The University of Queensland, School of Dentistry, Herston, Queensland, Australia.
Biomed Mater. 2018 Aug 22;13(6):065003. doi: 10.1088/1748-605X/aad916.
The immunomodulatory effects of lithium have been reported across a range of models and contexts. Lithium appears to have a positive effect on osteogenesis in vivo, while in vitro outcomes throughout the literature are varied. Tissue engineering approaches have rarely targeted local lithium delivery within a regenerative setting. We hypothesized that part of the positive effects of lithium in vivo may be due to an immunomodulatory effect manifesting in a local environment. To achieve a sustained lithium release from scaffold constructs, we blended lithium carbonate, a soluble salt of lithium, with the biomaterial polymer polycaprolactone (PCL). We printed constructs of PCL alone, and with 5% (5Li) and 10% (10Li) lithium carbonate. Mechanical testing revealed that mechanical properties were largely retained with lithium carbonate incorporation, and we measured a consistent release of the ion over a 7 day period. The efficacy of our construct system was then assessed using a primary mouse macrophage culture, and a differentiated osteoclast culture. We found that the lithium released from constructs had a great effect on macrophage polarization, resulting in pronounced upregulation of immunomodulatory (M2) genes, and a decrease in pro-inflammatory (M1) genes. This was reflected in cytokine expression, and illustrated through immunofluorescent staining. Osteoclast activity was greatly suppressed by the lithium incorporation, with a marked effect on gene expression and actin ring formation. Our work demonstrated an effective system for local lithium delivery, confirmed the pronounced effects that lithium has on macrophage and osteoclast response, and sets the stage for further innovations in ion release for targeted tissue engineering.
锂的免疫调节作用已在多种模型和环境中得到报道。锂似乎对体内成骨有积极作用，而文献中的体外结果则各不相同。组织工程方法很少针对再生环境中局部锂的输送。我们假设锂在体内的部分积极作用可能归因于局部环境中的免疫调节作用。为了从支架结构中实现持续的锂释放，我们将碳酸锂（一种可溶的锂盐）与生物材料聚合物聚己内酯（PCL）混合。我们单独打印了 PCL 结构，以及含有 5%（5Li）和 10%（10Li）碳酸锂的结构。力学测试表明，力学性能在很大程度上保留了碳酸锂的掺入，并且我们在 7 天内测量到了锂离子的持续释放。然后，我们使用原代小鼠巨噬细胞培养物和分化的破骨细胞培养物评估了我们的构建体系统的功效。我们发现，从构建体中释放的锂对巨噬细胞极化有很大影响，导致免疫调节（M2）基因的显著上调，并降低促炎（M1）基因。这反映在细胞因子表达上，并通过免疫荧光染色进行了说明。碳酸锂的掺入极大地抑制了破骨细胞的活性，对基因表达和肌动蛋白环形成有显著影响。我们的工作展示了一种有效的局部锂输送系统，证实了锂对巨噬细胞和破骨细胞反应的显著影响，并为针对组织工程的离子释放的进一步创新奠定了基础。
