BMP-non-responsive Sca1+ CD73+ CD44+ mouse bone marrow derived osteoprogenitor cells respond to combination of VEGF and BMP-6 to display enhanced osteoblastic differentiation and ectopic bone formation
Authors: Ching-Ju Li
Gary Balian
Abhijit S Dighe
Quanjun Cui
Vedavathi Madhu
Journal: PLoS ONE (2014)
Discipline: Multidisciplinary
Keywords: fracture repair; bone morphogenetic proteins (BMPs); mesenchymal stem cells (MSCs); vascular endothelial growth factor (VEGF); osteoblastic differentiation
Affiliations: Orthopaedic Research Laboratories, Department of Orthopaedic Surgery, University of Virginia, Charlottesville, Virginia, United States of America.

Abstract:  Clinical trials on fracture repair have challenged the effectiveness of bone morphogenetic proteins (BMPs) but suggest that delivery of mesenchymal stem cells (MSCs) might be beneficial. It has also been reported that BMPs could not increase mineralization in several MSCs populations, which adds ambiguity to the use of BMPs. However, an exogenous supply of MSCs combined with vascular endothelial growth factor (VEGF) and BMPs is reported to synergistically enhance fracture repair in animal models. To elucidate the mechanism of this synergy, we investigated the osteoblastic differentiation of cloned mouse bone marrow derived MSCs (D1 cells) in vitro in response to human recombinant proteins of VEGF, BMPs (-2, -4, -6, -9) and the combination of VEGF with BMP-6 (most potent BMP). We further investigated ectopic bone formation induced by MSCs pre-conditioned with VEGF, BMP-6 or both. No significant increase in mineralization, phosphorylation of Smads 1/5/8 and expression of the ALP, COL1A1 and osterix genes was observed upon addition of VEGF or BMPs alone to the cells in culture. The lack of CD105, Alk1 and Alk6 expression in D1 cells correlated with poor response to BMPs indicating that a greater care in the selection of MSCs is necessary. Interestingly, the combination of VEGF and BMP-6 significantly increased the expression of ALP, COL1A1 and osterix genes and D1 cells pre-conditioned with VEGF and BMP-6 induced greater bone formation in vivo than the non-conditioned control cells or the cells pre-conditioned with either VEGF or BMP-6 alone. This enhanced bone formation by MSCs correlated with higher CADM1 expression and OPG/RANKL ratio in the implants. Thus, combined action of VEGF and BMP on MSCs enhances osteoblastic differentiation of MSCs and increases their bone forming ability, which cannot be achieved through use of BMPs alone. This strategy can be effectively used for bone repair. 

Retracted: No

PubPeer comments:
 This paper has two corrections. Correction 1, September 2014, found here: https: journals.plos.org plosone article?id=10.1371 journal.pone.0110204 - This corrects a missing label in Figure 4C. Correction 2, January 2019, found here: https: journals.plos.org plosone article?id=10.1371 journal.pone.0211782 - It reads:  After publication of this article [1], concerns were raised about Figs 1 and 2. There were errors in the preparation of the left panel of Fig 1 which resulted in duplication of wells within the figure. A detailed visual guide to the errors generated while copying the wells from the original images is provided as Supporting Information (S1 File). Please see the corrected Fig 1 here, which was prepared by copying the first row of every experimental group for the sake of uniformity and clarity. The errors did not affect the data charts shown in Fig 1 nor the results and conclusions reported. Here are the concerns about Figure 1, as reported to the journal in October 2015. ![file] ,