In vitro proliferation and adhesion of basic fibroblast growth factor-producing fibroblasts on platinum coils

Topographic distribution of inflammation factors in a healing aneurysm

BACKGROUND

Healing of intracranial aneurysms following endovascular treatment relies on the organization of early thrombus into mature scar tissue and neointima formation. Activation and deactivation of the inflammation cascade plays an important role in this process. In addition to timely evolution, its topographic distribution is hypothesized to be crucial for successful aneurysm healing.

METHODS

Decellularized saccular sidewall aneurysms were created in Lewis rats and coiled. At follow-up (after 3 days (n = 16); 7 days (n = 19); 21 days (n = 8)), aneurysms were harvested and assessed for healing status. In situ hybridization was performed for soluble inflammatory markers (IL6, MMP2, MMP9, TNF-α, FGF23, VEGF), and immunohistochemical analysis to visualize inflammatory cells (CD45, CD3, CD20, CD31, CD163, HLA-DR). These markers were specifically documented for five regions of interest: aneurysm neck, dome, neointima, thrombus, and adjacent vessel wall.

RESULTS

Coiled aneurysms showed enhanced patterns of thrombus organization and neointima formation, whereas those without treatment demonstrated heterogeneous patterns of thrombosis, thrombus recanalization, and aneurysm growth (p = 0.02). In coiled aneurysms, inflammation markers tended to accumulate inside the thrombus and in the neointima (p < 0.001). Endothelial cells accumulated directly in the neointima (p < 0.0001), and their presence was associated with complete aneurysm healing.

CONCLUSION

The presence of proinflammatory cells plays a crucial role in aneurysm remodeling after coiling. Whereas thrombus organization is hallmarked by a pronounced intra-thrombotic inflammatory reaction, neointima maturation is characterized by direct invasion of endothelial cells. Knowledge concerning topographic distribution of regenerative inflammatory processes may pave the way for future treatment modalities which enhance aneurysm healing after endovascular therapy.

Lumen-oriented versus wall-oriented treatment strategies for intracranial aneurysms - A systematic review of suggested therapeutic concepts

The development of new treatment strategies for intracranial aneurysms (IAs) has been and continues to be a major interest in neurovascular research. Initial treatment concepts were mainly based on a physical-mechanistic disease understanding for IA occlusion (lumen-oriented therapies). However, a growing body of literature indicates the important role of aneurysm wall biology (wall-oriented therapies) for complete IA obliteration. This systematic literature review identified studies that explored endovascular treatment strategies for aneurysm treatment in a preclinical setting. Of 5278 publications screened, 641 studies were included, categorized, and screened for eventual translation in a clinical trial. Lumen-oriented strategies included (1) enhanced intraluminal thrombus organization, (2) enhanced intraluminal packing, (3) bridging of the intraluminal space, and (4) other, alternative concepts. Wall-oriented strategies included (1) stimulation of proliferative response, (2) prevention of aneurysm wall cell injury, (3) inhibition of inflammation and oxidative stress, and (4) inhibition of extracellular matrix degradation. Overall, lumen-oriented strategies numerically still dominate over wall-oriented strategies. Among the plethora of suggested preclinical treatment strategies, only a small minority were translated into clinically applicable concepts (36 of 400 lumen-oriented and 6 of 241 wall-oriented). This systematic review provides a comprehensive overview that may provide a starting point for the development of new treatment strategies.

Monocyte Chemotactic Protein-1-Interleukin-6-Osteopontin Pathway of Intra-Aneurysmal Tissue Healing

BACKGROUND AND PURPOSE

We have previously demonstrated that the local delivery of monocyte chemotactic protein-1 (MCP-1) via an MCP-1-releasing poly(lactic-co-glycolic acid)-coated coil promotes intra-aneurysmal tissue healing. In this study, we demonstrate that interleukin-6 (IL-6) and osteopontin are downstream mediators in the MCP-1-mediated aneurysm-healing pathway.

METHODS

Murine carotid aneurysms were created in C57BL/6 mice. Drug-releasing coils (MCP-1, IL-6, and osteopontin) and control poly(lactic-co-glycolic acid) coils were created and then implanted into the aneurysms to evaluate their intra-aneurismal-healing capacity. To investigate the downstream mediators for aneurysm healing, blocking antibodies for IL-6 receptor and osteopontin were given to the mice implanted with the MCP-1-releasing coils. A histological analysis of both murine and human aneurysms was utilized to cross-validate the data.

RESULTS

We observed increased expression of IL-6 in MCP-1-coil-treated aneurysms and not in control-poly(lactic-co-glycolic acid)-only-treated aneurysms. MCP-1-mediated intra-aneurysmal healing is inhibited in mice given blocking antibody to IL-6 receptor. MCP-1-mediated intra-aneurysmal healing is also inhibited by blocking antibody to osteopontin. The role of IL-6 in intra-aneurysmal healing is in recruiting of endothelial cells and fibroblasts. Local delivery of osteopontin to murine carotid aneurysms via osteopontin-releasing coil significantly promotes intra-aneurysmal healing, but IL-6-releasing coil does not, suggesting that IL-6 cannot promote aneurysm healing independent of MCP-1. In the MCP-1-mediated aneurysm healing, osteopontin expression is dependent on IL-6; inhibition of IL-6 receptor significantly inhibits osteopontin expression in MCP-1-mediated aneurysm healing.

CONCLUSIONS

Our findings suggest that IL-6 and osteopontin are key downstream mediators of MCP-1-mediated intra-aneurysmal healing.

