Lysophosphatidic acid-functionalised titanium as a superior surface for supporting human osteoblast (MG63) maturation

Abstract

Covalent modifications of titanium with small molecules known to promote human osteoblast maturation are especially attractive in developing superior biomaterials. An important step in securing competent bone formation at implant sites is promoting the formation of mature osteoblasts, either from committed pre-osteoblasts or from their mesenchymal progenitors. To this end our research has focussed on identifying molecules that enhance human osteoblast formation and maturation and to develop ways of covalently attaching these molecules to implant surfaces so that they are more likely to withstand the rigors of the implantation process whilst still retaining their bioactivity. Herein we report the novel production of lipid-functionalised titanium using lysophosphatidic acid or a related compound, (3S) 1-fluoro-3-hydroxy-4-butyl-1-phosphonate. Both lipids were especially effective at co-operating with calcitriol to promote human osteoblast maturation at these modified Ti surfaces in vitro. The novel findings presented offer enticing new developments towards the fabrication of next-generation implant devices with the potential to significantly enhance the osseointegration process and with it improvements in future prosthesis performance and longevity.

24,25-Dihydroxyvitamin D3 cooperates with a stable, fluoromethylene LPA receptor agonist to secure human (MG63) osteoblast maturation

“…What remains to be determined is whether 24R,25D can promote hOB maturation when co-administered with agents known to synergistically co-operate with 1,25D; it is becoming clear that 1,25D often needs to interact with other factors to prosecute the desired response in target cells [13]. In our hands we consistently find that hOBs do not mobilise alkaline phosphatase (ALP) when treated with 1,25D in a serum-free in vitro setting and will only do so when the cells are in receipt of both 1,25D and certain growth factors such as epidermal growth factor [14], lysophosphatidic acid (LPA) or certain LPA receptor selective agonists [15][16][17][18]. Whilst a significant body of work is emerging on the role of LPA in osteoblast, and indeed skeletal biology in general, we will not expand on those areas here.…”

“…The treatment of cells to quantify ALP activity was similar to that described by us recently [17]. Briefly, the MTS/PMS reagent was removed and the monolayers incubated for a further 15 min in fresh phenol red-free DMEM/ F12 to remove the residual formazan.…”

“…Our focus for using FHBP stems from its development as a phosphataseresistant, -fluoromethylene LPA analog with selective agonistic activity for the LPA3 receptor [26,27]. Of relevance to hOB fate, we recently reported that much lower concentrations of this compound, relative to LPA, co-operate with 1,25D in driving hOB maturation [17]. Importantly hOBs and human bone marrow stem cells express LPA3 receptors [25] and so the application of LPA3 agonists is entirely appropriate when 4 examining their interaction with non-calcaemic VDR ligands.…”

Lysophosphatidic Acid and Sphingosine-1-Phosphate: A Concise Review of Biological Function and Applications for Tissue Engineering

“…Although the hydrogel-based systems that have been investigated for cell survival and therapeutic angiogenesis are only mildly osteoinductive, we have shown that the addition of mineralized PLGA microspheres to fibrin gels further enhances osteogenic differentiation 113 ; such a system would allow for similar physical entrapment of LPA and presentation. Alternately, other groups are pursuing the covalent attachment of LPA to titanium constructs with the goal of stimulating osteoblast maturation and osseointegration 114 on scaffolds better suited to load-bearing applications. Given the pro-angiogenic and pro-arteriogenic nature of S1P, exogenous delivery has also been used in approaches for enhancing tissue-engineered bone regeneration.…”

Alkaline phosphatase binds tenaciously to titanium; implications for biological surface evaluation following bone implant retrieval

“…In ascertaining the stability of our lysophosphatidate-functionalised Ti materials [2][3] to bone insertion, recovered and non-inserted functionalised controls were seeded with MG63 osteoblasts, cultured under conventional conditions for three days, and an assessment of cellular maturation determined via TNSALP activity assay. To our surprise we unexpectedly found that inserted, lysophosphatidate-functionalised dental implants were associated with the greatest TNSALP activity (~9 times greater) compared to irrigated, non-inserted, functionalised controls.…”