Matrix-Induced Autologous Chondrocyte Implantation (MACI) Using a Cell-Seeded Collagen Membrane Improves Cartilage Healing in the Equine Model.

BACKGROUND: Autologous chondrocyte implantation (ACI) using a collagen scaffold (matrix-induced ACI; MACI) is a next-generation approach to traditional ACI that provides the benefit of autologous cells and guided tissue regeneration using a biocompatible collagen scaffold. The MACI implant also has inherent advantages including surgical implantation via arthroscopy or miniarthrotomy, the elimination of periosteal harvest, and the use of tissue adhesive in lieu of sutures. This study evaluated the efficacy of the MACI implant in an equine full-thickness cartilage defect model at 1 year. METHODS: Autologous chondrocytes were seeded onto a collagen type-I/III membrane and implanted into one of two 15-mm defects in the femoral trochlear ridge of 24 horses. Control defects either were implanted with cell-free collagen type-I/III membrane (12 horses) or were left ungrafted as empty defects (12 horses). An additional 3 horses had both 15-mm defects remain empty as nonimplanted joints. The repair was scored by second-look arthroscopy (12 weeks), and necropsy examination (53 weeks). Healing was assessed by arthroscopic scoring, gross assessment, histology and immunohistology, cartilage matrix component assay, and gene expression determination. Toxicity was examined by prostaglandin E2 formation in joint fluid, and lymph node morphology combined with histologic screening of organs. RESULTS: MACI-implanted defects had improved gross healing and composite histologic scores, as well as increases in chondrocyte predominance, toluidine blue-stained matrix, and collagen type-II content compared with scaffold-only implanted or empty defects. There was minimal evidence of reaction to the implant in the synovial membrane (minor perivascular cuffing), subchondral bone, or cartilage. There were no adverse clinical effects, signs of organ toxicity, or evidence of chondrocytes or collagen type-I/III membrane in draining lymph nodes. CONCLUSIONS: The MACI implant appeared to improve cartilage healing in a critical-sized defect in the equine model compared with collagen matrix alone. CLINICAL RELEVANCE: These results indicate that the MACI implant is quick to insert, provides chondrocyte security in the defect, and improves cartilage healing compared with ACI.

Diagnosis of Tuberculosis in Three Zoo Elephants and a Human Contact - Oregon, 2013.

In 2013, public health officials in Multnomah County, Oregon, started an investigation of a tuberculosis (TB) outbreak among elephants and humans at a local zoo. The investigation ultimately identified three bull elephants with active TB and 118 human contacts of the elephants. Ninety-six (81%) contacts were evaluated, and seven close contacts were found to have latent TB infection. The three bulls were isolated and treated (elephants with TB typically are not euthanized) to prevent infection of other animals and humans, and persons with latent infection were offered treatment. Improved TB screening methods for elephants are needed to prevent exposure of human contacts.

Mechanical characterization of matrix-induced autologous chondrocyte implantation (MACI®) grafts in an equine model at 53 weeks.

There has been much interest in using autologous chondrocytes in combination with scaffold materials to aid in cartilage repair. In the present study, a total of 27 animals were used to compare the performance of matrix-assisted chondrocyte implantation (MACI®) using a collagen sponge as a chondrocyte delivery vehicle, the sponge membrane alone, and empty controls. A total of three distinct types of mechanical analyses were performed on repaired cartilage harvested from horses after 53 weeks of implantation: (1) compressive behavior of samples to measure aggregate modulus (HA) and hydraulic permeability (k) in confined compression; (2) local and global shear modulus using confocal strain mapping; and (3) boundary friction coefficient using a custom-built tribometer. Cartilage defects receiving MACI® implants had equilibrium modulus values that were 70% of normal cartilage, and were not statistically different than normal tissue. Defects filled with Maix™ membrane alone or left empty were only 46% and 51-63% of control, respectively. The shear modulus of tissue from all groups of cartilage defects were between 4 and 10 times lower than control tissue, and range from 0.2 to 0.4 MPa. The average values of boundary mode friction coefficients of control tissue from all groups ranged from 0.42 to 0.52. This study represents an extensive characterization of the mechanical performance of the MACI® grafts implant in a large animal model at 53 weeks. Collectively, these data demonstrate a range of implant performance, revealing similar compressive and frictional properties to native tissue, with inferior shear properties.

Overexpression of cystatin C in synovium does not reduce synovitis or cartilage degradation in established osteoarthritis.

