Table 2.

Expression of membrane-bound MMPs in normal tissues.

	Gene/name	cDNA	Expression in normal tissues
	MMP-14 (MT1-MMP)	Isolated from a human placenta cDNA library [73]	Highly expressed in ossifying tissues and during mouse embryogenesis, where it is coexpressed with MMP-2 [74]. Low expression in normal conditions.
Type I transmembrane MMPs	MMP-15 (MT2-MMP)	Isolated from a mouse lung cDNA library [75]	Highly expressed in T cells [76], rat smooth muscle cells [77], and endothelial cells [78]. Expressed in hepatocytes and biliary epithelial cells [79], in cytotrophoblasts [80], in activated NK-cells [81], and in microglial cells [82].
	MMP-16 (MT3-MMP)	Isolated from placenta cDNA library [63]	Expressed in human brain tissues (microglial cells) [62]; T cells [76]; endothelial cells [78, 83]; Langerhans cells following cell activation [84].
	MMP-24 (MT5-MMP)	Isolated from mouse brain cDNA library [54]	Predominantly expressed in the central nervous system [85] and in T lymphocytes [76].
GPI-anchored MMPs	MMP-17 (MT4-MMP)	Isolated from a human breast carcinoma cDNA library [66]	Expressed in monocytic cells [86], leukocytes, brain, ovary, testis, and colon [66].MMP-17 mRNA is significantly represented in B cells [76].
	MMP-25 (MT6-MMP)	Isolated from peripheral blood leukocytes [64]	Predominantly expressed in leukocytes [64]. In rats, mRNA peak expression levels in testis, kidney, and skeletal muscle [85].
Type II transmembrane MMPs	MMP-23	Isolated from an ovarian cDNA library [3]	Abundantly expressed in normal tissues in adults under quiescent conditions and predominantly expressed in reproductive tissues and others such as heart [3].