Physical inactivity and knee osteoarthritis in guinea pigs.

OBJECTIVE: To investigate whether and how a sedentary lifestyle contributes to knee osteoarthritis (OA) incidence and severity. DESIGN: An experiment was conducted using Hartley guinea pigs, an established idiopathic knee OA model. To simulate a sedentary lifestyle, growing animals (n = 18) were housed for 22 weeks in small cages that restricted their mobility, while another group of animals (n = 17) received daily treadmill exercise to simulate moderate physical activity. After the experiment, histological assessments, biochemical assays, and mechanical testing were conducted to compare tibial articular cartilage structure, strength, and degree of OA degeneration between sedentary and physically active animals. Groups were also compared based on body weight and composition, as well as gut microbial community composition assessed using fecal 16S rRNA gene sequencing. RESULTS: Prevalence of knee OA was similar between sedentary and physically active animals, but severity of the disease (cartilage lesion depth) was substantially greater in the sedentary group (P = 0.02). In addition, during the experiment, sedentary animals developed cartilage with lower aggrecan quantity (P = 0.03) and accumulated more body weight (P = 0.005) and visceral adiposity (P = 0.007). Groups did not differ greatly, however, in terms of cartilage thickness, collagen quantity, or stiffness, nor in terms of muscle weight, subcutaneous adiposity, or gut microbial community composition. CONCLUSIONS: Our findings indicate that a sedentary lifestyle promotes the development of knee OA, particularly by enhancing disease severity rather than risk of onset, and this potentially occurs through multiple pathways including by engendering growth of functionally deficient joint tissues and the accumulation of excess body weight and adiposity.

Sustained efficacy of a single intra-articular dose of FX006 in a rat model of repeated localized knee arthritis.

OBJECTIVE: To evaluate the efficacy of a single intra-articular (IA) dose of FX006, an extended-release formulation of triamcinolone acetonide (TCA) in poly(lactic-co-glycolic acid) (PLGA) microspheres, on the sequelae of repeated episodes of synovitis. DESIGN: Three flares of localized synovitis in the right knee of rats were induced over 4 weeks following a single IA injection of various doses of FX006, Kenalog(®) (TCA immediate release or TCA IR), or vehicle. Gait scores were employed to assess analgesic effect, and the joints were evaluated by histology at the end of the study. TCA plasma concentrations and corticosterone levels were monitored through the study. RESULTS: A single IA dose of 0.28 mg FX006 significantly improved gait scores through all three reactivations. TCA IR at 0.06 mg (providing comparable plasma TCA exposure, 10-fold higher Cmax) demonstrated comparable benefit through the first reactivation only and reduced-to-no efficacy thereafter. Significantly improved histological joint scores were observed with effective doses of FX006 but not with TCA IR. Corticosterone levels were initially decreased following both TCA IR and FX006 treatment, but recovered by Day 14. CONCLUSIONS: In localized, repeated synovitis in rats, sustained release of TCA following a single IA injection of FX006 significantly prolonged analgesia relative to TCA IR and significantly improved histological scores with no adverse effect on the HPA axis. Since synovitis can contribute to the pathophysiology of multiple joint diseases such as osteoarthritis (OA), RA and gout, FX006 may be an important treatment option for these conditions.

The OARSI histopathology initiative - recommendations for histological assessments of osteoarthritis in the rat.

OBJECTIVE: During the development of disease-modifying osteoarthritis (OA) drugs, rat models of OA are frequently used for a first assessment of in vivo efficacy. The most efficacious compound in the rat model may then be tested in a larger animal model before entering human trials. The aim of this study was to describe a histologic scoring system for use in different models of OA in rats that allows standardization and comparison of results obtained by different investigators. METHODS: The experience of the authors with current scoring systems and the range of lesions observed in rat and human OA studies were considered in recommending this common paradigm for rat histologic scoring. Considerations were made for reproducibility and ease of use for new scorers. Additional scoring paradigms may be employed to further identify specific effects of some disease-modifying drugs. RESULTS: Although the described scoring system is more complex than the modified Mankin scores, which are recommended for some other species, the reliability study showed that it is easily understood and can be reproducibly used, even by inexperienced scorers. CONCLUSIONS: The scoring paradigm described here has been found to be sufficiently sensitive to discriminate between treatments and to have high reproducibility. Therefore we recommend its use for evaluation of different rat OA models as well as assessment of disease-modifying effects of treatments in these models.

