Loss of epigenetic information as a cause of mammalian aging

All living things experience an increase in entropy, manifested as a loss of genetic and epigenetic information. In yeast, epigenetic information is lost over time due to the relocalization of chromatin-modifying proteins to DNA breaks, causing cells to lose their identity, a hallmark of yeast aging. Using a system called "ICE" (inducible changes to the epigenome), we find that the act of faithful DNA repair advances aging at physiological, cognitive, and molecular levels, including erosion of the epigenetic landscape, cellular exdifferentiation, senescence, and advancement of the DNA methylation clock, which can be reversed by OSK-mediated rejuvenation. These data are consistent with the information theory of aging, which states that a loss of epigenetic information is a reversible cause of aging.

Metformin improves healthspan and lifespan in mice

Metformin is a drug commonly prescribed to treat patients with type 2 diabetes. Here we show that long-term treatment with metformin (0.1% w/w in diet) starting at middle age extends healthspan and lifespan in male mice, while a higher dose (1% w/w) was toxic. Treatment with metformin mimics some of the benefits of calorie restriction, such as improved physical performance, increased insulin sensitivity, and reduced low-density lipoprotein and cholesterol levels without a decrease in caloric intake. At a molecular level, metformin increases AMP-activated protein kinase activity and increases antioxidant protection, resulting in reductions in both oxidative damage accumulation and chronic inflammation. Our results indicate that these actions may contribute to the beneficial effects of metformin on healthspan and lifespan. These findings are in agreement with current epidemiological data and raise the possibility of metformin-based interventions to promote healthy aging.

Age-related cataract in dogs: a biomarker for life span and its relation to body size

Clinical data from 72 dog breeds of varying size and life expectancy were grouped according to breed body mass and tested for prevalence at ages 4 to 5, ages 7 to 10, and lifetime incidence of non-hereditary, age-related cataract (ARC). The incidence of ARC was found to be directly related to the relative life expectancies in the breed groups: The smallest dog breeds had a lower ARC prevalence between ages 4 and 5 than mid-size breeds and these, in turn, a lower prevalence than the giant breeds. A similar sequence was evident for ages 7 to 10 and for overall lifetime incidence of ARC. These differences became more significant when comparing small and giant breeds only. We could also confirm the inverse relationship between body size and life expectancy in these same sets of dog breeds. Our results show that body size, life expectancy, and ARC incidence are interrelated in dogs. Given that ARC has been shown to be at least partially caused by oxidative damage to lens epithelial cells and the internal lens, we suggest that it can be considered not only as a general biomarker for life expectancy in the canine and possibly other species, but also for the systemic damages produced by reactive oxygen species. This suggests new approaches to examine the gene expression pathways affecting the above-noted linkages.

Disruption of protein kinase A in mice enhances healthy aging

Mutations that cause a reduction in protein kinase A (PKA) activity have been shown to extend lifespan in yeast. Loss of function of mammalian RIIbeta, a regulatory subunit of PKA expressed in brain and adipose tissue, results in mice that are lean and insulin sensitive. It was therefore hypothesized that RIIB null (RIIbeta(-/-)) mice would express anti-aging phenotypes. We conducted lifespan studies using 40 mutant and 40 wild type (WT) littermates of equal gender numbers and found that both the median and maximum lifespans were significantly increased in mutant males compared to WT littermates. The median lifespan was increased from 884 days to 1005 days (p = 0.006 as determined by the log rank test) and the 80% lifespan (defined here as 80% deaths) was increased from 941 days to 1073 days (p = 0.004 as determined by the Wang-Allison test). There was no difference in either median or 80% lifespan in female genotypes. WT mice of both genders became increasingly obese with age, while mutant mice maintained their lean phenotype into old age. Adiposity was found to correlate with lifespan for males only. 50% of male mice between 30 and 35 g, corresponding to about 5% body fat, for either genotype lived over 1000 days. No male mouse outside of this weight range achieved this lifespan. During their last month of life, WT mice began losing weight (a total of 8% and 15% of body weight was lost for males and females, respectively), but RIIbeta(-/-) male mice maintained their lean body mass to end of life. This attenuation of decline was not seen in female mutant mice. Old male mutant mice were insulin sensitive throughout their life. Both genders showed modestly lower blood glucose levels in old mutants compared to WT. Male mutants were also resistant to age-induced fatty liver. Pathological assessment of tissues from end of life male mutant mice showed a decrease in tumor incidence, decreased severity of renal lesions, and a trend towards a decrease in age-related cardiac pathology. These findings help establish the highly conserved nature of PKA and suggest that disruption of PKA affects physiological mechanisms known to be associated with healthy aging.

Reduced Age-Related Cataracts Among Elderly Persons Who Reach Age 90 With Preserved Cognition: A Biomarker of Successful Aging?

Tissue damage due to oxidative stress has been implicated in aging, memory loss, and cataract formation. We hypothesized that persons who achieved exceptional longevity with preserved cognition (successful aging [SAG]) would exhibit a lower rate of age-related cataract (ARC) than the general population. The age-specific rates of ARC for a group of 100 (50 male, 50 female) elderly persons who reached at least age 90 years with preserved cognition were compared to the corresponding rates of ARC reported in five population-based studies. The principal finding of this report was that the SAG group manifested a significant reduction in the age-specific rate and lifetime cumulative incidence of ARC compared to the general population. Steroid use, alcohol consumption, gout, and skin lesions resulting from excessive sun exposure emerged as risk factors. Our findings suggest that the progressive development of lens opacities may be reflective of degenerative events occurring more generally throughout the body.

Cellular debris and ROS in age-related cortical cataract are caused by inappropriate involution of the surface epithelial cells into the lens cortex

PURPOSE

To quantify changes in the lens epithelial cells and underlying lens cortex responsible for age-related cortical cataract (ARCC) in the rat.

METHODS

Freshly isolated lenses were stained vitally for DNA with Hoechst 33342. Reactive oxygen species (ROS) and mitochondria were visualized and quantified by dihydrorhodamine 123 (DHR). The fluorescence was quantified using Laser Scanning Confocal Microscopy (LSCM) of vitally stained lenses. Cortical DNA was verified as such by DNAse I digestion. Cataract reflections were determined from digitalized images of light reflections taken with a low magnification light microscope, or with the LSCM.

RESULTS

The anterior surface epithelia of old rat lenses were full of gaps and ragged in appearance with a decrease of over 50% in lens epithelial cell (LEC) density. The surface LECs were frequently seen to have involuted into the cortex at inappropriate sites, forming deposits full of DNA, nuclear and mitochondrial debris, and abundant ROS. These involutions frequently originated near open gaps in the surface epithelia, where they appear to have detached from the capsular membrane. Cortical cataracts in the rat lenses were seen to co-localize with these LEC involutions, as had been seen previously in mice with ARCC.

CONCLUSIONS

ARCC in rats co-localized with inappropriate accumulations of nuclei, mitochondria, DNA, and expression of ROS in debris filled foci. These were the result of both involution of surface LECs into areas of cortical ARCC, and by an extension of the normal bow region deep into the anterior and posterior of cataractous lenses. These results were in complete agreement with our previous studies on ARCC in mice.

Intraclonal plasticity for bone, smooth muscle, and adipocyte lineages in bone marrow stroma fibroblastoid cells

Bone marrow stroma fibroblastoid cells (BMSFC) develop from a single clone of cells within each of the in vitro fibroblastoid colonies (CFU-F) derived from either murine or human bone marrow. All of the clones represented by these colonies displayed antigenic and product markers for osteoblast, smooth muscle, and adipocyte lineages when tested separately for each marker. Separate sets of fibroblastoid colonies derived from the same individual donor's culture tested positive with antibodies specific for smooth muscle-specific heavy chain myosin (SMMHC), smooth muscle alpha actin-1, bone sialoprotein, osteocalcin, or alkaline phosphatase, and developed von Kossa-positive deposits shown by X-ray microanalysis and electron diffraction to be hydroxyapatite. Individual cells were positive for both SMMHC and osteocalcin. All cells in the multiple clones tested were capable of metabolizing a fatty acid to form intracellular lipid droplets. PCR transcripts obtained from the human cell cultures that provided these BMSFC clones were consistent with the immunocytochemical findings. Transcripts for PPAR (gamma)-2 and Cbfa-1 were dependent upon the culture medium content, suggesting an osteoblast/adipocyte differentiation switch point. Cell lineage specificity for markers and RNA transcripts was determined by comparison to skin fibroblast controls. These findings demonstrate a high degree of interlineage plasticity in vitro for BMSFC.

