved therapy. We review the extensive preclinical research and modest clinical research to date, which has led to the central conclusion that the osteoclast is the primary target. We also allude to the significant changes in health care, unabated safety concerns about chronic immunosuppressive/antiinflammatory therapies, industry's complete lack of interest in developing an intervention for this condition, and the practical issues that have narrowly focused the possibilities for a biologic treatment for wear debris-induced osteolysis. WHERE DO WE NEED TO GO?: Based on the conclusions from research, and the economic, regulatory, and practical issues that limit the future directions toward the development of a biologic treatment, there are a few rational approaches that warrant investigation. These largely focus on FDA-approved osteoporosis therapies that target the osteoclast (bisphosphonates and anti-RANK ligand) and recombinant parathyroid hormone (teriparatide) prophylactic treatment to increase osseous integration of the prosthesis to overcome high-risk susceptibility to aseptic loosening. The other roadblock that must be overcome if there is to be an approved biologic therapy to prevent the progression of periprosthetic osteolysis and aseptic loosening is the development of radiological measures that can quantify a significant drug effect in a randomized, placebo-controlled clinical trial. We review the progress of volumetric quantification of osteolysis in animal studies and clinical pilots. HOW DO WE GET THERE?: Accepting the aforementioned rigid boundaries, we describe the emergence of repurposing FDA-approved drugs for new indications and public (National Institutes of Health, FDA, Centers for Disease Control and Prevention) and private (universities and drug and device manufactures) partnerships as the future roadmap for clinical translation. In the case of biologic treatments for wear debris-induced osteolysis, this will involve combined federal and industry funding of multicenter clinical trials that will be run by thought leaders at large medical centers.

Divergent gene activation in peripheral blood and tissues of patients with rheumatoid arthritis, psoriatic arthritis and psoriasis following infliximab therapy

Objective

The immune inflammatory disorders rheumatoid arthritis (RA), psoriatic arthritis (PsA) and psoriasis (Ps) share common pathologic features and show responsiveness to anti-tumor necrosis factor (TNF) agents yet they are phenotypically distinct. The aim of this study was to examine if anti-TNF therapy is associated with divergent gene expression profiles in circulating cells and target tissues of patients with these diseases.

Methods

Peripheral blood CD14⁺ and CD14⁻ cells were isolated from 9 RA, 12 PsA and 10 Ps patients before and after infliximab (IFX) treatment. Paired synovial (n = 3, RA, PsA) and skin biopsies (n = 5, Ps) were also collected. Gene expression was analyzed by microarrays.

Results

26 out of 31 subjects responded to IFX. The transcriptional response of CD14⁺ cells to IFX was unique for the three diseases, with little overlap (<25%) in significantly changed gene lists (with PsA having the largest number of changed genes). In Ps, altered gene expression was more pronounced in lesional skin (relative to paired, healthy skin) compared to blood (relative to healthy controls). Marked suppression of up-regulated genes in affected skin was noted 2 weeks after therapy but the expression patterns differed from uninvolved skin. Divergent patterns of expression were noted between the blood cells and skin or synovial tissues in individual patients. Functions that promote cell differentiation, proliferation and apoptosis in all three diseases were enriched. RA was enriched in functions in CD14⁻ cells, PsA in CD14⁺ cells and Ps in both CD14⁺ and CD14⁻ cells, however, the specific functions showed little overlap in the 3 disorders.

Conclusion

Divergent patterns of altered gene expression are observed in RA, PsA and Ps patients in blood cells and target organs in IFX responders. Differential gene expression profiles in the blood do not correlate with those in target organs.

Passive immunization with anti-glucosaminidase monoclonal antibodies protects mice from implant-associated osteomyelitis by mediating opsonophagocytosis of Staphylococcus aureus megaclusters

Towards the development of a methicillin-resistant Staphylococcus aureus (MRSA) vaccine we evaluated a neutralizing anti-glucosaminidase (Gmd) monoclonal antibody (1C11) in a murine model of implant-associated osteomyelitis, and compared its effects on LAC USA300 MRSA versus a placebo and a Gmd-deficient isogenic strain (ΔGmd). 1C11 significantly reduced infection severity, as determined by bioluminescent imaging of bacteria, micro-CT assessment of osteolysis, and histomorphometry of abscess numbers (p < 0.05). Histology also revealed infiltrating macrophages, and the complete lack of staphylococcal abscess communities (SAC), in marrow abscesses of 1C11 treated mice. In vitro, 1C11 had no direct effects on proliferation, but electron microscopy demonstrated that 1C11 treatment phenocopies ΔGmd defects in binary fission. Moreover, addition of 1C11 to MRSA cultures induced the formation of large bacterial aggregates (megaclusters) that sedimented out of solution, which was not observed in ΔGmd cultures or 1C11 treated cultures of a protein A-deficient strain (ΔSpa), suggesting that the combined effects of Gmd inhibition and antibody-mediated agglutination are required. Finally, we demonstrated that macrophage opsonophagocytosis of MRSA and megaclusters is significantly increased by 1C11 (p < 0.01). Collectively, these results suggest that the primary mechanism of anti-Gmd humoral immunity against MRSA osteomyelitis is macrophage invasion of Staphylococcal abscess communities (SAC) and opsonophagocytosis of megaclusters. .