Estimation of aneurysm wall stresses created by treatment with a shape memory polymer foam device

In this study, compliant latex thin-walled aneurysm models are fabricated to investigate the effects of expansion of shape memory polymer foam. A simplified cylindrical model is selected for the in-vitro aneurysm, which is a simplification of a real, saccular aneurysm. The studies are performed by crimping shape memory polymer foams, originally 6 and 8 mm in diameter, and monitoring the resulting deformation when deployed into 4-mm-diameter thin-walled latex tubes. The deformations of the latex tubes are used as inputs to physical, analytical, and computational models to estimate the circumferential stresses. Using the results of the stress analysis in the latex aneurysm model, a computational model of the human aneurysm is developed by changing the geometry and material properties. The model is then used to predict the stresses that would develop in a human aneurysm. The experimental, simulation, and analytical results suggest that shape memory polymer foams have potential of being a safe treatment for intracranial saccular aneurysms. In particular, this work suggests oversized shape memory foams may be used to better fill the entire aneurysm cavity while generating stresses below the aneurysm wall breaking stresses.

Endovascular histologic effects of ultrathin gold- or vitronectin-coated platinum aneurysm coils in a rodent arterial occlusion model: a preliminary investigation

BACKGROUND AND PURPOSE

Novel stratagems to improve the efficacy of platinum coils in occluding cerebral aneurysms have primarily involved coating coils with materials thought likely to provoke more desirable histologic reactions. No investigations to date, however, have evaluated the utility of gold or vitronectin coatings, despite known endovascular histologic effects of these agents, which may be favorable for treating cerebral aneurysms. This study was conducted to evaluate the degree of endovascular histologic change associated with ultrathin gold- or vitronectin-coated platinum coils. It was hypothesized that such coatings would increase intra-aneurysmal intimal hyperplasia and the degree of luminal occlusion compared with standard platinum coils.

MATERIALS AND METHODS

The ligated carotid artery rat model was used to study 4 different aneurysm coil conditions: no coil (sham-surgery controls), uncoated platinum coil, and gold- or vitronectin-coated platinum coil. Two weeks postimplantation, the aneurysms were harvested and stained with hematoxylin-eosin. Slides were evaluated for the degree of neointimal response by a pathologist blinded to treatment. Additional quantitative evaluation was performed blindly by using the ratio of intimal-to-luminal cross-sectional area.

RESULTS

A gold- or vitronectin-coated platinum aneurysm coil produced a statistically significant increase in neointimal response compared with a sham (no coil). Arterial segments treated with gold-coated platinum coils also demonstrated a statistically significant 100% increase in neointimal response compared with those treated with bare platinum coils.

CONCLUSIONS

In concordance with our hypothesis, ultrathin coatings of gold provoked a neointimal response and degree of luminal occlusion greater than that of plain platinum aneurysm coils in a rat arterial occlusion model.

Endovascular treatment of intracranial aneurysms using Matrix coils: short- and mid-term results in ruptured and unruptured aneurysms

OBJECTIVE

A prospective multicenter registry was conducted in France to evaluate the safety and efficacy of Matrix coils (Boston Scientific Neurovascular, Fremont, CA). The short- and mid-term results are presented.

METHODS

From January to October 2004, 236 patients harboring ruptured (Group I) or unruptured (Group II) aneurysms were treated via an endovascular approach with Matrix coils and were included in this registry. In-hospital morbidity and mortality was determined. One-year clinical follow-up data were obtained in 218 patients (92.4%). One-year angiographic follow-up data were obtained in 165 patients (171 aneurysms, 70.1%).

RESULTS

In Group I, in-hospital morbidity and mortality rates were 5.8 and 6.5%, respectively, with a procedure-related morbidity and mortality of 3.6 and 1.4%, respectively. At 1 year, the morbidity and mortality rates were 2.4 and 11.0%, respectively. In Group II, procedure-related morbidity and mortality rates were 1.0 and 0.0%, respectively. At 1 year, the morbidity and mortality rates were 1.1 and 0%, respectively. For both groups, no bleeding or rebleeding was observed during the follow-up period. The only factor associated with an increased rate of complications was delay before treatment of more than 2 days after bleeding. Aneurysm recanalization was observed in 44 aneurysms (25.7%).

CONCLUSION

In-hospital and 1-year morbidity and mortality rates in patients harboring ruptured or unruptured aneurysms treated with Matrix coils were similar to those previously reported with the use of bare coils. The efficacy of Matrix coils to prevent aneurysm recanalization was not demonstrated, despite a high percentage of progressive thrombosis that suggests biological activity resulting from Matrix coils.

Endovascular treatment of experimental aneurysms with use of fibroblast transfected with replication-deficient adenovirus containing bone morphogenetic protein-13 gene

BACKGROUND AND PURPOSE

Modified coils have failed to improve long-term recanalization of aneurysms. This study examined whether ex vivo transduction of replication-deficient adenovirus containing the bone morphogenetic protein-13 gene (Ad-BMP-13) in fibroblast allografts would improve angiographic results via increased collagen synthesis, compared with fibroblast-coated platinum coils (FBC) and bare platinum coils (PA).

MATERIALS AND METHODS

Aneurysms were embolized with Ad-BMP-13-coated coils (n = 20). Rabbits were sacrificed at 14 days and at 1, 3, and 6 months after implantation. Digital subtraction angiography (DSA) evaluated stability after embolization. Histologic specimens were examined with a qualitative grading system. Masson trichrome evaluated collagen deposition. Findings were compared with previously reported controls for PA and FBC in the same model and time points.

