Of experimental design (permanent occlusion vs. reperfusion). Since the environment of

Of experimental design (permanent occlusion vs. reperfusion). Since the environment of the aging heart in regards to fibroblast activation and leukocyte infiltration resembles (to a lesser extent) the setting of the injured young heart, we decided to analyze bone wall MSC (BW-MSC) derived from young and aging mice. Bone wall, rather than bone marrow, has been shown to be a major source of MSC in the adult mouse, so therefore we isolated these cells according to a protocol developed by Zhu and colleagues [68]. Surprisingly, BW-MSC isolated from aging animals (24?0 month-old) did not display the same defects as observed in cardiac resident MSC; their expression of Nanog was comparable to the levels expressed by cells isolated from young animals and Aprotinin biological activity fibroblasts derived from these BW-MSC did not display differences in TRI, RasGrf1, MCP-1 and IL-6 levels between these two age groups (unpublished observation, n= 6, 4 for cells derived from 3 and 24?0 month-old mice respectively) as opposed to fibroblasts derived from cardiac MSC [26, 27]. These results imply that the alteration of the environment in the aging heart (or circulating factors) may be responsible for the change of cardiac MSC phenotype, since BW-MSC are unaffected by age.J Mol Cell Cardiol. Author manuscript; available in PMC 2017 February 01.Trial et al.Page3. Potential therapeutic strategies targeting inflammatory mediators released by fibroblastsBoth clinical and experimental studies of aging have suggested potential roles for inflammation in the cardiac disease of aging associated with heart failure and cardiac fibrosis. Our studies have demonstrated increases in the renin angiotensin axis and we reported an increase in the endogenous renin angiotensin system in aging animals [2]. Angiotensin is known to generate a pro-inflammatory environment in young animals. Part of the angiotensin-induced inflammation may be due to reactive oxygen species production. However, the effects of reactive oxygen based strategies has been widely studied in aging without any definitive results; to be more specific, strategies aimed at the origins of increased reactive oxygen in the heart may be necessary. Our previous and current work led us to delineate the mechanistic link between the upregulated Ras-FTase-Erk pathway and fibrosis. Below we list potential therapeutic strategies that may provide benefits for the aging heart based on these findings (see also Fig. 4). 3.1. Insulin A majority of aging mice on standard laboratory chow and the majority of old patients are obese [69, 70]. In aging this is associated with increased circulating insulin levels [25, 35] that appear to participate in the downstream signal dysregulation. Thus far, our studies have shown that pathophysiologic concentrations of insulin result in the reduction of Nanog expression in MSC and stimulation of collagen synthesis and FTase activity in fibroblasts. In obese or aging mice, we have also previously demonstrated increased myocardial fibrosis and defective cardiac scar formation [71, 72]. Therefore a pharmacological approach to reduce the insulin resistance and normalize the circulating insulin levels may moderate the progression of interstitial fibrosis. The potential usefulness of this direction is also bolstered by the large amount of literature Vesnarinone chemical information demonstrating that calorie restriction is associated with improved healthspan in patients [73]. 3.2. FTase Aberrant activation of the FTase-Erk pathway as seen in fibroblasts d.Of experimental design (permanent occlusion vs. reperfusion). Since the environment of the aging heart in regards to fibroblast activation and leukocyte infiltration resembles (to a lesser extent) the setting of the injured young heart, we decided to analyze bone wall MSC (BW-MSC) derived from young and aging mice. Bone wall, rather than bone marrow, has been shown to be a major source of MSC in the adult mouse, so therefore we isolated these cells according to a protocol developed by Zhu and colleagues [68]. Surprisingly, BW-MSC isolated from aging animals (24?0 month-old) did not display the same defects as observed in cardiac resident MSC; their expression of Nanog was comparable to the levels expressed by cells isolated from young animals and fibroblasts derived from these BW-MSC did not display differences in TRI, RasGrf1, MCP-1 and IL-6 levels between these two age groups (unpublished observation, n= 6, 4 for cells derived from 3 and 24?0 month-old mice respectively) as opposed to fibroblasts derived from cardiac MSC [26, 27]. These results imply that the alteration of the environment in the aging heart (or circulating factors) may be responsible for the change of cardiac MSC phenotype, since BW-MSC are unaffected by age.J Mol Cell Cardiol. Author manuscript; available in PMC 2017 February 01.Trial et al.Page3. Potential therapeutic strategies targeting inflammatory mediators released by fibroblastsBoth clinical and experimental studies of aging have suggested potential roles for inflammation in the cardiac disease of aging associated with heart failure and cardiac fibrosis. Our studies have demonstrated increases in the renin angiotensin axis and we reported an increase in the endogenous renin angiotensin system in aging animals [2]. Angiotensin is known to generate a pro-inflammatory environment in young animals. Part of the angiotensin-induced inflammation may be due to reactive oxygen species production. However, the effects of reactive oxygen based strategies has been widely studied in aging without any definitive results; to be more specific, strategies aimed at the origins of increased reactive oxygen in the heart may be necessary. Our previous and current work led us to delineate the mechanistic link between the upregulated Ras-FTase-Erk pathway and fibrosis. Below we list potential therapeutic strategies that may provide benefits for the aging heart based on these findings (see also Fig. 4). 3.1. Insulin A majority of aging mice on standard laboratory chow and the majority of old patients are obese [69, 70]. In aging this is associated with increased circulating insulin levels [25, 35] that appear to participate in the downstream signal dysregulation. Thus far, our studies have shown that pathophysiologic concentrations of insulin result in the reduction of Nanog expression in MSC and stimulation of collagen synthesis and FTase activity in fibroblasts. In obese or aging mice, we have also previously demonstrated increased myocardial fibrosis and defective cardiac scar formation [71, 72]. Therefore a pharmacological approach to reduce the insulin resistance and normalize the circulating insulin levels may moderate the progression of interstitial fibrosis. The potential usefulness of this direction is also bolstered by the large amount of literature demonstrating that calorie restriction is associated with improved healthspan in patients [73]. 3.2. FTase Aberrant activation of the FTase-Erk pathway as seen in fibroblasts d.