INTRODUCTION: Cathepsin K (catK) expression is increased in cartilage, bone and synovium during osteoarthritis (OA). To study the role of catK expression and elevated cathepsin activity in the synovium on cartilage destruction in established OA, we overexpressed cystatin C (cysC), a natural cysteine protease inhibitor, in the synovium of rabbit OA joints. METHODS: The ability of cysC to inhibit activity of cathepsins in rabbit OA synovium lysates was tested in vitro using protease activity assay. In vivo, the tissue localization of recombinant adeno-associated virus (rAAV) with LacZ gene after intra-articular injection was determined by ß-galactosidase staining of rabbit joints 4 weeks later. To inhibit cathepsin activity in the synovium, a rAAV2-encoding cysC was delivered intra-articularly into rabbit joints 4 weeks after OA was induced by anterior cruciate ligament transection (ACLT). Seven weeks postinjection, endogenous catK and cysC levels as well as the vector-derived cysC expression in the synovium of normal and OA joints were examined by RNA quantification. Synovial cathepsin activity and catK, catB and catL protein levels were determined by activity and Western blot analyses, respectively. Synovitis and cartilage degradation were evaluated by histopathological scoring. RESULTS: In vitro, the ability of cysC to efficiently inhibit activity of purified catK and OA-induced cathepsins in rabbit synovial lysates was demonstrated. In vivo, the intra-articular delivery of rAAV2/LacZ showed transduction of mostly synovium. Induction of OA in rabbit joints resulted in fourfold increase in catK mRNA compared to sham controls while no change was detected in endogenous cysC mRNA levels in the synovium. Protein levels for catK, catB and catL were also increased in the synovium with a concomitant fourfold increase in cathepsin activity. Joints treated with rAAV2/cysC showed both detection of vector genomes and vector-derived cysC transcripts in the synovium. Production of functional cysC by the vector was demonstrated by complete block of cathepsin activity in the synovium. However, this did not decrease synovitis, bone sclerosis or progression of cartilage degradation. CONCLUSIONS: Increased production of natural cathepsin inhibitor, cysC, in OA synovium does not alleviate synovitis or cartilage pathology during a preexisting OA.

The degradation of chondrogenic pellets using cocultures of synovial fibroblasts and U937 cells.

Osteoarthritis (OA) of the knee is often characterized by joint space narrowing on X-ray, knee pain, and a loss of joint function through progressive cartilage degradation and intermittent synovial inflammation. The objective of this work was to develop an in vitro model in a clinically relevant system. Normal human synovial fibroblasts were cultured with U937 cells for 3 days then combined with a chondrogenic stem cell pellet for another 4 days. This culture system mimicked many of the aspects of early stage OA including production of cytokines and degradative enzymes, MMP-1 and MMP-3, resulting in a conditioned medium profile similar to OA synovial fluid. This catabolic environment resulted in the release of glycosaminoglycan (GAG) from the pellet. In a similar manner to early stage OA, the pellet had increased aggrecan and collagen II expression. All of these effects are hallmarks of early stage OA. This relatively simple tissue model containing a 3D cartilage component interacting with synoviocytes and macrophages could be useful to understand early causes and progression of OA. It can be scaled easily thus useful for high throughput screening of disease modifying drugs in a clinically relevant system.

Disease modification: promising targets and impediments to success.

Osteoarthritis (OA) is a significant and growing concern to a large segment of the population. Effective treatments for slowing or stopping the progression of the disease are not available despite a great deal of investment-backed effort on the part of academia, government, and the pharmaceutical industry. Target selection has been problematic. Progress may also have been hindered to some extent by the prevalent cartilage-centric view of OA. Significant clinical development challenges remain for novel therapeutics in this area. This review elaborates on the challenges of disease-modifying OA drug development and points out specific therapeutic intervention strategies recently tried or currently being pursued.

High-affinity VEGF antagonists by oligomerization of a minimal sequence VEGF-binding domain.

Vascular endothelial growth factor (VEGF) neutralizing antagonists including antibodies or receptor extracellular domain Fc fusions have been applied clinically to control angiogenesis in cancer, wet age-related macular degeneration, and edema. We report here the generation of high-affinity VEGF-binding domains by chemical linkage of the second domain of the VEGF receptor Flt-1 (D2) in several configurations. Recombinant D2 was expressed with a 13 a.a. C-terminal tag, including a C-terminal cysteine to enable its dimerization by disulfide bond formation or by attachment to divalent PEGs and oligomerization by coupling to multivalent PEGs. Disulfide-linked dimers produced by Cu(2+) oxidation of the free-thiol form of the protein demonstrated picomolar affinity for VEGF in solution, comparable to that of a D2-Fc fusion (sFLT01) and ~50-fold higher than monomeric D2, suggesting the 26 a.a. tag length between the two D2 domains permits simultaneous interaction of both faces of the VEGF homodimer. Extending the separation between the D2 domains by short PEG spacers from 0.35 kD to 5 kD produced a modest ~2-fold increase in affinity over the disulfide, thus defining the optimal distance between the two D2 domains for maximum affinity. By surface plasmon resonance (SPR), a larger (~5-fold) increase in affinity was observed by conjugation of the D2 monomer to the termini of 4-arm PEG, and yielding a product with a larger hydrodynamic radius than sFLT01. The higher affinity displayed by these D2 PEG tetramers than either D2 dimer or sFLT01 was largely a consequence of a slower rate of dissociation, suggesting the simultaneous binding by these tetramers to neighboring surface-bound VEGF. Finally, disulfide-linked D2 dimers showed a greater resistance to autocatalytic fragmentation than sFLT01 under elevated temperature stress, indicating such minimum-sequence constructs may be better suited for sustained-release formulations. Therefore, these constructs represent novel Fc-independent VEGF antagonists with ultrahigh affinity, high stability, and a range of hydrodynamic radii for application to multiple therapeutic targets.