RESULTS

The grading system showed a greater total score (P = .0002) in Ad-BMP-13 (6.8 +/- 1.6) and FBC (6.3 +/- 2.4) compared with PA (4.7 +/- 2.4). A group main effects test showed that aneurysm neck tissue coverage in Ad-BMP-13 (2.5 +/- 1.1) was higher (P = .0007) than both FBC (1.6 +/- 1.4) and PA (0.9 +/- 1.1). Ad-BMP-13 had more (P < .0001) collagen deposition than the FBC and PA. One- and 3-month Ad-BMP-13 collagen depositions increased (P < .05) over the FBC and PA. Finally, Ad-BMP-13 showed radiographic stability in 15 (75%) cases, coil compaction in 4 (20%) cases, and progressive occlusion in 1 (5%) case. There were no differences in angiographic results (P = .6522).

CONCLUSION

The Ad-BMP-13-coated coils can improve neck coverage and dome fibrosis in the rabbit model, even in the absence of observed differences in angiographic outcome.

Efficient transmicrocatheter delivery of functional fibroblasts with a bioengineered collagen gel-platinum microcoil complex: toward the development of endovascular cell therapy for cerebral aneurysms

BACKGROUND AND PURPOSE

Endoaneurysmal implantation of fibroblasts may promote healing of aneurysms and reduce recanalization after therapeutic embolization. The purpose of our study was to develop a device for delivery of fibroblasts with use of current microcoil technology.

MATERIALS AND METHODS

Cell carrier devices and cell-free devices were fabricated by associating collagen gels (with or without fibroblasts) with platinum microcoils. During the propagation of control cell carrier devices for 1 week in culture, cell-mediated gel contraction (CMGC) occurred. Modified cell carrier devices created by glutaraldehyde cross-linking, ascorbate coculture, or extended CMGC were also characterized in vitro. Devices were deployed through microcatheters (533 microm lumen, 160 cm length). Gel retention, cell retention, cell death, and the ability to support local cell migration were analyzed in vitro.

RESULTS

Cell viability was reduced by glutaraldehyde cross-linking but not by microcatheter transit. During microcatheter transit, cell carrier devices liberated minimal particulate matter and cellular DNA. Liberated particulate matter was reduced by glutaraldehyde cross-linking (P < .05) and extended CMGC (P < .04). Only cell carrier devices treated with glutaraldehyde cross-linking did not exhibit cell migration after microcatheter transit. Passage of cell-free devices through microcatheters sheared off most of their collagen gel.

CONCLUSION

Collagen gel-platinum microcoil complexes can mediate efficient transmicrocatheter delivery of viable, migration-capable fibroblasts. CMGC is a necessary component of the process of gel stabilization that enables successful microcatheter transit. Although extended CMGC and glutaraldehyde cross-linking enhance gel stabilization, glutaraldehyde cross-linking decreases cell viability and migratory potential.

Vascular Dynamics of a Shape Memory Polymer Foam Aneurysm Treatment Technique

The vascular dynamics of a shape memory polymer foam aneurysm treatment technique are assessed through the simulated treatment of a generic basilar aneurysm using coupled fluid dynamics and heat transfer calculations. The shape memory polymer foam, which expands to fill the aneurysm when heated, is modeled at three discrete stages of the treatment procedure. To estimate an upper bound for the maximum amount of thermal damage due to foam heating, a steady velocity is specified through the basilar artery, corresponding to a minimum physiological flow velocity over a cardiac cycle. During expansion, the foam alters the flow patterns within the aneurysm by shielding the aneurysm dome from a confined jet that issues from the basilar artery. The time scales for thermal damage to the artery walls and surrounding blood flow are computed from the temperature field. The flow through the post-treatment bifurcation is comprised of two counter-rotating vortex tubes that are located beneath the aneurysm neck and extend downstream into the outlet arteries. Beneath the aneurysm neck, a marked increase in the wall shear stress is observed due to the close proximity of the counter-rotating vortex tubes to the artery wall.

Endovascular treatment of experimental aneurysms by use of fibroblast-coated platinum coils: an angiographic and histopathologic study

BACKGROUND AND PURPOSE

The purpose of this study was to determine whether implanting exogenous fibroblasts on platinum coils could enhance intra-aneurysmal fibrosis. Hypotheses included: (1) fibroblast-coated (FBC) platinum coils can improve angiographic results after embolization; and (2) FBC platinum coils can accelerate histological healing of embolized aneurysms.

METHODS

Experimental aneurysms in rabbits were embolized with control platinum coils (n=18) or FBC coils (n=18). Subjects were euthanized at 14 days, 1 month, 3 months and 6 months after implantation. Digital subtraction angiography was used to evaluate stability after embolization. Histological samples were examined with a grading system (range, 0 to 12) based on neck and dome healing.

RESULTS

Histology total scores and fibrosis ratio at 14 days were significantly greater in the FBC coil group compared with controls (6.6+/-1.9 versus 2.5+/-1.1, 1.2+/-0.6% versus 0.2+/-0.3%, respectively; P=0.0090). Cavities embolized with FBC coils showed cellular proliferation and thrombus organization, with an endothelialized membrane bridging the neck. There were no differences between groups in the later timepoints. The FBC coil group showed radiographic stability in 11 (61%) cases, coil compaction in 2 (11%) cases, and progressive occlusion in 5 (28%) cases. No progressive occlusion was seen in controls; 3 (17%) of 18 control cases exhibited coil compaction (P=0.0546).

CONCLUSIONS

FBC coils can accelerate early histological healing compared with control coils in the rabbit aneurysm model.

