Therapeutic blockade of CCL17 in obesity-exacerbated osteoarthritic pain and disease

Abstract

Objectives: We previously reported that CCL17 gene-deficient mice are protected from developing pain-like behaviour and exhibit less disease in destabilization of medial meniscus (DMM)-induced OA, as well as in high-fat diet (HFD)-exacerbated DMM-induced OA. Here, we explored if therapeutic neutralization of CCL17, using increasing doses of a neutralizing monoclonal antibody (mAb), would lead to a dose-dependent benefit in these two models.

Design: DMM-induced OA was initiated in male mice either fed with a control diet (7% fat) or 8 weeks of a 60% HFD, followed by therapeutic intraperitoneal administration (i.e. when pain is evident) of an anti-CCL17 mAb (B293, 25mg/kg, 5mg/kg or 1mg/kg) or isotype control (BM4; 25mg/kg). Pain-like behaviour and arthritis were assessed by relative static weight distribution and histology, respectively. The effects of B293 (25mg/kg) on HFD-induced metabolic changes, namely oral glucose tolerance test, insulin tolerance test and liver triglyceride levels, were examined.

Results: Therapeutic administration of B293 results in a dramatic amelioration of DMM-induced OA pain-like behaviour and the inhibition of disease progression, compared to BM4 (isotype control) treatment. A similar therapeutic effect was observed in HFD-exacerbated OA pain-like behaviour and disease. B293 treatment did not alter the measured HFD-induced metabolic changes.

Conclusions: Based on the data presented, CCL17 could be a therapeutic target in OA patients with joint injury alone or with obesity.

Fig 1. Therapeutic blockade of CCL17 ameliorates DMM-induced OA pain and disease.

The DMM-induced OA model was initiated in WT male mice. The administration of B293 (anti-CCL17 mAb; 25mg/kg, 5mg/kg or 1mg/kg) or BM4 (isotype control; 25mg/kg) began at week 9 twice weekly. (A) Change in weight distribution (pain-like behaviour) over time. Numerical summaries are provided in detail in S1 Table. (B) Representative histologic pictures of knee joints (Safranin O/fast green stain, original magnification x4) for cartilage damage (indicated by black arrows) and osteophyte formation (indicated by orange arrows) (week 12). (C) DMM-induced OA cartilage damage, (D and E) osteophyte maturity and size, and (F) synovitis were quantified. (G) Sera were collected at week 12 for CCL17 quantification via ELISA. Results are expressed as the mean ± 95% CI; n = 10/treatment group; F, femur; T, tibia. Scale bar indicates 100μm. *represents p-values between BM4 vs. B293 (25mg/kg) or B293 (5mg/kg).

Fig 2. Therapeutic blockade of CCL17 ameliorates HFD-exacerbated DMM-induced OA pain and disease.

WT male mice were fed with 60% high-fat diet (HFD) for 8 weeks, after which DMM-induced OA was initiated. The administration of B293 (anti-CCL17 mAb; 25mg/kg, 5mg/kg or 1mg/kg) or BM4 (isotype control; 25mg/kg) began at week 7 twice weekly. (A) Change in weight distribution (pain-like behaviour) over time. Numerical summaries are provided in detail in S2 Table. (B) Representative histologic pictures of knee joints (Safranin O/fast green stain, original magnification x4) for cartilage damage (indicated by black arrows) and osteophyte formation (indicated by orange arrows) (week 12). (C) DMM-induced OA cartilage damage, (D and E) osteophyte maturity and size, and (F) synovitis were quantified. (G) Sera were collected at week 12 for CCL17 quantification via ELISA. Results are expressed as the mean ± 95% CI; n = 10/treatment group; F, femur; T, tibia. Scale bar indicates 100μm. *represents p-values between BM4 vs. B293 (25mg/kg) or B293 (5mg/kg).

Fig 3. The effects of GM-CSF gene deficiency on obesity-associated metabolic changes.

WT and GM-CSF^-/- male mice were fed with 60% high-fat diet (HFD) for 8 weeks. (A) Absolute body weight (g). (B) Plasma glucose and insulin levels during oGTT. (C) Plasma glucose levels during ITT. (D) Triglyceride levels in liver. Results are expressed as the mean ± 95% CI; n = 9/group. *p<0.05, **p<0.01, WT vs. GM-CSF^-/- mice.

Fig 4. The effects of CCL17 neutralization on obesity-associated metabolic changes.

WT male mice were fed with 60% high-fat diet (HFD) for 8 weeks with B293 (anti-CCL17 mAb; 25mg/kg) or BM4 (isotype control; 25mg/kg) being administered at week 4 twice weekly. (A) Sera were collected at week 8 for CCL17 quantification (ELISA). (B) Absolute body weight (g). (C) Plasma glucose and insulin levels during oGTT. (D) Plasma glucose levels during ITT. (E) Triglyceride levels in liver. (E) Sera were collected for CCL17 quantification (ELISA). Results are expressed as the mean ± 95% CI; n = 5/treatment group.