GFP chimeric models exhibited a biphasic pattern of mesenchymal cell invasion in tendon healing

J Cell Physiol. 2007 Mar;210(3):684-91. doi: 10.1002/jcp.20876.


The healing of an injured musculoskeletal system requires an influx of mesenchymal cells that can differentiate into osteoblasts, fibroblasts, chondroblasts, and skeletal myoblasts. However, whether these mesenchymal cells arise from the circulation (bone marrow) or the injured tissues themselves has been controversial. To reveal the spatiotemporal characteristics of the reparative mesenchymal cells, we investigated the healing process after patellar tendon injury using two types of green fluorescent protein (GFP) chimeric rats; one expressing GFP in the circulating cells, and the other expressing it in the patellar tendon. We analyzed the behavior of GFP-positive cells after experimental tendon injury in both chimeric rats to clarify the origin of reparative cells. At 24 h after the injury, the wound contained circulation-derived cells but not tendon-derived cells. Tendon-derived cells first appeared in the wounded area at 3 days after the injury, and had significantly increased in number with time and had maintained a high level of proliferative activity until 7 days after the injury, whereas the circulation-derived cells had decreased in number and had been replaced by the tendon-derived cells. These findings suggest that circulation-derived and tendon-derived cells contribute to the healing of tendons in different periods as part of a biphasic process.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Animals, Genetically Modified
  • Bone Marrow Cells / cytology
  • Bone Marrow Cells / metabolism
  • Cell Movement / physiology
  • Cell Proliferation
  • Chimera / genetics*
  • Female
  • Gene Expression Regulation / physiology
  • Green Fluorescent Proteins / metabolism
  • Mesenchymal Stem Cells / cytology*
  • Mesenchymal Stem Cells / metabolism
  • Models, Biological
  • Rats
  • Tendon Injuries / metabolism
  • Tendon Injuries / physiopathology*
  • Tendons / blood supply
  • Tendons / cytology*
  • Tendons / metabolism
  • Wound Healing / genetics
  • Wound Healing / physiology*


  • Green Fluorescent Proteins