Polyglycolide/polylactide-coated platinum coils for patients with ruptured and unruptured cerebral aneurysms: a single-center experience

BACKGROUND AND PURPOSE

Recanalization of cerebral aneurysm is a limitation of bare platinum coils (BPCs). In a swine aneurysm model, polyglycolide/polylactide (a polymer)-coated platinum coils (Matrix) accelerated clot fibrosis and reduced recanalization rate and aneurysmal volume. We aimed to evaluate the safety of Matrix coils in patients with intracranial aneurysm.

METHODS

This is a single-center, prospective study of patients with intracranial aneurysms treated with Matrix alone or in combination with BPCs. Follow-up evaluation included a 1-month clinical evaluation and a 6- and 12-month clinical and angiographic examination. Primary adverse events included death, stroke, and permanent neurological deficits.

RESULTS

Between May 2002 and January 2004, 52 patients (range 34 to 79 years of age; 38 females) were treated for 54 aneurysms (size 7.9+/-4.6 mm; neck 3.9+/-1.5 mm; 26 ruptured). Matrix alone was used in 13 aneurysms. In 39, we used a combination of Matrix and BPCs. Twenty-one aneurysms had a 6-month follow-up examination (11 Matrix; 10 Matrix combined with bare platinum), and 11 completed the 12-month follow-up evaluation (Matrix only). Adverse events not related to the procedure were 2 deaths (ruptured basilar aneurysms) and 1 stroke at day 10 postcoiling secondary to vasospasm. Procedure-related adverse events were 2 strokes. At 6-month follow-up (n=21) evaluation, 2 of 3 recanalizations needed retreatment. At 12-month follow-up (n=11), there was no recanalization in patients treated with Matrix alone and no significant reduction in aneurysmal size.

CONCLUSIONS

Polyglycolide/polylactide-coated coils had a satisfactory safety profile. Significant aneurysmal size reduction after coiling was not observed.

Immobilization of basic fibroblast growth factor on a platinum microcoil to enhance tissue organization in intracranial aneurysms

OBJECT

To enhance tissue organization in an aneurysm lumen, the authors prepared a platinum microcoil carrying basic fibroblast growth factor (bFGF) and analyzed its effectiveness in the treatment of aneurysms.

METHODS

Ultrathin multiorganic layers were assembled on a platinum coil through successive deposition of cationic polyethylenimine and anionic heparin, and then bFGF was immobilized through an affinity interaction with heparin. The bFGF was effectively immobilized on the surface of the platinum coil without deterioration of the coil's mechanical properties. Coil embolization of aneurysms constructed using a canine common carotid artery was performed via the endovascular approach. The aneurysms together with parent arteries were harvested 2 weeks after coil embolization. Platinum coils unmodified, coated with heparin, or immobilized with heparin and bFGF were examined. The percentage of occlusion at the aneurysm orifice in animals treated with bFGF-immobilized coils (92.99+/-7.94%) was significantly greater than that in animals treated with heparin-coated coils (57.26+/-10.76%) or unmodified coils (52.86+/-8.54%). The histological score of the aneurysms treated with bFGF-immobilized coils was also significantly greater than the scores in the control group.

CONCLUSIONS

These results indicated that bFGF-immobilized microcoils may be beneficial in the obliteration of aneurysms.

Enhancement of intravascular sclerotherapy by tissue engineering: short-term results

BACKGROUND/PURPOSE

Treatment of vascular malformations with sclerotherapy is often complicated by reexpansion secondary to endothelial recanalization. This study examined the use of an autologous fibroblast construct to enhance intraluminal scar formation after sclerotherapy.

METHODS

New Zealand rabbits (n = 15) underwent ethanol sclerotherapy of a segment of the facial vein. After intraluminal saline flush, animals were equally divided into 3 groups. In group I, no further manipulations were performed. In groups II and III, collagen hydrogel was injected into the sclerosed vein, respectively, without and seeded with autologous green fluorescent protein-labeled fibroblasts. One week postoperatively, the vein segments were examined for patency and resected for histology.

RESULTS

The sclerosed vein segments remained occluded in all animals. Histological examination of luminal thrombi demonstrated numerous viable fibroblasts in group III, whereas there were none in the control specimens from groups I and II. The presence of the injected autologous green fluorescent protein-labeled fibroblasts within thrombi of group III was confirmed by immunohistochemistry.

CONCLUSIONS

An injectable tissue-engineered construct enhances sclerotherapy of the jugular vein in a leporine model by reliably delivering fibroblasts that populate the resultant thrombus. Further analysis of this novel therapeutic concept as a means to augment permanent scar formation and reduce luminal recanalization is warranted.

Fibered electrolytically detachable platinum coils used for the endovascular treatment of intracranial aneurysms. Initial experiences and mid-term results in 474 aneurysms

