Macrophage-specific metalloelastase (MMP-12) immunoexpression in the osteochondral unit in osteoarthritis correlates with BMI and disease severity.

BACKGROUND: Metalloproteinase 12 (MMP-12) is induced in chondrocytes during fetal development and malignant transformation. OBJECTIVES: The aim of our study is to examine the expression of MMP-12 in the cartilage and the subchondral bone of patients with osteoarthritis (OA) and to correlate its expression with disease severity and anthropometric characteristics. METHODS: Overall, 60 sections from 20 patients with idiopathic OA, were examined for the immunolocalization of MMP-12. As controls, we used the femoral heads of 4 patients treated with seniarthroplasty after fracture. Demographic characteristics and Body Mass Index (BMI) were calculated for all subjects. RESULTS: Specimens were divided into four groups based on the Mankin histological severity score. The immunohistochemical study showed MMP-12 expression in the cartilage and subchonral bone of OA patients, while there was no expression in normal controls. At the moderate OA changes (Mankin score: 6-7), MMP-12 was detected mainly at the matrix of fibrocartilage tissue. During disease progression, MMP-12 was expressed at the sides of the cartilage and bone erosion and in the bone cysts. Furthermore, it was traced in the osteocytes of the subchondral bone. Osteoblast-like cells and bone lining cells express MMP-12 during the stage of severe OA (Mankin: ≥8). Osteoclasts expressing MMP-12 were also detected in the group of severe OA. Interestingly, MMP-12 expression was positively correlated with the age and the BMI of OA patients. CONCLUSION: The increased expression of MMP-12 in the bone-cartilage unit of OA patients suggests a possible role in OA pathogenesis and progression. LEVEL OF EVIDENCE: III, prospective comparative study.

Expression of the growth factor pleiotrophin and its receptor protein tyrosine phosphatase beta/zeta in the serum, cartilage and subchondral bone of patients with osteoarthritis.

OBJECTIVES: Pleiotrophin is a heparin-binding growth factor expressed in embryonic but not mature cartilage, suggesting a role in cartilage development. Elucidation of the molecular changes observed during the remodelling process in osteoarthritis is of paramount importance. This study aimed to investigate serum pleiotrophin levels and expression of pleiotrophin and its receptor protein tyrosine phosphatase beta/zeta in the cartilage and subchondral bone of osteoarthritis patients. METHODS: Serum samples derived from 16 osteoarthritis patients and 18 healthy donors. Pleiotrophin and receptor protein tyrosine phosphatase beta/zeta in the cartilage and subchondral bone were studied in 29 patients who had undergone total knee or hip replacement for primary osteoarthritis and in 10 control patients without macroscopic osteoarthritis changes. RESULTS: Serum pleiotrophin levels and expression of pleiotrophin in chondrocytes and subchondral bone osteocytes significantly increased in osteoarthritis patients graded Ahlback II to III. Receptor protein tyrosine phosphatase beta/zeta was mainly detected in the subchondral bone osteocytes of patients with moderate osteoarthritis and as disease severity increased, in the osteocytes and bone lining cells of the distant trabeculae. CONCLUSIONS: These data render pleiotrophin and receptor protein tyrosine phosphatase beta/zeta promising candidates for further studies towards developing targeted therapeutic schemes for osteoarthritis.

Integrity of posterior retinaculum after displaced femoral neck fractures.

INTRODUCTION: It is widely thought that the posterior retinaculum is intact only in relatively undisplaced intracapsular fractures, and interruption of the arterial flow through the retinacular arteries to the femoral head is the main cause of avascular necrosis after fracture of the neck. PATIENTS: In order to test the hypothesis that the posterior retinaculum is torn after a displaced femoral neck fracture, 112 patients (45 males and 67 females), 75 years old on average, underwent a hemiarthroplasty for a displaced femoral neck fracture. There were 71 Garden type III and 41 Garden type IV fractures. The integrity of the posterior retinaculum was examined intraoperatively in every patient during the procedure. RESULTS: The posterior retinaculum was found intact in all of the Garden type III fractures and in 39 Garden type IV fractures. The posterior retinaculum was found torn in two Garden type IV fractures. There was no tearing in any other part of the capsule of the hip joint in any patient. CONCLUSIONS: The posterior retinaculum of the hip joint remains intact after a displaced femoral neck fracture in all of Garden type III fractures and in the great majority of Garden type IV fractures.