In situ Preparation of a Phospholipid Gel Co-Loaded with Methotrexate and Dexamethasone for Synergistic Rheumatoid Arthritis Treatment

Abstract

Background: Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by arthrocele, cartilage damage and disability. Although several anti-RA drugs have been developed for long-term treatment, they require frequent local injection and lead to multiple adverse effects such as osteoporosis and myelosuppression.

Purpose: Reducing the amount and frequency of anti-RA drugs methotrexate (MTX) and dexamethasone sodium phosphate (DSP) by local injection of phospholipid-based phase separation gel (PPSG) coloaded the two drugs, which presented PPSG-(+).

Methods: First, We characterized PPSG-(+). And we used UV spectrophotometry and high performance liquid chromatography (HPLC) to detect drug concentration, which can clarify the drug release in vitro and in vivo, respectively. We also injected PPSG-(+) into the joint cavity of healthy rabbits to prove the safety of PPSG-(+). Then, we injected PPSG-(+) into the joint cavity of RA modeled rabbits to demonstrate the effect in anti-RA of PPSG-(+) including the thickness of joints, tumor necrosis factor (TNF)-α and interleukin (IL)-1β detection, hematoxylin-eosin (H&E) staining and computed tomography (CT) of joints.

Results: Suspended particles show a tight and uniform arrangement in PPSG-(+). The gel underwent a phase transition at 20 min in vitro and 8 h in vivo, and vesicular structures reflecting its degradation and phase transition were observed in vivo. PPSG-(+) released both drugs in a sustained and fixed ratio for more than 14 days, while it proved to be safe for intra-articular injection and did not induce inflammation in a rabbit. Eventually, PPSG-(+) showed a good anti-RA effect and its potency can be maintained for 3 weeks.

Conclusion: PPSG-(+) is a drug delivery system offering good biocompatibility and sustained release of MTX and DSP, leading to long-lasting anti-RA effect.

Keywords: anti rheumatoid arthritis; drug delivery system; in situ gel; sustained release.

Figure 1

Schematic illustration of PPSG-(+) administration into an inflamed joint.

Figure 2

(A and B) Photographs of (A) suspended and (B) gelled PPSG-(+). (C) SEM of PPSG-(+). (D) Rheological characterization of PPSG-(+) in phosphate-buffered saline (pH 7.4). (E) FTIR of MTX, DSP, PPSG, PPSG-(+), gelled PPSG and PPSG-(+). Data are shown as mean ± SD (n = 3).

Figure 3

(A) Changes in the appearance and structure of PPSG-(+) over time in vivo, arrows point at vesicular structures associated with phase transition and degradation. (B) Histopathological changes in the knee joints of healthy rabbits after intra-articular injection of PPSG-(+). (C) Changes in ethanol and water content during phase transition in vivo. Data are shown as mean ± SD (n = 3).

Figure 4

(A) Cumulative release in vitro and (B) residual amount in vivo of methotrexate (MTX) and dexamethasone sodium phosphate (DSP) during 14 days.

Figure 5

(A) Schematic illustration of rheumatoid arthritis (RA) development and treatment in vivo. (B) Thickness of rabbit knee joints after treatment with different formulations. (C and D) Levels of (C) tumor necrosis factor-α (TNF-α) and (D) interleukin (IL)-1β after three weeks of treatment with various formulations. Data are shown as mean ± SD (n = 5). *P < 0.05, **P < 0.01 vs saline group.

Figure 6

(A) Histopathological analysis and (B) computed tomography of knee joints from rabbits with rheumatoid arthritis after various treatments.