Elevated senescence in the bone marrow mesenchymal stem cells of acquired aplastic anemia patients: A possible implication of DNA damage responses and telomere attrition

Background: Bone marrow mesenchymal stem cells (BM-MSC) are an integral part of the BM niche that is essential to maintain hematopoietic homeostasis. In aplastic anemia (AA), a few studies have reported phenotypic defects in the BM-MSC, such as reduced proliferation, imbalanced differentiation, and apoptosis; however, the alterations at the molecular level need to be better characterized. Therefore, the current study aims to identify the causative factors underlying the compromised functions of AA BM-MSC that might eventually be contributing to the AA pathobiology. Methods: We performed RNA sequencing (RNA-Seq) using the Illumina platform to comprehend the distinction between the transcriptional landscape of AA and control BM-MSC. Further, we validated the alterations observed in senescence by Senescence- associated beta-galactosidase (SA -beta-gal) assay, DNA damage by gamma H2AX staining, and telomere attrition by relative telomere length assessment and telomerase activity assay. We used qRT-PCR to analyze changes in some of the genes associated with these molecular mechanisms. Results: The transcriptome profiling revealed enrichment of senescence-associated genes and pathways in AA BMMSC. The senescent phenotype of AA BM-MSC was accompanied by enhanced SA -beta-gal activity and elevated expression of senescence associated genes TP53, PARP1, and CDKN1A. Further, we observed increased gamma H2AX foci indicating DNA damage, reduced telomere length, and diminished telomerase activity in the AA BM-MSC. Conclusion: Our results highlight that AA BM-MSC have a senescent phenotype accompanied by other cellular defects like DNA damage and telomere attrition, which are most likely driving the senescent phenotype of AA BM-MSC thus hampering their hematopoiesis supporting properties as observed in AA.