Protective effects of a cathepsin K inhibitor, SB-553484, in the canine partial medial meniscectomy model of osteoarthritis.

OBJECTIVE: Cathepsin K (cat K), a cysteine protease expressed in osteoclasts, chondrocytes and synovial fibroblasts, degrades several bone and cartilage matrix components suggesting its potential role in osteoarthritis (OA). We investigated the effects of SB-553484, an inhibitor of cat K, on lesion severity and biomarkers of collagen degradation in the canine partial medial meniscectomy model. METHODS: A partial medial meniscectomy was performed in mature female beagle dogs. Animals were dosed orally with vehicle or SB-553484 at 50mg/kg BID for 28 days. The femorotibial joints were evaluated for gross and microscopic histological changes. Biomarkers of collagen degradation were also analyzed. RESULTS: In dogs treated with SB-553484, subjective gross and calculated degeneration scores decreased significantly by 29% and 46%, respectively. Histopathologic evaluation demonstrated that the summed tibial degeneration score decreased significantly by 21%. Inhibition of tibial cartilage degeneration was significant in zone 1 (32%) and the depth ratio of any tibial matrix change was decreased significantly by 28%. Urinary biomarkers of bone and cartilage degradation were also significantly reduced. CONCLUSION: Treatment with SB-553484 resulted in mild to moderate beneficial effects on gross and histopathological parameters. Reduction of biomarkers of collagen type I and II degradation indicated a direct effect of the compound on bone and cartilage. These data suggest that the prevention of cartilage degradation by cat K inhibition may represent a valid strategy for pharmacological intervention in OA and that monitoring collagen degradation biomarkers may provide an indication of the protective effects of inhibition of bone and cartilage degradation.

Fibroblast growth factor-18 stimulates chondrogenesis and cartilage repair in a rat model of injury-induced osteoarthritis.

OBJECTIVE: Osteoarthritis (OA) is the most common form of arthritis and a primary cause of disability, however, there are no treatments that can slow disease progression or repair damaged joint cartilage. Fibroblast growth factor-18 (FGF18) has been reported to have significant anabolic effects on cartilage. We therefore examined its effects on repair of cartilage damage in a rat meniscal tear model of OA. DESIGN: Surgical damage to the meniscus in rats leads to joint instability and significant damage to the articular cartilage at 3 weeks post-surgery. At this time, animals received bi-weekly intra-articular injections of FGF18 for 3 weeks, and the knee joints were then harvested for histologic examination. RESULTS: FGF18-induced dose-dependent increases in cartilage thickness of the tibial plateau, due to new cartilage formation at the articular surface and the joint periphery. The generation of new cartilage resulted in significant reductions in cartilage degeneration scores. The highest dose of FGF18 also induced an increase in chondrophyte size and increased remodeling of the subchondral bone. CONCLUSIONS: The results of this study demonstrate that FGF18 can stimulate repair of damaged cartilage in a setting of rapidly progressive OA in rats.

Induction of osteoarthritis in the rat by surgical tear of the meniscus: Inhibition of joint damage by a matrix metalloproteinase inhibitor.

OBJECTIVE: Characterize a model of osteoarthritis (OA) induced by a surgically transecting the medial collateral ligament and meniscus. Evaluate the effectiveness of a matrix metalloproteinase (MMP) inhibitor in this model. METHODS: The medial collateral ligament of the right knee of rats was transected and a single full thickness cut was made through meniscus. Rats were sacrificed at various times after the surgery to assess the severity of gross cartilage damage using an image analyser and microscopically by histology. The effect of an MMP inhibitor in this model was assessed by administering compound twice daily for the 21 days and evaluating gross and histological joint damage at day 21. The in vitro potency of the MMP inhibitor (MMPI) against a panel of human recombinant MMPs was assessed kinetically using a quenched fluorescent substrate. RESULTS: Surgical transection of the medial collateral ligament and meniscus resulted in a time dependent increase in the severity of the cartilage lesion (depth) as measured histologically but only a slight increase in the area of the lesion as assessed grossly by image analysis. Administration of a MMPI orally twice daily (b.i.d.) at 25mg/kg to rats in the meniscal tear model resulted in significant inhibition of cartilage degradation and osteophyte formation (total joint score) of 39+/-7% (mean+/-S.E.M., from four separate experiments). CONCLUSION: These results demonstrate that MMP inhibition is effective in reducing the joint damage that occurs in the meniscal tear model of OA and support a potential therapeutic role for MMP inhibition in the treatment of human OA.

