Therapeutic angiogenesis

Effects of hypoxic-ischemic pre-treatment on microvesicles derived from endothelial progenitor cells

Endothelial progenitor cells (EPCs) have protective roles in ischemic injury due to their ability to improve endothelial function and modulate angiogenesis. Microvesicles (MVs) are small membrane particles released by various cell types, including EPCs, which affect various target cells by transferring carried genetic information, including microRNAs (miRNAs/miRs). Depending on the stimuli and cell types, MVs exert different functions. In the present study, oxygen-glucose deprivation (OGD) was used to mimic ischemic-hypoxic (HI) insult, where the effects of HI insult on EPC-derived MVs (EPC-MVs) were subsequently investigated. OGD induced Ca²⁺ influx in EPCs and increased the release of EPC-MVs compared with normoxic conditions. In addition, MVs prepared from EPCs cultured under normoxic conditions or OGD conditions (OGD-EMVs) had the ability to stimulate the proliferation of EPCs. Furthermore, OGD-EMVs induced stronger effects on proliferation, which may be associated with the upregulation of miR-210 in EPC-MVs. In conclusion, the present results indicated that HI insult promoted the release of MVs from EPCs and upregulated miR-210 in MVs, leading to positive modulation of the proliferation of EPCs cultured under normoxic conditions.

Safety and Effectiveness of Bone Marrow Cell Concentrate in the Treatment of Chronic Critical Limb Ischemia Utilizing a Rapid Point-of-Care System

Critical limb ischemia (CLI) is the end stage of lower extremity peripheral vascular disease (PVD) in which severe obstruction of blood flow results in ischemic rest pain, ulcers and/or gangrene, and a significant risk of limb loss. This open-label, single-arm feasibility study evaluated the safety and therapeutic effectiveness of autologous bone marrow cell (aBMC) concentrate in revascularization of CLI patients utilizing a rapid point-of-care device. Seventeen (17) no-option CLI patients with ischemic rest pain were enrolled in the study. Single dose of aBMC, prepared utilizing an intraoperative point-of-care device, the Res-Q™ 60 BMC system, was injected intramuscularly into the afflicted limb and patients were followed up at regular intervals for 12 months. A statistically significant improvement in Ankle Brachial Index (ABI), Transcutaneous Oxygen Pressure (TcPO₂), mean rest pain and intermittent claudication pain scores, wound/ ulcer healing, and 6-minute walking distance was observed following aBMC treatment. Major amputation-free survival (mAFS) rate and amputation-free rates (AFR) at 12 months were 70.6% and 82.3%, respectively. In conclusion, aBMC injections were well tolerated with improved tissue perfusion, confirming the safety, feasibility, and preliminary effectiveness of aBMC treatment in CLI patients.

Quality of life in patients with no-option critical limb ischemia underlines the need for new effective treatment

OBJECTIVE

To provide a solid baseline reference for quality of life (QoL) in patients with no-option critical limb ischemia (CLI). CLI is associated with surgery, endovascular interventions, hospitalization, and a poor prognosis. An increasing number of clinical trials are, therefore, investigating new treatment strategies (eg, therapeutic neovascularization) in patients with CLI. QoL serves as an important secondary endpoint in many of these trials, but solid reference QoL data for patients with no-option CLI are lacking.

METHODS

The Medical Outcomes Study Short Form 36 (SF-36) and the EuroQol-5D (EQ-5D) questionnaires were used to obtain baseline QoL scores from 47 patients with no-option CLI participating in a therapeutic neovascularization trial. To allow for easy comparability, a norm-based scoring (NBS) method was used to report the results of the SF-36. Scores of patients with CLI were furthermore compared with scores of patients with milder forms of peripheral arterial disease (PAD) and with patients with cardiovascular risk factors only. Determinants of QoL in patients with PAD were identified using multiple linear regression methods.

RESULTS

Patients with no-option CLI reported QoL scores below the general population mean on every health dimension of the SF-36. Physical functioning, role physical functioning, and bodily pain were affected most intensively. These poor physical QoL scores were further underlined when compared with other patients with milder forms of PAD or patients with cardiovascular risk factors only. Patients with CLI scored poorly on the pain/discomfort and the usual activities domain of the EQ-5D. Diabetes, female gender, body mass index, and the ankle-brachial index at rest were significant determinants of the QoL in PAD on multivariate analysis.

CONCLUSION

The QoL data of patients with no-option CLI using NBS methods for the SF-36 provide a baseline reference for ongoing clinical trials on new treatment strategies. Our data stress the need for new revascularization therapies in patients with no-option CLI.

The importance of engraftment in flap revascularization: confirmation by laser speckle perfusion imaging

BACKGROUND

The delivery of proangiogenic agents in clinical trials of wound healing has produced equivocal results, the lack of real-time assessment of vascular growth is a major weakness in monitoring the efficacy of therapeutic angiogenesis, and surgical solutions fall short in addressing the deficiency in microvascular blood supply to ischemic wounds. Therefore, elucidation of the mechanisms involved in ischemia-induced blood vessel growth has potential diagnostic and therapeutic implications in wound healing.

