Abstract

Stromal cell-derived factor-1α (SDF-1α) plays a significant role in mobilizing and recruiting mesenchymal stem cells (MSCs) to the sites of injury. This study investigated the potential of SDF-1α released in the degenerative intervertebral disc (IVD) to activate and recruit endogenous nucleus pulposus-derived stem cells (NPSCs) for regeneration in situ. We found SDF-1α was highly expressed and secreted by the native disc cells when cultured in the proinflammatory mediators in vitro mimicking the degenerative settings. Immunohistochemical staining also showed that the expression level of SDF-1α was significantly higher in the degenerative group compared to that in the normal group. In addition to enhancement of viability, SDF-1α significantly increased the number of NPSCs migrating into the center of the nucleotomized bovine IVD ex vivo. After the systemic delivery of exogenous PKH26-labelled NPSCs into the rats in vivo, there was a significant difference in the distribution of the migrated cells between the normal and the degenerative IVDs, which might be caused by the different expression levels of SDF-1α. However, blocking CXC chemokine receptor 4 (CXCR4) with AMD3100 effectively abrogated SDF-1α-stimulated proliferation and migration. Taken together, SDF-1α may be a key chemoattractant that is highly produced in response to the degenerative changes, which can be used to enhance the proliferation and recruitment of endogenous stem cells into the IVDs. These findings may be of importance for understanding IVD regenerative mechanisms and development of regenerative strategies in situ for IVD degeneration.

Highlights

  • Intervertebral disc (IVD) degeneration is one major cause of low back pain (LBP) in the modern society [1, 2]

  • Cell Counting Kit-8 (CCK-8) assay was used to analyze the proliferation of nucleus pulposus-derived stem cells (NPSCs) in response to Stromal cell-derived factor-1α (SDF-1α)

  • The result showed that the proliferation capacity of NPSCs was not affected by SDF-1α until the 5th day

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Summary

Introduction

Intervertebral disc (IVD) degeneration is one major cause of low back pain (LBP) in the modern society [1, 2] It is characterized by chronically increased levels of numerous proinflammatory factors secreted by the native disc cells that promote matrix degradation, chemokine production, and cell phenotype changes [3]. Release of chemokines from the degenerative IVD promotes the activation and infiltration of immune cells, amplifying the inflammatory cascade [3]. Some of these chemokines have been shown to be involved in the IVD self-repairing process by activation and recruitment of endogenous disc cells [4].

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