Venkatachalam Sankar, Neelamegan Sridharan, Okuda Tetsuhito, Marcus Akiva, Woodbury Dale, Grumet Martin
Department of Cell Biology and Neuroscience, W. M. Keck Center for Collaborative Neuroscience, Rutgers University, Piscataway, NJ, USA.
Department of Anatomy, University of Madras, Taramani Campus, Chennai, Tamilnadu, India.
Restor Neurol Neurosci. 2018;36(3):387-396. doi: 10.3233/RNN-170786.
Mesenchymal stem/stromal cells (MSC) promote recovery after spinal cord injury (SCI) using adult bone marrow MSC (BM-MSC). Newborn tissues are a convenient source of MSC that does not involve an invasive procedure for cell collection. In this study the authors tested the effects of rat amnion MSC clone (rAM-MSC) in SCI.
We tested intra-parenchymal injection of a GFP+ rat rAM-MSC clone derived from E18.5 rats in rat SCI and measured behavioral recovery (BBB scores), histology and X-ray opacity. Expression of aggrecan was measured in culture after treatment with TGFß.
Injection of rAM-MSC after SCI did not improve BBB scores compared to control vehicle injections; rather they reduced scores significantly over 6 weeks. Spinal cords injected with rAM-MSC were hard in regions surrounding the SCI site, which was confirmed by X-ray opacity. Whole mount imaging of these cords showed minimal tissue loss in the SCI site that occurred in SCI controls, and persistence of GFP+ rAM-MSC. Mason's Trichrome staining of tissue sections showed more intense staining for extracellular matrix (ECM) surrounding and extending beyond the SCI site with injections of rAM-MSC but not in controls. In response to TGF-ß treatment in culture, chondrogenic aggrecan was expressed at higher levels in rAM-MSC than in rBM-MSC, suggesting that the upregulation of TGF-ß in SCI sites may promote chondrogenic differentiation.
Acute injection after SCI of a clonally expanded rAM-MSC resulted in aberrant differentiation towards a chondrocytic phenotype that disrupts the spinal cord and inhibits behavioral recovery after SCI. It will be critical to ensure that injection of extensively expanded neonatal cells do not differentiate aberrantly in traumatic CNS tissue and disrupt recovery.
间充质干/基质细胞（MSC）可促进脊髓损伤（SCI）后的恢复，目前使用的是成人骨髓间充质干细胞（BM-MSC）。新生组织是间充质干细胞的便利来源，无需通过侵入性程序采集细胞。在本研究中，作者测试了大鼠羊膜间充质干细胞克隆（rAM-MSC）对脊髓损伤的影响。
我们在大鼠脊髓损伤模型中测试了经实质内注射源自E18.5大鼠的绿色荧光蛋白阳性大鼠rAM-MSC克隆，并测量了行为恢复情况（BBB评分）、组织学变化和X射线不透光性。在用转化生长因子β（TGFß）处理后，在培养物中测量聚集蛋白聚糖的表达。
与注射对照载体相比，脊髓损伤后注射rAM-MSC并未改善BBB评分；相反，在6周内评分显著降低。注射rAM-MSC的脊髓在脊髓损伤部位周围变硬，X射线不透光性证实了这一点。这些脊髓的整体成像显示，脊髓损伤部位的组织损失在脊髓损伤对照组中最小，并且绿色荧光蛋白阳性rAM-MSC持续存在。组织切片的Mason三色染色显示，注射rAM-MSC后，脊髓损伤部位周围及以外的细胞外基质（ECM）染色比对照组更强烈。在培养物中对TGF-β处理的反应中，rAM-MSC中软骨生成聚集蛋白聚糖的表达水平高于rBM-MSC，这表明脊髓损伤部位TGF-β的上调可能促进软骨生成分化。
脊髓损伤后急性注射克隆扩增的rAM-MSC导致向软骨细胞表型的异常分化，破坏脊髓并抑制脊髓损伤后的行为恢复。确保注射大量扩增的新生细胞不会在创伤性中枢神经系统组织中异常分化并干扰恢复至关重要。
