Identification of Aberrantly Expressed Genes during Aging in Rat Nucleus Pulposus Cells.

Nucleus pulposus cells (NPCs) play a vital role in maintaining the homeostasis of the intervertebral disc (IVD). Previous studies have discovered that NPCs exhibited malfunction due to cellular senescence during disc aging and degeneration; this might be one of the key factors of IVD degeneration. Thus, we conducted this study in order to investigate the altered biofunction and the underlying genes and pathways of senescent NPCs. We isolated and identified NPCs from the tail discs of young (2 months) and old (24 months) SD rats and confirmed the senescent phenotype through SA-ß-gal staining. CCK-8 assay, transwell assay, and cell scratch assay were adopted to detect the proliferous and migratory ability of two groups. Then, a rat Gene Chip Clariom™ S array was used to detect differentially expressed genes (DEGs). After rigorous bioinformatics analysis of the raw data, totally, 1038 differentially expressed genes with a fold change > 1.5 were identified out of 23189 probes. Among them, 617 were upregulated and 421 were downregulated. Furthermore, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were conducted and revealed numerous number of enriched GO terms and signaling pathways associated with senescence of NPCs. A protein-protein interaction (PPI) network of the DEGs was constructed using the Search Tool for the Retrieval of Interacting Genes (STRING) database and Cytoscape software. Module analysis was conducted for the PPI network using the MCODE plugin in Cytoscape. Hub genes were identified by the CytoHubba plugin in Cytoscape. Derived 5 hub genes and most significantly up- or downregulated genes were further verified by real-time PCR. The present study investigated underlying mechanisms in the senescence of NPCs on a genome-wide scale. The illumination of molecular mechanisms of NPCs senescence may assist the development of novel biological methods to treat degenerative disc diseases.

The inflammatory cytokine TNF-α regulates the biological behavior of rat nucleus pulposus mesenchymal stem cells through the NF-κB signaling pathway in vitro.

Nucleus pulposus (NP) mesenchymal stem cells (NPMSCs) are a potential cell source for intervertebral disc (IVD) regeneration; however, little is known about their response to tumor necrosis factor-α (TNF-α), a critical inflammation factor contributing to accelerating IVD degeneration. Accordingly, the aim of this study was to investigate the regulatory effects of TNF-α at high and low concentrations on the biological behaviors of healthy rat NPMSCs, including proliferation, migration, and NP differentiation. In this study, NPMSCs were treated with different concentration of TNF-α (0-200 ng/mL). Then we used annexin V/propidium iodide flow cytometry analysis to detect the apoptosis rate of NPMSCs. Cell Counting Kit-8, Edu assay, and cell cycle test were used to examine the proliferation of NPMSCs. Migration ability of NPMSCs was detected by wound healing assay and transwell migration assay. Pellets method was used to induce NP differentiation of NPMSCs, and immunohistochemical staining, real-time polymerase chain reaction, and Western blot analysis were used to examine the NPC phenotypic genes and proteins. The cells were further treated with the nuclear factor-κB (NF-κB) pathway inhibitor Bay 11-7082 to determine the role of the NF-κB pathway in the mechanism underlying the differentiation process. Results showed that treatment with a high concentration of TNF-α (50-200 ng/mL) could induce apoptosis of NPMSCs, whereas a relatively low TNF-α concentration (0.1-10 ng/mL) promoted the proliferation and migration of NPMSCs, but inhibited their differentiation toward NP cells. Moreover, we identified that the NF-κB signaling pathway is activated during the TNF-α-inhibited differentiation of NPMSCs, and the NF-κB signal inhibitor Bay 11-7082 could partially eliminate the adverse effect of TNF-α on the differentiation of NPMSCs. Therefore, our findings provide important insight into the dynamic biological behavior reactivity of NPMSCs to TNF-α during IVD degeneration process, thus may help us understanding the underlying mechanism of IVD degeneration.

Fifty top-cited spine articles from mainland China: A citation analysis.

Objective To identify the 50 top-cited spine articles from mainland China and to analyze their main characteristics. Methods Web of Science was used to identify the 50 top-cited spine articles from mainland China in 27 spine-related journals. The title, year of publication, number of citations, journal, anatomic focus, subspecialty, evidence level, city, institution and author were recorded. Results The top 50 articles had 29-122 citations and were published in 11 English-language journals; most (32) were published in the 2000s. The journal Spine had the largest number of articles and The Lancet had the highest impact factor. The lumber spine was the most discussed anatomic area (18). Degenerative spine disease was the most common subspecialty topic (22). Most articles were clinical studies (29); the others were basic research (21). Level IV was the most common evidence level (17). Conclusions This list indicates the most influential articles from mainland China in the global spine research community. Identification of these articles provides insights into the trends in spine care in mainland China and the historical contributions of researchers from mainland China to the international spine research field.

