Suppression of glomerulonephritis in lupus-prone NZB × NZW mice by RN486, a selective inhibitor of Bruton's tyrosine kinase.

OBJECTIVE: Bruton's tyrosine kinase (BTK) plays a critical role in B cell development and function. We recently described a selective BTK inhibitor, RN486, that blocks B cell receptor (BCR) and Fcγ receptor signaling and is efficacious in animal models of arthritis. The aim of this study was to examine the potential efficacy of BTK in systemic lupus erythematosus (SLE), using an NZB × NZW mouse model of spontaneous SLE. METHODS: Mice received RN486 or its vehicle (administered in chow) at a final concentration of 30 mg/kg for 8 weeks, starting at 32 weeks of age. RESULTS: The administration of RN486 completely stopped disease progression, as determined by histologic and functional analyses of glomerular nephritis. The efficacy was associated with striking inhibition of B cell activation, as demonstrated by a significant reduction in CD69 expression in response to BCR crosslinking. RN486 markedly reduced the secretion of IgG anti-double-stranded DNA (anti-dsDNA) secretion, as determined by enzyme-linked immunosorbent and enzyme-linked immunospot assays. Flow cytometric analysis demonstrated depletion of CD138(high) B220(low) plasma cells in the spleen. RN486 inhibited secretion of IgG anti-dsDNA but not IgM anti-dsDNA, suggesting that pharmacologic blockade of BTK resembles the reported transgenic expression of low levels of endogenous BTK in B cells. In addition, RN486 may also impact the effector function of autoantibodies, as evidenced by a significant reduction in immune complex-mediated activation of human monocytes in vitro and down-regulation of the expression of macrophage-related and interferon-inducible genes in both the kidneys and spleens of treated mice. CONCLUSION: Collectively, our data suggest that BTK inhibitors may simultaneously target autoantibody-producing and effector cells in SLE, thus constituting a promising therapeutic alternative for this disease.

Effects of hydroxyapatite on titanium foam as a bone ingrowth surface in acetabular shells: a canine study.

This study investigated a highly porous titanium foam with and without a PeriApetite coating as an alternative surface for implant fixation. Twelve mongrel canines received staged total hip replacements under International Animal Care and Use Committee (IACUC) approval from our institution. Animals were randomly placed in three- or six-month groups for sacrifice. Seventeen total hips were available for evaluation. The area and depth of ingrowth was measured by SEM. At three months, PeriApetite Ti foam had 37% more depth and almost 10% more bone ingrowth. Both groups were found not to be different at the six-month mark with over 36% of ingrowth calculated on SEM. The results prove not only that titanium foam is a viable ingrowth surface but also that PA coating can enhance the time to bony incorporation.

Tendon reattachment to a metallic implant using an allogenic bone plate augmented with rhOP-1 vs. autogenous cancellous bone and marrow in a canine model.

Functionality of endoprosthetic reconstruction may be improved through secure and lasting soft tissue reattachment directly to the metallic implant surface. Tendon reattachment to the metallic surface of a titanium implant (enhanced tendon anchor, ETA) using autogenous bone plate as an interpositional structure between the tendon and metal, augmented with autogenous bone chips and marrow, provided successful mechanical and functional outcome. However, preparation of the autogenous bone plate is not practical in a clinical setting, but application of an allogenic bone plate could be an alternative. The autogenous cancellous bone and marrow may also be substituted by bone growth factors so that no autogenous bone graft is required. We hypothesized that the reconstitution of the direct tendon-bone insertion morphology in tendon reattachment to metallic implant could be achieved using allogenic cancellous bone plate augmented with autogenous cancellous bone and marrow, and that the autogenous bone grafts could be replaced by recombinant human osteogenic protein-1 (rhOP-1). In two canine groups the supraspinatus tendon was reattached unilaterally to a modified ETA implant with a highly porous metallic surface known as Tritanium Dimensionalized Metal. Allogenic bone plates saturated with rhOP-1-collagen putty were used in the OP-1 (OP) group, while plates saturated with autogenous cancellous bone and marrow were used in the bone marrow (BM) group. Functional, radiographical, mechanical and histomorphological analysis results were compared between both groups. At 15 weeks, gait analysis showed 78% and 81% recovery of preoperative weight-bearing in OP and BM groups, respectively. The calcified area around the tendon in OP group was 5.2 times larger than that in BM group (p<0.001). The ultimate tensile strength of the reattachment was 24% and 38% of the intact contralateral side in OP and BM groups, respectively, without significant difference between them. There was evidence of tendon-bone insertion transitional zones, tissue ingrowth and adhesion to the metallic surface in both groups. In conclusion, the use of the allograft combined with rhOP-1 had a similar effect as combined with autogenous cancellous bone and marrow in the tendon reattachment to the metallic surface.

Ectopic bone formation using osteogenic protein-1 carried by a solution precipitated hydroxyapatite.

Solution precipitation of calcium and phosphate is a technique to generate hydroxyapatite [Peri-Apatitetrade mark (PA), Stryker Orthopaedics, Mahwah, NJ] on metal substrate. This study was carried out to determine the capacity of PA to adsorb osteogenic protein-1 (OP-1) and the time course of release, and to determine the osteoinductive activity of OP-1. The adsorption and release studies were conducted with (125)I-labeled OP-1- and PA-coated titanium alloy disks. The results indicate that the adsorption of OP-1 on the PA-coated disks is linear with the concentration of OP-1 up to 5 mg/mL. There is an initial release of 75% to 80% of adsorbed OP-1 within the first hour, and 92% of OP-1 is released in 3 days. The osteoinductive activity of OP-1 was determined in the rat intramuscular ectopic bone formation assay. A total of 24 titanium alloy disks were evenly divided into 3 groups with different treatments for implantation, plain disks (group A), disks coated with PA (group B), and disks coated with PA plus 40 microg OP-1 (group C). Osteogenic protein-1, 40 microg in solution, was injected into the muscle pouch in animals of group D (n = 8). The rats were sacrificed 3 weeks postoperatively and the implants were retrieved. Ectopic bone formation was evaluated with radiography and histology. Results demonstrated that OP-1 induced ectopic bone in all the animals of group C and group D. The titanium alloy disks were surrounded by trabecular bone and marrow tissue. None of the animals of group A or group B showed any evidence of osteoinduction. Our findings indicate that PA can deliver OP-1 directly to titanium alloy implants and maintain the osteoinductive activity of OP-1.

Osteogenic protein-1 enhances osseointegration of titanium implants coated with peri-apatite in rabbit femoral defect.

This study evaluated the effect of osteogenic protein-1 (OP-1) carried by Peri-Apatite (PA) on bone healing in the gap surrounding implants in a rabbit model. Cylindrical titanium implants (3 x 9 mm) were uniformly coated with PA precipitated from a calcium and phosphate solution. OP-1 solution containing 60 microg OP-1 was directly loaded on the implants immediately before implantation for the experimental group, whereas buffer solution was loaded on the implants for the control. The implant was placed in the distal femur and surrounded by a 1-mm gap. The implants were retrieved and examined 6 weeks after implantation. Mechanical testing (push-out) data showed that OP-1 enhanced implant fixation by 80%. Histomorphometric measurements indicated that bone ingrowth in the initial gap expressed as a percentage of the whole gap was significantly higher in the specimens treated with OP-1 than the control group (25.4% vs. 8.9%, p < 0.05). The percentage of the surface of implants, which was covered by bone, was significantly higher in the OP-1-treated group compared to the control group (65% vs. 25%, p < 0.05). This study suggests that OP-1 can be loaded on orthopedic implants through PA to enhance the osseointegration of orthopedic implant.