White light-mediated DNA strand breaks in lens epithelial cells

It was hypothesized that white light can induce DNA single-strand breaks/alkali labile sites in lens epithelial cells during the dissection process when lenses are being collected for study. Dissection of lenses in white light significantly increased 'Integrated Intensity' (P=0.0216), an index of DNA single strand breaks/alkali labile sites, using the alkaline microgel electrophoresis assay. In addition, we investigated the DNA damaging effect of visible light in a human lymphocyte model in which cells were exposed to white light, red light or minimal indirect light for 5 min. Results of these experiments confirm our conclusion that visible light induces DNA damage in cells. These findings may be relevant in a genotoxicity study on cells ex vivo.

DNA double-strand breaks in mouse kidney cells with age

A Biojector device fitted with a CO2 cartridge was used to prepare single cell suspensions from kidneys of 12-month- (middle-aged) and 24-month-old (old) C57B1/6 mice. Microgel electrophoresis of DNA from these cells revealed a modest but significant 7.3% increase (P = 0.04) in DNA double-strand breaks in old mice. This increase is equivalent to the DNA damage induced by 0.1 Gray of X-rays (5 double-strand breaks) in kidney cells of 10-month-old mice, as determined by a standard calibration curve. Greater DNA damage with aging was also positively correlated with higher levels of pathology in the kidneys.

Age-related telomere shortening occurs in lens epithelium from old rats and is slowed by caloric restriction

We have investigated whether the average relative telomere length of lens epithelial cells (LECs) from brown Norway rats decreases with the age of the donor animal, and whether chronic caloric restriction (CR) of the rats delays the telomere shortening. Our previous studies have demonstrated that clonal proliferative potential of rodent LECs as well as the in vivo rate of DNA synthesis decreases with age and that this decrease is slowed by chronic lifelong caloric restriction (CR). In order to determine if telomeric shortening might be involved in this loss of proliferative potential, we examined relative telomeric lengths in young, old ad lib fed (AL), and old calorically restricted (CR) brown Norway rats. We used fluorescence in situ hybridization with a peptide nucleic acid probe (PNA) complementary to the telomeric repeat sequence to quantitate relative telomere lengths in LECs in lens sections (TELO-FISH). Control experiments demonstrated that the PNA probe binding was restricted almost entirely to the terminal portions of the rat chromosomes with less than 5% bound at interstitial sites in typical metaphase spreads. The relative telomere lengths of interphase human fibroblast standards, as determined by TELO-FISH, were in good agreement with terminal restriction fragment analyses of the same standards and with literature values for rat cells. The average telomere lengths of interphase nuclei in the old AL rat LECs were found to be 21% shorter than paired young AL controls (P < 0.01 by Wilcoxian signed rank test). The calorically restricted old rats had less telomere erosion (12%) than the old AL group (P < 0.05). Although it is not clear whether such moderate telomeric erosion can limit cell division in rodent LECs, the telomeric shortening correlated well with previous studies demonstrating reduced clonal, replicative potential, and reduced rates of in vivo DNA replication in LECs from old rodents and a delay in this attenuation in animals on chronic CR.

The effect of high and very low fluorescent light exposure levels on age-related cataract in a pigmented mouse strain

This study examined the effect of fluorescent light on the timing and severity of age-related cataracts in a fully pigmented mouse strain, the (C57BL/6 x C3H)F1, that normally develops slowly progressing age-related cataracts only beyond middle age. Two groups of 56 animals each were exposed, respectively, either to a daily range of 66-222 foot candles (FC) or to 1 FC of standard fluorescent lighting for a period beginning at 5 weeks of age and ending at 33.5 months (by which time approximately 65% of the colony had died). Contrary to previous reports involving albino rats or mice and a strain of pigmented but cataract-prone transgenic mice, the two groups of animals in this experiment did not differ for cataract development in time of first occurrence, rate of advancement, or degree of severity. It was concluded that genetic predisposition, based on levels of oxidative free radical production vs antioxidant enzyme and repair enzyme protection in the lens, was probably the major factor governing the rate and degree of age-related cataract development in these animals. The effect of relatively intense life-long fluorescent light exposure was so minimal as not to be manifested in this strain of mice under the conditions of this experiment. Remarkably, maintaining the one group of mice in semi-darkness from 5 weeks of age to beyond their mean lifespans did nothing to delay or reduce the incidence or severity of their age-related cataracts.

Mirror neurons, procedural learning, and the positive new experience: a developmental systems self psychology approach

In summary, we are impressed with the existence of a mirror neuron system in the prefrontal cortex that serves as part of a complex neural network, including afferent and efferent connections to the limbic system, in particular the amygdala, in addition to the premotor and motor cortex. We think it is possible to arrive at an integration that postulates the mirror neuron system and its many types of associated multimodal neurons as contributing significantly to implicit procedural learning, a process that underlies a range of complex nonconscious, unconscious, preconscious and conscious cognitive activities, from playing musical instruments to character formation and traumatic configurations. This type of brain circuitry may establish an external coherence with developmental systems self psychology which implies that positive new experience is meliorative and that the intentional revival of old-old traumatic relational configurations might enhance maladaptive procedural patterns that would lead to the opposite of the intended beneficial change. When analysts revive traumatic transference patterns for the purpose of clarification and interpretation, they may fail to appreciate that such traumatic transference patterns make interpretation ineffective because, as we have stated above, the patient lacks self-reflection under such traumatic conditions. The continued plasticity and immediacy of the mirror neuron system can contribute to positive new experiences that promote the formation of new, adaptive, implicit-procedural patterns. Perhaps this broadened repertoire in the patient of ways of understanding interrelational events through the psychoanalytic process allows the less adaptive patterns ultimately to become vestigial and the newer, more adaptive patterns to emerge as dominant. Finally, as we have stated, we believe that the intentional transferential revival of trauma (i.e., the old-old relational configuration) may not contribute to therapeutic benefit. In contrast, the revival of trauma in the old-new configuration (i.e., in the presence of a helpful other who can reduce anxiety and foster eventual positive new experience) can be beneficial, as trauma research has demonstrated. This is the process that promotes new implicit-procedural learning, new-new relational configurations, and a richer understanding of the self narrative.

Normal mouse and rat strains as models for age-related cataract and the effect of caloric restriction on its development

The purpose of this study was to determine: (1) which of the commonly used strains of laboratory rats and mice provide good models for human age-related cataract, and (2) whether long term caloric restriction, a regimen that prolongs both median and maximum life span in rodents, would also delay the time of appearance of this age-related pathology. Three strains of mice and two rat strains commonly used in laboratory work and maintained on either ad libitum (AL) or calorically restricted (CR) diets in the National Institutes of Aging and Diet Restriction colony were examined by slit lamp for age-related cataracts at four or more time points during their life spans. These strains were Brown Norway and Fischer 344 rats, and C57BL/6, (C57BL6 x DBA/2)F1 and (C57BL/6 x C3H)F1 mice. None of these strains develop congenital cataracts. Various stages of cataract were found in the great majority of these animals in old age. In both rat strains and one mouse strain the cataracts occurred after mid-life, were most advanced late in life, and were similar in locations and appearance to those in humans. In the two mouse strains in which some cataracts appeared as early as 10-14 months of age, previously identified genetic defects affecting the eye were probably involved in the early appearances. CR extended life spain in all five rat and mouse strains and also delayed both the time of first appearances and the subsequent increase in cataract severity over time in the four dark-eyed strains. CR did not delay cataract formation in the single albino rat strain studied. In summation: (1) commonly used strains of laboratory rats and mice that are free of congenital or early appearing cataracts due to genetic defects would appear to serve as appropriate models for human age-related cataract, (2) caloric restriction (CR) provides a protective effect, delaying development of cataracts in the dark-eyed mouse and rat strains, while also extending their life spans, (3) CR did not delay the development of lens damage in the nonpigmented eye of the single albino strain studied, although it extended life span.