SUMMARY

Between 1992 and 2003, a total of 2029 aneurysms in 1748 patients were treated by endovascular occlusion with electrolytically detachable coils. In this series, electrolytically detachable platinum coils with Nylon fibers (Sapphire Detachable Coil System, MTI, Irvine, CA, USA) were used in 474 aneurysms solely or in combination with bare coils from various manufacturers. To determine the safety and clinical efficacy of Nylon fibered coils for the endovascular treatment of intracranial aneurysms in comparison to bare platinum coils a thorough retrospective statistical analysis by means of logistic regression and matched pairs analysis was performed. Only treatments with data for all matching variables were used, resulting in 421 matched pairs. The analysis was performed with respect to clinical status and numerous parameters concerning individual aneurysm characteristics (e.g., location, neck width, fundus diameter). Treatment-related parameters included the use and percentage of fibered coils, occlusion rate, procedural complications, early clinical outcome and Glasgow Outcome Scale (GOS) scores. Finally, long-term follow-up results (particularly recurrence, cause of recurrence and post treatment haemorrhage) were evaluated. Both logistic regression and matched pairs analysis showed a statistically improved occlusion rate if fibered coils had been used (96% largely occluded with the use of fibered coils vs. 84-85% with the exclusive use of bare coils). However, the amount of fibered coils calculated as percentage of coil length did not seem to have significant impact. Procedures with fibered coils did not lead to a higher rate of thromboembolic events (8.0% for fibered vs. 10.5% for bare coils).The apparently better clinical outcome in the group treated with fibered coils determined by both postprocedural outcome and GOS, did not reach statistical significance. Analysis of the anatomical properties showed no differences between the groups treated with bare and fibered coils in terms of neck width, fundus diameter, and anatomic location. As expected, a higher occlusion rate was achieved in aneurysms with smaller neck and fundus independent from the type of coil used. On follow up angiography, there was an apparently lower rate of recurrence secondary to coil compaction in the group treated with fibered coils, but these data were compromised by the fact that up to date only about one third of 474 aneurysms treated with fibered coils had undergone angiographic follow-up and this did not reach statistical significance. From our experiences, we conclude that the use of fibered electrolytically detachable platinum coils in aneurysm treatment leads to significantly improved occlusion rates compared to the sole use of bare platinum coils. We hope that with increasing follow-up data we will be able to confirm that the apparently reduced recurrence rates for aneurysms treated with fibered coils can be proven with statistical significance.

Vascular Endothelial Growth Factor Immobilized on Platinum Microcoils for the Treatment of Intracranial Aneurysms: Experimental Rat Model Study

Platinum microcoils coated with immobilized recombinant human vascular endothelial growth factor (rhVEGF) were prepared and the effectiveness for the embolization of aneurysms was investigated using a rat model. Platinum coils were prepared by successive deposition of cationic polyethyleneimine and anionic heparin, and VEGF was immobilized through affinity interaction with heparin. Unmodified, heparin-coated, or rhVEGF-immobilized platinum coil segments were inserted into the ligated external carotid arteries at the bifurcation of the common carotid artery (CCA) of adult female rats. The bifurcation segments of the CCA were harvested 2 weeks after the coil placement. rhVEGF-immobilized coils showed significantly greater endothelial formation at the aneurysm orifice and cell infiltration in the aneurysm body compared with the unmodified and heparin-coated coils. The percentage of sac occlusion was significantly greater in the rhVEGF-immobilized group (77.53 +/- 27.58%) than in the heparin-coated group (44.81 +/- 38.30%) and unmodified group (34.99 +/- 28.15%). Scanning electron microscopy showed a tendency for more fibrotic and cellular collections on the coil surface and more tissue mass filling in the coil lumen in the rhVEGF-immobilized group. Platinum microcoils coated with immobilized rhVEGF may be effective for the obliteration of aneurysms.

Basic fibroblast growth factor released from a platinum coil with a polyvinyl alcohol core enhances cellular proliferation and vascular wall thickness: an in vitro and in vivo study

OBJECTIVE

We developed a new type of platinum coil that has a polyvinyl alcohol (PVA) core to absorb and release various biologically active materials for the endovascular treatment of intracranial aneurysms. We evaluated its efficacy as an embolic material with basic fibroblast growth factor (bFGF) in an in vitro and in vivo study.

METHODS

A small PVA thread was inserted into the central space of the primary coil. This coil was named the PVA-core coil. Ten-millimeter segments of the PVA-core coil were used in this study. PVA-core coils were immersed in a bFGF solution for 1 hour. The PVA-core coil, which absorbed bFGF in the PVA-core, was named the FGF-core coil. Initially, the dose of bFGF released from the PVA core into saline was measured by performing an enzyme-linked immunosorbent assay. In the in vitro study, FGF-core coils, PVA-core coils, and unmodified coils were cultured with fibroblasts (NIH3T3), and then their surfaces were observed with electron microscopy. In the in vivo study, each coil was implanted into a rat common carotid artery. The rats were killed, and the arterial lumen was histologically examined at 14 and 28 days after coil implantation.

RESULTS

BFGF was released from the PVA core into saline within 24 hours by performing an enzyme-linked immunosorbent assay. Electron microscopic findings demonstrated remarkable cellular adhesion to the surfaces of the FGF-core coils, but no adhesion to the surfaces of the PVA-core coils and the unmodified coils was found. Histologically, remarkable cell proliferation in the vascular lumen was demonstrated in the common carotid arteries of the FGF-core coil implantation group at the 14th and 28th days. Cellular components proliferated around the implanted coil, and these components mainly stained blue with Masson trichrome. These changes did not occur in the PVA-core coil group and the unmodified coil group.

CONCLUSION

We suggest that FGF-core coils may be effective in inducing fibrotic changes inside aneurysms. These coils may be used as an embolic material to cure cerebral aneurysms.

Matrix and bioabsorbable polymeric coils accelerate healing of intracranial aneurysms: long-term experimental study

BACKGROUND AND PURPOSE

Acceleration of intra-aneurysmal clot organization and fibrosis may be a solution to preventing aneurysm recanalization after endovascular treatment. The purpose of this study was to evaluate the short-term efficacy and long-term safety of the new Matrix coil system.

