X-Message-Number: 25786 Date: Sun, 13 Mar 2005 12:12:35 -0800 (PST) From: Doug Skrecky <> Subject: bone marrow may regulate the greater part of aging [In addition to osteoporosis, bone marrow also may be primarily responsible for the development of sarcopenia as well as atherosclerosis. Could oxidized low density lipoprotein be a connecting factor?] Nature. 2005 Feb 17;433(7027):760-4. Rejuvenation of aged progenitor cells by exposure to a young systemic environment. The decline of tissue regenerative potential is a hallmark of ageing and may be due to age-related changes in tissue-specific stem cells. A decline in skeletal muscle stem cell (satellite cell) activity due to a loss of Notch signalling results in impaired regeneration of aged muscle. The decline in hepatic progenitor cell proliferation owing to the formation of a complex involving cEBP-alpha and the chromatin remodelling factor brahma (Brm) inhibits the regenerative capacity of aged liver. To examine the influence of systemic factors on aged progenitor cells from these tissues, we established parabiotic pairings (that is, a shared circulatory system) between young and old mice (heterochronic parabioses), exposing old mice to factors present in young serum. Notably, heterochronic parabiosis restored the activation of Notch signalling as well as the proliferation and regenerative capacity of aged satellite cells. The exposure of satellite cells from old mice to young serum enhanced the expression of the Notch ligand (Delta), increased Notch activation, and enhanced proliferation in vitro. Furthermore, heterochronic parabiosis increased aged hepatocyte proliferation and restored the cEBP-alpha complex to levels seen in young animals. These results suggest that the age-related decline of progenitor cell activity can be modulated by systemic factors that change with age. Clin Exp Pharmacol Physiol. 2004 Jul;31(7):407-13. Oxidized low-density lipoprotein induces endothelial progenitor cell senescence, leading to cellular dysfunction. 1. Recent studies have revealed an association between coronary risk factors and both the number and function of bone marrow-derived endothelial progenitor cells (EPC). We investigated the effect of oxidized low-density lipoprotein (ox-LDL) on the senescence of EPC, leading to cellular dysfunction. 2. Endothelial progenitor cells were isolated from human peripheral blood and characterized. The exposure of cultured EPC to ox-LDL (10 microg/mL) significantly accelerated the rate of senescence compared with control during 20 days in culture as determined by acidic beta-galactosidase staining. Oxidized LDL-induced EPC senescence was significantly inhibited by pretreatment with either lectin-like ox-LDL receptor-1 (LOX-1) antibody (Ab) or atorvastatin (P < 0.01). 3. Because cellular senescence is critically influenced by telomerase, which elongates telomeres, we measured telomerase activity using a polymerase chain reaction-ELISA-based assay. Oxidized LDL significantly diminished telomerase activity to approximately 50%, an effect that was significantly abolished by pretreatment with either LOX-1 Ab or atorvastatin (P < 0.01). 4. We examined whether ox-LDL-induced EPC senescence translates into EPC dysfunction. An MTS assay disclosed an inhibitory effect of ox-LDL on EPC proliferation. In a Matrigel assay, EPC treated with ox-LDL were less likely to participate in network formation compared with controls. 5. In conclusions, ox-LDL accelerates the onset of EPC senescence, which may be related to telomerase inactivation. Oxidized LDL-induced EPC senescence leads to the impairment of proliferative capacity and network formation. Am Heart J. 2003 Oct;146(4 Suppl):S5-12. Loss of bone marrow-derived vascular progenitor cells leads to inflammation and atherosclerosis. BACKGROUND: Aging represents the most powerful risk for the development of atherosclerosis and atherosclerotic thromboembolic complications. Yet, the mechanism by which aging affects the arterial wall and its deterioration has remained essentially uncharacterized. FINDINGS: Chronic injuries to the arterial wall contribute to the development of atherosclerosis. However, it is important to note that a complex repair system that involves both local and bone marrow-derived cells maintains arterial homeostasis and integrity. With this review, we explain how the age-dependent failure of the bone marrow to produce vascular progenitor cells responsible for such arterial repair--an inability that results from the impact of a lifetime of risk factors such as hyperlipidemia--drives atherosclerosis and its thromboembolic complications. As a consequence of such failure, the normal processes of arterial wall repair and rejuvenation are impaired. The disequilibrium that ensues between injury of the arterial wall and repair leads to atherosclerotic inflammation and consequent thromboembolic complications. CONCLUSION: The bone marrow and derived progenitor cells represent key regulators of atherosclerosis, and progress in the prevention and treatment of atherosclerosis and its thromboembolic complications will need to take into account this new dimension for the disease process. Circulation. 2003 Jul 29;108(4):457-63. Epub 2003 Jul 14. Aging, progenitor cell exhaustion, and atherosclerosis. BACKGROUND: Atherosclerosis is largely attributed to chronic vascular injury, as occurs with excess cholesterol; however, the effect of concomitant vascular aging remains unexplained. We hypothesize that the effect of time in atherosclerosis progression is related to obsolescence of endogenous progenitor cells that normally repair and rejuvenate the arteries. METHODS AND RESULTS: Here we show that chronic treatment with bone marrow-derived progenitor cells from young nonatherosclerotic ApoE-/- mice prevents atherosclerosis progression in ApoE-/- recipients despite persistent hypercholesterolemia. In contrast, treatment with bone marrow cells from older ApoE-/- mice with atherosclerosis is much less effective. Cells with vascular progenitor potential are decreased in the bone marrow of aging ApoE-/- mice, but cells injected from donor mice engraft on recipient arteries in areas at risk for atherosclerotic injury. CONCLUSIONS: Our data indicate that progressive progenitor cell deficits may contribute to the development of atherosclerosis. Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=25786