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May J Reed

Publications and source records attributed to May J Reed.

14 recordsLinked to original sources
PubMed2007

The effects of aging on tumor growth and angiogenesis are tumor-cell dependent.

It is generally accepted that histologically similar tumors grow more slowly, with less angiogenesis, in aged mice relative to young mice. We subcutaneously implanted TRAMP-C2 tumor cells, a prostate cancer cell line not previously examined in aging, into syngeneic C57/Bl6 young (4 month) and aged (20 month) mice and compared tumor growth and angiogenesis. Unexpectedly, the prostate tumors grew as fast in aged as in young mice. Angiogenesis in TRAMP-C2 tumors was robust, with no differences between the young and aged mice in the number of vessels, distribution of vessel sizes or features of vessel maturation. Aged mice had lower levels of serum testosterone than the young mice. VEGF levels were similar in the tumors and sera of the young and aged mice. Comparison with B16/F10 melanoma, a cancer cell line that is representative of previous studies in aged mice, showed that B16/F10 tumors grew minimally in the aged mice. In contrast to the B16/F10, TRAMP-C2 tumors had an extracellular matrix with significantly higher levels of MMP2 and MMP9 expression and activity. These unique results demonstrate that tumor progression can be as robust in aged tissues as young tissues. The ability of aged mice to grow large, vascularized prostate tumors is associated with high levels of MMP2/9 activity that may produce a permissive environment for tumor growth and angiogenesis. These data demonstrate that tumor-cell specific features determine the effect of aging on tumor growth and angiogenesis.

Aging↗
PubMed2005

Enhanced angiogenesis characteristic of SPARC-null mice disappears with age.

The impairment of angiogenesis in aging has been attributed, in part, to alterations in proteins associated with the extracellular matrix (ECM). SPARC (secreted protein acidic and rich in cysteine/osteonectin/BM-40) is a matricellular protein that regulates endothelial cell function as well as cell-ECM interactions. We have previously shown that angiogenesis, as reflected by fibrovascular invasion into subcutaneously implanted polyvinyl alcohol (PVA) sponges, is increased in SPARC-null mice (6-9 months of age) relative to their wild-type (WT) counterparts. In this study, we define the influence of aging on (a) the expression of SPARC and (b) fibrovascular invasion into sponge implants in SPARC-null and WT mice. The expression of SPARC in fibroblasts and endothelial cells derived from young donors (humans mean age less than 30 years and mice 4-6 months of age) and old donors (humans mean age over 65 years and mice 22-27 months of age) decreased 1.6 to 2.3-fold with age. Analysis of fibrovascular invasion into sponges implanted into old (22-27 months) SPARC-null and WT mice showed no differences in percent area of invasion or collagenous ECM. Moreover, sponges from old SPARC-null and WT mice contained similar levels of VEGF that were significantly lower than those from young (4-6 months) mice. In contrast to fibroblasts from young SPARC-null mice, dermal fibroblasts from old SPARC-null mice did not migrate farther, proliferate faster, or produce greater amounts of VEGF relative to their old WT counterparts. However, when stimulated with TGF-beta1, primary cells isolated from the sponge implants, and dermal fibroblasts from both old SPARC-null and WT mice, showed marked increases in VEGF secretion. These data indicate that aging results in a loss of enhanced angiogenesis in SPARC-null mice, as a result of the detrimental impact of age on cellular functions, collagen deposition, and VEGF synthesis. However, the influence of aging on these processes may be reversed, in part, by growth factor stimulation.

Adult↗
PubMed2005

SPARC-thrombospondin-2-double-null mice exhibit enhanced cutaneous wound healing and increased fibrovascular invasion of subcutaneous polyvinyl alcohol sponges.

Secreted protein acidic and rich in cysteine (SPARC) and thrombospondin-2 (TSP-2) are structurally unrelated matricellular proteins that have important roles in cell-extracellular matrix (ECM) interactions and tissue repair. SPARC-null mice exhibit accelerated wound closure, and TSP-2-null mice show an overall enhancement in wound healing. To assess potential compensation of one protein for the other, we examined cutaneous wound healing and fibrovascular invasion of subcutaneous sponges in SPARC-TSP-2 (ST) double-null and wild-type (WT) mice. Epidermal closure of cutaneous wounds was found to occur significantly faster in ST-double-null mice, compared with WT animals: histological analysis of dermal wound repair revealed significantly more mature phases of healing at 1, 4, 7, 10, and 14 days after wounding, and electron microscopy showed disrupted ECM at 14 days in these mice. ST-double-null dermal fibroblasts displayed accelerated migration, relative to WT fibroblasts, in a wounding assay in vitro, as well as enhanced contraction of native collagen gels. Zymography indicated that fibroblasts from ST-double-null mice also produced higher levels of matrix metalloproteinase (MMP)-2. These data are consistent with the increased fibrovascular invasion of subcutaneous sponge implants seen in the double-null mice. The generally accelerated wound healing of ST-double-null mice reflects that described for the single-null animals. Importantly, the absence of both proteins results in elevated MMP-2 levels. SPARC and TSP-2 therefore perform similar functions in the regulation of cutaneous wound healing, but fine-tuning with respect to ECM production and remodeling could account for the enhanced response seen in ST-double-null mice.

