Hydroxyapatite nanoparticle injectable hydrogel scaffold to support osteogenic differentiation of human mesenchymal stem cells

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Thorpe, Abbey ; Creasey, Stuart ; Sammon, Chris ; Le Maitre, Christine (2016)
  • Publisher: A O Foundation

Bone loss associated with degenerative disease and trauma\ud is a clinical problem increasing with the aging population.\ud Thus, effective bone augmentation strategies are required;\ud however, many have the disadvantages that they require\ud invasive surgery and often the addition of expensive\ud growth factors to induce osteoblast differentiation. Here,\ud we investigated a Laponite crosslinked, pNIPAMDMAc\ud copolymer (L-pNIPAM-co-DMAc) hydrogel\ud with hydroxyapatite nanoparticles (HAPna), which can\ud be maintained as a liquid ex vivo, injected via narrowgauge\ud needle into affected bone, followed by in situ\ud gelation to deliver and induce osteogenic differentiation\ud of human mesenchymal stem cells (hMSC). L-pNIPAMco-DMAc\ud hydrogels were synthesised and HAPna added\ud post polymerisation. Commercial hMSCs from one donor\ud (Lonza) were incorporated in liquid hydrogel, the mixture\ud solidified and cultured for up to 6 weeks. Viability of hMSCs\ud was maintained within hydrogel constructs containing\ud 0.5 mg/mL HAPna. SEM analysis demonstrated matrix\ud deposition in cellular hydrogels which were absent in\ud acellular controls. A significant increase in storage modulus\ud (G’) was observed in cellular hydrogels with 0.5 mg/mL\ud HAPna. Semi-quantitative immunohistochemistry and\ud histological analysis demonstrated that bone differentiation\ud markers and collagen deposition was induced within 48 h,\ud with increased calcium deposition with time. The thermally\ud triggered hydrogel system, described here, was sufficient\ud without the need of additional growth factors or osteogenic\ud media to induce osteogenic differentiation of commercial\ud hMSCs. Preliminary data presented here will be expanded\ud on multiple patient samples to ensure differentiation is seen\ud in these samples. This system could potentially reduce\ud treatment costs and simplify the trea
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