Animal models of osteoarthritis in an era of molecular biology.

Animal models of osteoarthritis (OA) are used to study the pathogenesis of cartilage degeneration and to evaluate potential anti-arthritic drugs for clinical use. In general, these models fall into 2 categories, spontaneous and induced (surgical instability or genetic manipulation). Animal models of naturally occurring OA occur in knee joints of guinea pigs, mice and Syrian hamsters. Commonly utilized surgical instability models include medial meniscal tear in guinea pigs and rats, medial or lateral partial meniscectomy in rabbits, medial partial or total meniscectomy or anterior cruciate transection in dogs. Transgenic models have been developed in mice. These models all have potential use in the study of molecular mechanisms associated with OA development via use of immunohistochemistry, biochemistry and molecular probes to identify altered matrix molecules at different stages in disease progression. Testing of specific types of inhibitors developed through evaluation of matrix changes in the disease process will ultimately help identify key processes which initiate and perpetuate the disease and will lead to discovery of new disease modifying pharmaceutical agents for OA patients. This paper will focus on the discussion of several models which are likely to be useful in the molecular dissection of processes involved in cartilage degeneration.

Animal models of osteoarthritis.

Animal models of osteoarthritis are used to study the pathogenesis of cartilage degeneration and to evaluate potential antiarthritic drugs for clinical use. Animal models of naturally occurring osteoarthritis (OA) occur in knee joints of guinea pigs, mice and other laboratory animal species. Transgenic models have been developed in mice. Commonly utilized surgical instability models include medial meniscal tear in guinea pigs and rats, medial or lateral partial meniscectomy in rabbits, medial partial or total meniscectomy or anterior cruciate transection in dogs. Additional models of cartilage degeneration can be induced by intra-articular iodoacetate injection or by administration of oral or parenteral quinolone antibiotics. None of these models have a proven track record of predicting efficacy in human disease since there are no agents that have been proven to provide anything other than symptomatic relief in human OA. However, agents that are active in these models are currently in clinical trials. Methodologies, gross and histopathologic features and comparisons to human disease will be discussed for the various models.

Phase I/II trial of recombinant methionyl human tumor necrosis factor binding protein PEGylated dimer in patients with active refractory rheumatoid arthritis.

OBJECTIVE: To evaluate the safety, immunogenicity, pharmacokinetics, and efficacy of intravenous administration of tumor necrosis factor binding protein (TNFbp) dimer in patients with rheumatoid arthritis (RA). METHODS: This phase I/II study was a multicenter, randomized, double blind, placebo controlled, ascending dose study evaluating TNFbp dimer administered by i.v. infusion. Thirty-three patients with RA divided into 3 cohorts received TNFbp dimer (30, 100, 300 microg/kg) or placebo during a 5 min infusion at baseline and at 3 and 6 weeks; patients were followed at routine intervals after each infusion through 77 days postinfusion. Pharmacokinetics were analyzed using a log-linear regimen and comparisons were made between half-life after first, 2nd, and 3rd doses. Plasma TNFbp dimer concentrations and serum antibody levels were used in the measurement of pharmacokinetics. RESULTS: Administration of 30 microg/kg of TNFbp dimer was generally well tolerated; the maximum tolerated dose was 100 microg/kg. No serious adverse events were reported. A significant antibody response affected the half-life and clearance of TNFbp dimer at each dose group. Anti-TNFbp antibodies were noncytotoxic and nonagonistic. Clinical evaluations provided evidence of in vivo activity of TNFbp dimer in these patients. CONCLUSION: TNFbp dimer administered to patients with long standing RA resulted in significant antibody production to the study drug. This effect reduced the half-life and clearance of the TNFbp. This TNFbp will not be a viable option for treating patients with RA secondary to immunogenicity.