Animals↗
PubMed2004

Defects in activation of nitric oxide synthases occur during delayed angiogenesis in aging.

Angiogenesis, the formation of new vessels from pre-existing vasculature, is impaired in aging. This is due, in part, to a lack of regulatory molecules such as nitric oxide (NO). We wished to test the hypothesis that there are deficits in the pathways that mediate NO production during angiogenesis (as defined by fibrovascular invasion into a polyvinyl alcohol (PVA) sponge implant), in aged mice in comparison to young mice. Sponges were implanted subcutaneously in young (6-8 months old, n=11) and aged (23-25 months old, n=13) mice and sampled at 14 and 19 days. Sections from the implants were stained with antibodies against vascular endothelial growth factor receptor 2 (VEGFR-2), Akt, phosphorylated Akt (p-Akt), endothelial nitric oxide synthase (eNOS), phosphorylated eNOS (p-eNOS), inducible NOS (iNOS), and 3-nitrotyrosine (3-NT, a marker for nitrosylated proteins). Expression of VEGFR-2 was similar in the sponges of young and aged mice. Moreover, there were no significant differences in levels of Akt or its phosphorylated form in sponges from young and aged mice at 14 and 19 d. In marked contrast, levels of eNOS, p-eNOS and iNOS were significantly decreased in sponges from aged mice relative to young mice (p<0.02 for eNOS, p-eNOS and <0.01 for iNOS between young and aged mice). Concomitantly, there was diminished expression of 3-NT in the sponges from aged mice (p<0.05). Our data indicate that defects in the activation of nitric oxide synthases result in decreased NO production in aged tissues relative to young tissues. We propose that the subsequent lack of NO contributes to impaired angiogenesis in aging.

Aging↗
PubMed2004

Impaired angiogenesis in the aged.

The process of angiogenesis, during which new blood vessels are formed, is impaired during aging. This Perspective describes many of the myriad components of the angiogenic response that are altered with age. In addition, the impact of impaired angiogenesis on wound healing, vascular disease, and cancer in the aged is discussed.

Aged↗
PubMed2003

Aging and angiogenesis.

Angiogenesis is impaired in aged tissues. It is probable that this deficit contributes to the increased severity of vascular diseases observed in older persons. The changes in angiogenesis that occur with aging have been noted at the molecular, cellular, and physiologic levels of regulation. Components of the neovascular process that are influenced by age include endothelial cells, the hemostatic cascade, neuro-chemical mediators, and growth factors and their cognate receptors. The structural and regulatory components of the matrix scaffold that surround newly formed vessels is also altered in aged tissues. These myriad changes result in delayed and impaired neovascularization. The clinical consequences of the decreased potential of aged tissues to form new vessels is detrimental during the revascularization of the ischemic heart and during the repair of injured tissues, but may be of benefit in slowing the growth of tumors. In this context, clinical strategies to improve the function of the aging vasculature in general, and the angiogenic response in particular, must be targeted to specific disease states in order to maximize the potential benefit to older individuals.

Aging↗
PubMed2003

Inhibition of TIMP1 enhances angiogenesis in vivo and cell migration in vitro.

Neovascular invasion into a 3-dimensional matrix is controlled, in part, by matrix metalloproteinases (MMPs) and their inhibitors, tissue inhibitors of metalloproteinases (TIMPs). We tested the hypothesis that increasing MMP activity, via a specific blocking antibody to TIMP1, would enhance fibrovascular invasion into a PVA sponge. In vivo, inhibition of TIMP1 doubled the amount of angiogenic invasion (percentage area of invasion 33.5 +/- 3.5 vs 16.9 +/- 9.5, P = 0.003). The blocking antibody to TIMP1 did not increase the proportion of cells that were proliferating in the sponge implants, underscoring the importance of migration. In vitro, human microvascular endothelial cells (hmEC) and dermal fibroblasts treated with the antibody did not secrete greater amounts of collagenase but migrated significantly farther on collagen I (increase in distance migrated 26.6 +/- 9.4%, P = 0.003). Human dermal microvascular endothelial cells exposed to the TIMP1 blocking antibody exhibited a significant change in cell shape to a more elongated morphology. In conclusion, inhibition of TIMP1 increased angiogenesis into a PVA sponge in vivo and enhanced the migration of dermal hmEC and fibroblasts on collagen I in vitro. We propose that blocking TIMP1 improves angiogenesis by increasing cell motility during fibrovascular invasion.

