title: Effects of low-level laser therapy on collagen expression and neutrophil infiltrate in 5-fluorouracil-induced oral mucositis in hamsters.
abstract: OBJECTIVE
  Several studies have suggested that low-level laser therapy (LLLT) can ameliorate oral mucositis; however, the mechanisms involved are not well understood. The aim of this study was to investigate the mechanisms of action of LLLT on chemotherapy-induced oral mucositis, as related to effects on collagen expression and inflammation.
  
  
  METHODS
  A hamster cheek pouch model of oral mucositis was used with all animals receiving intraperitoneal 5-fluorouracil, followed by surface irritation. Animals were randomly allocated into three groups, and treated with an InGaAIP diode laser at a wavelength of 660 nm and output power of 35 or 100 mW laser, or no laser. Clinical severity of mucositis was assessed at four time-points by a blinded examiner. Buccal pouch tissue was harvested from a subgroup of animals in each group at four time-points. Collagen was qualitatively and quantitatively evaluated after picrosirius staining. The density of the neutrophil infiltrate was also scored.
  
  
  RESULTS
  Peak clinical severity of mucositis was reduced in the 35 mW laser group as compared to the 100 mW and control groups. The reduced peak clinical severity of mucositis in the 35 mW laser group was accompanied by a decrease in the number of neutrophils and an increase in the proportion of mature collagen as compared to the other two groups. The total quantity of collagen was significantly higher in the control (no laser) group at the day 11 time-point, as compared to the 35 mW laser group, consistent with a more prolonged inflammatory response in the control group.
  
  
  CONCLUSIONS
  This study supports two mechanisms of action for LLLT in reducing mucositis severity. The increase in collagen organization in response to the 35 mW laser indicates that LLLT promotes wound healing. In addition, LLLT also appears to have an anti-inflammatory effect, as evidenced by the reduction in neutrophil infiltrate.
authors.affiliation: Department of Experimental Surgery, Federal University of São Paulo, São Paulo CEP 04023-062, Brazil. nnflopes@terra.com.br
authors.forename: Nilza Nelly Fontana
authors.initials: NN
authors.lastname: Lopes
authors.forename: Hélio
authors.initials: H
authors.lastname: Plapler
authors.forename: Rajesh V
authors.initials: RV
authors.lastname: Lalla
authors.forename: Maria Cristina
authors.initials: MC
authors.lastname: Chavantes
authors.forename: Elisabeth Mateus
authors.initials: EM
authors.lastname: Yoshimura
authors.forename: Marco Antonio Bastos
authors.initials: MA
authors.lastname: da Silva
authors.forename: Maria Teresa Seixas
authors.initials: MT
authors.lastname: Alves
mesh_terms: D000818:Animals; D000964:Antimetabolites, Antineoplastic / Q000009:adverse effects; D003094:Collagen / Q000378:metabolism*; D006224:Cricetinae; D005260:Female; D005472:Fluorouracil / Q000009:adverse effects; D028022:Low-Level Light Therapy; D009061:Mouth Mucosa / Q000378:metabolism / Q000473:pathology; D020556:Neutrophil Infiltration / Q000528:radiation effects*; D009504:Neutrophils / Q000378:metabolism; D011897:Random Allocation; D012720:Severity of Illness Index; D013280:Stomatitis / Q000139:chemically induced / Q000378:metabolism / Q000473:pathology / Q000628:therapy*; D014945:Wound Healing / Q000528:radiation effects
chemical_list: D000964:Antimetabolites, Antineoplastic; D003094:Collagen; D005472:Fluorouracil