Pharmacologic actions of the second generation leukotriene B4 receptor antagonist LY29311: in vivo pulmonary studies.

We examined the in vivo actions of LY293111 sodium (2-[2-propyl-3-[3-[2-ethyl-4-(4-fluorophenyl)-5-hydroxyphenoxy]pro poxy]phenoxy] benzoic acid sodium salt). Guinea pigs were used to evaluate the effect of this agent on (1) acute airway obstruction produced by intravenous leukotriene B4, (2) pulmonary granulocyte infiltration and delayed onset airway obstruction resulting from a 4-h leukotriene B4 inhalation and (3) lung inflammation after aerosol challenge with the divalent cationic ionophore A23187 (6S-[6alpha(2S*,3S*),8beta(R*),9beta,11alpha]-5- (methylamino)-2-[[3,9,11-trimethyl-8-[1-methyl-2-oxo-2-(1H-pyrrol-2-yl)e thyl]-1,7-dioxaspiro[5.5]undec-2-yl]methyl]-4-benzoxazole carboxylic acid). Airway obstruction was quantitated using pulmonary gas trapping measurements and lung inflammation was evaluated by bronchoalveolar lavage (BAL) and histology. LY293111 sodium produced a dose-related inhibition of acute leukotriene B4-induced airway obstruction when administered i.v. (ED50=14 microg/kg) or p.o. (ED50=0.4 mg/kg). In contrast, LY293111 sodium did not inhibit the pulmonary gas trapping caused by aerosols of histamine, leukotriene D4, or the thromboxane mimetic U46619 (15 [(S)-hydroxy11a,9a-(epoxymethano)prosta-5Z,13E-dienoic acid]). Oral LY293111 sodium inhibited leukotriene B4-induced bronchoalveolar lavage granulocyte infiltration and delayed onset airway obstruction at doses as low as 0.3 mg/kg. In A23187-challenged animals, pulmonary inflammation was markedly inhibited at 1 h, but not 2 h and 4 h post-exposure. We conclude that LY293 11 sodium is a selective leukotriene B4 receptor antagonist with potent pulmonary anti-inflammatory activity.

Combination benefit of treatment with the cytokine inhibitors interleukin-1 receptor antagonist and PEGylated soluble tumor necrosis factor receptor type I in animal models of rheumatoid arthritis.

OBJECTIVE: To determine the potential for additive or synergistic effects of combination therapy with the recombinant anticytokine agents interleukin-1 receptor antagonist (IL-1Ra) and PEGylated soluble tumor necrosis factor receptor type I (PEG sTNFRI) in established type H collagen-induced arthritis (CIA) and developing adjuvant-induced arthritis (AIA) in rats. METHODS: Rats with established CIA or developing AIA were treated with various doses of IL-1Ra in a slow-release hyaluronic acid vehicle or with PEG sTNFRI, either alone or in combination with the IL-1Ra. The effects of treatment were monitored by sequential caliper measurements of the ankle joints or hind paw volumes, final paw weights, and histologic evaluation with particular emphasis on bone and cartilage lesions. RESULTS: Combination therapy with IL-1Ra and PEG sTNFRI in rats with CIA resulted in an additive effect on clinical and histologic parameters when moderately to highly efficacious doses of each protein were administered. Greater-than-additive effects were seen when an inactive dose of IL-1Ra was given in combination with moderately to minimally active doses of PEG sTNFRI. Plasma levels associated with the latter effect (for both proteins) were similar to those seen in rheumatoid arthritis (RA) patients in clinical trials with these agents. Combination therapy in the AIA model generally resulted in additive effects, but some parameters showed a greater-than-additive benefit. CONCLUSION: The results provide preclinical support for the hypothesis that IL-1Ra administered in combination with PEG sTNFRI might provide substantially more clinical benefit to RA patients than either agent alone at blood levels that are currently achievable in patients.

