Bone marrow-derived heparan sulfate potentiates the osteogenic activity of bone morphogenetic protein-2 (BMP-2)

Abstract

Lowering the efficacious dose of bone morphogenetic protein-2 (BMP-2) for the repair of critical-sized bone defects is highly desirable, as supra-physiological amounts of BMP-2 have an increased risk of side effects and a greater economic burden for the healthcare system. To address this need, we explored the use of heparan sulfate (HS), a structural analog of heparin, to enhance BMP-2 activity. We demonstrate that HS isolated from a bone marrow stromal cell line (HS5) and heparin each enhances BMP-2-induced osteogenesis in C2C12 myoblasts, through increased ALP activity and osteocalcin mRNA expression. Commercially available HS variants from porcine kidney and bovine lung failed to generate similar effects. Heparin and HS5 influence BMP-2 activity by (i) prolonging BMP-2 half-life, (ii) reducing interactions between BMP-2 with its antagonist noggin, and (iii) modulating BMP2 distribution on the cell surface. Importantly, long-term supplementation of HS5 but not heparin greatly enhances BMP-2-induced bone formation in vitro and in vivo. These results show that bone marrow-derived HS effectively support bone formation, and suggests its applicability in bone repair by selectively facilitating the delivery and bioavailability of BMP-2.

Sustained dual release of placental growth factor-2 and bone morphogenic protein-2 from heparin-based nanocomplexes for direct osteogenesis

“…the osteogenic effects is complex, mainly owing to the reversible, noncovalent interactions between heparin and heparin-binding GFs, which ensure minimal impact on GF structure. 13,30,37,39,43,44,[48][49][50][51][52] We demonstrated that the nanocomplexes in our study not only effectively loaded and sustained release of PlGF-2/BMP-2, but also maintained their bioactivities for bone regeneration. A key result in this study was the bioactivity of the released PlGF-2 being comparable to that of the released BMP-2, despite its dose being half that of BMP-2.…”

“…38,39,43 Also, Martino et al 40 showed that domain II (Fg β15-66 (2) ) of heparin exhibits high affinity for GFs in general, but with heparin displaying a fourfold stronger affinity for PlGF-2 than for BMP-2; 44 they also revealed a specific heparin-binding portion of PlGF-2 spanning residues 123-144 and having the sequence RRPKGRGKRRREKQRPTDCHL. 44 However, in our study, the difference of loading efficiency between PlGF-2 and BMP-2 was not so prominent, perhaps because both GFs were applied at overall low doses and exhibited high affinity to heparin.…”

Exogenous heparin binds and inhibits bone morphogenetic protein 6 biological activity

“…We also showed that exogenous heparin dosedependently inhibited BMP6-mediated ectopic bone formation in rats which is in contrast to previous results showing that heparin potentiates BMP2 osteogenic activity [50,53]. These differences are consistent with in vitro data, showing that heparin influences the activity of various BMPs differently [15,30,50].…”

Dynamic and Responsive Growth Factor Delivery from Electrospun and Hydrogel Tissue Engineering Materials

“…[62] Heparin sulfate, which is less negatively charged and which shows less generalized affinity than heparin, has been used to mitigate this problem with BMP-2. [63] More interestingly, this effect has also been specifically used to improve therapeutic outcomes. A customized heparin hydrogel system was designed for maximal binding of inflammatory cytokines, which inhibit wound healing, and was shown to outperform the commercial Promogran product in reducing inflammation and promoting wound healing in mice.…”