Effect of Targeted Cytokine Inhibition on Progression of Post-Traumatic Osteoarthritis Following Intra-Articular Fracture.

Intra-articular fractures (IAF) result in significant and prolonged inflammation, increasing the chances of developing post-traumatic osteoarthritis (PTOA). Interleukin-one beta (IL-1ß) and Tumor Necrosis Factor-alpha (TNF-α) are key inflammatory factors shown to be involved in osteochondral degradation following IAF. As such, use of targeted biologics such as Infliximab (INX), a TNF-α inhibitor, and Anakinra (ANR), an interleukin-one (IL-1) receptor antagonist (IL1RA), may protect against PTOA by damping the inflammatory response to IAF and reducing osteochondral degradation. To test this hypothesis, IAFs were induced in the hindlimb knee joints of rats treated with INX at 10 mg/kg/day, ANR at 100 g/kg/day, or saline (vehicle control) by subcutaneous infusion for a period of two weeks and healing was evaluated at 8-weeks post injury. Serum and synovial fluid (SF) were analyzed for soluble factors. In-vivo microcomputed tomography (µCT) scans assessed bone mineral density and bone morphometry measurements. Cationic CA4+ agent assessed articular cartilage composition via ex vivo µCT. Scoring according to the Osteoarthritis Research Society International (OARSI) guidelines was performed on stained histologic tibia sections at the 56-day endpoint on a 0-6 scale. Systemically, ANR reduced many pro-inflammatory cytokines and reduced osteochondral degradation markers Cross Linked C-Telopeptide Of Type II (CTXII, p < 0.05) and tartrate-resistant acid phosphatase (TRAP, p < 0.05). ANR treatment resulted in increased chemokines; macrophage-chemotractant protein-1 (MCP-1), MPC-3, macrophage inhibitory protein 2 (MIP2) with a concomitant decrease in proinflammatory interleukin-17A (IL17A) at 14 days post-injury within the SF. Microcomputed tomography (µCT) at 56 days post-injury revealed ANR Treatment decreased epiphyseal degree of anisotropy (DA) (p < 0.05) relative to saline. No differences were found with OARSI scoring but contrast-enhanced µCT revealed a reduction in glycosaminoglycan content with ANR treatment. These findings suggest targeted cytokine inhibition, specifically IL-1 signaling, as a monotherapy has minimal utility for improving IAF healing outcomes but may have utility for promoting a more permissive inflammatory environment that would allow more potent disease modifying osteoarthritis drugs to mitigate the progression of PTOA after IAF.

Development and characterization of an intra-articular fracture mediated model of post-traumatic osteoarthritis.

PURPOSE: This study aimed to develop and characterize a closed intra-articular fracture (IAF) mediated post-traumatic osteoarthritis (PTOA) model in rats to serve as a testbed for putative disease modifying interventions. METHODS: Male rats were subject to a 0 Joule (J), 1 J, 3 J, or 5 J blunt-force impact to the lateral aspect of the knee and allowed to heal for 14 and 56 days. Micro-CT was performed at time of injury and at the specified endpoints to assess bone morphometry and bone mineral density measurements. Cytokines and osteochondral degradation markers were assayed from serum and synovial fluid via immunoassays. Histopathological analyses were performed on decalcified tissues and assessed for evidence of osteochondral degradation. RESULTS: High-energy (5 J) blunt impacts consistently induced IAF to the proximal tibia, distal femur, or both while lower energy (1 J and 3 J) impacts did not. CCL2 was found to be elevated in the synovial fluid of rats with IAF at both 14- and 56-days post-injury while COMP and NTX-1 were upregulated chronically relative to sham controls. Histological analysis showed increased immune cell infiltration, increased osteoclasts and osteochondral degradation with IAF relative to sham. CONCLUSION: Based on results from the current study, our data indicates that a 5 J blunt-forced impact adequately and consistently induces hallmark osteoarthritic changes to the articular surface and subchondral bone at 56 days after IAF. Marked development of PTOA pathobiology suggest this model will provide a robust testbed for screening putative disease modifying interventions that might be translated to the clinic for militarily relevant, high-energy joint injuries.

