title: Expression of chondro-osteogenic BMPs in clinical samples of patellar tendinopathy.
abstract: OBJECTIVE
  The pathogenesis of patellar tendinopathy remains unclear. Expression of BMP-2/-4/-7 was reported in an ossified failed tendon healing animal model of patellar tendinopathy. This study aimed to investigate the expression of these chondro-osteogenic BMPs in clinical samples of patellar tendinopathy.
  
  
  METHODS
  Patellar tendon samples were collected from 16 consecutive patients with patellar tendinopathy and 16 consecutive controls undergoing anterior cruciate ligament reconstruction with bone-patellar tendon-bone autograft in the authors' hospital after getting their consent. The expression of BMP-2/-4/-7 was examined in all samples using immunohistochemistry. Ossification observed in two tendinopathy samples was characterized by histology, alizarin red S staining, alcian blue staining, TRAP staining and immunohistochemical staining of Sox9, osteopontin (OPN) and osteocalcin (OCN).
  
  
  RESULTS
  Regions of hypo- and hyper-cellularity and vascularity, with loss of crimp structure of collagen matrix, were observed in patellar tendinopathy samples. Round cells and in some cases, cells with typical chondrocyte phenotype were observed. For the ossified tendinopathy samples with positive alizarin red S staining, OPN-positive and Sox9-positive chondrocyte-like cells in alcian blue-stained extracellular matrix, OCN-positive osteoblast-like cells and TRAP-positive multi-nucleated cells were observed around the ossified deposits. No expression of BMP-2/-4/-7 was observed in healthy patellar tendons. However, the expression of BMP-2/-4/-7 was observed in all patellar tendinopathy samples with or without ossification.
  
  
  CONCLUSIONS
  Clinical samples of patellar tendinopathy showed ectopic expression of BMP-2/-4/-7. This was not evident in control samples from healthy patellar tendons.
  
  
  METHODS
  Prognostic studies, Level III.
authors.affiliation: Department of Orthopaedics and Traumatology, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong SAR, China.
authors.forename: Yun Feng
authors.initials: YF
authors.lastname: Rui
authors.forename: Pauline Po Yee
authors.initials: PP
authors.lastname: Lui
authors.forename: Christer Gustav
authors.initials: CG
authors.lastname: Rolf
authors.forename: Yin Mei
authors.initials: YM
authors.lastname: Wong
authors.forename: Yuk Wa
authors.initials: YW
authors.lastname: Lee
authors.forename: Kai Ming
authors.initials: KM
authors.lastname: Chan
mesh_terms: D000135:Acid Phosphatase / Q000378:metabolism; D000328:Adult; D019485:Bone Morphogenetic Proteins / Q000378:metabolism*; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D007527:Isoenzymes / Q000378:metabolism; D008297:Male; D008853:Microscopy; D009999:Ossification, Heterotopic / Q000378:metabolism / Q000473:pathology; D015675:Osteocalcin / Q000378:metabolism; D053495:Osteopontin / Q000378:metabolism; D017847:Patellar Ligament / Q000378:metabolism* / Q000473:pathology; D010784:Photomicrography; D055758:SOX9 Transcription Factor / Q000378:metabolism; D013194:Staining and Labeling; D000071681:Tartrate-Resistant Acid Phosphatase; D052256:Tendinopathy / Q000378:metabolism* / Q000473:pathology
chemical_list: D019485:Bone Morphogenetic Proteins; D007527:Isoenzymes; D055758:SOX9 Transcription Factor; D015675:Osteocalcin; D053495:Osteopontin; D000135:Acid Phosphatase; D000071681:Tartrate-Resistant Acid Phosphatase