Why the dog? Analogy of the anatomy Surgically Induced canine OA models: Anterior (cranial) cruciate ligament transection model Pond MJ, Nuki G. Ann Rheum Dis 1973 (and > 100 others) Meniscal disruption models o Menisectomy model Lindhorst E, et al. J Orthop Res 2000 (and others) o Meniscal release model Luther JK, et al. Vet Surg 2009 Groove model Marijnissen AC, et al. OA Cartilage 2002 (and others) Arthrotomy vs. Arthroscopy Outcome Measures Clinical Relevance Clinical Canine Patients
Histological/histochemical Grading System Mankin HJ, et al. 1971 J Bone Joint Surg Am Category Subcategory Structure Normal Surface irregularities Pannus and surface irregularities Clefts to transitional zone Clefts to radial zone Clefts to calcified zone Complete disorganization Cells Normal Diffuse hypercellularity Cloning Hypocellularity Proteoglycan staining (Safranin O) Normal Slight reduction Moderate reduction Severe reduction No dye noted Tidemark integrity Intact Crossed by blood vessels Scor e 0 1 Total 0 14 0 1 2 3 4 5 6 0 1 2 3 0 1 2 3 4 Inadequate differentiation between mild OA and moderate OA Ostergaard et al. Ann Rheum Dis 1999 Inadequate reproducibility and validity Ostergaard et al. Arthritis Rheum 1997 Inadequate representation/weight of the relative importance Lack of a standardized sampling method Lack of global assessment of articular cartilage Lack of assessment of the joint as a whole
Grade (key feature) 0 (surface intact, cartilage morphology intact) 1 (surface intact) 2 (surface discontinuity) 3 (vertical fissures/clefts) 4 (erosion) 5 (denudation) 6 (deformation) Associated criteria Matrix: Normal architecture Cells: Intact, appropriate orientation Matrix: Superficial zone intact, edema, and/or superficial fibrillation, focal superficial matrix condensation Cells: Death, proliferation (clusters), hypertrophy, superficial zone As above + matrix discontinuity at superficial zone (deep fibrillation) +/- cationic stain matrix depletion upper 1/3 of cartilage +/- focal perichondral increased stain (mid zone) +/- disorientation of chondrone columns Cells: Death, proliferation (clusters), hypertrophy As above + vertical fissures into mid zone, branched fissures +/- cationic stain depletion into lower 2/3 of cartilage (deep zone) +/- new collagen formation Cells: Death, regeneration (clusters), hypertrophy, cartilage domains adjacent to fissures Cartilage matrix loss: delamination of superficial layer, mid layer cyst formation Excavation: matrix loss superficial layer and mid zone Surface: sclerotic bone or reparative tissue including fibrocartilage within denuded surface. Microfracture with repair limited to bone surface. Bone remodelling (more than osteophyte formation only) including microfracture with fibrocartilaginous and osseous repair extending above the previous surface OA score = grade x *stage *% area involvement in a tissue section 0: no OA, 1: < 10%, 2: 10-25%, 3: 25-50%, 4: >50%
Articular cartilage: Human vs. Dog Human femoral condyle Canine femoral condyle S M D C Human Canine Thickness (mm) 2.26 0.67 Cell density (10 4 /mm 3 ) 1.4 4.4 Stockwell RA. J Anat 1971
Macroscopic assessment of cartilage E A Smooth surface 0 B Slightly fibrillated/roughened surface 1 C Fibrillated surface with focal partial thickness lesions 2 D Deep lesions with surrounding damage 3 E Large areas of severe damage 4 Macroscopic cartilage scoring for each weight bearing compartment, based on Outerbridgeclassification (J Bone Joint SurgBr 1961) and modified from Masterbergen et al (Rheumatology 2006)
