Acta Biomaterialia ( IF 9.4 ) Pub Date : 2023-08-26 , DOI: 10.1016/j.actbio.2023.08.045 Sarah A Schoonraad 1 , Alan A Jaimes 2 , Arjun J X Singh 3 , Kiera J Croland 3 , Stephanie J Bryant 4
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While bone morphogenic protein-2 (BMP-2) is one of the most widely studied BMPs in bone tissue engineering, BMP-9 has been purported to be a highly osteogenic BMP. This work investigates the individual osteogenic effects of recombinant human (rh) BMP-2 and rhBMP-9, when tethered into a hydrogel, on encapsulated human mesenchymal stem cells (MSCs). A matrix-metalloproteinase (MMP)-sensitive hydrogel nanocomposite, comprised of poly(ethylene glycol) crosslinked with MMP-sensitive peptides, tethered RGD, and entrapped hydroxyapatite nanoparticles was used. The rhBMPs were functionalized with free thiols and then covalently tethered into the hydrogel by a thiol-norbornene photoclick reaction. rhBMP-2 retained its full bioactivity post-thiolation, while the bioactivity of rhBMP-9 was partially reduced. Nonetheless, both rhBMPs were highly effective at enhancing osteogenesis over 12-weeks in a chemically-defined medium. Expression of ID1 and osterix, early markers of osteogenesis; collagen type I, a main component of the bone extracellular matrix (ECM); and osteopontin, bone sialoprotein II and dentin matrix protein I, mature osteoblast markers, increased with increasing concentrations of tethered rhBMP-2 or rhBMP-9. When comparing the two BMPs, rhBMP-9 led to more rapid collagen deposition and greater mineralization long-term. In summary, rhBMP-2 retained its bioactivity post-thiolation while rhBMP-9 is more susceptible to thiolation. Despite this shortcoming with rhBMP-9, both rhBMPs when tethered into this hydrogel, enhanced osteogenesis of MSCs, leading to a mature osteoblast phenotype surrounded by a mineralized ECM.
Statement of significance
Osteoinductive hydrogels are a promising vehicle to deliver mesenchymal stem cells (MSCs) for bone regeneration. This study examines the in vitro osteoinductive capabilities when tethered bone morphogenic proteins (BMPs) are incorporated into a degradable biomimetic hydrogel with cell adhesive ligands, matrix metalloproteinase sensitive crosslinks for cell-mediated degradation, and hydroxyapatite nanoparticles. This study demonstrates that BMP-2 is readily thiolated and tethered without loss of bioactivity while bioactivity of BMP-9 is more susceptible to immobilization. Nonetheless, when either BMP2 or BMP9 are tethered into this hydrogel, osteogenesis of human MSCs is enhanced, bone extracellular matrix is deposited, and a mature osteoblast phenotype is achieved. This bone-biomimetic hydrogel is a promising design for stem cell-mediated bone regeneration.
中文翻译：
共价栓系 rhBMP-2 和 rhBMP-9 在 MMP 敏感的 PEG 水凝胶纳米复合材料中的成骨效应
虽然骨形态发生蛋白-2 （BMP-2） 是骨组织工程中研究最广泛的 BMP 之一，但 BMP-9 据称是一种高度成骨的 BMP。这项工作研究了重组人 （rh） BMP-2 和 rhBMP-9 在拴系到水凝胶中时对包膜人间充质干细胞 （MSC） 的个体成骨作用。使用了基质金属蛋白酶 （MMP） 敏感的水凝胶纳米复合材料，该复合材料由聚乙二醇与 MMP 敏感肽交联、栓系 RGD 和包埋的羟基磷灰石纳米颗粒组成。rhBMPs 用游离硫醇功能化，然后通过硫醇-降冰片烯光点击反应共价拴系到水凝胶中。rhBMP-2 在硫醇化后保留了其全部生物活性，而 rhBMP-9 的生物活性部分降低。尽管如此，两种 rhBMPs 在化学定义的培养基中 12 周内对增强成骨反应非常有效。ID1 和 osterix 的表达，成骨的早期标志物;I 型胶原蛋白，骨细胞外基质 （ECM） 的主要成分;骨桥蛋白、骨唾液蛋白 II 和牙本质基质蛋白 I，成熟成骨细胞标志物，随着栓系 rhBMP-2 或 rhBMP-9 浓度的增加而增加。在比较两种 BMP 时，rhBMP-9 导致更快速的胶原蛋白沉积和更长期的矿化。总之，rhBMP-2 在硫醇化后保留了其生物活性，而 rhBMP-9 更容易受到硫醇化的影响。尽管 rhBMP-9 存在这一缺点，但当拴在这种水凝胶中时，两种 rhBMP 都增强了 MSC 的成骨作用，导致成熟的成骨细胞表型被矿化 ECM 包围。
重要性声明
骨诱导水凝胶是一种很有前途的载体，可用于递送间充质干细胞 （MSC） 以进行骨再生。本研究检查了当栓系骨形态发生蛋白 （BMP） 掺入具有细胞粘附配体、用于细胞介导降解的基质金属蛋白酶敏感交联和羟基磷灰石纳米颗粒的可降解仿生水凝胶中时的体外成骨诱导能力。本研究表明，BMP-2 易于硫醇化和栓系而不会失去生物活性，而 BMP-9 的生物活性更容易被固定化。尽管如此，当 BMP2 或 BMP9 拴系到这种水凝胶中时，人 MSC 的成骨作用增强，骨细胞外基质沉积，并获得成熟的成骨细胞表型。这种仿生水凝胶是一种很有前途的干细胞介导的骨再生设计。
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