Emerging drugs for osteoarthritis.

INTRODUCTION: Osteoarthritis (OA), the most prevalent form of joint disease, affects as much as 13% of the world's population. In the USA, it is the leading cause of disability in people over age 65 and is characterized by progressive cartilage loss, bone remodeling, osteophyte formation and synovial inflammation with resultant joint pain and disability. There are no treatments marketed for structural disease modification; current treatments mainly target symptoms, with > 75% of patients reporting need for additional symptomatic treatment. AREAS COVERED: Drugs in later development (Phase II - III) for OA pain and joint structural degeneration are reviewed. Topics that are not covered in this article are procedural-based (e.g., arthrocentesis, physical therapy), behavioral-based (e.g., weight loss, pain coping techniques) or device-based (e.g., knee braces, surgical implants) treatments. EXPERT OPINION: More in-depth understanding of the pathophysiology of the disease, as well as elucidation of the link between clinical symptomatology and structural changes in the joint will likely lead to the development of novel target classes with promising efficacy in the future. Efficacy notwithstanding, there remain significant hurdles to overcome in clinical development of these therapeutics, inherent in the progression pattern of the disease as well as challenges with readouts for both pain and structure modification trials.

Autologous chondrocyte implantation drives early chondrogenesis and organized repair in extensive full- and partial-thickness cartilage defects in an equine model.

Autologous chondrocyte implantation (ACI) has been used clinically for over 15 years and yet definitive evidence of chondrocyte persistence and direct impact on cartilage repair in full-thickness lesions is scant and no data are available on ACI in partial-thickness defects in any animal model. This study assessed the effect of chondrocytes secured using periosteal overlay in partial- and full-thickness cartilage defects in the equine model. Paired cartilage defects 15 mm in diameter were made in the patellofemoral joint of 16 horse and repaired with ACI or periosteal flap alone. Response was assessed at 8 weeks by clinical, microradiographic, and histologic appearance, and by collagen type II immunohistochemistry, and proteoglycan and DNA quantification. ACI improved histologic scores in partial- and full-thickness cartilage defects, including defect filling, attachment to the underlying subchondral bone, and presence of residual chondrocyte accumulations. For partial-thickness defects chondrocyte predominance, collagen type II content, and toluidine stained matrix were enhanced, and attachment to the surrounding cartilage improved. DNA and PG content of grafted partial-thickness defects was improved by chondrocyte implantation. Periosteal patches alone did not induce cartilage repair. This study indicated implantation of chondrocytes to cartilage defects improved healing with a combination of persisting chondrocyte regions, enhanced collagen type II formation, and better overall cartilage healing scores. Use of ACI in the more challenging partial-thickness defects also improved histologic indices and biochemical content. The equine model of cartilage healing closely resembles cartilage repair in man, and results of this study confirm cell persistence and improved early cartilage healing events after ACI.

STR/ort mice, a model for spontaneous osteoarthritis, exhibit elevated levels of both local and systemic inflammatory markers.

Osteoarthritis is a common joint disease that currently lacks disease-modifying treatments. Development of therapeutic agents for osteoarthritis requires better understanding of the disease and cost-effective in vivo models that mimic the human disease. Here, we analyzed the joints of STR/ort mice, a model for spontaneous osteoarthritis, for levels of inflammatory and oxidative stress markers and measured serum cytokines to characterize the local and systemic inflammatory status of these mice. Markers of low-grade inflammatory and oxidative stress-RAGE, AGE, S100A4, and HMGB1-were evaluated through immunohistochemistry. Of these, AGE and HMGB1 levels were elevated strongly in hyperplastic synovium, cartilage, meniscus, and ligaments in the joints of STR/ort mice compared with CBA mice, an osteoarthritis-resistant mouse strain. These increases (particularly in the synovium, meniscus, and ligaments) correlated with increased histopathologic changes in the cartilage. Serum analysis showed higher concentrations of several cytokines including IL1ß, IL12p70, MIP1ß, and IL5 in STR/ort mice, and these changes correlated with worsened joint morphology. These results indicate that STR/ort mice exhibited local and systemic proinflammatory conditions, both of which are present in human osteoarthritis. Therefore, the STR/ort mouse model appears to be a clinically relevant and cost-effective small animal model for testing osteoarthritis therapeutics.