Bone Research Laboratory, Faculty of Health Sciences, School of Oral Health Sciences, University of the Witwatersrand , Johannesburg, South Africa .
Tissue Eng Part A. 2017 Nov;23(21-22):1197-1209. doi: 10.1089/ten.tea.2017.0321.
Tissue engineering still needs to assign the molecular basis of pattern formation, tissue induction, and morphogenesis: What next to morphogens and stem cells? Macroporous biomimetic matrices per se, without the addition of the soluble osteogenic molecular signals of the transforming growth factor-β (TGF-β) supergene family, remarkably initiate the induction of bone formation. Carving geometries within different calcium phosphate-based macroporous bioreactors we show that geometric cues imprinted within the macroporous spaces initiate the spontaneous induction of bone. Concavities biomimetize the remodeling cycle of the primate osteonic bone and are endowed with functionalized smart geometric cues that per se initiate osteoblasts' differentiation with the expression and secretion of osteogenic molecular signals that induce bone as a secondary response. To study the role of calcium ions (Ca) and osteoclastogenesis, coral-derived calcium carbonate (CC)/hydroxyapatite (HA) bioreactors with limited conversion to HA (7% HA/CC) were preloaded with 500 μg of the L-type voltage gated calcium channel blocker verapamil hydrochloride. Bioreactors were also loaded with 240 μg of the bisphosphonate zoledronate, an osteoclast inhibitor, and implanted in heterotopic sites of the rectus abdominis muscle of Papio ursinus. Bisphosphonate-treated specimens were characterized by a delayed profoundly inhibited induction of tissue patterning with limited induction of bone. Macroporous constructs pretreated with verapamil hydrochloride yielded limited bone formation. Similarly, 125 or 150 μg human Noggin previously adsorbed onto the macroporous bioreactors resulted in minimal bone formation by induction, indirectly showing that the initiation of bone formation is through the bone morphogenetic protein (BMP) pathway. Downregulation of BMP-2 and osteogenic protein-1 (OP-1) with upregulation of Noggin correlated with limited bone induction. Angiogenesis, capillary sprouting, and Ca provide chemotactic signals for myoendothelial, myoblastic, and pericytic stem cell differentiation into osteoblastic-like cells expressing the osteogenic soluble molecular signals of the TGF-β supergene family. Secreted gene products are embedded directly onto the substratum within its regulatory concavities. The protected microenvironment of the concavities biomimetizes the phylogenetically ancient repetitive multitested designs and topographies of Nature. Migrating cells onto the primed substratum by osteoclastic nanotopographical geometric inductive modifications convert geometrical cues set by osteoclastogenesis into BMP gene expression pathways that ultimately set into motion the spontaneous induction of bone formation.
组织工程仍需要确定形态发生、组织诱导和形态发生的分子基础：除了形态发生因子和干细胞之外，还有什么？本身具有大孔仿生基质，而不添加转化生长因子-β（TGF-β）超基因家族的可溶性成骨分子信号，可显著启动骨形成的诱导。在不同的基于磷酸钙的大孔生物反应器中进行雕刻几何形状，我们表明，在大孔空间内刻印的几何线索会自发启动骨的诱导。凹面仿生灵长类骨骨重建周期，并具有功能化的智能几何线索，这些线索本身会启动成骨细胞的分化，并表达和分泌成骨分子信号，从而诱导骨作为次级反应。为了研究钙离子（Ca）和破骨细胞生成的作用，用有限量转化为 HA（7％HA/CC）的珊瑚衍生碳酸钙（CC）/羟基磷灰石（HA）生物反应器预先装载 500μg L 型电压门控钙通道阻滞剂盐酸维拉帕米。生物反应器还装载了 240μg 双膦酸盐唑来膦酸，一种破骨细胞抑制剂，并植入 Papio ursinus 腹直肌的异位部位。用双膦酸盐处理的标本表现为组织模式形成的诱导被严重延迟和抑制，骨的诱导有限。用盐酸维拉帕米预处理的大孔构建体产生的骨形成有限。同样，先前吸附在大孔生物反应器上的 125 或 150μg 人 Noggin 通过诱导产生的骨形成也很少，间接表明骨形成的启动是通过骨形态发生蛋白（BMP）途径。BMP-2 和骨形成蛋白-1（OP-1）的下调与 Noggin 的上调相关，与有限的骨诱导相关。血管生成、毛细血管发芽和 Ca 为肌内皮细胞、成肌细胞和成纤维细胞的分化提供趋化信号，分化为表达 TGF-β 超基因家族成骨可溶性分子信号的成骨样细胞。分泌的基因产物直接嵌入其调节凹面内的基质上。凹面的保护微环境模拟了进化上古老的重复多测试设计和自然的地形。破骨细胞成骨纳米拓扑几何诱导修饰使细胞迁移到预制基质上，将破骨细胞形成的几何线索转化为 BMP 基因表达途径，最终启动骨形成的自发诱导。