Animals↗
PubMed2003

Inhibited angiogenesis in aging: a role for TIMP-2.

Factors responsible for age-associated impairment of angiogenesis are poorly understood. We observed that in aged mice, new fibrovascular tissue within subcutaneous polyvinyl alcohol sponges expressed more tissue inhibitor of metalloproteinases (TIMP)-2 than did corresponding tissue from young mice. In complementary studies in vitro, we utilized young and aged human microvascular endothelial cell lines (hmEC36 and hmEC90, respectively) and compared their morphogenetic capacity within three-dimensional collagen. HmEC90 exhibited poor formation of tubular, capillary-like structures in vitro, diminished expression of active matrix metalloproteinase (MMP)-2, and similar or lesser amounts of MT1-MMP relative to hmEC36. Correspondingly, the MMP inhibitor GM6001 decreased tubulogenesis by hmEC36 to levels observed for hmEC90. In vitro, hmEC90 expressed similar quantities of TIMP-1, but more TIMP-2 than did hmEC36. Accordingly, purified TIMP-2 inhibited tubulogenesis by hmEC36. Collectively, our studies indicate that elevated levels of TIMP-2 modulate decreased angiogenesis in aged tissues, most likely via TIMP-2-mediated inhibition of MMP-2 and MT1-MMP.

Age Factors↗
PubMed2003

Impaired angiogenesis in aging is associated with alterations in vessel density, matrix composition, inflammatory response, and growth factor expression.

It is generally accepted that angiogenesis is delayed in aging. To define the effects of age on the neovascular response, polyvinyl alcohol sponges were implanted SC in young (6-8 months old, n=11) and aged (23-25 months old, n=13) mice and sampled at 14 and 19 days. Angiogenic invasion was significantly delayed in aged mice at 14d relative to young at 14d (% area of invasion 9.0 +/- 3.7 vs 19.0 +/- 5.6; p=0.02). Although microvessel morphology and basement membrane composition were similar between the age groups, a significant decrease in capillary density was noted in aged tissues at 14d (7.5 +/- 4.1) and 19d (12.1 +/- 2.8) relative to young at 14d (18.7 +/- 2.3) (p<0.01 A14d vs Y14d). In comparison to young at 14d, the inflammatory response was decreased by 43 +/- 2.9% and 36 +/- 7.8% in aged mice at 14d and 19d, respectively. Tissues of aged mice showed less newly deposited collagen. There was a lack of expression of transforming growth factor-beta1 (TGF-beta1) and vascular endothelial growth factor (VEGF) in aged mice at 14d (0.63 +/- 0.3) and 19d (1.14 +/- 0.5) vs young at 14d (1.92 +/- 0.5) (p< or =0.01 A14d vs Y14d for VEGF). However, similar production of VEGF receptor2 was observed. In contrast to young mice, there was significantly increased expression of thrombospondin-2 (TSP-2) in aged mice from 14d (14.6 x 10(3) +/- 7.3 x 10(3)) to 19d (34.9 x 10(3) +/- 17 x 10(3)). We conclude that angiogenesis in aging is not merely delayed, but is altered due to multiple impairments.

Aging↗
PubMed2002

MT1-MMP, but not secreted MMPs, influences the migration of human microvascular endothelial cells in 3-dimensional collagen gels.

Matrix metalloproteinases (MMPs) and their specific inhibitors the TIMPs play significant roles in angiogenesis. We investigated how the expression of specific MMPs and TIMPs by human microvascular endothelial cells (hmECs) was modulated by culture of the cells in 3-dimensional (3D) type I collagen gels versus 2-dimensional (2D) collagen-coated surfaces. By reverse-transcription polymerase chain reaction (RT-PCR), levels of mRNA for MMPs-1, -2, and -13, MT1-MMP, and TIMPs-1 and -2 were similar in 2D versus 3D cultures. By Western blot assay, TIMP-1 and proMMP-1 were present and were expressed similarly in media from 2D versus 3D cultures, whereas active MMPs-1, -9, and -13 were not detected. Active MMP-13 was present in cell lysates (CL) and was increased in lysates from 3D cultures relative to 2D cultures. Relative to 2D cultures, CL and media from 3D cultures exhibited a decrease in expression of TIMP-2 and an increased conversion of proMMP-2 and proMT1-MMP to active or processed forms. The MMP inhibitor GM6001 interfered with the migration of hmECs in 3D cultures, but not in 2D cultures. Addition of active MMP-1 or blocking antibodies to TIMP-1 did not affect the migration of hmECs in 3D collagen. Migration in 3D collagen was decreased by TIMP-2 (an inhibitor of MT1-MMP), but not by TIMP-1 (a poor inhibitor of MT1-MMP, but an efficient inhibitor of MMP-2). Collectively, our data indicate that MT1-MMP contributes significantly to the movement of hmECs through 3D collagen, in contrast to secretory-type MMPs-1, -2, -9, and -13, which are not critical for this movement.

