Administrations of Peripheral Blood CD34-positive Cells Contribute to Medial Collateral Ligament Healing via Vasculogenesis

¹ Department of Orthopedic Surgery, Kobe University Graduate School of Medicine
² Department of Orthopedic Surgery, Kobe University Graduate School of Medicine; Stem Cell Translational Research, Kobe Institute of Biomedical Research and Innovation/RIKEN Center for Developmental Biology
³ Stem Cell Translational Research, Kobe Institute of Biomedical Research and Innovation/RIKEN Center for Developmental Biology
⁴ Stem Cell Translational Research, Kobe Institute of Biomedical Research and Innovation/RIKEN Center for Developmental Biology; Department of Regenerative Medicine Science, Tokai University School of Medicine

^* To whom correspondence should be addressed. E-mail: kurodar{at}med.kobe-u.ac.jp.

	Abstract

Neoangiogenesis is a key process in the initial phase of ligament healing. Adult human circulating CD34+ cells, an endothelial/hematopoietic progenitor-enriched cell population, have been reported to contribute to neoangiogenesis, however the therapeutic potential of CD34+ cells for ligament healing is still unclear. Therefore, we performed a series of experiments to test our hypothesis that ligament healing is supported by CD34+ cells via vasculogenesis. Granulocyte-stimulating factor mobilized peripheral blood (GM-PB) CD34+ cells with atelocollagen (CD34+ group), GM-PB mononuclear cells (MNCs) with atelocollagen (MNC group) or only atelocollagen (control group) were locally transplanted after creating medial collateral ligament injury in immunodeficient rats. Reverse transcriptase-polymerase chain reaction (RT-PCR) and immunohistochemical staining at the injury site demonstrated molecular and histological expression of human-specific markers for endothelial cells was higher in the CD34+ group compared with the other groups at week 1. Endogeneous effect assessed by capillary density and mRNA expression of vascular endothelial growth factor was significantly higher in CD34+ cell group than the other groups. In addition to the significantly higher gene expression of ligament-specific marker in the CD34+ group assessed by real time RT-PCR than the other groups, ligament healing assessed by macroscopic, histological and biomechanical examinations was significantly enhanced by CD34+ cell transplantation compared with the other groups. Our data strongly suggest that local transplantation of circulating human CD34+ cells may augment the ligament healing process by promoting a favorable environment through neovascularization.