Macrophages undergo fusion to form multinucleated giant cells in several pathologic conditions, including the foreign body response (FBR). We detected high levels of matrix metalloproteinase (MMP)-9 ...during macrophage fusion in vitro and in foreign body giant cells (FBGCs) in vivo. Wild-type (WT) bone marrow-derived macrophages were induced to fuse with IL-4 in the presence of MMP-9 function-blocking antibodies and displayed reduced fusion. A similar defect, characterized by delayed shape change and abnormal morphology, was observed in MMP-9 null macrophages. Analysis of the FBR in MMP-9 null mice was then pursued to evaluate the significance of these findings. Specifically, mixed cellulose ester disks and polyvinyl alcohol sponges were implanted s.c. in MMP-9 null and WT mice and excised 2-4 weeks later. Histochemical and immunohistochemical analyses indicated equal macrophage recruitment between MMP-9 null and WT mice, but FBGC formation was compromised in the former. In addition, MMP-9 null mice displayed abnormalities in extracellular matrix assembly and angiogenesis. Consistent with a requirement for MMP-9 in fusion, we also observed reduced MMP-9 levels in MCP-1 null macrophages, previously shown to be defective in FBGC formation. Collectively, our studies show abnormalities in MMP-9 null mice during the FBR and suggest a role for MMP-9 in macrophage fusion.
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Implantation of biomaterials elicits a foreign body response characterized by fusion of macrophages to form foreign body giant cells and fibrotic encapsulation. Studies of the ...macrophage polarization involved in this response have suggested that alternative (M2) activation is associated with more favorable outcomes. Here we investigated this process in vivo by implanting mixed cellulose ester filters or polydimethylsiloxane disks in the peritoneal cavity of wild-type (WT) and monocyte chemoattractant protein-1 (MCP-1) knockout mice. We analyzed classical (M1) and alternative (M2) gene expression via quantitative polymerase chain reaction, immunohistochemistry and enzyme-linked immunosorbent assay in both non-adherent cells isolated by lavage and implant-adherent cells. Our results show that macrophages undergo unique activation that displays features of both M1 and M2 polarization including induction of tumor necrosis factor α (TNF), which induces the expression and nuclear translocation of p50 and RelA determined by immunofluorescence and Western blot. Both processes were compromised in fusion-deficient MCP-1 KO macrophages in vitro and in vivo. Furthermore, inclusion of BAY 11-7028, an inhibitor of NFκB activation, reduced nuclear translocation of RelA and fusion in WT macrophages. Our studies suggest that peritoneal implants elicit a unique macrophage polarization phenotype leading to induction of TNF and activation of the NFκB pathway.
Sustained changes in blood flow modulate the size of conduit arteries through structural alterations of the vessel wall that are dependent on the transient accumulation and activation of perivascular ...macrophages. The leukocytic infiltrate appears to be confined to the adventitia, is responsible for medial remodeling, and resolves once hemodynamic stresses have normalized without obvious intimal changes. We report that inward remodeling of the mouse common carotid artery after ligation of the ipsilateral external carotid artery is dependent on the chemokine receptor CXCR3. Wild-type myeloid cells restored flow-mediated vascular remodeling in CXCR3-deficient recipients, adventitia-infiltrating macrophages of Gr1(low) resident phenotype expressed CXCR3, the perivascular accumulation of macrophages was dependent on CXCR3 signaling, and the CXCR3 ligand IP-10 was sufficient to recruit monocytes to the adventitia. CXCR3 also contributed to selective features of macrophage activation required for extracellular matrix turnover, such as production of the transglutaminase factor XIII A subunit. Human adventitial macrophages displaying a CD14(+)/CD16(+) resident phenotype, but not circulating monocytes, expressed CXCR3, and such cells were more frequent at sites of disturbed flow. Our observations reveal a CXCR3-dependent accumulation and activation of perivascular macrophages as a necessary step in homeostatic arterial remodeling triggered by hemodynamic stress in mice and possibly in humans as well.