Effects of PEGylated soluble tumor necrosis factor receptor type I (PEG sTNF-RI) alone and in combination with methotrexate in adjuvant arthritic rats.

OBJECTIVE: To determine the potential combination benefit of treatment with PEG sTNF-RI and methotrexate in adjuvant arthritic rats. METHODS: Lewis rats with adjuvant arthritis were treated by sc injections of either 3.0 or 0.3 mg/kg PEG sTNF-RI on days 9, 11, and 13 of adjuvant arthritis. The effects of PEG sTNF-RI treatment alone were compared to treatment with daily oral methotrexate (0.075, 0.06 or 0.045 mg/kg) or methotrexate in combination with PEG sTNF-RI. Efficacy was monitored by volume measurement of ankle joints, final paw weights and histologic evaluation with particular emphasis on bone lesions. RESULTS: Treatment with 3.0 or 0.3 mg/kg PEG sTNF-RI alone resulted in 52% or 28% inhibition, respectively, of paw swelling as assessed by final paw weight. Treatment with methotrexate at either 0.075, 0.06, or 0.045 mg/kg gave 84%, 51% or 18% inhibition and combination treatment resulted in additive inhibitory effects. Histologic evaluation of ankle joints demonstrated 68% or 25% inhibition of bone resorption with PEG sTNF-RI alone at 3.0 or 0.3 mg/kg. Treatment with 0.075, 0.06 or 0.045 mg/kg methotrexate resulted in 98%, 76% or 40% inhibition of bone resorption. Additive benefit was best seen with the lower doses of methotrexate. CONCLUSION: Combination therapy with PEG sTNF-RI and methotrexate results in additive benefit, with the final result being excellent inhibition of all arthritis parameters. Data from these studies supports the clinical investigation of the use of combination therapy of PEG sTNF-RI and methotrexate in rheumatoid arthritis patients.

Combination benefit of PEGylated soluble tumor necrosis factor receptor type I (PEG sTNF-RI) and dexamethasone or indomethacin in adjuvant arthritic rats.

OBJECTIVE: To determine the potential combination benefit receptor of treatment with PEGylated soluble tumor necrosis factor type I (PEG sTNF-RI) and dexamethasone (dex) or indomethacin (indo) in adjuvant arthritic rats. SUBJECTS: 160 male Lewis Rats. TREATMENT: PEG sTNF-RI, dex, indo. METHODS: Rats with adjuvant arthritis were given daily oral dex (0.025 or 0.006 mg/kg) or indo (0.5 or 0.25 mg/kg) day 9-14, alone or in combination with PEG sTNF-RI (sc on days 9, 11, and 13 of arthritis). Efficacy was monitored by volume measurement of ankle joints, final paw weights and histologic evaluation with particular emphasis on bone lesions. RESULTS: Treatment with 1 mg/kg PEG sTNF-RI alone resulted in 27% inhibition of final paw weights, dex alone (0.025 mg/kg) gave 25% inhibition and the combination resulted in 58% inhibition. Histologic evaluation of ankle joints demonstrated 48% inhibition of bone resorption with PEG sTNF-RI alone, 55% inhibition with dex alone and the combination treatment inhibited bone resorption by 100%. Inactive doses of PEG sTNF-RI (0.3 mg/kg) and dex (0.006 mg/kg) when combined resulted in 39% inhibition of paw swelling (AUC) and 39% inhibition of bone resorption. Combination treatment with indomethacin resulted in slight additive effects on inflammation parameters but no additive effects on bone resorption. CONCLUSION: Combination therapy with PEG sTNF-RI and dexamethasone results in additive or synergistic effects depending on the dose. Combination therapy with indomethacin resulted in slight additive effects on paw swelling parameters, but no additive benefit on bone resorption. Data from these studies support the clinical investigation of the use of combination therapy of PEG sTNF-RI and dex or other corticosteroids in rheumatoid arthritis patients.

Regulatory decision strategy for entry of a novel biological therapeutic with a clinically unmonitorable toxicity into clinical trials: pre-IND meetings and a case example.