Effects of Adjunct Antifibrotic Treatment within a Regenerative Rehabilitation Paradigm for Volumetric Muscle Loss.

The use of a rehabilitation approach that promotes regeneration has the potential to improve the efficacy of pro-regenerative therapies and maximize functional outcomes in the treatment of volumetric muscle loss (VML). An adjunct antifibrotic treatment could further enhance functional gains by reducing fibrotic scarring. This study aimed to evaluate the potential synergistic effects of losartan, an antifibrotic pharmaceutical, paired with a voluntary wheel running rehabilitation strategy to enhance a minced muscle graft (MMG) pro-regenerative therapy in a rodent model of VML. The animals were randomly assigned into four groups: (1) antifibrotic with rehabilitation, (2) antifibrotic without rehabilitation, (3) vehicle treatment with rehabilitation, and (4) vehicle treatment without rehabilitation. At 56 days, the neuromuscular function was assessed, and muscles were collected for histological and molecular analysis. Surprisingly, we found that the losartan treatment decreased muscle function in MMG-treated VML injuries by 56 days, while the voluntary wheel running elicited no effect. Histologic and molecular analysis revealed that losartan treatment did not reduce fibrosis. These findings suggest that losartan treatment as an adjunct therapy to a regenerative rehabilitation strategy negatively impacts muscular function and fails to promote myogenesis following VML injury. There still remains a clinical need to develop a regenerative rehabilitation treatment strategy for traumatic skeletal muscle injuries. Future studies should consider optimizing the timing and duration of adjunct antifibrotic treatments to maximize functional outcomes in VML injuries.

Age-Dependent Cellular and Behavioral Deficits Induced by Molecularly Targeted Drugs Are Reversible.

Newly developed targeted anticancer drugs inhibit signaling pathways commonly altered in adult and pediatric cancers. However, as these pathways are also essential for normal brain development, concerns have emerged of neurologic sequelae resulting specifically from their application in pediatric cancers. The neural substrates and age dependency of these drug-induced effects in vivo are unknown, and their long-term behavioral consequences have not been characterized. This study defines the age-dependent cellular and behavioral effects of these drugs on normally developing brains and determines their reversibility with post-drug intervention. Mice at different postnatal ages received short courses of molecularly targeted drugs in regimens analagous to clinical treatment. Analysis of rapidly developing brain structures important for sensorimotor and cognitive function showed that, while adult administration was without effect, earlier neonatal administration of targeted therapies attenuated white matter oligodendroglia and hippocampal neuronal development more profoundly than later administration, leading to long-lasting behavioral deficits. This functional impairment was reversed by rehabilitation with physical and cognitive enrichment. Our findings demonstrate age-dependent, reversible effects of these drugs on brain development, which are important considerations as treatment options expand for pediatric cancers.Significance: Targeted therapeutics elicit age-dependent long-term consequences on the developing brain that can be ameliorated with environmental enrichment. Cancer Res; 78(8); 2081-95. ©2018 AACR.

GABAergic regulation of cerebellar NG2 cell development is altered in perinatal white matter injury.

Diffuse white matter injury (DWMI), a leading cause of neurodevelopmental disabilities in preterm infants, is characterized by reduced oligodendrocyte formation. NG2-expressing oligodendrocyte precursor cells (NG2 cells) are exposed to various extrinsic regulatory signals, including the neurotransmitter GABA. We investigated GABAergic signaling to cerebellar white matter NG2 cells in a mouse model of DWMI (chronic neonatal hypoxia). We found that hypoxia caused a loss of GABAA receptor-mediated synaptic input to NG2 cells, extensive proliferation of these cells and delayed oligodendrocyte maturation, leading to dysmyelination. Treatment of control mice with a GABAA receptor antagonist or deletion of the chloride-accumulating transporter NKCC1 mimicked the effects of hypoxia. Conversely, blockade of GABA catabolism or GABA uptake reduced NG2 cell numbers and increased the formation of mature oligodendrocytes both in control and hypoxic mice. Our results indicate that GABAergic signaling regulates NG2 cell differentiation and proliferation in vivo, and suggest that its perturbation is a key factor in DWMI.