The relationships of animal age and caloric intake to cellular replication in vivo and in vitro: a review

This brief review examines aging at the cellular level as expressed by cell replication rates in vivo, clone size limits in vitro, and cell function in several tissues and organs. Studies are presented in which in vivo and in vitro cell replication measurements were made for several cell types and organs in relation to animal age, diet, life span, and specific age-related pathologies. Among the events examined that affect cell replication and cell survival in vitro and in vivo over a lifetime are oxidative damage, telomere shortening, and hormone and hormone receptor level changes. Long-term caloric restriction (CR) is favorable or protective for all of these events when measured in later life and comparisons are made to ad libitum (AL)-fed animals, and it is accompanied by more youthful rates of cell replication. It is proposed that in vivo and in vitro measures of cellular replication constitute biomarkers of aging when applied to comparisons of CR and AL diet rodents, where they correlate with the delay of disease and extension of life span. Longitudinal studies are needed to confirm this. The occurrence of certain age-related pathophysiologic states, such as immune (T cell) insufficiency, cataract, and senile osteopenia/osteoporosis, are accompanied by major diminishments of replication rates, numbers, and functions of the essential cell types in the organs and tissues involved. However, direct evidence is lacking that diminished cell replication in specific organs contributes to the limitation of life span.

Cellular proliferation potential during aging and caloric restriction in rhesus monkeys (Macaca mulatta)

Caloric restriction (CR) is the most successful method of extending both median and maximal lifespans in rodents and other short-lived species. It is not yet clear whether this method of life extension will be successful in longer-lived species, possibly including humans; however, trials in rhesus monkeys are underway. We have examined the cellular proliferative potential of cells from CR and AL (ad libitum fed) monkey skin cells using two different bioassays: colony size analysis (CSA) of dermal fibroblasts isolated and cloned directly from the skin and beta-galactosidase staining at pH 6.0 (BG-6.0) of epidermal cells in frozen sections of skin. Decreases in both proliferative markers occurred with age, but no differences were observed between CR and AL animals. Skin biopsies were obtained from AL and CR rhesus monkeys from two different aging colonies, one at the National Institute on Aging (NIA) and one at the University of Maryland-Baltimore (UMB). These biopsies were used as a source of tissue sections and cells for two biomarkers of aging assays. The CR monkeys had been maintained for 9-12 years on approximately 70% of the caloric intake of control AL animals. In the CSA studies, the fraction of small clones increased significantly and the fraction of large clones decreased significantly with increasing age in AL monkeys. The frequency of epidermal BG-6.0 staining cells increased with age in older (>22 years) AL monkeys, but most predominately in those of the UMB colony, which were somewhat heavier than the NIH AL controls. Old monkeys on CR tended to have fewer BG-6.0-positive cells relative to old AL-derived epidermis, but this effect was not significant. These results indicate that cellular proliferative potential declined with age in Macaca mulatta, but was not significantly altered by CR under these conditions. Although these experiments are consistent with an absence of effect of CR on monkey skin cell proliferative potential, we have found in previous experiments with mice that a longer duration of CR (as a fraction of total lifespan) was needed to demonstrate CR-related improvement in clone size in mice. Further studies on the now mid-aged monkeys will be needed as their age exceeds 20 years to conclusively rule out an effect of CR on proliferative potential of skin cells from these primates.

Response of lens epithelial cells to hydrogen peroxide stress and the protective effect of caloric restriction

Hydrogen peroxide (H2O2) has been reported to be present at significant levels in the lens and aqueous humor in some cataract patients and suggested as a possible source of chronically inflicted damage to lens epithelial (LE) cells. We measured H2O2 effects on bovine and mouse LE cells and determined whether LE cells from old calorically restricted mice were more resistant to H2O2-induced cellular damage than those of same age ad libitum fed (AL) mice. Bovine lens epithelial cells were exposed to H2O2 at 40 or 400 microM for 2 h and then allowed to recover from the stress. The cells were assayed for DNA damage, DNA synthesis, cell viability, cell morphology, response to growth stimuli, and proliferation potential. Hydrogen peroxide-treated cells showed an increased DNA unwinding 50% greater than that for untreated controls. These DNA strand breaks appeared to be almost completely rejoined by 30 min following removal of the cells from a 2-h exposure. The 40 microM exposure did not produce a significantly lower DNA synthesis rate than the control, it responded to growth factor stimuli, and it replicated as did the control cells after removal of H2O2. The 400 microM H2O2 severely affected DNA synthesis and replication, as shown by increased cell size and by markedly reduced clonal cell growth. The cells did not respond to growth stimulation by serum or growth factors and lost irreversibly the capacity to proliferate. The responses of LE cells from old adlib diet (AL) and calorically restricted (CR) mice to H2O2 were significantly different. Exposure of LE cells to 20, 40, or 100 microM H2O2 for 1 h induces a significant loss of cellular proliferation in cells from old AL mice. LE cells from long-term CR mice of the same strain and age were more resistant to oxidative damage at all three concentrations of H2O2 than those of both old and young AL mice and showed a significantly higher proliferation potential following treatment. It is concluded that CR results in superior resistance to reactive oxygen radicals in the lens epithelium.

Effects of age and long-term caloric restriction on the aqueous collecting channel in the mouse eye

PURPOSE

The mouse aqueous collecting channel, part of the mouse aqueous outflow pathway, was measured using a computer-assisted image analysis system. We used ad libitum-fed and calorie-restricted mice to investigate the effects of age and long-term caloric restriction on the lumen size of the channel.

RESULTS

The ad libitum-fed mice showed a significant age-related reduction in the lumen area. In the ad libitum-fed group, the lumen area of the channel decreased by 30% at 30-35 months of age (p < 0.01), and the anteroposterior width declined by 21% (p < 0.001) as compared with mice 3-5 months of age. The calorie-restricted mice did not display any reduction with age in the lumen area or the anteroposterior width of the channel. When compared with the age-matched calorie-restricted mice, the lumen area of the channel of the ad libitum-fed mice measured less by 34%, and anteroposterior width less by 21% at 30-35 months of age (p < 0.01).

CONCLUSIONS

These results indicate that an age-related morphological alteration in the mouse aqueous collecting channel occurred and that it is delayed by long-term caloric restriction. This suggests a possible role of life-long caloric restriction in reducing glaucomatous damages and perhaps delaying glaucoma development.

Long-term caloric restriction delays age-related decline in proliferation capacity of murine lens epithelial cells in vitro and in vivo

PURPOSE

The goal of this study was to examine the effects of age and long-term caloric restriction on the proliferation capacity of murine lens epithelial (LE) cells in vitro and in vivo.

METHODS

B6D2F1 (C57BL/6 X DBA/2) F1 mice 4 to 45 months of age were obtained and fed either an ad libitum (AL) or a calorically restricted (CR) diet (60% of AL intake). Cellular proliferation capacity in vitro was measured using the colony size distribution assay for 10-day clonal growth of mouse LE cells. Proliferation rate in vivo was assayed using immunostaining for 5-bromo-2'-deoxyuridine (BrdU) in mouse LE cells after 2-week osmotic pump delivery of BrdU.

