Increased levels of apoptosis and p53 in partial-thickness supraspinatus tendon tears.
OBJECTIVE
The role of apoptosis in the progression of rotator cuff tendinopathy remains poorly understood. In particular, the extent of apoptosis in the partially torn supraspinatus tendon has not been well examined.


METHODS
Biopsies were obtained from nine partially torn supraspinatus tendons, from the matched intact subscapularis tendons, and from 10 reference subscapularis tendons. Immunohistochemistry was used to assess the density of apoptotic cells (activated caspase-3; Asp175), proliferation (Ki67), and p53 (M7001), a key protein involved in regulating cell death. The Bonar scale was used to evaluate tendon degeneration.


RESULTS
The density of apoptotic tendon cells and the density of cells expressing p53 were significantly increased in both the partially torn supraspinatus tendons and in the matched subscapularis tendons, compared with uninjured reference tendons. The Bonar score revealed significant tendon degeneration in the partially torn supraspinatus tendons compared with both matched and reference subscapularis tendons. Tendon cell proliferation was significantly increased in the partially torn supraspinatus tendons compared with reference subscapularis tendons.


CONCLUSIONS
Partial-thickness tears of the supraspinatus tendon demonstrated an increased density of apoptotic, p53+ tendon cells. The fact that apoptosis was accompanied by increased tendon cell proliferation suggests that apoptosis may be related to an ongoing injury-repair process. Increased tenocyte apoptosis may be a relatively early feature in rotator cuff tendinopathy and could represent a possible target for therapeutic intervention.
Department of Orthopaedics, Lovisenberg Deaconal Hospital, Oslo Sports Trauma Research Center , Lovisenberggata 17, 0456 Oslo, Norway. kirsten.lundgreen@lds.no
Kirsten
K
Lundgreen
Øystein
Ø
Lian
Alex
A
Scott
Lars
L
Engebretsen
D017209:Apoptosis; D001706:Biopsy; D053148:Caspase 3 / Q000378:metabolism; D049109:Cell Proliferation; D018450:Disease Progression; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D010446:Peptide Fragments / Q000378:metabolism*; D017006:Rotator Cuff / Q000166:cytology / Q000378:metabolism*; D000070636:Rotator Cuff Injuries; D013708:Tendon Injuries / Q000378:metabolism*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*
D010446:Peptide Fragments; D016159:Tumor Suppressor Protein p53; C509415:p53 protein (325-355), human; D053148:Caspase 3