The following material was derived from a synthesis of case histories taken from investigational new drug (IND) applications and drug sponsors' experiences, utilizing fictionalized data to avoid any resemblance to any proprietary information; any such resemblance is accidental. These examples are used as an instructional scenario to illustrate appropriate handling of a difficult toxicology issue. In this scenario, a drug caused a toxicity in animals that was detected only by histopathologic analysis; if it were to develop in patients, no conventional clinical methods could be identified to monitor for it. It is not unusual for a firm to cancel clinical development plans for a lead drug candidate that causes such a toxicity, especially if such a drug is intended for use as a chronic therapeutic in a population of patients with a chronic disease. This case synthesis was inspired by a Food and Drug Administration (FDA) agreement to allow such a product to proceed into clinical trials after substantive pre-IND discussions and agreement on well-considered toxicology program designs. The scientists most closely involved in the strategy development included the sponsor's toxicologist, veterinary toxicologic pathologist, and pharmacokineticist, as well as the FDA's reviewing pharmacologist. The basis of this decision was thorough toxicity characterization (1-month studies in 2 species); correlating toxicities with a particular cumulative area under the curve (AUC) in both species; identification of the most sensitive species (the species that showed the lower AUC correlating with toxicity); allometric assessment of clearance of the drug in 3 nonhuman species; construction of a model of human kinetics (based on extrapolation from animal kinetics); and finally, estimation of clinical safety factors (ratios of the human estimated cumulative AUC at the proposed clinical doses, over the animal cumulative AUC that correlated with the no adverse effect levels). Industry and FDA scientists negotiated a joint assessment of risk and benefit in patients, resulting in the FDA permitting such a compound to enter into clinical trials for a serious autoimmune disease. Such constructive, early communication starts with the pre-IND meeting, and the conduct and planning for this meeting can be very important in establishing smooth scientific and regulatory groundwork for the future of a drug under IND investigation.

Different roles of tumour necrosis factor alpha and interleukin 1 in murine streptococcal cell wall arthritis.

In this study two different aspects of tumour necrosis factor alpha (TNF-alpha) and interleukin 1 (IL-1) in locally induced murine streptococcal cell wall arthritis (SCW) were investigated. First, the kinetics and interdependence of TNF-alpha and IL-1 release; and second; their involvement in inflammation and cartilage destruction. Kinetic studies showed that the TNF-alpha peak level preceded the IL-1 peak level. However, in vivo neutralization of TNF-alpha did not result in decreased IL-1 bioactivity or immunoreactivity, suggesting that there is no dominant TNF-alpha-dependent IL-1 release in this model. Inflammation was studied by measuring knee joint swelling and inflammatory cell influx. Impact on cartilage was studied by measuring chondrocyte proteoglycan synthesis and cartilage proteoglycan depletion. The role of TNF-alpha in these phenomena was investigated using anti-TNF-alpha antibodies and tumour necrosis factor binding protein (TNFbp). Similarly, the role of IL-1 was studied using anti-IL-1 antibodies or IL-1 receptor antagonist (IL-1Ra). Anti-TNF-alpha treatment significantly reduced joint swelling, whereas this effect was not found by using anti-IL-1 or IL-1Ra. In contrast, neutralization of IL-1, but not TNF-alpha, resulted in a significant decrease of chondrocyte proteoglycan synthesis inhibition. Moreover, histology revealed that anti-IL-1 treatment reduced cartilage proteoglycan depletion and inflammatory cell influx. Combined anti-TNF-alpha/anti-IL-1 treatment significantly suppressed both inflammation and cartilage damage. However, the impact on these separate parameters did not exceed the effects of either anti-TNF-alpha or anti-TNF-1. It can be concluded that both TNF-alpha and IL-1 exert specific activities in SCW arthritis. The involvement of TNF-alpha in this model is limited to joint swelling, whereas IL-1 plays a dominant role in cartilage destruction and inflammatory cell influx.

Prevention of murine collagen-induced arthritis in the knee and ipsilateral paw by local expression of human interleukin-1 receptor antagonist protein in the knee.