MATERIALS AND METHODS

Three surgical models of wound ischemia, a cranial-based myocutaneous flap, an identical flap with underlying silicone sheeting to prevent engraftment, and a complete incisional flap without circulation were created on C57BL6 transgenic mice. Laser speckle contrast imaging was utilized to study the pattern of ischemia and return of revascularization. Simultaneous analysis of wound histology and microvascular density provided correlation of wound perfusion and morphology.

RESULTS

Creation of the peninsular-shaped flap produced a gradient of ischemia. Laser speckle contrast imaging accurately predicted the spatial and temporal pattern of ischemia, the return of functional revascularization, and the importance of engraftment in distal flap perfusion and survival. Histologic analysis demonstrated engraftment resulted in flap revascularization by new blood vessel growth from the recipient bed and dilatation of pre-existing flap vasculature.

CONCLUSIONS

Further research utilizing this model of graded wound ischemia and the technology of laser speckle perfusion imaging will allow monitoring of the real-time restitution of blood flow for correlation with molecular biomarkers of revascularization in an attempt to gain further understanding of wound microvascular biology.

Human basic fibroblast growth factor fused with Kringle4 peptide binds to a fibrin scaffold and enhances angiogenesis

Appropriate three-dimensional (3D) scaffolds and signal molecules could accelerate tissue regeneration and wound repair. In this work, we targeted human basic fibroblast growth factor (bFGF), a potent angiogenic factor, to a fibrin scaffold to improve therapeutic angiogenesis. We fused bFGF to the Kringle4 domain (K4), a fibrin-binding peptide from human plasminogen, to endow bFGF with specific fibrin-binding ability. The recombinant K4bFGF bound specifically to the fibrin scaffold so that K4bFGF was delivered in a site-specific manner, and the fibrin scaffold provided 3D support for cell migration and proliferation. Subcutaneous implantation of the fibrin scaffolds bound with K4bFGF but not with bFGF induced neovascularization. Immunohistochemical analysis showed significantly more proliferation cells in the fibrin scaffolds incorporated with K4bFGF than in those with bFGF. Moreover, the regenerative tissues were integrated well with the fibrin scaffolds, suggesting its good biocompatibility. In summary, targeted delivery of K4bFGF could potentially improve therapeutic angiogenesis.

Monitoring of the biological response to murine hindlimb ischemia with 64Cu-labeled vascular endothelial growth factor-121 positron emission tomography

BACKGROUND

Vascular endothelial growth factor-121 (VEGF121), an angiogenic protein secreted in response to hypoxic stress, binds to VEGF receptors (VEGFRs) overexpressed on vessels of ischemic tissue. The purpose of this study was to evaluate 64Cu-VEGF121 positron emission tomography for noninvasive spatial, temporal, and quantitative monitoring of VEGFR2 expression in a murine model of hindlimb ischemia with and without treadmill exercise training.

METHODS AND RESULTS

64Cu-labeled VEGF121 and a VEGF mutant were tested for VEGFR2 binding specificity in cell culture. Mice (n=58) underwent unilateral ligation of the femoral artery, and postoperative tissue ischemia was assessed with laser Doppler imaging. Longitudinal VEGFR2 expression in exercised and nonexercised mice was quantified with 64Cu-VEGF121 positron emission tomography at postoperative day 8, 15, 22, and 29 and correlated with postmortem gamma-counting. Hindlimbs were excised for immunohistochemistry, Western blotting, and microvessel density measurements. Compared with the VEGF mutant, VEGF121 showed specific binding to VEGFR2. Perfusion in ischemic hindlimbs fell to 9% of contralateral hindlimb on postoperative day 1 and recovered to 82% on day 29. 64Cu-VEGF121 uptake in ischemic hindlimbs increased significantly (P < 0.001) from a control level of 0.61+/-0.17% ID/g (percentage of injected dose per gram) to 1.62+/-0.35% ID/g at postoperative day 8, gradually decreased over the following 3 weeks (0.59+/-0.14% ID/g at day 29), and correlated with gamma-counting (R2 = 0.99). Compared with nonexercised mice, 64Cu-VEGF121 uptake was increased significantly (P < or = 0.0001) in exercised mice (at day 15, 22, and 29) and correlated with VEGFR2 levels as obtained by Western blotting (R2 = 0.76). Ischemic hindlimb tissue stained positively for VEGFR2. In exercised mice, microvessel density was increased significantly (P<0.001) compared with nonexercised mice.

CONCLUSIONS

64Cu-VEGF121 positron emission tomography allows longitudinal spatial and quantitative monitoring of VEGFR2 expression in murine hindlimb ischemia and indirectly visualizes enhanced angiogenesis stimulated by treadmill exercise training.