Base Sequence↗
PubMed2002

SPARC-null mice exhibit accelerated cutaneous wound closure.

Expression of SPARC (secreted protein acidic and rich in cysteine; osteonectin, BM-40), an extracellular matrix (ECM) associated protein, is coincident with matrix remodeling. To further identify the functions of SPARC in vivo, we have made excisional wounds on the dorsa of SPARC-null and wild-type mice and monitored closure over time. A significant decrease in the size of the SPARC-null wounds, in comparison to that of wild-type, was observed at Day 4 and was maximal at Day 7. Although substantial differences in the percentage of proliferating cells were not apparent in SPARC-null relative to wild-type wounds, primary cultures of SPARC-null dermal fibroblasts displayed accelerated migration, relative to wild-type fibroblasts, in wound assays in vitro. Although the expression of collagen I mRNA in wounds, as measured by in situ hybridization (ISH), was not significantly different in SPARC-null vs wild-type mice, the collagen content of unwounded skin appeared to be substantially lower in the SPARC-null animals. By hydroxyproline analysis, the concentration of collagen in SPARC-null skin was found to be half that of wild-type skin. Moreover, we found an inverse correlation between the efficiency of collagen gel contraction by dermal fibroblasts and the concentration of collagen within the gel itself. We propose that the accelerated wound closure seen in SPARC-null dermis results from its decreased collagen content, a condition contributing to enhanced contractibility.

Animals↗
PubMedDate not supplied

Elongation and secretion of tissue inhibitor of metalloproteinases 1 by human microvascular endothelial cells cultured in collagen gels is stimulated by mitomycin c.

During angiogenesis, interactions between endothelial cells (ECs) and the surrounding extracellular matrix are influenced by matrix metalloproteinases (MMPs) and their cognate inhibitors, the TIMPs. The authors discovered that the secretion of TIMP-1 by human microvascular ECs (hmECs) cultured within gels of native, fibrillar collagen was increased robustly by mitomycin C (MMC), an inhibitor of cell proliferation. In contrast, hmECs cultured on plastic coated with gelatin or with native fibrillar collagen exhibited nil (on gelatin) or very modest (on native collagen) increases in TIMP-1 upon exposure to MMC. Notably, none of the cultures altered the secretion of TIMP-2, or MMP-1 and -2, in response to MMC. hmECs cultured within collagen gels elongated significantly after exposure to MMC, a response the authors concluded was mediated by TIMP-1, because elongation could be inhibited completely with a function-blocking antibody to TIMP-1. Moreover, substitution of purified human TIMP-1 for MMC induced a similar elongation by hmECs. hmECs cultured within collagen gels did not proliferate under the conditions used in this study; therefore, inhibited proliferation was not a factor in the altered cell shape and TIMP-1 secretion elicited by MMC. These results illustrate that antiproliferative compounds should be used with caution in studies of MMP regulation by ECs.

Cell Proliferation↗
PubMedDate not supplied

Age-related differences in repair of dermal wounds and myocardial infarcts attenuate during the later stages of healing.

BACKGROUND: It is unclear whether delays in wound repair due to the age of the host persist into the later stages of healing. Late stage healing of dermal wounds and myocardial infarcts in rodents was examined to determine if aged animals "catch up" to their younger counterparts. MATERIALS AND METHODS: Excisional dermal wounds (5 mm) were made by punch biopsy and myocardial infarctions were produced by ligation of the left anterior descending coronary artery in young and aged mice and rats, respectively. Dermal wounds at day 11 and myocardial infarctions at day 14 were analyzed for wound area, angiogenesis, deposition of basement membrane proteins, and remodeling of collagen. RESULTS: Analyses demonstrated that wound areas, the deposition of basement membrane proteins and angiogenic responses were similar in young and aged rodents at late stages of wound repair. The dermal wounds of young mice had larger quantities of mature, compacted collagen fibers relative to aged mice, but immature collagen fibers predominated in myocardial infarcts in both young and aged rats. CONCLUSION: These results show that, with the exception of dermal collagen remodeling, aged animals catch up to their young counterparts with respect to many features of tissue repair. Consequently, therapies that target age-related deficiencies in healing will be most effective when administered shortly after the initial insult.

Aging↗