RESULTS

Proliferative capacity of cells from old AL mice decreased significantly in comparison to cells from young AL and old CR mice, as determined by the fractions of cells capable of forming small (no or one cell division) and large (four or more cell divisions) colonies in vitro. There was also a decline in cell replicative rate as measured by BrdU labeling index (LI) in vivo with increasing age in AL and CR mice. However, this decline was marked in AL mice between 10 and 30 months of age and minimal in CR mice. Significant differences in BudU LI between AL and CR mice occurred when animals were 30 months of age or older. This finding indicates that an age-related decline in cellular proliferation rate in vivo was delayed by CR.

CONCLUSIONS

A significantly reduced proliferative capacity of LE cells is associated with increased age of mice and is delayed by long-term caloric restriction as measured in vitro and in vivo. How caloric restriction mediates its effects on LE cell proliferation remains to be investigated further.

Enhanced cell proliferation and biosynthesis mediate improved wound repair in refed, caloric-restricted mice

Aged mice that have undergone long-term caloric-restriction (CR) have improved health and enhanced longevity in comparison to aged mice that are ad libitum-fed (AL). However, caloric-restriction does not benefit the impaired wound healing of aged mice. To test the hypothesis that CR mice have the capacity for enhanced wound repair, but require a short-term period of additional nutrient intake to show this advantage, we assessed wound healing in CR mice that had been refed (RF) an ad libitum diet for 4 weeks prior to wounding. Two strains of AL young (Y AL) (4-6 months), AL middle-aged (M AL) (15-17 months), and three different, matched cohorts of old mice (O) (30-33 months): O AL, O CR, and O RF were studied. Two full-thickness 4 mm diameter punch biopsy skin wounds were created on the dorsum of each mouse. Animals were sacrificed and wounds were harvested at 1,2,3,5, and 7 days post-wounding. Repair of wounds was slower in O AL and O CR mice compared to Y AL and M AL animals. In contrast, the O RF mice healed similarly to that of the Y AL and M AL mice, as assessed by measures of wound area and histologic criteria. O RF mice demonstrated enhanced synthesis of type I collagen mRNA in comparison to O AL and O CR mice. A greater number of endothelial cells and fibroblasts at the wound edge of the O RF mice exhibited replication in vivo as measured by uptake of BrdU. O RF mice had higher levels of insulin-like binding protein 3 (IGFBP-3). Furthermore, fibroblasts derived from the explant of the punch biopsy of O CR mouse skin revealed enhanced proliferation and contraction in vitro, in comparison to fibroblasts from the O AL mice. In conclusion, O RF mice demonstrate an enhanced capacity to undergo wound repair in comparison to O AL mice. This effect appears to be mediated, in part, by enhanced cell proliferation, contraction, and collagen biosynthesis. In addition, short-term refeeding induced an increase in the serum level of IGFBP-3, the major binding protein for IGF-1. These data confirm that cells from O CR animals have a preserved proliferative, biosynthetic, and contractile capacity, but that an adequate source of nutrients is necessary to demonstrate this advantage in wound healing.

Interaction of stem cell factor and its receptor c-kit mediates lodgment and acute expansion of hematopoietic cells in the murine spleen

The phenotypes of mice that harbor a defect in the genes encoding either stem cell factor (SCF) or its receptor, c-kit, indicate that this ligand/receptor pair is necessary for maintenance of normal hematopoiesis in the adult. Our objective was to determine whether SCF, like erythropoietin, is necessary for acute erythroid expansion during recovery from hemolytic anemia. Monoclonal antibody ACK2, which recognizes the murine c-kit receptor, was used to selectively block the hematopoietic growth-promoting effects of SCF. Mice were treated with phenylhydrazine on day 0 and day 1 to induce hemolytic anemia and also received no antibody, control IgG, or ACK2 on day 0. The mice were killed on day 3 and the hematocrit (Hct), reticulocyte count, and numbers of erythroid and myeloid hematopoietic progenitor cells (colony-forming unit-erythroid [CFU-E], burst-forming unit [BFU]-E, and CFU-granulocyte-macrophage [GM]) were quantitated in the femoral marrow and spleen using hematopoietic colony-forming assays. Induction of hemolytic anemia with phenylhydrazine resulted in a drop in the Hct from approximately 50% to 30%, and an approximate 8- to 10-fold increase in the reticulocyte count. The numbers of CFU-E increased modestly in the femur, and approximately 25- to 50-fold in the spleen, in comparison with normal mice. BFU-E and CFU-GM values did not increase in the femur but expanded 6- to 10-fold in the spleen, in comparison with normal mice. This confirms that much of the erythroid expansion in response to hemolytic anemia occurs in the murine spleen. Neutralizing quantities of the ACK2 antibody reduced femoral CFU-E, BFU-E, and CFU-GM content to less than half that found in phenylhydrazine-treated control mice and nearly totally ablated splenic hematopoiesis. These results suggest that c-kit receptor function may be required for optimal response to acute erythropoietic demand and that erythropoiesis in the splenic microenvironment is more dependent on SCF/c-kit receptor interaction than is erythropoiesis in the marrow microenvironment. Because expansion of late erythropoiesis in the spleen was preferentially blocked, we tested the hypothesis that homing of more primitive hematopoietic cells to the spleen was dependent on c-kit receptor function. Lethally irradiated mice were injected with marrow cells obtained from mice that had received phenylhydrazine plus control IgG or with marrow cells obtained from mice that had received phenylhydrazine plus ACK2. In parallel experiments, normal murine marrow cells were treated in vitro with control IgG or with ACK2 and were injected into lethally irradiated mice. The fraction of BFU-E and CFU-GM retrieved from the marrow and spleen of the recipient mice 4 hours later was reduced by approximately 75% when progenitor cells had been exposed to ACK2, in comparison with control IgG. These data suggest that interaction of SCF with the c-kit receptor affects the homing behavior of hematopoietic progenitor cells in the adult animal.

Transforming growth factor beta 1 directly and reversibly inhibits the initial cell divisions of long-term repopulating hematopoietic stem cells

Hematopoiesis appears to be regulated, in part, by a balance between extracellular positive and negative growth signals. Transforming growth factor beta-1 (TGF-beta 1) has been shown to be a negative regulator of primitive hematopoietic cells. This study examined the direct effect of TGF-beta 1 on the proliferation and differentiation of long-term repopulating hematopoietic stem cells (LTR-HSC) in vitro. We previously reported a cell fractionation approach that includes the selection of low Hoescht 33342/low Rhodamine 123 (low Ho/Rh) cell fractions that are highly enriched for long-term repopulating cells (LTR-HSC) and also clone to a very high efficiency in the presence of stem cell factor (SCF) + interleukin-3 (IL-3) + IL-6: 90% to 100% of individually cultured low Ho/Rh cells formed high proliferative potential clones. This high cloning efficiency of an LTR-HSC enriched cell population enabled proliferation inhibition studies to be more easily interpreted. In this report, we show that the continuous presence of TGF-beta 1 directly inhibits the cell division of essentially all low Ho/Rh cells (in a dose-dependent manner) during their 0 to 5th cell division in vitro. Therefore, it follows that TGF-beta 1 must directly inhibit the proliferation of LTR-HSC contained within these low Ho/Rh cells. The time required for some low Ho/Rh cells to undergo their first cell division in vitro was also prolonged in the presence of TGF-beta 1. Furthermore, when low Ho/Rh cells were exposed to TFG-beta 1 for varying lengths of time before neutralization of the TGF-beta 1 by monoclonal antibody, the ability to form macroclones was markedly decreased after approximately 4 days of TGF-beta 1 exposure. In addition, 1 to 10 ng/mL of TGF-beta 1 resulted in a maintenance of high proliferative potential-colony-forming cell (HPP-CFC) during 8 days of culture compared with loss of HPP-CFC in cultures with no added TGF-beta 1. In conclusion, this study shows that TGF-beta 1 directly inhibits the initial stages of proliferation of LTR-HSC and appears to slow the differentiation of daughter cells of low Ho/Rh cells.

