title: The effect of injection volume on disc degeneration in a rat tail model.
abstract: METHODS
  A prospective study to compare the effects of injection of various doses of phosphate-buffered saline (PBS) solution into the intervertebral disc.
  
  
  OBJECTIVE
  To evaluate the effect of injection volume on disc degeneration in a rat tail-disc model.
  
  
  BACKGROUND
  There are many studies on disc degeneration models induced by needle injection. Recently, novel treatments for disc degeneration have been developed that are administered by injection. However, it is unknown whether injection volume affects disc degeneration.
  
  
  METHODS
  A total of 180 Sprague Dawley rats were randomized into five groups and injected with 0(control), 1.0, 2.0, 2.5, or 3.0 μL of PBS solution. Discs were harvested at weeks 1, 2, and 4 after injection and were evaluated using radiography, histology, and biochemistry (glycosaminoglycan, hydroxyproline, and water content).
  
  
  RESULTS
  No significant differences in radiography, biochemistry, or histology were observed at any of the three sampling times between the 1.0, 2.0 μL groups and the control. The 2.5 and 3.0 μL groups exhibited significant decrease in radiographic disc height index and water content since week 2. The glycosaminoglycan content of 2.5 μL group decreased significantly by week 4 and that of 3.0 μL group decreased at weeks 2 and 4. Significant hydroxyproline content decrease was only observed for 3.0 μL group during week 4. Significantly higher histologic score was observed in 3.0 μL group since week 1 and 2.5 μL group since week 2. The three parameters of 3.0 μL group indicated more severe disc degeneration than those of 2.5 μL group, particularly during week 4.
  
  
  CONCLUSIONS
  When the volume of PBS injected into the rat tail-disc exceeded a threshold, it rapidly exhibited degenerative changes according to radiographic, biochemical, and histologic analysis. The degenerative changes were dose-dependent and increased as the dose increased.
authors.affiliation: Department of Orthopedic Surgery, Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, People's Republic of China.
authors.forename: Hua-jie
authors.initials: HJ
authors.lastname: Mao
authors.forename: Qi-xin
authors.initials: QX
authors.lastname: Chen
authors.forename: Bin
authors.initials: B
authors.lastname: Han
authors.forename: Fang-cai
authors.initials: FC
authors.lastname: Li
authors.forename: Jie
authors.initials: J
authors.lastname: Feng
authors.forename: Zhong-li
authors.initials: ZL
authors.lastname: Shi
authors.forename: Min
authors.initials: M
authors.lastname: Lin
authors.forename: Jun
authors.initials: J
authors.lastname: Wang
mesh_terms: D000818:Animals; D004305:Dose-Response Relationship, Drug; D006025:Glycosaminoglycans / Q000378:metabolism; D006909:Hydroxyproline / Q000378:metabolism; D007267:Injections / Q000009:adverse effects*; D007403:Intervertebral Disc / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D055959:Intervertebral Disc Degeneration / Q000000981:diagnostic imaging / Q000209:etiology*; D008297:Male; D009339:Needles / Q000009:adverse effects; D010710:Phosphates / Q000737:chemistry; D011859:Radiography; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D012965:Sodium Chloride / Q000008:administration & dosage* / Q000009:adverse effects / Q000737:chemistry; D013997:Time Factors; D014867:Water / Q000378:metabolism
chemical_list: D006025:Glycosaminoglycans; D010710:Phosphates; D014867:Water; D012965:Sodium Chloride; D006909:Hydroxyproline