title: The Role of Cells in Meniscal Guided Tissue Regeneration: A Proof of Concept Study in a Goat Model.
abstract: OBJECTIVE
  Successful repair of defects in the avascular zone of meniscus remains a challenge in orthopedics. This proof of concept study aimed to investigate a guided tissue regeneration approach for treatment of tears in meniscus avascular zone in a goat model.
  
  
  METHODS
  Full-depth longitudinal tear was created in the avascular zone of the meniscus and sutured. In the two treatment groups, porcine collagen membrane was wrapped around the tear without (CM) or with injection of expanded autologous chondrocytes (CM+cells), whereas in the control group the tear remained only sutured. Gait recovery was evaluated during the entire follow-up period. On explantation at 3 and 6 months, macroscopic gross inspection assessed healing of tears, degradation of collagen membrane, potential signs of inflammation, and osteoarthritic changes. Microscopic histology scoring criteria were developed to evaluate healing of tears, the cellular response, and the inflammatory response.
  
  
  RESULTS
  Gait recovery suggested protective effect of collagen membrane and was supported by macroscopical evaluation where improved tear healing was noted in both treated groups. Histology scoring in CM compared to suture group revealed an increase in tear margins contact, newly formed connective tissue between margins, and cell formations surrounded with new matrix after 3 months yet not maintained after 6 months. In contrast, in the CM+cells group these features were observed after 3 and 6 months.
  
  
  CONCLUSIONS
  A transient, short-term guided tissue regeneration of avascular meniscal tears occurred upon application of collagen membrane, whereas addition of expanded autologous chondrocytes supported more sustainable longer term tear healing.
authors.affiliation: Institute of Pathology, University of Bern, Bern, Switzerland ; FREY-TOX GmbH, Herzberg, Germany.
authors.forename: Henriette
authors.initials: H
authors.lastname: Jülke
authors.affiliation: Institute of Pathology, University of Bern, Bern, Switzerland ; AGINKO Research AG, Fribourg, Switzerland.
authors.forename: Pierre
authors.initials: P
authors.lastname: Mainil-Varlet
authors.affiliation: Hopital Cantonal de Fribourg, Fribourg, Switzerland ; Route du lac 161, 1787 Môtier, Switzerland.
authors.forename: Roland P
authors.initials: RP
authors.lastname: Jakob
authors.affiliation: Faculty of Veterinary Medicine, Large Animal Clinic for Surgery, University of Leipzig, Leipzig, Germany.
authors.forename: Walter
authors.initials: W
authors.lastname: Brehm
authors.affiliation: Geistlich Pharma AG, Wolhusen, Switzerland.
authors.forename: Birgit
authors.initials: B
authors.lastname: Schäfer
authors.affiliation: Institute of Pathology, University of Bern, Bern, Switzerland ; Department of Clinical Research, University of Bern, Bern, Switzerland.
authors.forename: Dobrila
authors.initials: D
authors.lastname: Nesic
keywords: animal models; biomaterials; chondrocytes; histology scoring system; meniscus