Abstract
Demineralized bone matrix (DBM) is commonly used for the reconstruction of bone defects. Early graft consolidation involves a transient inflammatory process. It is, however, unclear whether DBM can modulate this process. To test this possibility, we prepared acid lysates of demineralized ground cortical (DGC) and moldable demineralized fibers (MDF). Murine RAW 264.7 and primary bone marrow macrophages were exposed to acid lysates of DGC and MFD prior to provoking an inflammatory response with lipopolysaccharide (LPS). Similarly, murine ST2 mesenchymal cells were exposed to DGC and MFD with and without interleukin 1β (IL1) and TNFα. We show here that acid lysates of DGC and MFD reduced the expression of IL1 and IL6 in RAW 264.7 macrophages, as determined by RT-PCR and, for IL6, by immunoassay. This response was confirmed with primary macrophages. Likewise, desalted acid lysates exert anti-inflammatory properties on RAW 264.7 cells and in ST2 cells, the forced expression of IL6, inducible nitric oxide synthase (iNOS) and chemokine ligand 5 (CCL5) was reduced. These in vitro findings suggest that DGC and MFD lower the inflammation-induced expression of inflammatory mediators in murine cell-based bioassays.
Highlights
Demineralized bone matrix (DBM) is used to reconstruct bony defects [1], including in dental [2,3], trauma [4] and spinal surgery [5]
We have recently identified TGF-β to be released into a liquid fraction from bone allografts, e.g., demineralized ground cortical (DGC) and moldable demineralized fibers (MDF) [13]
Strong support for the anti-inflammatory activity of DGC and MDF comes from experiments with primary macrophages where DGC and MDF consistently reduced the expression of interleukin 1β (IL1) and IL6 of LPS-treated cells (Figure 4)
Summary
Demineralized bone matrix (DBM) is used to reconstruct bony defects [1], including in dental [2,3], trauma [4] and spinal surgery [5]. Demineralized bone is derived from cadaver bone that undergoes multiple steps of processing until it is available as a ready-to-use allograft [1] This processing pays particular attention to maintain the activity of the growth factors stored in the extracellular matrix, most of all the members of the bone morphogenetic protein (BMP) family with their unique osteoinductive properties [7,8]. Inducible nitric oxide synthases (iNOS) is involved in fracture healing [24] and mesenchymal cells expressing chemokine ligand 5 (CCL5; known as RANTES) support revascularization [25] In this pilot study, we show in vitro data suggesting that acid lysates prepared from DGC and MDF lower the expression of inflammatory mediators
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