The effect of thrombopoietin on the proliferation and differentiation of murine hematopoietic stem cells

In this study, we explored whether thrombopoietin (Tpo) has a direct in vitro effect on the proliferation and differentiation of long-term repopulating hematopoietic stem cells (LTR-HSC). We previously reported a cell separation method that uses the fluorescence-activated cell sorter selection of low Hoescht 33342/low Rhodamine 123 (low Ho/low Rh) fluorescence cell fractions that are highly enriched for LTR-HSC and can reconstitute lethally irradiated recipients with fewer than 20 cells. Low Ho/low Rh cells clone with high proliferative potential in vitro in the presence of stem cell factor (SCF) + interleukin-3 (IL-3) + IL-6 (90% to 100% HPP-CFC). Tpo alone did not induce proliferation of these low Ho/low Rh cells. However, in combination with SCF or IL-3, Tpo had several synergistic effects on cell proliferation. When Tpo was added to single growth factors (either SCF or IL-3 or the combination of both), the time required for the first cell division of low Ho/low Rh cells was significantly shortened and their cloning efficiency increased substantially. Moreover, the subsequent clonal expansion at the early time points of culture was significantly augmented by Tpo. Low Ho/low Rh cells, when assayed in agar directly after sorting, did not form megakaryocyte colonies in any growth condition tested. Several days of culture in the presence of multiple cytokines were required to obtain colony-forming units-megakaryocyte (CFU-Mk). In contrast, more differentiated, low Ho/high Rh cells, previously shown to contain short-term repopulating hematopoietic stem cells (STR-HSC), were able to form megakaryocyte colonies in agar when cultured in Tpo alone directly after sorting. These data establish that Tpo acts directly on primitive hematopoietic stem cells selected using the Ho/Rh method, but this effect is dependent on the presence of pluripotent cytokines. These cells subsequently differentiate into CFU-Mk, which are capable of responding to Tpo alone. Together with the results of previous reports of its effects on erythroid progenitors, these results suggest that the effects of Tpo on hematopoiesis are greater than initially anticipated.

Aged murine T-lymphocytes are more resistant to oxidative damage due to the predominance of the cells possessing the memory phenotype

Glutathione (GSH) is the most important cytosolic antioxidant. Since GSH levels are decreased with age, we hypothesized that T-lymphocytes from old mice would be more sensitive to oxidative stress. T-lymphocytes from young and old mice were exposed to hypoxanthine/xanthine oxidase, and lymphocyte viability, proliferation, GSH content, and calcium signaling were measured. Before exposure, proliferation of T-lymphocytes from young mice was greater than that of old; following exposure, the converse was true. This was in spite of the fact that old mice had lower total GSH levels and greater levels of glutathione disulfide. After oxidative challenge, intracellular calcium responses to anti-CD3 were decreased in naive T-lymphocytes from all mice, while memory lymphocytes were less affected. Higher proportions of memory lymphocytes in old mice resulted in their greater overall preservation of lymphocyte function following oxidative injury, contrary to expectations that lower lymphocyte GSH content with age would increase susceptibility to oxidative stress.

Support versus inhibition of hematopoiesis by two characterized stromal cell types

Stromal cells are believed to regulate hematopoiesis through direct cell-cell contact interactions and the release of growth factors. Many questions remain, however, about their lineage derivation and functional heterogeneity. We have previously shown that the adherent nontransformed, nonimmortalized murine bone marrow stromal cell population consists of three cell types which could be grown separately in vitro. Based on the phenotype characterization and expression of surface antigens, we proposed a classification listing for murine bone marrow stromal cells as macrophages, endothelial-like cells and myofibroblasts that display smooth muscle-like characteristics in culture. The present study describes the ability of each of these freshly isolated separated murine stromal cell populations to support the growth of primitive hematopoietic stem cells previously characterized as highly enriched in long-term repopulating cells (LTRC). Of the three stromal cell types tested only the myofibroblasts were capable of support for multilineage hematopoiesis derived in vitro from LTRC in a cloning ring culture system. Endothelial-like cells had an inhibitory effect on the proliferation of LTRC and their descendant cells that was induced by exogenous growth factors. This inhibitory activity was present in a low molecular weight filtrate of endothelial-like cells culture medium. This suggests an essential role for marrow stroma myofibroblasts in the support of proliferation of hematopoietic cells at the stage of early divisions of primitive hematopoietic stem cells and endothelial-like cells as negative regulators of this proliferation.

The VLA4/VCAM-1 adhesion pathway defines contrasting mechanisms of lodgement of transplanted murine hemopoietic progenitors between bone marrow and spleen

Selective lodgement or homing of transplanted hemopoietic stem cells in the recipient's bone marrow (BM) is a critical step in the establishment of long-term hemopoiesis after BM transplantation. However, despite its biologic and clinical significance, little is understood about the process of homing. In the present study, we have concentrated on the initial stages of homing and explored the functional role in vivo of some of the adhesion pathways previously found to mediate in vitro adhesion of hemopoietic cells to cultured BM stroma. We have found that homing of murine hemopoietic progenitors of the BM of lethally irradiated recipients at 3 h after transplant was significantly reduced after pretreatment of the donor cells with an antibody to the integrin very late antigen 4 (VLA4). This inhibition of marrow homing was accompanied by an increase in hemopoietic progenitors circulating in the blood and an increased uptake of these progenitors by the spleen. Similar results were obtained by treatment of the recipients with an antibody to vascular cell adhesion molecule 1 (VCAM-1), a ligand for VLA4. Furthermore, we showed that administration of the same antibodies (anti-VLA4 or anti-VCAM-1) to normal animals causes mobilization of hemopoietic progenitors into blood. These data suggest that hemopoietic cell lodgement in the BM is a regulatable process and can be influenced by VLA4/VCAM-1 adhesion pathway. Although additional molecular pathways are not excluded and may be likely, our data establish VCAM-1 as a BM endothelial addressin, analogous to the role that mucosal addressin cell adhesion molecule (MAdCAM) plays in lymphocyte homing. Whether splenic uptake of hemopoietic progenitors is passive or controlled through different mechanisms remains to be clarified. In addition, we provide experimental evidence that homing and mobilization are related phenomena involving, at least partly, similar molecular pathways.

Caloric restriction: conservation of in vivo cellular replicative capacity accompanies life-span extension in mice

In male mice of a long-lived hybrid strain (B6D2F1), long-term 40% caloric restriction (CR) extended both mean and maximum life spans by 36 and 20%, respectively, over that of ad libitum fed (AL) controls. Measurements of entry into S-phase were made in vivo of six different cell types in five different organs using 2-week exposures to BrdU. The labeling index (L.I.) in all organs studied was lower in young CR mice than in young AL fed mice. In most cases, the L.I. in AL mice fell to the levels of that in the CR mice by 13 months of age, and the two groups then remained so through old age. However, when the L.I. was measured in old CR mice which had been placed on the AL diet for a period of 4 weeks (this was termed refeeding (RF), it was found to be above that of similar age AL or CR mice and almost at the level of young AL mice. This was still true, but to a lesser degree, in a repeat study using an 8-week period of RF. In a separate but parallel in vitro study (companion paper, this volume), the superiority of CR over AL for retention of cellular replication capacity was confirmed by clone size distribution measurements made in several cell types in mice of several age groups. These results indicate that: (1) the rate of cell replication in AL diet mice diminishes greatly by early middle age in all organ sites studied and then plateaus or declines much more slowly; (2) CR broadly preserves in vivo cellular replicative capacity but often requires the energy levels provided by a switch to AL feeding to demonstrate this late in life; (3) accordingly, the replicative deficit in AL fed mice appears to be cumulative and is significant only in old age. The mechanism(s) involved is yet to be discovered but may be related to, or even the same as, that which extends life spans in CR animals. Correspondingly, and with corroborative data from our in vitro companion study, (W. R. Pendergrass et al., 1995. Exp. Cell. Res. 217, 309-316), we suggest that cell populations sustain an accrual of biochemical damage or physiological alterations which increasingly limit their replicative capacity as the animal ages, and that CR reduces the accrual of this damage.