Homotypic cell fusion occurs in several cell types including macrophages in the formation of foreign body giant cells. Previously, monocyte chemoattractant protein-1 (MCP-1) was demonstrated to be ...required for foreign body giant cell formation in the foreign body response. The present study investigated the fusion defect in MCP-1–null macrophages by implanting biomaterials intraperitoneally in wild-type and MCP-1–null mice and monitoring the macrophage response at 12 hours to 4 weeks. MCP-1–null mice exhibited reduced accumulation and fusion of macrophages on implants, which was associated with attenuation of the foreign body response. Consistent with previous in vitro findings, the level of matrix metalloproteinase-9 (MMP-9) was reduced in MCP-1–null macrophages adherent to implants. In contrast, CCR2 expression was unaffected. In vitro studies revealed reduced tumor necrosis factor-α (TNF-α) production and abnormal subcellular redistribution of E-cadherin and β-catenin during fusion in MCP-1–null macrophages. Exogenous TNF-α caused an increase in the production of MMP-9 and rescued the fusion defect. Addition of GM6001 (MMP inhibitor) or NSC23766 (Rac1 inhibitor) indicated two distinct induction pathways, one for E-cadherin/β-catenin and one for MCP-1, TNF-α, and MMP-9. Considered together, these observations demonstrate that induction of E-cadherin/β-catenin is not sufficient for fusion in the absence of MCP-1 or the downstream mediators TNF-α and MMP-9. Moreover, attenuation of the foreign body response in intraperitoneal implants in MCP-1–null mice demonstrates that the process depends on tissue-specific factors.
INTRODUCTION
Pragmatic research studies that include diverse dyads of persons living with dementia (PLWD) and their family caregivers are rare.
METHODS
Community‐dwelling dyads were recruited for a ...pragmatic clinical trial evaluating three approaches to dementia care. Four clinical trial sites used shared and site‐specific recruitment strategies to enroll health system patients.
RESULTS
Electronic health record (EHR) queries of patients with a diagnosis of dementia and engagement of their clinicians were the main recruitment strategies. A total of 2176 dyads were enrolled, with 80% recruited after the onset of the pandemic. PLWD had a mean age of 80.6 years (SD 8.5), 58.4% were women, and 8.8% were Hispanic/Latino, and 11.9% were Black/African American. Caregivers were mostly children of the PLWD (46.5%) or spouses/partners (45.2%), 75.8% were women, 9.4% were Hispanic/Latino, and 11.6% were Black/African American.
DISCUSSION
Health systems can successfully enroll diverse dyads in a pragmatic clinical trial.
Thrombospondin 2 (TSP2) can inhibit angiogenesis in vitro by limiting proliferation and inducing apoptosis of endothelial cells (ECs). TSP2 can also modulate the extracellular levels of gelatinases ...(matrix metalloproteases, MMPs) and potentially influence the remodeling of the extracellular matrix (ECM). Here, we tested the hypothesis that by regulating MMPs, TSP2 could alter EC-ECM interactions. By using a three-dimensional angiogenesis assay, we show that TSP2, but not TSP1, limited angiogenesis by decreasing gelatinolytic activity in situ . Furthermore, TSP2-null fibroblast-derived ECM, which contains irregular collagen fibrils, was more permissive for EC migration. Investigation of the role of TSP2 in physiological angiogenesis in vivo , using excision of the left femoral artery in both TSP2-null and wild-type mice, revealed that TSP2-null mice displayed accelerated recovery of blood flow. This increase was attributable, in part, to an enhanced arterial network in TSP2-null muscles of the upper limb. Angiogenesis in the lower limb was also increased and was associated with increased MMP-9 deposition and gelatinolytic activity. The observed changes correlated with the temporal expression of TSP2 in the ischemic muscle of wild-type mice. Taken together, our observations implicate the matrix-modulating activity of TSP2 as a mechanism by which physiological angiogenesis is inhibited.
