This is how collagen is made…. Collagen is synthesized inside fibroblasts through a tightly regulated, multi-step process that begins with gene transcription and ends with extracellular cross-linking. It starts in the nucleus, where specific collagen genes are transcribed and translated into pre-procollagen chains. These chains undergo post-translational modifications in the endoplasmic reticulum, primarily hydroxylation of proline and lysine residues, a process entirely dependent on vitamin C a