Validation of GAITRite and PROMIS as high-throughput physical function outcome measures following ACL reconstruction

New healthcare demands for quality measures of elective procedures, such as anterior cruciate ligament (ACL) reconstructive surgery, warrant the establishment of high throughput outcomes for high volume clinics. To this end, we evaluated the PROMIS and GAITRite as physical function outcome measures to quantify early healing and post-operative complications in 106 patients at pre-operative and 3, 10, 20 and 52 weeks post-ACL reconstruction with bone-tendon-bone autograft, and compared the results to the current IKDC validated outcome measure. The results showed that both PROMIS and GAITRite were significantly quicker to administer versus IKDC (p<0.0001). Additional advantages were that PROMIS and GAITRite detected a significant decrease in physical function at 3 weeks post-operative, and a significant improvement at 10 weeks post-operative versus pre-operative (p<0.001), which were not detected with IKDC. GAITRite was limited by a low ceiling that could not detect improvement of physical function beyond 20 weeks, while both PROMIS and IKDC detected significant improvement out to 52 weeks post-operative (p<0.001). Linear regressions demonstrated a significant relationship between IKDC and PROMIS, with a combined correlation value of 0.8954 (p<0.001) for all time points. Finally, ROC curve analysis demonstrated that PROMIS is a diagnostic test for poor outcomes.

Aging periosteal progenitor cells have reduced regenerative responsiveness to bone injury and to the anabolic actions of PTH 1-34 treatment

A stabilized tibia fracture model was used in young (8-week old) and aged (1-year old) mice to define the relative bone regenerative potential and the relative responsiveness of the periosteal progenitor population with aging and PTH 1-34 (PTH) systemic therapy. Bone regeneration was assessed through gene expressions, radiographic imaging, histology/histomorphometry, and biomechanical testing. Radiographs and microCT showed increased calcified callus tissue and enhanced bone healing in young compared to aged mice. A key mechanism involved reduced proliferation, expansion, and differentiation of periosteal progenitor cell populations in aged mice. The experiments showed that PTH increased calcified callus tissue and torsional strength with a greater response in young mice. Histology and quantitative histomorphometry confirmed that PTH increased callus tissue area due primarily to an increase in bone formation, since minimal changes in cartilage and mesenchyme tissue area occurred. Periosteum examined at 3, 5, and 7 days showed that PTH increased cyclin D1 expression, the total number of cells in the periosteum, and width of the periosteal regenerative tissue. Gene expression showed that aging delayed differentiation of both bone and cartilage tissues during fracture healing. PTH resulted in sustained Col10a1 expression consistent with delayed chondrocyte maturation, but otherwise minimally altered cartilage gene expression. In contrast, PTH 1-34 stimulated expression of Runx2 and Osterix, but resulted in reduced Osteocalcin. β-Catenin staining was present in mesenchymal chondroprogenitors and chondrocytes in early fracture healing, but was most intense in osteoblastic cells at later times. PTH increased active β-catenin staining in the osteoblast populations of both young and aged mice, but had a lesser effect in cartilage. Altogether the findings show that reduced fracture healing in aging involves decreased proliferation and differentiation of stem cells lining the bone surface. While PTH 1-34 enhances the proliferation and expansion of the periosteal stem cell population and accelerates bone formation and fracture healing, the effects are proportionately reduced in aged mice compared to young mice. β-Catenin is induced by PTH in early and late fracture healing and is a potential target of PTH 1-34 effects.

Freeze-dried allograft-mediated gene or protein delivery of growth and differentiation factor 5 reduces reconstructed murine flexor tendon adhesions

Advances in allograft processing have opened new horizons for clinical adaptation of flexor tendon allografts as delivery scaffolds for antifibrotic therapeutics. Recombinant adeno-associated-virus (rAAV) gene delivery of the growth and differentiation factor 5 (GDF-5) has been previously associated with antifibrotic effects in a mouse model of flexor tendoplasty. In this study, we compared the effects of loading freeze-dried allografts with different doses of GDF-5 protein or rAAV-Gdf5 on flexor tendon healing and adhesions. We first optimized the protein and viral loading parameters using reverse transcription polymerase chain reaction (RT-PCR), enzyme-linked immunosorbent assay (ELISA), and in vivo bioluminescent imaging. We then reconstructed flexor digitorum longus (FDL) tendons of the mouse hindlimb with allografts loaded with low and high doses of recombinant GDF-5 protein and rAAV-Gdf5 and evaluated joint flexion and biomechanical properties of the reconstructed tendon. In vitro optimization studies determined that both the loading time and concentration of the growth factor and viral vector had dose-dependent effects on their retention on the freeze-dried allograft. In vivo data suggest that protein and gene delivery of GDF-5 had equivalent effects on improving joint flexion function, in the range of doses used. Within the doses tested, the lower doses of GDF-5 had more potent effects on suppressing adhesions without adversely affecting the strength of the repair. These findings indicate equivalent antifibrotic effects of Gdf5 gene and protein delivery, but suggest that localized delivery of this potent factor should also carefully consider the dosage used to eliminate untoward effects, regardless of the delivery mode.