Abstract

Abstract
Background: Osteoarthritis (OA) is a progressive degenerative joint disorder marked by cartilage breakdown, inflammation, and pain. Non-steroidal anti-inflammatory drugs (NSAIDs), such as meloxicam, are widely used to alleviate symptoms; however, prolonged use is associated with adverse effects. Citrullus colocynthis, a medicinal plant with reported anti-inflammatory and immunomodulatory properties, may offer a safer alternative. This study aimed to evaluate the anti-inflammatory and immunomodulatory effects of C. colocynthis compared to meloxicam in an experimentally induced rabbit model of OA.
Materials and Methods: Osteoarthritis was induced in rabbits by intraperitoneal injection of Staphylococcus aureus (NCTC 10788 / ATCC©). Following induction, animals were treated for 7 days with either meloxicam (0.2 mg/kg/day, intramuscularly) or C. colocynthis extract (100 mg/kg/day, orally). Clinical signs of OA were monitored throughout the study. Serum levels of inflammatory markers (C-reactive protein [CRP], tumor necrosis factor-alpha [TNF-α], interleukin-6 [IL-6], cyclooxygenase-2 [COX-2]), autoimmune indicators (rheumatoid factor [RF], antinuclear antibodies [ANA]), and the anti-inflammatory cytokine interleukin-10 [IL-10] were measured. Histopathological and ultrastructural changes in the knee joints were assessed using electron microscopy.
Results: Both meloxicam and C. colocynthis treatments significantly reduced joint swelling and decreased serum levels of CRP, TNF-α, IL-6, and COX-2, while increasing IL-10 concentrations. C. colocynthis exhibited therapeutic efficacy comparable to, and in some parameters slightly greater than, meloxicam—particularly in reducing CRP, COX-2, IL-6, and TNF-α by the second week after treatment. Ultrastructural analysis revealed diminished inflammatory cell infiltration and improved cartilage architecture in both treated groups, with better preservation observed in the C. colocynthis-treated joints.
Conclusion: Citrullus colocynthis exhibits potent anti-inflammatory and immunomodulatory activity comparable to meloxicam, supporting its potential as a natural alternative or adjunct therapy for osteoarthritis.

Key words: Keywords: Osteoarthritis, anti-inflammatory, Rabbits, Citrullus colocynthis, EM, Biochemical indices.