Localization and quantification of the insulin-like growth factor-1 receptor in mouse articular cartilage by confocal laser scanning microscopy.
Insulin-like growth factor-1 (IGF-1) is an essential anabolic growth factor in the regulation of cartilage metabolism and exerts its effects by binding to the IGF-1 Type 1 receptor on the chondrocyte membrane. We have localized and quantified in situ IGF-1 receptor expression in intact articular cartilage of normal mice. The IGF-1 receptor was detected immunohistochemically with antibodies to the IGF-1 receptor and visualized with conventional light microscopy and confocal laser scanning microscopy (CLSM). CLSM analysis enabled us to distinguish IGF-1 receptor immunoreactivity on the chondrocyte cell membrane from intracellular staining. We have established two approaches to quantify in confocal images low levels of fluorescence intensity of the immunolocalized IGF-1 receptor at the chondrocyte membrane, i.e., mean pixel measurement and area measurement. The majority of IGF-1 receptor fluorescence intensity was localized on chondrocytes in the middle and deeper zones of cartilage, whereas chondrocytes in the surface zone exhibited negligible fluorescence. The variable distribution of IGF-1 receptor in chondrocytes of articular cartilage suggests that effects of IGF-1 on chondrocytes may be distinctly heterogeneous in the different mouse articular cartilage zones.
Verschure
P J
PJ
Department of Rheumatology, University Hospital Nijmegen, The Netherlands.
van Marle
J
J
Joosten
L A
LA
Van den Berg
W B
WB
D000818:Animals; D002358:Cartilage, Articular / Q000166:cytology / Q000378:metabolism*; D005260:Female; D005455:Fluorescent Antibody Technique; D007124:Immunoenzyme Techniques; D051379:Mice; D008810:Mice, Inbred C57BL; D008853:Microscopy / Q000379:methods; D017526:Receptor, IGF Type 1 / Q000032:analysis* / Q000378:metabolism*
D017526:Receptor, IGF Type 1