Matrix metalloproteinase- (MMP-9) is involved in processes that occur during cutaneous wound healing such as inflammation, matrix remodeling, and epithelialization, To investigate its role in ...healing, full thickness skin wounds were made in the dorsal region of MMP-9-null and control mice and harvested up to 14 days post wounding. Gross examination and histological and immunohistochemical analysis indicated delayed healing in MMP-9-null mice. Specifically, MMP-9-null wounds displayed compromised reepithelialization and reduced clearance of fibrin clots. In addition, they exhibited abnormal matrix deposition, as evidenced by the irregular alignment of immature collagen fibers. Despite the presence of matrix abnormalities, MMP-9-null wounds displayed normal tensile strength. Ultrastructural analysis of wounds revealed the presence of large collagen fibrils, some with irregular shape. Keratinocyte proliferation, inflammation, and angiogenesis were found to be normal in MMP-9-null wounds. In addition, VEGF levels were similar in control and MMP-9-null wound extracts. To investigate the importance of MMP-9 in wound reepithelialization we tested human and murine keratinocytes in a wound migration assay and found that antibody-based blockade of MMP-9 function or MMP-9 deficiency retarded migration. Collectively, our observations reveal defective healing in MMP-9-null mice and suggest that MMP-9 is required for normal progression of wound closure.
OBJECTIVES
The Strategies to Reduce Injuries and Develop Confidence in Elders (STRIDE) study is testing the effectiveness of a multifactorial intervention to prevent serious fall injuries. Our aim ...was to describe procedures that were implemented to optimize participant retention; report retention yields by age, sex, clinical site, and follow‐up time; provide reasons for study withdrawals; and highlight the successes and lessons learned from the STRIDE retention efforts.
DESIGN
Pragmatic cluster randomized trial.
SETTING
A total of 86 primary care practices within 10 US healthcare systems.
PARTICIPANTS
A total of 5451 community‐living persons, 70 years of age or older, at high risk for serious fall injuries.
MEASUREMENTS
Study outcomes were collected every 4 months by a central call center. Reconsent was required to extend follow‐up beyond the originally planned 36 months.
RESULTS
Over a median follow‐up of 3.2 years (interquartile range = 2.8‐3.7 y), 439 (8.1%) participants died and 600 (11.0%) withdrew their consent or did not reconsent to extend follow‐up beyond 36 months, yielding rates (per 100 person‐years) of deaths and withdrawals of 2.6 and 3.6, respectively. The withdrawal rate increased with advancing age, was comparable for men and women, and did not differ much by clinical site. The most common reasons for withdrawal were illness and unable to contact for reconsent at 36 months. Completion of the follow‐up interviews was greater than 93% at each time point. Most participants completed all (71.8%) or all but one (9.2%) of the follow‐up interviews. The most common reason for not completing a follow‐up interview was unable to contact, with rates ranging from 2.8% at 40 months to 4.6% at 20 months.
CONCLUSION
Completion of the thrice‐yearly follow‐up interviews in STRIDE was high, and retention of participants over 44 months exceeded the original projections. The procedures used in STRIDE, together with lessons learned, should assist other investigators who are planning or conducting large pragmatic trials of vulnerable older persons. J Am Geriatr Soc 68:1242–1249, 2020.
We describe the recruitment of participants for Strategies to Reduce Injuries and Develop Confidence in Elders (STRIDE), a large pragmatic cluster randomized trial that is testing the effectiveness ...of a multifactorial intervention to prevent serious fall injuries. Eligible persons were 70 years or older, community-living, and at increased risk for serious fall injuries. The modified goal was to recruit 5,322 participants over 20 months from 86 primary care practices within 10 diverse health care systems across the United States.
The at-risk population was identified using two distinct but complementary screening strategies that included three questions administered centrally via the mail (nine sites) or in the clinic (one site), while recruitment was completed centrally by staff at Yale.
For central screening, 226,603 letters mailed to 135,118 patients yielded 28,719 positive screens (12.7% of those mailed and 46.5% of the 61,729 returned). In the clinic, 22,537 screens were completed, leading to 5,732 positive screens (25.4%). Of the 34,451 patients who screened positive for high risk of serious fall injuries, 31,872 were sent a recruitment packet and, of these, 5,451 (17.1%) were enrolled over 20 months (mean age: 80 years; 62% female). The participation rate was 34.0% among eligible patients. The enrollment yields were 3.6% (vs 5% projected) for each patient screened centrally, despite multiple screens, and 10.5% (vs 33.9% projected) for each positive clinic screen.
Despite lower-than-expected yields, the STRIDE Study exceeded its modified recruitment goal. If the STRIDE intervention is found to be effective, the two distinct strategies for identifying a high-risk population of older persons could be implemented by most health care systems.
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