Cartilage degeneration can be induced in virtually any species by the intra-articular injection of monoiodoacetic acid (MIA), an inhibitor of aerobic glycolysis, which kills chondrocytes. Depending on the concentration used and frequency, different degrees of killing and thus degeneration can be achieved. In guinea pigs, 2 intra-articular injections of MIA (0.1 ml of 3 mg/ml) at 24-hour intervals will result in the death of all chondrocytes on the tibial plateaus and femoral condyles.
Rats are anesthetized with Isoflurane, and the right knee area is injected with 1 mg of mono-iodoacetate (MIA) in a 40 µL volume.
Cartilage degeneration can be induced in virtually any species by the intra-articular injection of MIA, an inhibitor of aerobic glycolysis, which kills chondrocytes. Depending on the concentration used and frequency, different degrees of chondrocyte death (degeneration) can be achieved. In rats, a single 25 to 50 µL injection of 10 mg/mL sodium iodoacetate is sufficient to kill most of the chondrocytes.1 The chondrocytes at the far outer margins of the joint (marginal zone), in the area where chondrophytes/osteophytes form, usually survive this insult and ultimately proliferate to form these structures. IA injection in the presence of normal load bearing results in the progressive loss of proteoglycan (days 3 to 14 post-injection), as evidenced by decreased toluidine blue matrix staining, and atrophy of the remaining collagenous portion of the matrix. Fibrillation is a late change (day 15 to 21), as is the collapse of the remaining collagenous matrix into partially resorbed and degraded subchondral bone. The bone changes in this model are quite striking and form the basis for cartilage lesions observed macroscopically. Ultimately, large osteophytes occur in this model.2 Characterization of the time course of aggrecan and type II collagen degradation in this model revealed an increase in both aggrecanase- and MMP-generated epitopes with the NITEGE aggrecanase neoepitope being significantly elevated on days 7, 14 and 21 and the DIPEN MMP neoepitope elevated on days 7 and 14.1 The type II collagen neoepitope recognized by Col2-3/4Cshort was increased only on days 14 and 21, coinciding with the period of observable collagen degradation.
- Begin dosing X days prior to surgery or post surgery and continue until necropsy.
- Route of administration: SC, PO, IP, IV, IA
Rats are observed daily for abnormal swelling or gait alterations. Gait analysis is performed on days 0, 3, 4, 5, and 6. Body weights are taken on all of those days, as well as day 10.
Gait analysis is performed by applying ink to the ventral surface of the foot and documenting weight bearing during movement (footprints) across paper. The rear feet of rats are placed in ink, then rats are placed on paper and allowed to walk the full length. This process is repeated as necessary to generate 4 clear, evenly inked footprint pairs representing the overall pattern of gait. Gait is scored visually as follows (descriptions refer to diseased leg):
0 = Normal: Approximately equal ink staining to normal paw.
1 = Slight limp/pain: Reduced inking area relative to the normal paw, but no full regions or structures are missing.
2 = Mild limp/pain: Print extends to the end or near to the end of the “curlicue” structure. If normal paw has very little heel staining (rat walks mainly on toes/ball of foot), then slightly less staining.
3 = Moderate limp/pain: Toes and full ball of foot, extending to the top of the “curlicue” foot. If normal paw has very little heel staining (rat walks mainly on toes/ball of foot), then toes with small portion of ball of foot.
4 = Marked limp/pain: Toes and partial ball of foot, no heel or posterior foot. If normal paw has very little heel staining (rat walks mainly on toes/ball of foot), then toes only.
5 = Severe limp/pain: Toes only, no ball of foot, no heel. If normal paw has very little heel staining (rat walks mainly on toes/ball of foot), then partial toes or non-specific marks
6 = Hopping: Carrying leg, no footprint is evident.
Knees are cut in half in the frontal plane and both halves are embedded together in paraffin. Sections are cut and stained with toluidine blue (T. Blue). Scores and measurements are determined for the knee half with the most severe lesions in the central load bearing location. Percent loss and bone resorption are evaluated for each of the four surfaces (MTP, MFC, LTP, and LFC), and the mean values for the entire joint are also calculated. Other parameters represent the joint as a whole. Knees are examined microscopically by a board certified veterinary pathologist (Dr. Alison Bendele) according to these methods.
Potential uses for this model include evaluation of agents designed to inhibit acute proteoglycan loss mediated through aggrecanase or MMPs (day 7 to 14 termination) or collagen matrix degeneration via collagenase (day 21 termination) or induction of repair and evaluation of effects of agents on gait alterations that occur. Since osteophyte formation is a prominent feature, this model could be used to study their induction or inhibition of formation.
- PK/PD blood collections
- Cytokine/chemokine analysis via Luminex(R)
- Other sandwich ELISAs
- CBC/clinical chemistry analysis
- Soft tissue collection
- Histopathologic analysis
- Immunohistochemistry analysis
- Janusz MJ, Little CB, King LE, Hookfin EB, Brown KK, Heitmeyer SA, Caterson B, Poole AR, Taiwo YO. Detection of aggrecanase-and MMP-generated catabolic neoepitopes in the rat iodoacetate model of cartilage degeneration. Ostoarthritis Cartilage. 2004;12:720-728.
- Guingamp C, Gegout-Pottie P, Philippe L, Terlain B, Netter P, Gillet P. Mono-iodoacetate-induced experimental osteoarthritis:a dose-response study of loss of mobility, morphology and biochemistry. Arthritis Rheum 1997; 40:1670-1679.
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