Macroscopic assessment of cartilage Indian ink staining % area of cartilage damage
Sample collection for histopathology FEMUR 1 2 3 3 2 1 1 2 3 3 2 1 1 2 3 3 2 1 TIBIA 1 2 3 3 2 1
Scoring System Cartilage & Osteochondral tissues Tissue Articular cartilage Osteochondral tissue Categories (use one or more) Cartilage structure Chondrocytes Proteoglycan staining intensity Collagen integrity Tide mark integrity Subchondral bone changes C D 1/3 D 1/3 of section scored D + 1/3 of section scored D + 1/3 of section scored C = 6 + 2 = 8 Pathological Changes in Each Category < 1/3 (Focal) EXTENT OF SECTION AFFECTED < 2/3 (Multifocal, Focally extensive) >2/3 (Multifocal, Diffuse ) A Normal 0 0 0 B Less severe pathology 1 2 3 C 2 4 6 D 3 6 9 E Most severe pathology 4 8 12
Cartilage Pathology: Structural change SEVERITY OF CARTILAGE PATHOLOGY Characteristics EXTENT OF SECTION AFFECTED < 1/3 < 2/3 >2/3 A Normal volume, smooth surface with intact superficial zone 0 0 0 B Slight surface irregularities including fibrillations/fissures in 1 2 3 superficial zone C Clefts/fissures to mid zone and/or erosion of superficial zone 2 4 6 D Cleft/fissures that extend to deep zone and/or erosion through 3 6 9 mid zone E Full thickness loss/deformation of cartilage 4 8 12
Cartilage Pathology: Structural Change examples a a. Small focal area (<1/3) of fibrillation in superficial zone = 1 b b. Focally extensive area of erosion of superficial zone (<2/3) = 4 c c. Diffuse (>2/3) erosion through mid zone = 9 SEVERITY OF CARTILAGE PATHOLOGY Characteristics EXTENT OF SECTION AFFECTED < 1/3 < 2/3 >2/3 A Normal volume, smooth surface with intact superficial zone 0 0 0 B Slight surface irregularities including fibrillations/fissures in superficial zone 1 2 3 C Clefts/fissures to mid zone and/or erosion of superficial zone 2 4 6 D Cleft/fissures that extend to deep zone and/or erosion through mid zone 3 6 9 E Full thickness loss/derangement of cartilage 4 8 12
Cartilage Pathology: Chondrocyte change SEVERITY OF CHONDROCYTE PATHOLOGY Characteristics EXTENT OF SECTION AFFECTED < 1/3 < 2/3 >2/3 A Normal 0 0 0 B Relative hypocellularity at the articular surface or hypercellularity with occasional superficial clones 1 2 3 C Frequent clones, small cell clones predominate 2 4 6 D Frequent clones, large cell clones predominate 3 6 9 E Cell loss predominates 4 8 12 A C D Normal = 0 Frequent small clones (duos and trios) = 2 Frequent large cell clones = 3
Cartilage Pathology: Proteoglycan staining Toluidine blue CATIONIC STAINING (PROTEOGLYCAN) Characteristics Safranin O EXTENT OF SECTION AFFECTED < 1/3 < 2/3 >2/3 A Normal 0 0 0 B Reduction of staining in the superficial zone 1 2 3 C Reduction of staining into the mid zone 2 4 6 D Reduction of staining into the deep zone 3 6 9 E Full depth reduction of staining 4 8 12
Cartilage Pathology: Collagen integrity A B C Collagen type II Collagen type I Picrosirius red staining with polarized light COLLAGEN DERRANGEMENT Characteristics EXTENT OF SECTION AFFECTED < 1/3 < 2/3 >2/3 A Normal 0 0 0 B Loss of integrity of superficial zone 1 2 3 C Loss of integrity of surface and mid zones 2 4 6 D Loss of integrity of surface, mid and deep zones 3 6 9