METHODS

Matrix coils consist of thin platinum coils covered with a bioabsorbable, polymeric material (polyglycolic acid/lactide). Fifty-two experimental aneurysms were created in 26 swine. All of the aneurysms were tightly packed with Matrix or Guglielmi detachable coils (GDC). Comparative angiographic and histopathologic data were analyzed at 2 weeks (n=14), 3 months (n=6), and 6 months (n=6) after embolization.

RESULTS

Three aneurysms treated with GDC ruptured despite tight packing. No recanalization or rupturing was observed in the aneurysms embolized with Matrix coils. At 14 days after embolization, the aneurysms treated with Matrix coils exhibited a more extensive area of organized thrombus when compared with the aneurysms treated with GDC (87% versus 75%, P=0.008, n=11). At 3 months, both Matrix and GDC-treated aneurysms demonstrated complete clot organization. Neck tissue thickness was higher in Matrix-treated aneurysms at 14 days and 3 months, but not at 6 months. No untoward parent artery stenosis was observed in aneurysms treated with Matrix during follow-up. The angiographic cross-sectional area of the Matrix-treated aneurysms was smaller than those treated with GDC at the 3 months.

CONCLUSIONS

Matrix accelerated aneurysm fibrosis and neointima formation without parent artery stenosis. The Matrix system might prevent aneurysmal recanalization after endovascular treatment of cerebral aneurysms.

Novel Guglielmi detachable coils (GDCs) for the treatment of brain aneurysms. In vitro study of hydroxyapatite coating on Pt plate as GDCs model

With the use of an alternate soaking process a thin layer of hydroxyapatite (HAp) was formed on a platinum plate (Pt plate) which was used as a model for Guglielmi detachable coils (GDCs). The in vitro coagulant activity of the HAp-coated Pt plate was evaluated for the purpose of brain aneurysm treatment. In order to fix and to form the apatite layer homogeneously, beta-mercaptopropionic acid was immobilized onto the Pt surface prior to use. The HAp layer was formed on the beta-mercaptopropionic acid-fixed Pt plate surface, and quantitative control of apatite formation was achieved by controlling the number of alternate soaking process cycles. The HAp formed on the Pt plate surface was confirmed by X-ray diffraction and X-ray photoelectron spectroscopy studies. Blood interaction with the Pt plate was altered from nonthrombotic to highly thrombotic by forming a HAp layer on the surface. The alternate soaking process is an appropriate method to modify the GDCs. Complete treatment of brain aneurysms is expected with the use of HAp-coated GDCs, which would allow formation of a stable blood clot.

Endovascular treatment of experimentally induced aneurysms in rabbits using stents: a feasibility study

Although Guglielmi detachable coil (GDC) systems have been generally accepted for treatment of intracranial aneurysms, primary stenting of aneurysms using porous stents or implantation of coils after stent placement remains experimental. Testing of these new methods requires an animal model which imitates human aneurysms in size, configuration and neck morphology. We assessed in detail the technical requirements of and steps for transfemoral stent treatment of experimentally induced aneurysms at the top of the brachiocephalic trunk in rabbits. We created aneurysms in ten rabbits by distal ligation and intraluminal digestion of the right common carotid artery with elastase. We treated five animals with porous stents alone, and five with stents plus coiling via the meshes of the stent, which permitted dense packing of coils. No complications related to the procedures occurred. In all animals, even in those treated solely with porous stents, total occlusion of the aneurysm was achieved. Our animal model can be suitable for testing the biocompatibility and occlusion rate of new methods and devices for the treatment of experimental aneurysms.

Experimental polyvinyl alcohol core coil for a drug delivery system

SUMMARY

We developed a new type of coil with a polyvinyl alcohol core (PVA-core coil) to absorb and release various types of biologically active materials, for the endovascular treatment of intracranial aneurysms. A 10 mm segment of the PVA-core coil was used in this study. PVAcore coils were immersed in basic fibroblast growth factor (b-FGF) solution. The PVA-core coil, which absorbed b-FGF in the PVA core, was named FGF-core coil. This coil gradually released b-FGF in the solution without b-FGF. In vitro study, FGF-core coils, PVA-core coils and unmodified coils were cultured with fibroblasts (NIH3T3) respectively and their surface was observed with scanning electron microscopy (SEM). In vivo study, each coils were inserted into the rat common carotid artery. Rats were sacrificed and the arterial lumen were histologically examined 14 days and 28 days after coil implantation. Electron microscopy findings demonstrated remarkable cellular adhesion to the surface of the FGF-core coils, while no adhesion to the surface of the PVA-core coils and unmodified coils was found. Histologically, remarkable cellular proliferation and wall thickness like neointimal hyperplasia was demonstrated in the implanted common carotid artery of the FGF-core coil group at 14 days and 28 days. On the other hand, these changes did not occur in PVA-core coil group and unmodified coil group.We suggest that FGF-core coils may be effective to induce fibrotic changes inside cerebral aneurysms.

Embolization with autologous fibroblast-attached platinum coils in canine carotid artery aneurysms: histopathological differences from plain coil embolization

PURPOSE

This study was designed to evaluate the effect of autologous fibroblast-attached platinum coils on the promotion of intra-aneurysmal thrombus organization.

MATERIALS AND METHODS

Sidewall aneurysms were surgically created at common carotid arteries bilaterally in 5 dogs. Fibroblasts were obtained from the skins of the dogs and cultured and attached to unmodified platinum coils in a 5-day coculture. In each animal, one aneurysm was embolized with fibroblast-attached platinum coils (study group) and the other with plain platinum coils of the same size (control group).

