Background/Purpose: Osteoarthritis (OA) is the most common joint disorder, and growing evidence has identified inflammation to be a major driver of disease progression. During disease, the synovium is identified as a reservoir of inflammatory mediators and immune cells, primarily consisting of monocyte/macrophages.¹ CD14, a co-receptor of inflammatory toll-like receptor signaling and a macrophage-activation-related protein, has been identified within synovial fluid and positively associated with joint space narrowing and knee pain.² We previously reported that global genetic CD14 deficiency in mice protects against OA-associated bone-remodeling and pain-related joint dysfunction.³ Thus, we hypothesize an anti-CD14 therapeutic will mediate inflammatory activation in the synovium during OA, and mitigate disease progression and pain.

Methods: OA model (n=12-14): We performed destabilization of the medial meniscus (DMM) surgery to induce OA in skeletally mature (10-12 wk old) C57BL/6 mice.³

Intervention: Mice were treated intra-articularly with either an anti-CD14 monoclonal antibody (mAb, clone biG53) or an IgG2a control (both 0.5mg/kg), two dosing strategies were tested: 1) Prevention strategy:mice received anti-CD14 or IgG control weekly x 3 doses, starting 48 hrs post DMM. 2) Treatment strategy: mice received 3 weekly injections beginning 4 wks post DMM. Behavioral analysis: Evaluation of spontaneous cage behaviors was performed via the laboratory animal behavior observation registration and analysis system (LABORAS, Metris).³ Paw weight bearing analysis was performed via the advanced dynamic weight bearing (ADWB, Bioseb) system.⁴ Immunohistochemistry (n=3): In a separate early dosing 4-wk study, whole knee joints were fixed, decalcified, paraffin embedded, and sectioned. Sagittal sections underwent antigen retrieval and overnight incubation with primary antibodies (monocyte: Ly6C/D, macrophage: CD64), followed by incubation with fluorescent secondary antibodies, and lastly cover-slipped with mounting medium containing DAPI nuclear dye and imaged.

¹Sanchez 2012 ²Lieberthal 2015 ³Sambamurthy 2018 ⁴Krug 2019

Results: Prevention strategy: Early CD14 blockade increased total distance traveled and rearing time at 4- and 8-wks post DMM, compared to control mice (p< 0.05) (Fig. 1). Front to rear paw weight ratio 8-wks post DMM had a strong decreasing trend (p=0.057) in CD14 inhibitor treated mice compared to controls (Fig. 1). Treatment strategy: When treatment was delayed (4 wks post-DMM), no significant behavior or weight bearing changes were observed between groups (Fig. 2). Evaluating inflammation, early CD14 blocked increased the presence of Ly6C/G+ cells within the synovial lining layer compared to control at 4-wks post DMM (Fig. 3). Few CD64+ cells were observed (Fig. 3).

Conclusion: Results revealed early delivery of a CD14 blocking mAb after DMM injury was more effective at improving mobility, compared to delayed dosing. Immunostaining suggests that anti-CD14 treatment may be modulating myeloid cell activation, clearance, or differentiation within the synovium during OA progression. Results provide significant support for further evaluation of CD14 as a therapeutic for painful OA.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/cd14-inhibition-as-a-potential-therapeutic-in-post-traumatic-oa/