Caloric restriction: conservation of cellular replicative capacity in vitro accompanies life-span extension in mice

We have tested whether life-long caloric restriction (CR) slows or delays the age-related loss of cellular replicative potential that occurs during normal aging in ad libitum (AL) fed mice. Both mean and maximum life spans of the restricted animals (60% of AL intake) were significantly extended 30-40% by CR treatment. Proliferative potential, measured by determining the fraction of cells capable of forming large clones in vitro, was compared in five cell types from six tissue sites from two strains of mice (Male (C57BL/6 x DBA/2)F1("B6D2F1") and female (C57BL/6 x C3H)F1("B6C3F1")). This included four nonhematopoietic organ sites: fibroblast cells from ear skin, tail skin, and subdermal connective tissue and epithelial cells from the medullary part of the kidney and two cell types, myofibroblasts and endothelial-like cells, from spleen and bone marrow. The proliferative potential of cells from AL mice decreased progressively with age in all tissues sites of both mouse strains. CR delayed or decreased the loss of proliferative potential in all situations, but the timing of this was tissue specific. For cells from the four nonhematopoietic tissues sites from female B6C3F1 female mice, CR delayed the onset of proliferative loss, such that the fraction of large clones was significantly greater for the CR 18- to 24-month-old mice than in AL controls at three of four sites (as determined by the fraction of large clones after 1 week of clonal growth). The proliferative loss in CR tissues then accelerated from 24 to 30 months, so that both CR and AL mice had similar fractions of large clones after 30 months of age. CR was also seen to delay loss of proliferative potential in cells from skin and kidney of B6D2F1 male mice at 23-24 months of age when cloned for 2 weeks. For fibroblast and endothelial-like cells from bone marrow and spleen stromal sites from both strains of mice, CR also significantly decreased loss of proliferative potential; furthermore, in these tissues the proliferative advantages remained or increased from 24 to over 30 months of age. In companion studies (N.S. Wolf et al., 1995. Exp. Cell. Res. 217, 000-000), CR was seen to decrease age-related losses in the maximal rates of cell replication in vivo in a panel of tissues from B6D2F1 male mice.(ABSTRACT TRUNCATED AT 400 WORDS)

Developmental hematopoiesis from prenatal to young-adult life in the mouse model

Five measurements of hematopoietic function were made in the mouse from midfetal life to young adulthood. These included two in vivo (day-8 colony-forming unit-spleen [CFU-S8] and day-12 CFU-S [CFU-S12]) and two in vitro clonal measurements of hematopoietic stem and progenitor cells (high proliferative potential colony-forming cell [HPP-CFC] and CFC of low proliferative potential [LPP-CFC]) as well as an in vitro clonal measurement of colony-forming unit-fibroblast (CFU-F). The appearance, increase, subsequent decrease, and later emergence and increase of each of these parameters in the fetal-liver, newborn, growing-infant, and young-adult bone marrow were correlated and found to be in parallel. Exceptions to this included the earlier appearance in the fetal liver of CFU-F and the relatively differentiated hematopoietic LPP-CFC. The pattern of emergence of these progenitor cell subpopulations in the fetal liver may be related, in part to the timing of the hematopoietic microenvironment development and the relative frequencies of progenitor cell types in the circulation. This developmental study in the mouse model describes additional correlations between in vivo and in vitro colony-forming stem cells and fibroblastic stromal colony-forming cells, and it suggests the dependence of hematopoietic stem cells upon the stromal microenvironment for the necessary conditions for hematopoietic stem cell lodgment, growth, and maturation.

Influence of age, sex, and dietary restriction on intracellular free calcium responses of CD4+ lymphocytes in rhesus monkeys (Macaca mulatta)

The influence of aging and dietary restriction on increase in intracellular free calcium ([Ca2+]i) of CD4+ lymphocytes from Macaca mulatta was examined after stimulation with anti-CD3 mAb. We used a flow cytometric assay with the dye indo-1 and either direct or reciprocal immunofluorescent staining to identify CD4+ cells. After stimulation with anti-CD3 mAb, intracellular free calcium responses were reduced in CD4+ lymphocytes from old male and female ad libitum fed monkeys compared to young and adult male or female monkeys. Old female monkeys had significantly lower [Ca2+]i than did old male monkeys. The reduced responses were in part related to a decreased percentage of responding cells. Dietary restriction of males over a four-year period did not alter [Ca2+]i response compared to ad libitum fed male monkeys. Female monkeys of all ages (which were restricted only for four months) also had similar [Ca2+]i responses to ad libitum fed controls. Our data suggest that age-related changes in [Ca2+]i responses are similar between humans and M. mulatta, and that over these intervals, no effects of caloric restrictions can be detected.

Decrease in cellular replicative potential in "giant" mice transfected with the bovine growth hormone gene correlates to shortened life span

Adult mice, (C57BL/6 x Sjl)F1 hybrids, transfected with the bovine growth hormone gene (bGH) grow to twice normal size, but have a mean life span less than 50% that of control siblings without the transgene. The replicative potentials of cells from six different tissue sites (tail skin and ear skin dermal fibroblasts, tail subdermal connective tissue fibroblasts, kidney medulla epithelial cells, bone marrow myofibroblasts, and spleen myofibroblasts) were assayed in vitro using clone size distribution analysis. Cells from all of the above bGH+ tissues produced a smaller fraction of large clones, relative to age-matched controls, in all of these cell types. The loss of replicative potential did not appear to be the result of negative conditioning of the cloning media by the bGH+ cells, and was tightly correlated to the period of accelerated growth in these animals (3-12 weeks), a time when additional GH receptors are expressed.

In vivo and in vitro characterization of long-term repopulating primitive hematopoietic cells isolated by sequential Hoechst 33342-rhodamine 123 FACS selection

Subpopulations of very primitive hematopoietic cells were isolated by fluorescence-activated cell sorter (FACS) selection of density gradient-enriched, lineage-depleted marrow cells with blast cell light scatter characteristics that bound low levels of the DNA binding dye, Hoechst 33342 (Hö) and retained differential amounts of the mitochondrial binding dye, rhodamine 123 (Rh-123). The dyes were used sequentially in a single sorting operation. The subfractions of cells that stained most weakly with both dyes were highly coenriched for long-term repopulating cells (LTRC) and for in vitro high proliferative potential colony-forming cells (HPP-CFC). Furthermore, as populations of cells were progressively selected on the basis of decreasing Hö and Rh-123 fluorescence, first the CFU-S-8, then the CFU-S-12 diminished or disappeared entirely in the lowest Rh-123 fraction. In these low fluorescent populations, plating efficiency for HPP-CFC was very high when cultured in the combined presence of recombinant rat stem cell factor (rrSCF), recombinant human interleukin-1 (rhIL-1), recombinant murine interleukin-3 (rmIL-3) and recombinant human colony-stimulating factor-1 (rhCSF-1), apparently reaching 100% in some instances. When 20 male donor cells from this lowest fluorescent Hö/Rh-123 fraction were injected into lethally irradiated female recipients, along with a "compromised" marrow cell population (3x previously transplanted nonsorted female bone marrow cells), the sorted male donor cells were able to completely and exclusively repopulate the myeloid and the lymphoid B and T cell compartments of the recipients for at least 10 months posttransplant. Assays of cell fractions that were relatively more Rh-123 fluorescent demonstrated the presence of cell with progressively less repopulating capacity. When descendants of transplanted low fluorescent Rh-123 selected cells, as found in 12-day spleen colonies, were assayed for the capacity to provide long-term survival in secondary recipients, they were able to do so in a high proportion of lethally irradiated recipients. However, spleen colonies derived from the mid-high fluorescence fraction were completely unable to do so. In summary, we have demonstrated with a sequential Hö/Rh-123 sorting system that a subset of HPP-CFC cofractionate with LTRC with high frequency. Using this system, the enrichment of LTRC in the lowest Rh-123 compartment of the sequentially Hö/Rh-123 selected cells appears to be the greatest demonstrated thus far. In addition, this study further supports previous ones that identify a compartment of LTRC that are largely distinct from CFU-S-12.

