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Imaging IGF‐I Uptake in Growth Plate Cartilage Using in vivo Multiphoton Microscopy
Author(s) -
Serrat Maria,
Ion Gabriela
Publication year - 2015
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.29.1_supplement.12.5
Subject(s) - cartilage , microbiology and biotechnology , extracellular matrix , paracrine signalling , in vivo , growth factor , chemistry , chondrocyte , biomedical engineering , biophysics , anatomy , biology , medicine , biochemistry , receptor
Bone elongation occurs in cartilaginous growth plates located at the ends of the principal long bones. Linear growth is driven by a cascade of cellular signals initiated by endocrine and paracrine regulators acting on growth plate chondrocytes. Relative to our knowledge of their signaling mechanisms, surprisingly little is known about how these molecules physically reach avascular cartilage (which lacks a penetrating blood supply) or how they are transported from surrounding blood vessels through the dense extracellular matrix. In vivo multiphoton microscopy is a powerful imaging modality that enables the study of intact growth plates with cellular level resolution. This imaging approach has potential to fundamentally advance our understanding of bone lengthening processes by allowing us to track molecular delivery to cartilage in real time. We developed quantitative methods for measuring the uptake of biologically active IGF‐I into tibial growth plates of live 5‐week old mice. We demonstrate that fluorescently‐labeled IGF‐I is readily taken up in growth plate cartilage and localizes to chondrocytes. In vitro bioactivity tests confirmed that the labeled protein is functional, assessed by phosphorylation of its downstream targets. These results are relevant for understanding mechanisms of growth plate regulation and for developing strategies to modulate limb elongation rate through growth factor delivery to cartilage. Supported by ASBMR GAP, UK‐CCTS (NIH UL1TR000117), and the National Institute of Arthritis and Musculoskeletal and Skin Diseases (R15AR067451‐01).