Reconstitution of discoidin domain receptor 2 (DDR2) restores expression of crosslinking enzymes. (a) Quantitative reverse-transcription real-time (RT)-PCR analysis of lysyl oxidase (LOX), lysyl hydroxylase1 (LH1) and 'secreted protein, acidic and rich in cysteine' (SPARC) mRNA levels in cultured skin fibroblasts. Results are expressed as relative to glyceraldehyde 3-phosphate dehydrogenase (GAPDH) mRNA expression. *P < 0.05, significantly different compared with DDR2-/- skin fibroblasts retrovirally infected with full-length DDR2 (-/-/WTR2). (b) Representative western blot analysis of LOX, LH1 and SPARC protein levels in cultured skin fibroblasts. Tubulin expression was used as control for protein loading. Bands were quantified by scanning densitometry analysis and relativized to protein expression in DDR2+/+ cells.