RESULTS

All aneurysms were partially occluded; the mean occlusion rate was 67%. The histologic analyses performed 2 weeks after the embolization showed more advanced organization of intra-aneurysmal thrombus in the study group than in the control group (80% versus 53%, P = 0.02). Overgrowth of the organizing tissue and parent artery stenosis did not occur.

CONCLUSION

Our results suggest that autologous fibroblasts delivered with platinum coils could promote the organization of intra-aneurysmal thrombus. Although further research is needed, especially on the potential complications, endovascular treatment using autologous fibroblasts may be applied to aneurysm treatment.

Endovascular microcoil gene delivery using immobilized anti-adenovirus antibody for vector tethering

BACKGROUND AND PURPOSE

Endovascular microcoils are widely used in interventional procedures to treat cerebral aneurysms. In the present study we report for the first time successful use of an endovascular microcoil as a gene delivery system.

METHODS

Anti-adenoviral monoclonal antibodies were covalently attached to the collagen-coated surface of either platinum or polyglycolic acid microcoils. These antibodies were used to tether replication-deficient adenovirus (Ad-GFP [encoding green fluorescent protein] or Ad-LacZ [encoding beta-galactosidase]). Cell culture studies with rat arterial smooth muscle cells (A10) assessed transduction on or near the coil. Platinum coils coated with Ad-GFP were implanted into the ligated common carotid artery (CCA) of adult rats in a model of arterial stasis and pressurization. After 7 days, CCA segments were harvested, and coils were removed for histopathology and GFP expression studies, while organs were evaluated by polymerase chain reaction to assess viral biodistribution.

RESULTS

In cell culture studies, GFP-positive smooth muscle cells were detected only on the platinum coil surface, while LacZ-positive cells were detected only on the polyglycolic acid coil surface, thus demonstrating localized gene delivery. After 7-day implantation, GFP (according to fluorescence microscopy and confirmed with immunohistochemistry) was detected on the harvested platinum coil and in the organizing thrombus within the CCA but not in the arterial wall. Morphometric analyses revealed that 13.3+2.0% of cells within the organized thrombus were transduced with Ad-GFP via the gene delivery system. However, arterial smooth muscle cells were negative for GFP according to fluorescence microscopy and immunohistochemistry. Ad-GFP was not detectable by polymerase chain reaction in lung, liver, or kidney.

CONCLUSIONS

It is concluded that catheter deployment of platinum or biodegradable gene delivery endovascular microcoils represents an interventional device-based gene therapy system that can serve as a suitable platform for either single or multiple gene therapy vectors.

Cellular responses of bioabsorbable polymeric material and Guglielmi detachable coil in experimental aneurysms

BACKGROUND AND PURPOSE

Acceleration of healing mechanisms is a promising approach to improve current limitations of endovascular aneurysm therapy with the use of platinum coils. We evaluated a new endovascular therapeutic, bioabsorbable polymeric material (BPM), which may promote cellular reaction in the aneurysms.

METHODS

Four different concentrations of lactide/glycolic acid copolymer [poly(D-L-lactic-co-glycolic acid)] (PLGA), 85/15, 75/25, 65/35, and 50/50, were used as BPMs. Sixteen experimental aneurysms were created in 8 swine. Eight-millimeter-long spiral-shaped BPMs were surgically implanted in the aneurysms without tight packing (n=3 for each BPM). Guglielmi detachable coils (GDCs) were used as control (n=4). The animals were killed 14 days after embolization, and angiographic, histological, and immunohistochemical analyses were performed.

RESULTS

Despite loose packing of aneurysms with BPMs, faster BPMs such as 50/50 or 65/35 PLGA demonstrated more mature collagen formation and fibrosis in the sac and neck of the aneurysm. One aneurysm treated with 65/35 PLGA, 1 treated with 75/25 PLGA, and all 3 treated with 85/15 PLGA showed a neck remnant on angiography. There was a linear relationship between collagen levels and polymer degradation properties (r=-0.9513).

CONCLUSIONS

This preliminary animal study indicates that acceleration of aneurysm healing with the use of BPM is feasible. This concept can be applied to decrease and perhaps prevent aneurysmal recanalization after endovascular treatment of cerebral aneurysms.

Biodegradable Polyglycolide Endovascular Coils Promote Wall Thickening and Drug Delivery in a Rat Aneurysm Model

OBJECTIVE

We designed biodegradable polyglycolide coils (BPCs) and compared the histopathological response to the coils with that to platinum Guglielmi detachable coils (GDCs), after insertion into ligated common carotid arteries (CCAs) of adult rats. BPCs were also tested for use in local drug delivery.

METHODS

Segments (4-mm) of unmodified BPCs, unmodified GDCs, or BPCs coated with Type I bovine collagen and recombinant human vascular endothelial growth factor-165 (500 μg/ml) were inserted into ligated CCAs of adult rats for 14 days, and specimens were compared with contralateral CCA control specimens.

RESULTS

Arterial segments with BPCs exhibited substantially increased wall thickening, compared with GDCs (0.33 mm versus 0.10 mm, P &lt; 0.005), which reduced the luminal diameter by 40%, relative to untreated contralateral control specimens (P &lt; 0.05, n = 6). Arterial segments with BPCs also exhibited a marked reduction (P &lt; 0.05, n = 6) in luminal area (0.72 ± 0.93 mm2), with marked cellular proliferation within the coil diameter, indicating coil integration. Arterial segments with collagen/recombinant human vascular endothelial growth factor-coated BPCs also exhibited a marked 2.9-fold increase (P &lt; 0.005, n = 5) in wall thickness (0.29 ± 0.11 mm) and a 34% reduction in luminal diameter, compared with contralateral control vessels. There was marked proliferation of cells within the coil lumen of vessels treated with BPCs with collagen/recombinant human vascular endothelial growth factor.