Dissecting the hematopoietic microenvironment. IX. Further characterization of murine bone marrow stromal cells

We have previously shown the adherent nontransformed, nonimmortalized murine bone marrow stromal cell (BMSC) population to consist of phagocytic macrophage and endothelial-like cells and nonphagocytic fibroblasts. Both colonial and near confluent growth of each cell type was obtained following magnetic bead separation, subsequent passaging, and sustained culture with fetal bovine serum and cytokines. Monoclonal antibody staining of antigenic determinants was used to characterize the phenotype of the stromal cell population in primary platings of murine colony-forming unit fibroblast and long-term bone marrow cultures. The antibodies MECA-99, MECA-32, and MJ7-18, raised against murine vascular endothelial antigenic determinants, and von Willebrand's factor all stained selectively for the rounded endothelial-like cells. Endothelial-like cells as well as macrophages expressed the myeloid surface antigens F4/80, 7/4, and Mac-1 under our culture conditions. The cytoskeleton of the stromal fibroblasts in culture was shown to express smooth muscle-specific actin isoforms, as evidenced by positive staining of stress fibers for alpha smooth muscle-1, CGA-7 (alpha/gamma isoforms), and HHF-35 (recognizes all muscle-specific actins). Under culture conditions, stromal fibroblasts were also found to be positive for a polyclonal smooth muscle myosin. It was found that these fibroblasts stained for collagens type I, III, and IV in our cultures. Although collagen type IV is considered a by-product of endothelial cells, endothelial-like cells in our cultures did not stain for any of the collagen types. We propose a classification listing for murine BMSCs as macrophages, endothelial-like cells, and fibroblasts that display smooth muscle-like characteristics in culture.

An age-related reduction in the replicative capacity of two murine hematopoietic stroma cell types

Two stromal cell types, myofibroblasts and endothelial-like cells, that were identifiable by structural and antigenic specificities, were obtained from murine bone marrow and spleen of young, middle-aged, and old mice of two strains and sexes and grown in liquid culture for 9 or 10 days. As expected, there were more total nucleated cells per organ in the old mice (with larger organs) than in the young mice. However, the concentration of stromal colony forming cells was greater in the young mice, resulting in the number of colony forming cells per organ not being significantly different in most comparisons. The in vitro replicative capacity of the two stromal cell types from both organs in all age groups was determined by clone size distribution assays. In all instances the number of cell doublings achieved was statistically significantly greater in the stromal cell clones from young mice than those from old mice. The cell doubling capacity of the middle-aged mice fell between that of the young and the old mice and in most instances that difference was also statistically significant. It was concluded that these in vitro findings constituted a biomarker of aging in these tissues and that this was significant in relation to previous in vivo and in vitro work by these authors and by others reporting the inferiority of aged bone marrow and spleen stroma to regenerate and to support hematopoiesis.

The effect of long-term caloric restriction on function of T-cell subsets in old mice

The effect of caloric restriction (from weaning to old age) on CD3-stimulated CD4+ and CD8+ lymphocyte proliferation and calcium mobilization was examined. Young ad libitum (ad lib) fed, old ad lib fed, old calorically restricted, and old calorically restricted mice which were fed ad lib during the last 6 weeks of their life (restricted/refed) were compared in both BDF1 [(C57BL/6 x DBA/2)F1] and C57BL/6 mice. Proliferation of CD4+ cells was lower in old ad lib animals than in young animals; this difference was not seen in CD8+ cells. Those CD4+ cells which did proliferate in old ad lib animals underwent similar cell cycle progression as young cells. In calorically restricted and calorically restricted/refed animals, CD4+ cell proliferation was similar to the young animals, and CD8+ cells showed a higher proliferative capacity than cells from either young or old ad lib mice. Differences in proliferative capacity were not correlated with alterations in transmembrane signaling efficiency as peak [Ca2+]i was reduced in both T-cell subsets in all groups of old mice relative to young mice. Additionally, reduced [Ca2+]i was observed in the CD8+ subset for which there was no deficit in proliferation, and the enhanced proliferation seen in old restricted and old restricted/refed mice did not manifest as increased [Ca2+]i mobilization. The percentage of CD4+ cells from both mouse strains was reduced in all groups of old mice compared with young mice, while the percentage of CD8+ cells was generally similar in young and all groups of old mice. Our studies would suggest that lifelong caloric restriction of mice prevents the age-associated decrease in T-cell proliferative capacity but that the enhanced proliferation of these cells is not due to increased efficiency of transmembrane signaling.

A method to establish pure fibroblast and endothelial cell colony cultures from murine bone marrow

Studies on the effect of the microenvironment on hematopoiesis would benefit from the availability of pure populations of nontransformed cells of each of the stromal cell types. The adherent murine bone marrow stromal cell population in this study consisted of fibroblasts, endothelial cells, and macrophages. Fibroblasts were segregated from the phagocytic endothelial cells and macrophages by allowing the phagocytic cells to ingest magnetic beads, with subsequent exposure to a magnetic field, effecting cell separation. Pure colony cultures of fibroblasts and endothelial cells were formed by varying the bead-to-cell ratio and incubation period of the cells. For complete purification of the fibroblasts, subsequent passaging was also necessary. Near confluent growth of each type was obtained with subsequent passages and sustained culture. The cytokine granulocyte-macrophage colony-stimulating factor (GM-CSF) was used to enhance endothelial cell growth. We were not able to obtain pure populations of bone marrow macrophages in near confluent culture. The three cell types were identified by cellular morphology, acid and alkaline phosphatase staining, binding with the lectins Ulex europaeus and Bandeiraea simplicifolia, and the capacity to stain for the factor VIII-related antigen (von Willebrand's Factor).

Transplantation studies in mice with congenital hemolytic anemia

Sphha/sphha anemic mice have an abnormality in the erythroid membrane protein, alpha spectrin, and exhibit multiple related clinical abnormalities, including spherocytosis, shortened red cell survival, chronic hemolysis, hemosiderosis, and extramedullary hematopoiesis. In addition, these mutant mice exhibit a granulocytosis and lymphocytosis, lymph node hyperplasia, elevated serum immunoglobulins, membranoproliferative glomerulonephritis, and decreased lifespan--abnormalities that are less clearly attributable to a spectrin defect. In order to further elucidate the mechanisms of disease in these animals, we undertook a series of bone marrow transplantation experiments. Transplantation of anemic marrow into lethally irradiated congenic +/+ mice resulted in chronic spherocytosis, hemolytic anemia, peripheral leukocytosis, and extramedullary hematopoiesis. Additionally, transplant recipients of anemic marrow which had received a higher radiation dose (12 Gy) had increased numbers of peripheral blood CD4+ and CD8+ lymphocytes, a hypocellcular thymus, and a severe pneumonitis characterized by nodular areas of consolidation and edema. Mice receiving congenic +/+ marrow and irradiated with the same radiation dose exhibited minimal pulmonary abnormalities. Anemic mice transplanted with congenic +/+ marrow usually died, but the survivors exhibited reversal of some clinicopathological changes. These results would suggest that the clinical abnormalities of sphha/sphha mice are in part attributable to abnormalities of hematopoietic stem cells but may also involve defects in other cell types. The pathogenesis of the accompanying lymphoid abnormalities observed in this mutant anemic mouse and any correlation with the erythroid spectrin defect are presently unknown. The pulmonary disease that develops in the transplant recipients of anemic marrow needs to be characterized further but may represent a unique model of lung injury.

Dissecting the hematopoietic microenvironment. VIII. Clonal isolation and identification of cell types in murine CFU-F colonies by limiting dilution

In this study it was found that three kinds of cells, fibroblasts, endothelial cells, and macrophages, exist in fibroblastic colony-forming unit (CFU-F) colonies, consistent with the findings of others. However, when low enough bone marrow stromal cell numbers were cultured per dish, pure fibroblast, endothelial, and macrophage colonies were observed. When the cell number cultured in each dish was increased, all colonies were of mixed cell type. This evidence strongly suggests that the macrophages and endothelial cells contained in CFU-F colonies come from locally stimulated growth resulting in contamination and not from a common progenitor with fibroblasts or each other. In some longer term experiments, adipocytes were seen to appear within the colonies of late-passage pure fibroblast cultures.

