Translational Musculoskeletal Research Center, Corporal Michael J. Crescenz VA Medical Center, Philadelphia, PA, United States; McKay Orthopaedic Research Laboratory, Department of Orthopaedic Surgery, University of Pennsylvania, Philadelphia, PA, United States.
Translational Musculoskeletal Research Center, Corporal Michael J. Crescenz VA Medical Center, Philadelphia, PA, United States; McKay Orthopaedic Research Laboratory, Department of Orthopaedic Surgery, University of Pennsylvania, Philadelphia, PA, United States; School of Biomedical Engineering, Drexel Univeristy, Philadelphia, PA, United States.
Acta Biomater. 2018 Apr 1;70:154-164. doi: 10.1016/j.actbio.2018.01.050. Epub 2018 Feb 8.
Replacement of the intervertebral disc with a viable, tissue-engineered construct that mimics native tissue structure and function is an attractive alternative to fusion or mechanical arthroplasty for the treatment of disc pathology. While a number of engineered discs have been developed, the average size of these constructs remains a fraction of the size of human intervertebral discs. In this study, we fabricated medium (3 mm height × 10 mm diameter) and large (6 mm height × 20 mm diameter) sized disc-like angle ply structures (DAPS), encompassing size scales from the rabbit lumbar spine to the human cervical spine. Maturation of these engineered discs was evaluated over 15 weeks in culture by quantifying cell viability and metabolic activity, construct biochemical content, MRI T2 values, and mechanical properties. To assess the performance of the DAPS in the in vivo space, pre-cultured DAPS were implanted subcutaneously in athymic rats for 5 weeks. Our findings show that both sized DAPS matured functionally and compositionally during in vitro culture, as evidenced by increases in mechanical properties and biochemical content over time, yet large DAPS under-performed compared to medium DAPS. Subcutaneous implantation resulted in reductions in NP cell viability and GAG content at both size scales, with little effect on AF biochemistry or metabolic activity. These findings demonstrate that engineered discs at large size scales will mature during in vitro culture, however, future work will need to address the challenges of reduced cell viability and heterogeneous matrix distribution throughout the construct.
This work establishes, for the first time, tissue-engineered intervertebral discs for total disc replacement at large, clinically relevant length scales. Clinical translation of tissue-engineered discs will offer an alternative to mechanical disc arthroplasty and fusion procedures, and may contribute to a paradigm shift in the clinical care for patients with disc pathology and associated axial spine and neurogenic extremity pain.
用具有活力的组织工程构建物替代椎间盘，该构建物模拟天然组织的结构和功能，为治疗椎间盘病变提供了一种有吸引力的选择，可替代融合或机械关节置换。虽然已经开发了许多工程椎间盘，但这些构建物的平均尺寸仍然只是人类椎间盘尺寸的一小部分。在这项研究中，我们制造了中等（3mm 高×10mm 直径）和大（6mm 高×20mm 直径）尺寸的盘状角层结构（DAPS），涵盖了从兔腰椎到人类颈椎的尺寸范围。通过量化细胞活力和代谢活性、构建物生化含量、MRI T2 值和机械性能，在 15 周的培养过程中评估这些工程椎间盘的成熟情况。为了评估 DAPS 在体内空间中的性能，将预培养的 DAPS 植入无胸腺大鼠的皮下 5 周。我们的研究结果表明，两种尺寸的 DAPS 在体外培养过程中均在功能和组成上成熟，这表现为随着时间的推移机械性能和生化含量的增加，而大 DAPS 的表现不如中 DAPS。皮下植入导致在两种尺寸上 NP 细胞活力和 GAG 含量降低，对 AF 生化或代谢活性几乎没有影响。这些发现表明，在大尺寸范围内，工程椎间盘将在体外培养过程中成熟，但是，未来的工作需要解决细胞活力降低和整个构建体中基质分布不均匀的挑战。
这是首次在大的、临床相关的长度尺度上建立用于全椎间盘置换的组织工程椎间盘。组织工程椎间盘的临床转化将为机械椎间盘置换和融合手术提供替代方案，并可能促成治疗椎间盘病变及相关轴性脊柱和神经性肢体疼痛患者的临床护理范式转变。