OBJECTIVE: To determine the efficacy of local human interleukin-1 receptor antagonist (HuIL-1Ra) gene therapy in murine collagen-induced arthritis (CIA). METHODS: DBA/1 mice were immunized against bovine type II collagen. Before the onset of arthritis, NIH/3T3 fibroblasts transfected with pMFG-IRAP were transplanted into the knee cavity. Normal NIH/3T3 cells served as controls. Paws were evaluated macroscopically for redness, swelling, and deformities during the course of arthritis. Swelling of the knee joints was measured by external gamma counting of 99mtechnetium accumulation in the joint. Paws and knee joints were dissected and processed for histologic studies to evaluate inflammation and cartilage destruction. RESULTS: The NIH/3T3 fibroblasts survived in the joint cavity of DBA mice for at least 7 days. The transduced cells expressed immunoreactive and bioactive HuIL-1Ra in the knee joint, and produced sufficient amounts to block the effect of 1 ng of recombinant murine IL-1alpha on chondrocyte proteoglycan synthesis. The onset of CIA was almost completely prevented in knee joints containing HuIL-1Ra-producing cells, whereas joints containing normal cells showed severe inflammation and destruction of cartilage. Moreover, onset of CIA in the draining joints (ipsilateral paws) of the HuIL-1Ra gene-bearing knees was also prevented. CONCLUSION: Local production of HuIL-1Ra in the knee was able to ameliorate the effects of IL-1 on cartilage and could prevent the onset of CIA not only in that knee, but also in the "draining" paw. This indicates the feasibility of gene transfer as a therapeutic approach to modulating arthritis.

Aerosolized LTB4 produces delayed onset increases in pulmonary gas trapping.

Airway obstruction, as measured by increases in postmortem pulmonary gas trapping, and lung inflammatory changes were examined in guinea pigs exposed for up to 4 h to aerosols of leukotriene B4 (LTB4) or its non-chemotactic isomer, 6-trans-12-epi-LTB4. Airway obstruction and cytological responses in isomer-exposed animals were similar to those of unexposed control animals. LTB4-exposed animals had minimal inflammatory changes at 0.5 h but became dyspneic by 2 h and had increased airway obstruction, bronchoalveolar lavage neutrophils and eosinophils, and pulmonary tissue granulocyte scores. The LTB4-induced effects at 4 h were similar to those 2 h, except for further increase in BAL neutrophils and eosinophils. LTB4-induced airway obstructive and inflammatory changes were prevented by pretreatment with the LTB4 receptor antagonist SC-41930, but were unaffected by indomethacin. Thus, prolonged LTB4 inhalation can produce delayed onset airway obstruction that is stereospecific, cyclooxygenase-independent, and temporally associated with the influx of granulocytes into lung airways.

Hyperoxia increases airway cell S-phase traversal in immature rats in vivo.

Exposure of 21-day-old Sprague-Dawley rats to hyperoxia (> 95% O2 for 8 days) causes thickening of the airway epithelial and smooth muscle layers. To test the hypothesis that hyperoxic exposure increases airway layer DNA synthesis, we labeled the nuclei of cells undergoing S-phase by administering the thymidine analog bromodeoxyuridine (BrdU). BrdU was administered on days 3 and 4, 5 and 6, or 7 and 8 of air or O2 exposure, and the lungs were harvested immediately thereafter. Histologic sections were stained with an avidin-biotin-immunoperoxidase stain that revealed BrdU incorporation into nuclei, and a hematoxylin counterstain. After 4 days of air or O2 exposure, there was no difference in BrdU fractional labeling between control and hyperoxic animals. Thereafter, fractional BrdU labeling of the small airway (circumference < 1,000 microns) epithelium and smooth muscle layer was significantly increased in O2-exposed animals (P < 0.01, unpaired t test). The fractional labeling of larger, central airway smooth muscle layer cells was also increased after 8 days of O2 exposure (P < 0.01). In another cohort of O2-exposed animals, measurements of airway layer dimensions demonstrated increases in small airway epithelial and smooth muscle layer thickness that paralleled the time course seen for BrdU incorporation. We conclude that O2 exposure of immature rats increases airway epithelial and smooth muscle layer cellular DNA synthesis. These data suggest that hyperplasia of airway epithelial and smooth muscle layer cells may contribute to hyperoxia-induced airway remodeling.