Use of Limiting Dilution Method for Isolation of Nucleus Pulposus Mesenchymal Stem/Progenitor Cells and Effects of Plating Density on Biological Characteristics and Plasticity.

OBJECTIVES: To evaluate the effects of the limiting dilution method and plating density in rat nucleus pulposus mesenchymal stem/progenitor cells (NPMSCs). MATERIALS AND METHODS: Nucleus pulposus tissues were isolated from 12-week-old male Sprague-Dawley rats and NPMSCs were isolated using limiting dilution method. Cells were then classified into 3 groups according to plating density. Cell morphologies were observed, and colony-forming units, migration abilities, proliferative capacities, cell cycle percentages, multilineage differentiation capacities, stem cell biomarker expression levels, and immunophenotyping were also examined in each group. RESULTS: Low density group (LD) had higher morphological homogeneity, stronger colony-forming ability, higher cell proliferation capacity, and enhanced cell migration ability relative to the other two groups (p < 0.05). Moreover, LD had more cells entering S phase, with fewer cells arrested in G0/G1 phase (p < 0.05). While all three density groups showed a multilineage differentiation potential, LD showed a higher degree of observed and semiquantified lineage specific staining (p < 0.05). Furthermore, LD displayed higher expression levels of stem cell biomarkers (Nanog, Oct4, and Sox2) and showed higher percentages of CD29+, CD44+, and CD90+ cells (p < 0.05) following flow cytometry analysis. CONCLUSIONS: Limiting dilution method is suggested when isolating NPMSCs as a means of improving cell activity and plasticity.

Age-Related Changes in Nucleus Pulposus Mesenchymal Stem Cells: An In Vitro Study in Rats.

The functions of mesenchymal stem cells (MSCs) appear to decline with age due to cellular senescence, which could reduce the efficacy of MSCs-based therapies. Recently, MSCs have been identified in the nucleus pulposus, which offers great potential for intervertebral disc (IVD) repair. However, this potential might be affected by the senescence of nucleus pulposus MSCs (NPMSCs), but whether or not this exists remains unknown. The aim of this study was to investigate the age-related changes in NPMSCs. NPMSCs isolated from young (3-month-old) and old (14-month-old) Sprague-Dawley rats were cultured in vitro. Differences in morphology, proliferation, colony formation, multilineage differentiation, cell cycle, and expression of ß-galactosidase (SA-ß-gal) and senescent markers (p53, p21, and p16) were compared between groups. Both young and old NPMSCs fulfilled the criteria for definition as MSCs. Moreover, young NPMSCs presented better proliferation, colony-forming, and multilineage differentiation capacities than old NPMSCs. Old NPMSCs displayed senescent features, including significantly increased G0/G1 phase arrest, increased SA-ß-gal expression, decreased S phase entry, and significant p53-p21-pRB pathway activation. Therefore, this is the first study demonstrating that senescent NPMSCs accumulate in IVD with age. The efficacy of NPMSCs is compromised by donor age, which should be taken into consideration prior to clinical application.

Is surgical intervention more effective than non-surgical treatment for acute Achilles tendon rupture? A systematic review of overlapping meta-analyses.

OBJECTIVE: There is discordance in the results from meta-analyses on surgical versus non-surgical treatment for acute Achilles tendon rupture. We systematically reviewed the overlapping meta-analyses on this topic to provide information that will be helpful to decision makers when selecting treatments based on the current best available evidence. METHODS: We comprehensively searched multiple databases for systematic reviews that compared surgical and non-surgical treatments for acute Achilles tendon rupture. We only included meta-analyses that comprised randomized controlled trials (RCTs). The methodological quality and extracted data were assessed. The meta-analysis that offered the best evidence was ascertained with the Jadad decision algorithm. RESULTS: Nine meta-analyses were included in our study and all of them included RCTs with Level-II evidence. Assessment of Multiple Systematic Reviews (AMSTAR) scores ranged from 5 to 10 (median 7). The Jadad decision algorithm was used to select a high-quality meta-analysis with more RCTs. The results from this study showed that when functional rehabilitation was used, non-surgical intervention was similar to surgical treatment regarding the incidence of range of motion, rerupture, calf circumference and functional outcomes, and the incidence of other complications was reduced. Non-surgical intervention significantly increased the rerupture rate if functional rehabilitation was not considered. CONCLUSIONS: The findings of meta-analyses regarding surgical versus non-surgical treatment for acute Achilles tendon rupture are inconsistent. According to this systematic review of overlapping meta-analyses, the current best available evidence suggests that centers offering functional rehabilitation may prefer non-surgical intervention. Surgical treatment may be preferred at centers that do not have functional rehabilitation.