title: Protease inhibitors enhance extracellular collagen fibril deposition in human mesenchymal stem cells.
abstract: BACKGROUND
  Collagen is a widely used naturally occurring biomaterial for scaffolding, whereas mesenchymal stem cells (MSCs) represent a promising cell source in tissue engineering and regenerative medicine. It is generally known that cells are able to remodel their environment by simultaneous degradation of the scaffolds and deposition of newly synthesized extracellular matrix. Nevertheless, the interactions between MSCs and collagen biomaterials are poorly known, and the strategies enhancing the extracellular matrix deposition are yet to be defined. In this study, we aim to investigate the fate of collagen when it is in contact with MSCs and hypothesize that protease inhibition will enhance their extracellular deposition of collagen fibrils.
  
  
  METHODS
  Specifically, human MSCs (hMSCs) were exposed to fluorescence-labeled collagen with and without intracellular or extracellular protease inhibitors (or both) before tracing the collagen at both intracellular and extracellular spaces.
  
  
  RESULTS
  Collagen were internalized by hMSCs and degraded intracellularly in lysosomes. In the presence of protease inhibitors, both intracellular collagen fibril growth and extracellular deposition of collagen fibrils were enhanced. Moreover, protease inhibitors work synergistically with ascorbic acid, a well-known matrix deposition-enhancing reagent, in further enhancing collagen fibril deposition at the extracellular space.
  
  
  CONCLUSIONS
  These findings provide a better understanding of the interactions between hMSCs and collagen biomaterials and suggest a method to manipulate matrix remodeling and deposition of hMSCs, contributing to better scaffolding for tissue engineering and regenerative medicine.
authors.affiliation: Tissue Engineering Laboratory, Department of Mechanical Engineering, The University of Hong Kong, Room 711, Haking Wong Building, Pokfulam Road, Hong Kong Special Administrative Region, China. hansejin@gmail.com.
authors.forename: Sejin
authors.initials: S
authors.lastname: Han
authors.affiliation: Tissue Engineering Laboratory, Department of Mechanical Engineering, The University of Hong Kong, Room 711, Haking Wong Building, Pokfulam Road, Hong Kong Special Administrative Region, China. carolineyyli@gmail.com.
authors.forename: Yuk Yin
authors.initials: YY
authors.lastname: Li
authors.affiliation: Tissue Engineering Laboratory, Department of Mechanical Engineering, The University of Hong Kong, Room 711, Haking Wong Building, Pokfulam Road, Hong Kong Special Administrative Region, China. bpchan@hku.hk.
authors.forename: Barbara Pui
authors.initials: BP
authors.lastname: Chan
mesh_terms: D001205:Ascorbic Acid / Q000008:administration & dosage / Q000494:pharmacology; D001672:Biocompatible Materials / Q000378:metabolism; D002478:Cells, Cultured; D003094:Collagen / Q000378:metabolism*; D024042:Collagen Type I / Q000378:metabolism; D005109:Extracellular Matrix / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D008422:Materials Testing; D059630:Mesenchymal Stem Cells / Q000187:drug effects* / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D011480:Protease Inhibitors / Q000008:administration & dosage / Q000494:pharmacology*; D059748:Proteolysis / Q000187:drug effects; D044968:Regenerative Medicine; D023822:Tissue Engineering; D054457:Tissue Scaffolds
chemical_list: D001672:Biocompatible Materials; D024042:Collagen Type I; D011480:Protease Inhibitors; D003094:Collagen; D001205:Ascorbic Acid