Abstract
Background
In 2012, the National Joint Registry recorded 86,488 primary total hip replacements (THR) and 9,678 revisions (1). To date aseptic loosening remains the most common cause of revision in hip and knee arthroplasty, accounting for 40% and 32% of all cases respectively and emphasising the need to optimise osseointegration in order to reduce revisions. Clinically, osseointegration results in asymptomatic stable durable fixation of orthopaedic implants. Osseointegration is a complex process involving a number of distinct mechanisms affected by the implant surface topography, which is defined by surface orientation and surface roughness. Micro- and nano-topography levels have discrete effects on implant osseointegration and yet the role on cell function and subsequent bone implant function is unknown. Nanotopography such as collagen banding is a critical component influencing the SSC niche in vivo and has been shown to influence a range of cell behaviours in vitro (2,3). We have used unique fabricated nanotopographical pillar substrates to examine the function of human bone stem cells on titanium surfaces.
Aim
To investigate the effect of nanotopographical cues on adult skeletal stem cell (SSC) fate, phenotype and function within in-vitro environments.
Materials and methods
Adult human skeleltal stem cells (SSCs) were immunoselected and enriched using STRO-1 antibody and cultured on tissue culture plastic (TCP) and titanium-coated nanotopgraphical substrates (illustrated in Figure 1).
Following culture, metabolic activity of SSCs on TCP and Ti substrates was compared. Subsequently, osteoinductive potential was analysed under basal and osteogenic conditions (four groups: TCP in basal media, TCP in osteogenic media, Ti planar substrates basal and Ti pillar substrates basal).
Results
At 7 days, cell metabolic activity was significantly enhanced on Ti substrates, specifically on Ti pillars of defined height in comparison to TCP (Figure 2).
Following culture on defined topographies for 21 days, expression of the bone matrix protein, osteopontin, on Ti pillars was significantly enhanced when compared to TCP or Ti planar (Figure 3).
Conclusion
We demonstrate the ability of discrete raised nanopillars to modualte adult SSC populations in the absence of any chemical cues.
These results indicate the potential of discrete and defined nanopillar constructs to stimulate SSC function, an effect not observed on planar Ti constructs. These findings herald exciting opportunities to improve the bioactivity of implant design and, ultimately, osseointegration with clinical implications therein.
