Murine Metatarsus Bone and Joint Collagen-I Fiber Morphologies and Networks Studied With SHG Multiphoton Imaging

Chronic inflammatory disease of bones and joints (e.g., rheumatoid arthritis, gout, etc.), but also acute bone injury healing, or degenerative resorptive processes inducing osteoporosis, are associated with structural remodeling that ultimately have impact on function. For instance, stability is predominantly orchestrated by the arrangement extracellular matrix fibrillar networks, i.e., collagen-I, -IV, elastin, other proteins. These components may undergo distinct network density orientation alterations be causative for decreased toughness, resilience load bearing capacity even increased brittleness. Diagnostic approaches usually confined to coarse imaging modalities X-ray computer tomography only provide limited optical resolution lack specificity visualize fibrillary collagen network. However, studying structure at microscopic scale considerable interest understand mechanisms tissue pathologies. Multiphoton Second Harmonic Generation (SHG) microscopy, able sterical topology collagen-I in 3D, a minimally invasive label-free manner. Penetration depths exceed those conventional visible light can further optimized through employing decalcification clearing processing ex vivo . The goal this proof-of-concept study was use SHG two-photon excited fluorescence (2-PEF) mainly characterize organization within decalcified normal mouse metatarsus joint. results show technique resolved complete almost no artifacts enabled complex networks various fiber types (straight, crimped) arrangements mature woven high degree detail. Our approach identify cavities both cortical trabecular architecture as well interfaces sharply changing morphology bone, tendon ligament joint areas. possibilities highly advantageous since technology easily applied animal models, e.g., arthritis effects chronic inflammation, many others compare human bone.