Journal of Stem Cell Research & Therapy

Abstract

A Clinical Study of Circulating Cellular and Humoral Biomarkers Involved in Bone Regeneration Following Traumatic Lesions

Hans Gottlieb, Tobias W. Klausen, Martin Boegsted, Bo S. Olsen, Gunnar S. Lausten, Jens Kastrup, Julia S. Johansen, Mette Nyegaard, Karen Dybkaer and Hans E. Johnsen

Background: Fracture healing includes formation of cartilage, blood vessels and bone, which involves circulating progenitor cells, cytokines and growth factors in a complex homeostasis of tissue regeneration. Here we describe a clinical study of circulating cellular and humoral variables by a time dependent multiparametric approach following traumatic lesions. Materials and Methods: Two prospective cohorts of 50 patients, with ankle- or hip fracture (cohort 1) or planned hip replacements (cohort 2) were studied as was age matched healthy controls. Blood samples were timely collected during the post traumatic period and analysed for i) non-haematopoietic (CD45neg) mesenchymal subsets by multiparametric flow cytometry (MFC), ii) global gene expression profiling (GEP) by micro array and iii) serum inflammatory markers including the growth factor YKL-40 by immunoassays (ELISA). Integrated analyses were performed to identify cellular and humoral patterns with potential impact on tissue regeneration. Results: Posttraumatic levels of circulating white blood cells, immature progenitor subsets and platelets as well as YKL-40, IL-6 and CRP varied biphasic and correlated to type of traumas. Analytic MFC identified two minor CD45neg blood compartments which simultaneously expressed varying degrees of CD105, CD133, CD73, VEGF-R, CD144, or CD31, CD34, CD166, CXCR4, respectively, supporting that mesenchymal subsets are involved in fracture healing. Analysis by microarray identified posttraumatic significant changes in gene expression of specific genes with known relation to inflammation, bone regeneration and angiogenesis in circulating mononuclear cells (MNC). ELISA quantitation of YKL-40 revealed posttraumatic changes higher in hip traumas compared to patients with ankle fractures (MNC: p=0.0006; YKL-40: p=0.0004). YKL-40 also correlated to the type of bone trauma, documented by different levels in patients with planned surgical hip replacements and traumatic hip fractures (p=0.005). Conclusions: The present study describes a posttraumatic time dependent cellular and humoral response after planned hip replacements, ankle and hip fractures. The data identify and enumerate potential mesenchymal progenitor cells supporting a regenerative role. Finally the analysis documented a correlation between the growth factor YKL-40 and bone traumas separating it from IL-6 and CRP. These observations can be used to future identification, isolation and characterization of circulating cells with impact in bone regeneration.