title: Injectability and tissue compatibility of poly-(N-vinyl-2-pyrrolidone) in the skin of rats: a pilot study.
abstract: BACKGROUND
  Filling substances have been used in dermatologic surgery for decades, but an ideal agent has yet to be discovered. Poly-(N-vinyl-2-pyrrolidone) is a hydrogel that has been used in medical settings for more than 50 years, but not as a cutaneous filling agent.
  
  
  OBJECTIVE
  We investigated the intracutaneous injectability and tissue compatibility of this hydrogel in a rat model. Particular attention was paid to ease of injection through small needles, volume retention of the implant, clinical course, and histocompatibility.
  
  
  METHODS
  The shaved backs of 12 anesthetized Sprague-Dawley rats were injected with the sterilized hydrogel and the rats closely observed. The rats were sacrificed in groups of four at 2, 4, and 12 weeks after implantation. Implant size was measured, volume calculated, and biopsies taken at each time interval.
  
  
  RESULTS
  Poly-(N-vinyl-2-pyrrolidone) is easily injected through 30-gauge needles. All rats tolerated the implants well clinically. Histopathology revealed well-circumscribed implants with pseudoencapsulation, neoangiogenesis, and mixed inflammatory cells predominating at the periphery. Volume calculations revealed an average of 33% reduction at 4 weeks and 35% reduction at 12 weeks.
  
  
  CONCLUSIONS
  Poly-(N-vinyl-2-pyrrolidone) is easy to inject intracutaneously and is well tolerated in the rat model. Short-term volume retention is good. Histopathology suggests a subclinical inflammatory reaction expected with implantation of a synthetic substance into the skin. Additional studies are necessary to investigate the continued persistence of the hydrogel and its long-term effects on surrounding tissue.
authors.affiliation: Department of Dermatology, University of Iowa College of Medicine, Iowa City, Iowa 52242, USA. christopher-arpey@uiowa.edu
authors.forename: C J
authors.initials: CJ
authors.lastname: Arpey
authors.forename: L K
authors.initials: LK
authors.lastname: Chang
authors.forename: D C
authors.initials: DC
authors.lastname: Whitaker
mesh_terms: D000818:Animals; D001672:Biocompatible Materials; D062109:Dermatologic Surgical Procedures; D004195:Disease Models, Animal; D020100:Hydrogels; D007279:Injections, Subcutaneous; D008297:Male; D010865:Pilot Projects; D011205:Povidone; D051381:Rats; D017207:Rats, Sprague-Dawley; D012867:Skin / Q000473:pathology; D015625:Tissue Expansion Devices
chemical_list: D001672:Biocompatible Materials; D020100:Hydrogels; D011205:Povidone