Glycosaminoglycan chains of biglycan promote bone morphogenetic protein-4-induced osteoblast differentiation
Authors: Weikai Zhang
Jiang Wang
Weihua Hu
Fengjing Guo
Anmin Chen
Yaping Ye
Journal: International Journal of Molecular Medicine (2012)
Discipline: CLINICAL MEDICINE
Keywords: Biglycan; BMP-4; osteoblast differentiation; glycosaminoglycan chains; GAG-mutant
Affiliations: Department of Orthopedics, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, PR China.

Abstract:  Biglycan (BGN) has been reported to promote bone morphogenetic protein-4 (BMP-4) stimulated osteoblastic differentiation. However, the underlying mechanism has yet to be fully elucidated. The glycosaminoglycan (GAG) chains of BGN have a variety of biological functions. In the present study, we explored the potential role of the GAG chains of BGN in promoting BMP-4-induced osteoblast differentiation. BGN knockout (KO) murine calvarial cells were transfected with adenovirus overexpressing wild-type BGN (Adv-BGN), adenovirus expressing GAG-mutant BGN (Adv-BGNm) and adenovirus without BGN (Adv-Emp). Transfected cells were treated with or without BMP-4. Subsequently, BMP-4 signaling and function were assessed by evaluating the expression of the osteoblast differentiation-related proteins, Smad1/5/8 phosphorylation and alkaline phosphatase (ALP) activity. Furthermore, the binding specificity of the transfected cells to BMP-4 was also investigated using immunofluorescence staining. Our study demonstrated that a mutant BGN lacking GAG chains decreased BGN-assisted BMP-4 signaling and osteoblast differentiation and that the expression of this mutant BGN in biglycan knockout (BGN‑KO) calvarial osteoblasts could not rescue its differentiation deficiency as efficiently as wild-type (WT) BGN. These results strongly suggest that the GAG chains of BGN promote BGN-assisted BMP-4 function. 

Retracted: No

PubPeer comments:
 The Western blot panel in Figure 1A seems to be manipulated. Some lanes are more similar than they should be. ![file] , 
 Dear Indigofera Tanganyikensis, Thank you so much for your comment, I really appreciate your work. This paper was published in 2012 which was eight years ago. I re-examined the experimental results and raw data carefully during the past month. And I believe that western blot data in the paper including Fig1A, Fig1B, Fig2A, Fig2C, Fig5A are valid. In this paper, we showed that glycosaminoglycan (GAGs) chains of biglycan could promote BMP-4 induced osteoblast differentiation, and the expression of a mutant biglycan lacking GAGs binding sites cannot rescue the differentiation deficiency. Our paper was also cited by many different papers. For example, the paper u2018Biglycan and chondroitin sulfate play pivotal roles in bone toughness via retaining bound water in bone mineral matrixu2019 uff08Matrix Biol ,2020 Dec;94:95-109. uff09has cited our paper. And in this paper, the investigators also proved that Biglycan was critical in bone toughness by retaining bound water in the bone mineral matrix. I agree with you that there are some flaws in the western blot data in our paper and the data in Fig1A seems to be manipulated. I will try to perform the same experiments again in the future again to further verify the western blots. And I will contact the journal to check if I need to correct the data in this paper. Thank you again for your work, your comment means a lot to me. Best wishes to youuff01 ,