Dissecting the hematopoietic microenvironment. VII. The production of an autostimulatory factor as well as a CSF by unstimulated murine marrow fibroblasts

Purified normal murine bone marrow-derived fibroblasts were shown to produce a factor that stimulates the in vitro growth of fibroblastic colony-forming unit (CFU-F) colonies. Conditioned medium from the purified fibroblasts (F-CM) also stimulated pure marrow fibroblasts themselves. Analysis of the F-CM detected the presence of macrophage colony-stimulating factor (M-CSF), and low levels of interleukin 1 (IL-1) and interleukin 6 (IL-6), but no detectable levels of interleukin 3 (IL-3), interleukin 5 (IL-5), granulocyte-macrophage colony-stimulating factor (GM-CSF), or granulocyte colony-stimulating factor (G-CSF). Macrophages and endothelial cells, freed from other bone marrow components, required the F-CM if no other growth factors were added. We conclude that F-CM contains an autocrine factor, which the evidence suggests is IL-1, for bone marrow fibroblasts, and a paracrine factor (CSF-1) for macrophages and/or endothelial cells.

Dissecting the hematopoietic microenvironment. VI. The effects of several growth factors on the in vitro growth of murine bone marrow CFU-F

The effects of several growth factors on the proliferation of fibroblastic colony-forming units (CFU-F) were studied. In the present study CFU-F colonies were found to consist of fibroblasts, macrophages, and endothelial cells. Growth factors, including interleukin 3 (IL-3), interleukin 1 alpha (IL-1 alpha), epidermal growth factor (EGF), fibroblast growth factor (FGF), platelet-derived growth factor (PDGF), macrophage colony-stimulating factor (M-CSF), granulocyte-macrophage colony-stimulating factor (GM-CSF), and buffalo rat liver cell-conditioned medium (BRL-CM) were tested for stimulation of the proliferation of CFU-F in a standard culture in both 2% and 15% serum. Overall, the colony numbers produced in 15% serum were much higher than in 2% serum with or without growth factors. However, the influence of several growth factors on CFU-F cultured in 2% serum was relatively greater than in 15% serum when compared to controls. The stimulation of CFU-F by FGF only occurred in culture with 15% serum, and the stimulation by PDGF only occurred with 2% serum. Overall, the strongest stimulations were produced by PDGF, IL-3, and BRL-CM. Combining the other growth factors with IL-3, PDGF, or IL-1 alpha enhanced their effects only modestly. The stimulation by growth factors included increases of the cell numbers between and within colonies as well as an increase in the number of colonies. The study produced results that suggest a complex interaction mediated by growth factors between fibroblasts and other stromal cells within the CFU-F colonies and within the bone marrow itself.

Transplantation of hematopoietic stem cells obtained by a combined dye method fractionation of murine bone marrow

Hematopoietic stem cells were purified from murine bone marrow cells (BMC). Their characteristic density, size, internal complexity, Hoechst 33342 dye uptake, and wheat germ agglutinin (WGA) affinity were used to distinguish them from other cells in the bone marrow. BMC suspensions were centrifuged over Ficoll Lymphocyte Separation Media (Organon Teknika, Durham, NC; density 1.077 to 1.08). The lower-density cells were drawn off, stained with Hoechst and labeled with biotinylated WGA bound to streptavidin conjugated to phycoerythrin (WGA-B*A-PE) or with WGA conjugated to Texas Red. These cells were then analyzed and sorted by an Ortho Cytofluorograph 50-H cell sorter. The cells exhibiting medium to high forward light scatter, low to medium right angle light scatter, low Hoechst intensity, and high WGA affinity were selected. Sorted BMC (SBMC) were stained with Romanowsky-type stains for morphologic assay, and were assayed in lethally irradiated (LI) mice for their ability to produce colony-forming units in the spleen (CFU-S) and for their ability to produce survival. The spleen seeding factor for day 8 CFU-S upon retransplantation of the isolated cells was 0.1. The isolated cells were found to have consistent morphology, were enriched up to 135-fold as indicated by day 8 CFU-S assay, 195-fold as indicated by day 14 CFU-S assay, and 150 sorter-selected BMC were able to produce long-term survival in LI mice with retention of donor karyotype. When recipients of this first transplantation were themselves used as BMC donors, their number of day 8 and day 12 CFU-S were found to be reduced. However, 3 X 10(5) of their BMC provided 100% survival among secondary recipients. When the previously SBMC were competed after one transplantation against fresh nonsorted BMC in a mixed donor transplant, they showed the decline in hematopoietic potency normally seen in previously transplanted BMC. We conclude that the use of combinations of vital dyes for fluorescence-activated cell sorting (FACS) selection of survival-promoting murine hematopoietic stem cells provides results comparable with those produced by antibody-selected FACS and has the advantage of a method directly transferable to human BMC.

Cycling patterns of hemopoietic stem cell subpopulations in young and old BDF1 mice

We have previously reported that two or more different subpopulations of bone marrow stem cells exist in mice as determined by cycling status of day-8 and day-14 CFU-S in long term bromodeoxyuridine (BrdU) infusion studies. In the present report, comparisons between cycling of stem cell subpopulations in old and young mice show that, while the general patterns persist, there are some statistically significant differences between corresponding time points of early and late CFU-S cycling patterns in young and old BDF1 mice. In both populations of CFU-S there exist cells which do not enter cycle over a five week period. The method which we have employed allowed the cycling measurements to be made in unstimulated steady-state bone marrow cell populations, since no cell death is caused in vivo.

Clinicopathologic features of young and old sphha/sphha mice. Mutants with congenital hemolytic anemia

A colony of mice with congenital hemolytic anemia, sphha/sphha, were evaluated over a 3-year period. Prominent findings included decreased survivability, reticulocytosis, increased peripheral blood leukocytes, extramedullary hematopoiesis in liver and spleen, lymphoid hyperplasia and membranoproliferative glomerulonephritis. Older (12 to 21 months) anemic animals had elevated serum levels of IgG1 and IgA. There was deposition of C3, IgG, IgM, and IgA in renal glomeruli of both control and anemic mice, but deposition of IgM and IgA was more prominent and widely distributed in anemic animals and correlated with mesangial expansion and the presence of electron dense deposits in the mesangium and in glomerular capillary walls. Prominent renal tubular hemosiderosis was noted in young and old anemic mice. The relation between the hemolytic anemia and glomerular disease is unclear but these mice may be an animal model useful for exploration of changes attendant with chronic hemolysis and evaluation of renal disease that accompanies hemolytic anemia.

Evaluation of stem cell reserve using serial bone marrow transplantation and competitive repopulation in a murine model of chronic hemolytic anemia

Serial transplantation and competitive repopulation were used to evaluate any loss of self-replicative capacity of bone marrow stem cells in a mouse model with increased and persistent hemopoietic demands. Congenic marrows from old control and from young and old mice with hereditary spherocytic anemia (sphha/sphha) were serially transplanted at 35-day intervals into normal irradiated recipients. Old anemic marrow failed or reverted to recipient karyotype at a mean of 3.5 transplants, and young anemic marrow reverted at a mean of 4.0 transplants, whereas controls did so at a mean of 5.0 transplants. In a competitive assay in which a mixture of anemic and control marrow was transplanted, the anemic marrow persisted to 10 months following transplantation; anemic marrow repopulation was greater if anemic marrow sex matched with the host. It is possible that lifelong stress of severe anemia decreases stem cell reserve in the anemic sphha/sphha mouse marrow. However, marginal differences in serial transplantation number and the maintenance of anemic marrow in a competition assay would suggest that marrow stem cells, under prolonged stress, are capable of exhibiting good repopulating and self-replicating abilities.