The Possible Therapeutic Effect of Bone Marrow - Mesenchymal Stem Cells Versus Methotrexate in A Rat Model of Rheumatoid Arthritis. A Histological Study

Abstract

Rheumatoid arthritis (RA) is an autoimmune disease that leads to chronic inflammation of the joints with subsequent cartilage destruction, bone erosions and deformities. Synovitis is the hallmark of the disease that results in cartilage erosion and destruction. A rat model of RA was developed by using a single subcutaneous injection of complete Freund’s adjuvant (CFA). This model gives a pathological picture closely related to that seen in RA patients. Methotrexate is one of the commonly used disease-modifying anti-rheumatic drugs that promotes disease remission and prevents progressive joint destruction. Despite its efficacy, MTX has serious adverse effects, and most patients discontinued the treatment course. Efforts were made to discover new target therapies that had powerful effects with little or no adverse effects. One of these therapies is the use of BM-MSCs due to their profound immunosuppression activity. The present work was designed to study the effect of intra-articular injection of BM-MSCs in comparison to MTX on the structure of the knee joint in a rat model of RA. Thirty six adult male albino rats were used in the current study. They were divided into two main groups: • Group I (Control group): consisted of 16 rats subdivided into four subgroups, four animals each.  Subgroup Ia (Negative control group): Animals of this subgroup were left untreated.  Subgroup Ib: Animals of this subgroup received a single subcutaneous injection of 0.3 ml normal saline (the solvent of CFA) in the right footpad. Then, two rats were sacrificed after two weeks whereas, the other two were sacrificed after four weeks.  Subgroup Ic: Animals received normal saline in the same dose and the same route as subgroup Ib. After two weeks, the animals received subcutaneous injection of 0.3 ml saline and were left for additional two weeks. The animals were sacrificed after four weeks from the beginning of the experiment.  Subgroup Id: Animals received normal saline in the same dose and the same route as subgroup Ib. After two weeks, the animals received a single intra-articular injection of 0.25 ml phosphate buffered saline (the vehicle of stem cell) in the left knee joint and were left for additional two weeks. The animals were sacrificed four weeks from the beginning of the experiment. • Group II (RA group): consisted of 20 rats, in which RA was induced using a single subcutaneous injection of 0.1ml of CFA suspended in 0.2 normal saline in the metatarsal footpad of right hind limb in the first day of the experiment. Animals of this group were further subdivided into four subgroups, five rats each.  Subgroup IIa (two weeks after induction of RA): Animals of this subgroup were sacrificed after two weeks from the injection of CFA to confirm induction of RA.  Subgroup IIb (four weeks after induction of RA): Animals of this subgroup were sacrificed after four weeks from injection of CFA.  Subgroup IIc (MTX treated group): Two weeks after injection of CFA, animals of this subgroup received subcutaneous injection of 0.3mg/kg MTX twice weekly for two weeks, then, sacrificed.  Subgroup IId (BM-MSCs treated group): Two weeks after injection of CFA, animals of this subgroup received single intra-articular injection of pkH26 labeled BM-MSCs in a concentration of 2×106 and were sacrificed after additional two weeks. At the end of the experiment, all animals were sacrificed and the knee joints were processed for the following histological, histochemical and immune-histochemical techniques.