Abstract
BackgroundStem cell therapy is considered as a promising alternative to treat intervertebral disc degeneration (IDD). Extensive work had been done on identifying and comparing different types of candidate stem cells, both in vivo and in vitro. However, few studies have shed light on degenerative nucleus pulposus cells (NPCs), especially their biological behavior under the influence of exogenous stem cells, specifically the gene expression and regulation pattern. In the present study, we aimed to determine messenger RNAs (mRNAs) and long non-coding RNAs (lncRNAs), which are differentially expressed during the co-culturing process with adipose-derived mesenchymal stem cells (ASCs) and to explore the involved signaling pathways and the regulatory networks.MethodsWe compared degenerative NPCs co-cultured with ASCs with those cultured solely using lncRNA-mRNA microarray analysis. Based on these data, we investigated the significantly regulated signaling pathways based on the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway database. Moreover, 23 micro RNAs (miRNAs), which were demonstrated to be involved in IDD were chosen; we investigated their theoretic regulatory importance associated with our microarray data.ResultsWe found 632 lncRNAs and 1682 mRNAs were differentially expressed out of a total of 40,716 probes. We then confirmed the microarray data by real-time PCR. Furthermore, we demonstrated 197 upregulated, and 373 downregulated Gene Ontology terms and 176 significantly enriched pathways, such as the mitogen-activated protein kinase (MAPK) pathway. Also, a signal-net was constructed to reveal the interplay among differentially expressed genes. Meanwhile, a mRNA-lncRNA co-expression network was constructed for the significantly changed mRNAs and lncRNAs. Also, the competing endogenous RNA (ceRNA) network was built.ConclusionOur results present the first comprehensive identification of differentially expressed lncRNAs and mRNAs of degenerative NPCs, altered by co-culturing with ASCs, and outline the gene expression regulation pattern. These may provide valuable information for better understanding of stem cell therapy and potential candidate biomarkers for IDD treatment.
Highlights
Stem cell therapy is considered as a promising alternative to treat intervertebral disc degeneration (IDD)
In the present study, we identified a significant number of Messenger RNA (mRNA) and long non-coding RNAs (lncRNAs) differentially expressed by degenerative nucleus pulposus cells (NPCs) co-cultured with adipose-derived mesenchymal stem cells (ASCs), using the microarray analysis and in-depth data profiling
We identified that the nucleus pulposus (NP) marker gene expression, SOX-9 and Type Polymerase II (II) collagen (COL2A1), was increased in NPCs after the co-culture, indicating the upregulated synthesis and secretory activities of NPCs under the influence of mesenchymal stem cells (MSCs) [37, 38]
Summary
Stem cell therapy is considered as a promising alternative to treat intervertebral disc degeneration (IDD). Few studies have shed light on degenerative nucleus pulposus cells (NPCs), especially their biological behavior under the influence of exogenous stem cells, the gene expression and regulation pattern. Stem cell therapy, introducing mesenchymal stem cells (MSCs) or cytokines into target discs, appears as a promising strategy for the IDD treatment. This emerging modality was proved to be effective both in vitro [2,3,4] and in vivo [5, 6]. Adipose-derived mesenchymal stem cells (ASCs) co-cultured with NPCs expressed significantly upregulated expression of NP-related genes including sex determining region Y box 9 (SOX9), type II collagen (COL2A1), and aggrecan (ACAN) [8]. The underlying mechanism of these phenomena is still not fully understood
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