Table 1.

Alterations in extracellular matrix (ECM) composition, structure and biophysical properties in osteoporosis and osteogenesis imperfecta (OI).

				Osteoporosis	OI
Composition	Inorganic matrix	Mineralization		↓	↑
		Mutated genes		N/A	IFITM5, SERPINF1
	Organic matrix	Type I collagen		COL1A1 *	↓
		NCPs	OPN	OPN +/+ → bone mass ↓ OPN −/− → bone volume ↑	N/A
			OC	↓	↓
			ON	ON −/− → bone formation ↓ ON * → BMD ↓	↓ Mutations in SPARC
Structure	Cortical	TMD		↓	↑
		Porosity		↑	↑
		Elasticity		N/A	↓
		Areal BMD, cortical bone area		N/A	↓
	Trabecular	Bone volume		↓	↓
		Bone trabecular number		↓	↓
		Porosity		↑	N/A
		Trabecular spacing		N/A	↑
		Tissue heterogeneity		↑	N/A
		Thickness		N/A	↑
Biophysical properties	Collagen crosslinking	Enzymatic		↓	N/A
		Nonenzymatic		↑	N/A
		Mutated genes		N/A	SERPINH1, FKBP10, PLOD2
	Mineral composition	Mineral/organic ratio		↓	N/A
		Mineral/matrix ratio		N/A	↑
		Microhardness		↓	N/A
		Mineral particles	Size	N/A	=/↓
			Packing density	N/A	↑
		Crystallinity		↓	↓

* Polymorphisms; ↓ decrease; ↑ increase; ^+/+ wild type; ^−/− knockout, =/↓ similar or decrease; N/A, not available; for definitions of other abbreviations, please see the main text.