title: [Experimental study on collagen hydrogel scaffolds for cartilage tissue engineering].
abstract: OBJECTIVE
  To investigate the effect of collagen type I concentration on the physical and chemical properties of the collagen hydrogel, and to analyze the effect of different concentrations of collagen type I hydrogel on the phenotype and gene expression of the chondrocytes in vitro.
  
  
  METHODS
  Three kinds of collagen hydrogels with concentrations of 12, 8, and 6 mg/mL (C12, C8, and C6) were prepared, respectively. The micro-structure, compressive modulus, and swelling ratio of the hydrogels were measured and analyzed. The chondrocytes at 2nd passage were cocultured with three kinds of collagen hydrogels in vitro, respectively. After 1-day culture, the samples were stained with fluorescein diacetate (FDA)/ propidium iodide (PI) and the cell activity was observed under confocal laser microscope. After 14-day culture, HE staining and toluidine blue staining were carried out to observe the histological morphology, and mRNA expressions of chondrocytes related genes (collagen type II, Aggrecan, collagen type I, collagen type X, Sox9) were determined by real-time fluorescent quantitative PCR.
  
  
  RESULTS
  With the increase of collagen type I concentration from 6 to 12 mg/mL, the physical and chemical properties of the collagen hydrogels changed significantly: the fiber network became dense; the swelling ratios of C6, C8, and C12 were 0.260 +/- 0.055, 0.358 +/- 0.072, and 0.539 +/- 0.033 at 192 hours, respectively, showing significant differences among 3 groups (P < 0.05); and the compression modulus were (4.86 +/- 0.96), (7.09 +/- 2.33), and (11.08 +/- 3.18) kPa, respectively, showing significant differences among 3 groups (P < 0.05). After stained with FDA/PI, most cells were stained green, and few were stained red. The histological observation results showed that the chondrocytes in C12 hydrogels aggregated obviously with strong heterochromia, chondrocytes in C8 hydrogels aggregated partly with obvious heterochromia, and chondrcytes in C6 hydrogels uniformly distributed with weak heterochromia. Real-time fluorescent quantitative PCR results showed that the mRNA expressions of collagen type II and Aggrecan were at the same level in C12, C8, and C6; the expressions of collagen type I, Sox9, and collagen type X were up-regulated with the increase of collagen type I hydrogels concentration, and the expressions were the highest at 12 mg/mL and were the lowest at 6 mg/mL, showing significant differences among 3 groups (P < 0.05).
  
  
  CONCLUSIONS
  Increasing the concentration of collagen hydrogels leads to better mechanical properties and higher shrink-resistance, but it may induce the up-regulation of cartilage fibrosis and hypertrophy related gene expression.
authors.affiliation: National Engineering Research Center for Biomaterials, Sichuan University, Chengdu Sichuan, 610065, P.R.China.
authors.forename: Kuifeng
authors.initials: K
authors.lastname: Li
authors.forename: Likun
authors.initials: L
authors.lastname: Guo
authors.forename: Yujiang
authors.initials: Y
authors.lastname: Fan
authors.forename: Xingdong
authors.initials: X
authors.lastname: Zhang
mesh_terms: D053674:Aggrecans / Q000235:genetics / Q000378:metabolism; D000818:Animals; D002358:Cartilage, Articular / Q000166:cytology* / Q000378:metabolism; D049109:Cell Proliferation; D019902:Chondrocytes / Q000166:cytology* / Q000378:metabolism; D003094:Collagen / Q000235:genetics / Q000378:metabolism; D024042:Collagen Type I / Q000737:chemistry* / Q000378:metabolism; D005260:Female; D005786:Gene Expression Regulation; D020100:Hydrogels / Q000737:chemistry*; D008297:Male; D010641:Phenotype; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011817:Rabbits; D023822:Tissue Engineering / Q000379:methods; D054457:Tissue Scaffolds / Q000737:chemistry*; D015854:Up-Regulation
chemical_list: D053674:Aggrecans; D024042:Collagen Type I; D020100:Hydrogels; D012333:RNA, Messenger; D003094:Collagen