Functional Comparison of Chronological and In Vitro Aging: Differential Role of the Cytoskeleton and Mitochondria in Mesenchymal Stromal Cells

Abstract

Mesenchymal stromal cells (MSCs) are of high relevance for the regeneration of mesenchymal tissues such as bone and cartilage. The promising role of MSCs in cell-based therapies and tissue engineering appears to be limited due to a decline of their regenerative potential with increasing donor age, their limited availability in human tissues and the need of in vitro expansion prior to treatment. We therefore aimed to determine to which degree in vitro aging and chronological aging may be similar processes or if in vitro culture-related changes at the cellular and molecular level are at least altered as a function of donor age. For that purpose we established MSCs cultures from young (yMSCs) and aged (aMSCs) rats that were cultured for more than 100 passages. These long-term MSCs cultures were non-tumorigenic and exhibited similar surface marker patterns as primary MSCs of passage 2. During in vitro expansion, but not during chronological aging, MSCs progressively lose their progenitor characteristics, e.g., complete loss of osteogenic differentiation potential, diminished adipogenic differentiation, altered cell morphology and increased susceptibility towards senescence. Transcriptome analysis revealed that long-term in vitro MSCs cultivation leads to down-regulation of genes involved in cell differentiation, focal adhesion organization, cytoskeleton turnover and mitochondria function. Accordingly, functional analysis demonstrated altered mitochondrial morphology, decreased antioxidant capacities and elevated ROS levels in long-term cultivated yMSCs as well as aMSCs. Notably, only the MSC migration potential and their antioxidative capacity were altered by in vitro as well as chronological aging. Based on specific differences observed between the impact of chronological and in vitro MSC aging we conclude that both are distinct processes.

Umbilical Cord Mesenchymal Stromal Cells Affected by Gestational Diabetes Mellitus Display Premature Aging and Mitochondrial Dysfunction

“…These cells lost the beneficial effects on anti-Thy1.1 nephritis seen in MSCs obtained from healthy subjects. Limited regenerative potential of MSCs obtained from older donors was also associated with both morphological and functional changes in mitochondria [53,54]. hTERT-immortalized bone marrow-derived MSCs from patients with Parkinson's disease showed decreased mitochondrial complex I, II, and IV activities [55].…”

Putative mesenchymal stem cells isolated from adult human ovaries

“…Some studies have shown that aging increased senescence and reduced cell viability, proliferation and differentiation potential [34][35][36]. Furthermore, when performing in vitro studies, the long-term expansion of MSCs had a significantly negative impact on the characteristics of MSCs, regardless of donor age [35,37]. Additionally, it is postulated that MSCs consist of different cell subpopulations and that the results (gene expression, immunocytochemistry) may vary depending on the ratio between these sub-populations [38].…”

Aging Effects on Cardiac Progenitor Cell Physiology

“…In the MSC compartment of the old bone marrow there is a diminished expression of the genes coding for chemokine and cytokine receptors, which potentially interferes with cell activation and migration (55). A transcriptome analysis of aging MSCs has documented downregulation of the signaling pathways involved in cytoskeleton turnover and cell adhesion (111). Comparative studies of young and old human tendon progenitor cells have revealed that the most differentially expressed genes in these two populations regulate cell adhesion and migration (167).…”