Human iPS cell-derived cartilaginous tissue spatially and functionally replaces nucleus pulposus

The loss of nucleus pulposus (NP) precedes the intervertebral disk (IVD) degeneration that causes back pain. Here, we demonstrate that the implantation of human iPS cell-derived cartilaginous tissue (hiPS-Cart) restores this loss by replacing lost NP spatially and functionally. NP cells consist of notochordal NP cells and chondrocyte-like NP cells. Single cell RNA sequencing (scRNA-seq) analysis revealed that cells in hiPS-Cart corresponded to chondrocyte-like NP cells but not to notochordal NP cells. The implantation of hiPS-Cart into a nuclectomized space of IVD in nude rats prevented the degeneration of the IVD and preserved its mechanical properties. hiPS-Cart survived and occupied the nuclectomized space for at least six months after implantation, indicating spatial and functional replacement of lost NP by hiPS-Cart. Further scRNA-seq analysis revealed that hiPS-Cart cells changed their profile after implantation, differentiating into two lineages that are metabolically distinct from each other. However, post-implanted hiPS-Cart cells corresponded to chondrocyte-like NP cells only and did not develop into notochordal NP cells, suggesting that chondrocyte-like NP cells are nearly sufficient for NP function. The data collectively indicate that hiPS-Cart is a candidate implant for regenerating NP spatially and functionally and preventing IVD degeneration.

髓核（NP）的缺失先于导致背痛的椎间盘（IVD）退变。在此，我们证明人诱导多能干细胞衍生的软骨组织（hiPS - Cart）通过在空间和功能上替代缺失的髓核来修复这种缺失。髓核细胞由脊索样髓核细胞和软骨细胞样髓核细胞组成。单细胞RNA测序（scRNA - seq）分析显示，hiPS - Cart中的细胞对应于软骨细胞样髓核细胞，而非脊索样髓核细胞。将hiPS - Cart植入裸鼠椎间盘的髓核切除空间可防止椎间盘退变并保留其力学性能。hiPS - Cart在植入后至少6个月内存活并占据髓核切除空间，这表明hiPS - Cart在空间和功能上替代了缺失的髓核。进一步的scRNA - seq分析显示，hiPS - Cart细胞在植入后改变了其特性，分化为两个代谢上相互不同的谱系。然而，植入后的hiPS - Cart细胞仅对应于软骨细胞样髓核细胞，未发育为脊索样髓核细胞，这表明软骨细胞样髓核细胞几乎足以实现髓核功能。这些数据共同表明，hiPS - Cart是一种在空间和功能上再生髓核以及防止椎间盘退变的候选植入物。