Variations in chondrocyte apoptosis may explain the increased prevalence of osteoarthritis in some joints.
OBJECTIVE
To investigate whether there are any variations in chondrocyte susceptibility to an apoptotic stimulus between cells of articular cartilage (AC) from equine joints that differ in prevalence of osteoarthritis (OA).


METHODS
Cartilage from macroscopically normal equine metacarpophalangeal (MCP), proximal interphalangeal (PIP) and distal interphalangeal (DIP) joints was used. Prior to culture, chondrocyte viability was assessed using the fluorescein diacetate (FDA) and propidium iodide paravital staining method. AC explants were subsequently treated with tumour necrosis factor-α (TNF-α) in combination with Actinomycin D to induce apoptosis. Apoptosis of chondrocytes in cartilage sections was assessed by expression of active caspase-3 using indirect immunohistochemistry and sections also histologically graded using a 'modified' Mankin scoring system.


RESULTS
Prior to culture (mean ± standard deviation) chondrocyte viability was 80.7% (3.5). The extent of chondrocyte apoptosis induced by TNF-α/Actinomycin D varied markedly according to the joint type that the cartilage was sampled from. For MCP joints, the extent of overall chondrocyte apoptosis was significantly higher (P < 0.001) in stimulated explants (26.7%, 10.3) than that observed in unstimulated control samples (9.6%, 7.5). Conversely, chondrocytes from PIP and DIP joint cartilage did not respond significantly to apoptotic stimulation (P > 0.05). Significant variations in cellularity and thickness were also evident between cartilages of different joint types.


CONCLUSIONS
Data in this study demonstrate that chondrocytes from three equine joint types with varying prevalences of OA differ significantly in terms of susceptibility to apoptosis induction. This may provide a possible explanation for the joint-specific nature of the disease.
Thomas
C M
CM
Department of Anatomy, University of Bristol, Southwell Street, Bristol, BS2 8EJ, UK.
Whittles
C E
CE
Fuller
C J
CJ
Sharif
M
M
D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D002358:Cartilage, Articular / Q000473:pathology; D002478:Cells, Cultured; D019902:Chondrocytes / Q000473:pathology*; D004195:Disease Models, Animal; D005260:Female; D006734:Horse Diseases / Q000473:pathology*; D006736:Horses; D008297:Male; D008662:Metacarpophalangeal Joint / Q000473:pathology; D009928:Organ Specificity; D010003:Osteoarthritis / Q000453:epidemiology* / Q000473:pathology*; D015995:Prevalence; D014033:Toe Joint / Q000473:pathology; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology
D014409:Tumor Necrosis Factor-alpha
Osteoarthritis Cartilage. 2007 Jan;15(1):27-34
16859932
Connect Tissue Res. 2006;47(2):92-101
16754515
Lab Invest. 1996 Jan;74(1):232-40
8569187
J Orthop Res. 1998 Sep;16(5):551-6
9820277
Osteoarthritis Cartilage. 2006 May;14(5):435-41
16368252
Arch Orthop Trauma Surg. 2001 Jun;121(6):301-6
11482459
Acta Med Okayama. 2001 Dec;55(6):333-40
11779095
J Orthop Res. 2002 May;20(3):526-34
12038627
Osteoarthritis Cartilage. 2006 Jul;14(7):660-9
16492401
Vet Rec. 2001 Feb 17;148(7):204-6
11265997
Osteoarthritis Cartilage. 2003 Jul;11(7):538-47
12814617
Arthritis Rheum. 1998 Jul;41(7):1266-74
9663485
Biochem Biophys Res Commun. 2002 Jul 26;295(4):937-44
12127985
J Immunol. 2000 Feb 15;164(4):2233-9
10657679
Equine Vet J. 2001 Jul;33(4):360-5
11469768
Osteoarthritis Cartilage. 2005 Feb;13(2):93-103
15694570
Arthritis Rheum. 1998 Sep;41(9):1632-8
9751096
Orthopade. 2006 Jul;35(7):784-90
16609893
Equine Vet J. 1999 Jan;31(1):73-81
9952333
J Orthop Res. 2000 Sep;18(5):739-48
11117295
Osteoarthritis Cartilage. 2001 Jul;9(5):499-507
11467899
Vet J. 2003 Jul;166(1):52-7
12788017
Equine Vet J. 2006 Nov;38(6):538-42
17124844
J Orthop Res. 2000 May;18(3):356-63
10937621
Ann Rheum Dis. 1991 Jan;50(1):8-13
1994877
Ann Rheum Dis. 1999 Jan;58(1):27-34
10343537
Osteoarthritis Cartilage. 2001 Jan;9(1):49-55
11178947
Microsc Res Tech. 2000 Aug 1;50(3):236-42
10891889