Changes in stem cell biology and capabilities are considered important in age-related degeneration. For example: "A decline in cellular homeostasis in older individuals underlies age-related pathologies like osteoporosis and osteoarthritis. [Researchers] report key differences in the patterns of expressed mRNAs in bone-marrow mesenchymal stem cells (bmMSCs) of young donors compared with old human donors. The distinct subsets of expressed genes associated with glycobiology are consistent with the underlying age-related decline in bone marrow function. ... It is now well established that in older individuals stem cells can become 'aged' and thus incapable of renewing surrounding tissues and organs as efficiently as young individuals. Experimental and clinical evidence has revealed the importance of stem cell aging in bone marrow transplants, as recipients of bone marrow from older donors do not fare as well as recipients of bone marrow from younger donors. However, the molecular mechanisms governing stem cell aging are not well understood. An important first step towards this goal is to delineate the gene expression differences between stem cells from young and old individuals. Bone marrow stem cells are particularly well suited for such studies, as they are relatively easy to purify to homogeneity. ... bmMSCs showed age-increases in the expression of genes associated with the degradation of N-glycans and glycosaminoglycans and with the biosynthesis of glycosphingolipids. These results reveal major differences in the glycobiology and glycan compostion of young and old bmMSCs, associated with age-related changes in the cellular responses to autocrine and paracrine signals. The difference in glycan pathways may not be limited to bmMSCs or even to stem cells, but could be more widely prevalent among other cell types."