Nucleated cells circulating in the peripheral blood contribute to the repair of osteochondral defects only in the early phase of healing.
The role of cells circulating in the peripheral blood to participate in the natural repair process of osteochondral defects was evaluated in a green fluorescent protein (GFP) transgenic and wild rat parabiosis model. Two weeks after the parabiosis operation, vascular communication between the conjoined rats was confirmed by flow-cytometry analysis. A 1.5 mm diameter and 1.0 mm depth osteochondral defect was made in the patellar groove of each rat femoral bone. Histological examination was performed at 1, 2, 4 and 24 weeks following surgery. In the early postoperative phase (1-4 weeks) there were GFP-negative and -positive cells in the defects of both parabiotic rats. GFP-positive chondrocytes were confirmed partly in the repair tissue of the wild parabiotic rat. In the late postoperative phase (24 weeks), the repaired defects were occupied by cells originating from the adjacent tissue and not from the peripheral blood. The ratio of cells originating from the peripheral blood was approximately 30-40% in the repair tissue at 1 week after surgery, reduced to 0-7% at 24 weeks. From these results it is confirmed that cells circulating in the peripheral blood contributed to the repair of the osteochondral defects, particularly in the early phase of healing. Thus, peripheral blood not only supplies the factors needed for repair but also provides a cell population involved in the wound-healing process.
Department of Orthopaedic Surgery, Osaka City University Graduate School of Medicine, Japan.
Tadashi
T
Okano
Shigeyuki
S
Wakitani
Takahiro
T
Okabe
Masafumi
M
Takahashi
Tatsuya
T
Koike
Hiroaki
H
Nakamura
D000818:Animals; D001808:Blood Vessels / Q000378:metabolism; D002452:Cell Count; D002465:Cell Movement; D002467:Cell Nucleus / Q000378:metabolism*; D019902:Chondrocytes / Q000473:pathology*; D049452:Green Fluorescent Proteins / Q000378:metabolism; D007150:Immunohistochemistry; D007962:Leukocytes / Q000166:cytology* / Q000378:metabolism; D010227:Parabiosis; D051381:Rats; D055647:Rats, Transgenic; D013997:Time Factors; D014945:Wound Healing
D049452:Green Fluorescent Proteins