Osteochondral pathology: Tidemark integrity TIDEMARK INTEGRITY EXTENT OF SECTION AFFECTED < 1/3 < 2/3 >2/3 A Intact and distinct 0 0 0 B Not consistent or distinct (loss and/or duplication) 1 2 3 C Loss of tidemark which is crossed by blood vessels 2 4 6 A. Apparently normal tidemark = 0 B. Indistinct tidemark = 1 B.Duplication of tidemark = 1 C.Loss of tidemark with vascular penetration = 2
Osteochondral Pathology: Subchondral bone change EXTENT OF SECTION SUBCHONDRAL BON CHANGES AFFECTED < 1/3 < 2/3 >2/3 A Apparently normal thickness 0 0 0 B Mild to moderate increase in thickness 1 2 3 C Marked increase in thickness and/or subchondral pseudocysts 2 4 6 A B C Increased in thickness Subchondral pseudocysts
Synovial changes
Scoring system: Synovium Tissue Categories (use one or more) Synovium Synoviocytes Tissue morphology Cellular infiltrates Lateral Medial Axial 3 sections of synovium (medial, axial, and SEVERITY OF PATHOLOGY lateral compartments if possible) Lining cells characteristics (Synoviocyte changes) Lateral (1/3) Medial (1/3) Axial (1/3) A Normal (1 to 2 cell layers of thin synoviocytes) 0 0 0 B Hypertrophy and/or mild to moderate hyperplasia 1 2 3 C Marked hyperplasia (> 6 cell layers) 2 4 6 Lining characteristics (Tissue morphologic changes) A Normal 0 0 0 B Short villi formation 1 2 3 C Finger-like projections 2 4 6 Cell infiltration characteristics A No inflammatory cell infiltration 0 0 0 B Mild to moderate inflammatory cell infiltration 1 2 3 C Marked inflammatory cell infiltration, lymphoid proliferation 2 4 6
Synovial Pathology: Lining synoviocytes changes A B C Apparently normal synoviocytes= 0 Mild hyperplasia = 1 Marked hyperplasia = 2 SEVERITY OF PATHOLOGY Lining cells characteristics SECTION AFFECTED 1/3 1/3 1/3 A Normal (1 to 2 cell layers of thin synoviocytes) 0 0 0 B Hypertrophy and/or mild to moderate hyperplasia 1 2 3 C Marked hyperplasia (>6 cell layers) 2 4 6
Synovial Pathology: Synovial tissue morphologic changes A B C Apparently normal synovium= 0 Short villi formation = 1 Fronds-like projections = 2 SEVERITY OF PATHOLOGY Lining characteristics (Tissue morphologic changes) SECTION AFFECTED 1/3 1/3 1/3 A Normal 0 0 0 B Short villi formation 1 2 3 C Finger-like projections 2 4 6
Synovial Pathology: Cellular infiltration A B C No cellular infiltrates = 0 Mild lymphocytic infiltrates = 1 Lymphoid proliferation = 2 SEVERITY OF PAHTOLOGY Cellular infiltration characteristics SECTION AFFECTED 1/3 1/3 1/3 A No inflammatory cell infiltration 0 0 0 B Mild to moderate inflammatory cell infiltration 1 2 3 C Marked inflammatory cell infiltration, lymphoid proliferation 2 4 6
Meniscal Pathology: Sampling & Categories Cross section of meniscus Tissue Meniscus Tissue sampling for histology 3 3 2 2 1 Lateral 1 Medial Categories (use one or more) Meniscus structure Matrix content Cellular proliferation 3. Posterior 2. Middle 1. Anterior
Meniscal Pathology c 3 sections of med. & lat. meniscus SEVERITY OF PATHOLOGY (anterior, middle, posterior if possible) Tissue architecture Anterior 1/3 Middle Posterior 1/3 A Normal 0 0 0 B Mild disruption 1 1 1 C Moderate disruption with loss of tissue 2 2 2 D More than 50% loss of tissue architecture 3 3 3 Matrix Content A Normal 0 0 0 B Mild alterations in matrix content 1 1 1 C Moderate alterations in matrix content 2 2 2 D Severe loss of matrix content 3 3 3 Proliferative Response A None 0 0 0 B Mild proliferation of cells at synovial-meniscal junction 1 1 1 C Proliferation of cells at synovial junction and extending into tissue or along surface 2 2 2 D Marked proliferation of cells involving majority of remaining tissue 3 3 3