Human Circulating Peripheral Blood Mononuclear Cells for Calvarial Bone Tissue Engineering

Abstract

Large-scale production of engineered tissues requires an adequate source of expandable cells. Current strategies that involve harvesting of cells from donor tissue or bone marrow for tissue engineering are invasive and unfeasible for obtaining large quantities of cells in a clinical setting. Peripheral blood has been reported to contain circulating hematopoietic cells as well as, in significantly smaller quantities, mesenchymal cells An adherent subset of CD14+ mononuclear cells was isolated from human peripheral venous blood and characterized in vitro by light microscopy, immunohistochemistry, flow cytometry, and quantitative differentiation assays. These cells were then evaluated for the purposes of tissue engineering in a rat calvarial defect model, in combination with biodegradable polymer matrices made from poly-e-caprolactone. Specimens were analyzed 6 weeks after implantation with histologic analysis, microcomputed tomography, and HLA immunostaining. CD14+ mononuclear cells were induced to differentiate into osteoblast-like cells in vitro, with areas of mineralization. In a rat calvarial defect model, tissue-engineered bone with evidence of mineralization was formed within 6 weeks. HLA immunohistochemistry demonstrated that de novo bone formation originated from the transplanted human cells. These findings show, for the first time, to our knowledge, the derivation of bone from human blood. They also demonstrate the utility of circulating mononuclear cells as a minimally invasive, potentially unlimited pool of cells for tissue engineering and organ regeneration.