CONCLUSION

In this feasibility study, BPCs enhanced the vascular response of CCA segments, compared with GDCs, and were also suitable for local protein delivery to the vessel lumen, under conditions of stasis and arterial pressurization of vascular cells.

Transforming growth factor beta-coated platinum coils for endovascular treatment of aneurysms: an animal study

OBJECTIVE

To test the hypothesis that coating platinum coils with transforming growth factor beta (TGFbeta) would improve the cellular proliferation within experimental aneurysms relative to uncoated coils.

MATERIALS AND METHODS

Elastase-induced saccular aneurysms were created in 12 New Zealand White rabbits. These aneurysms were embolized with platinum coils, either "control" (unmodified) coils or "test" (coated with TGFbeta) coils. Subjects were killed either 2 weeks (n = 3, control; n = 3, test) or 6 weeks (n = 3, control; n = 3, test) after embolization. Aneurysm tissue was embedded in plastic, sectioned, and stained with hematoxylin and eosin. The thickness of tissue covering the coils at the coil-lumen interface was measured by use of a digital microscope, and was compared between groups by use of the Student's t test (P < or = 0.05).

RESULTS

Two-week implantation samples demonstrated mean thickness of tissue overlying TGFbeta-coated coils of 36+/-15 microm and mean thickness of overlying control coils of 3+/-5 microm, indicating significantly thicker tissue growth covering test versus control coils (P = 0.02). Six-week implantation samples demonstrated mean thickness of tissue overlying TGFbeta-coated coils of 86+/-74 microm versus mean thickness overlying control coils of 37+/-6 mu; this difference did not reach statistical significance (P = 0.30). Thickness of tissue covering TGFbeta-coated coils did not change significantly from 2 to 6 weeks (P = 0.31). Tissue thickness over control coils increased significantly between 2 and 6 weeks (P = 0.002).

CONCLUSION

TGFbeta-coated platinum coils undergo earlier cellular coverage than standard platinum coils, but differences in coverage between coated and control coils are no longer present at later time points. These data suggest that improvements in intra-aneurysmal cellular proliferation resulting from coil modifications, although significant in the early postembolization phase, may dissipate over time.

Treating complex nervous system vascular disorders through a "needle stick": origins, evolution, and future of neuroendovascular therapy

In the past few decades, dramatic improvements have occurred in the field of neuroendovascular surgery. Endovascular therapy today is a well-established treatment modality for a variety of cerebrovascular and nonvascular central nervous system diseases. The foundation of this spectacular evolution was laid by the efforts of pioneering visionaries who often worked alone and under difficult, almost impossible, conditions. Ongoing device development and refinement have revolutionized the field at a dizzying, exhilarating pace. With a better understanding of the molecular basis of diseases and further advancements in gene therapy, neuroendovascular techniques have an enormous potential for application to the entire spectrum of central nervous system diseases as a minimally invasive vehicle for the delivery of biological factors.

Bioabsorbable polymeric material coils for embolization of intracranial aneurysms: a preliminary experimental study

OBJECT

A new embolic agent, bioabsorbable polymeric material (BPM), was incorporated into Guglielmi detachable coils (GDCs) to improve long-term anatomical results in the endovascular treatment of intracranial aneurysms. The authors investigated whether BPM-mounted GDCs (BPM/GDCs) accelerated the histopathological transformation of unorganized blood clot into fibrous connective tissue in experimental aneurysms created in swine.

METHODS

Twenty-four experimental aneurysms were created in 12 swine. In each animal, one aneurysm was embolized using BPM/GDCs and the other aneurysm was embolized using standard GDCs. Comparative angiographic and histopathological data were analyzed at 2 weeks and 3 months postembolization. At 14 days postembolization, angiograms revealed evidence of neck neointima in six of eight aneurysms treated with BPM/GDCs compared with zero of eight aneurysms treated with standard GDCs (p < 0.05). At 3 months postembolization, angiograms demonstrated that four of four aneurysms treated with BPM/GDC were smaller and had neck neointima compared with zero of four aneurysms treated with standard GDCs (p = 0.05). At 14 days, histological analysis of aneurysm healing favored BPM/GDC treatment (all p < 0.05): the grade of cellular reaction around the coils was 3 +/- 0.9 (mean +/- standard deviation) for aneurysms treated using BPM/GDCs compared with 1.6 +/- 0.7 for aneurysms treated using GDCs alone; the percentage of unorganized thrombus was 16 +/- 12% compared with 37 +/- 15%, and the neck neointima thickness was 0.65 +/- 0.26 mm compared with 0.24 +/- 0.21 mm, respectively. At 3 months postembolization, only neck neointima thickness was significantly different (p < 0.05): 0.73 +/- 0.37 mm in aneurysms filled with BPM/GDCs compared with 0.16 +/- 0.14 mm in aneurysms filled with standard GDCs.

CONCLUSIONS

In experimental aneurysms in swine, BPM/GDCs accelerated aneurysm fibrosis and intensified neck neointima formation without causing parent artery stenosis or thrombosis. The use of BPM/GDCs may improve long-term anatomical outcomes by decreasing aneurysm recanalization due to stronger in situ anchoring of coils by organized fibrous tissue. The retraction of this scar tissue may also decrease the size of aneurysms and clinical manifestations of mass effect observed in large or giant aneurysms.

Topic review: surface modifications enhancing biological activity of guglielmi detachable coils in treating intracranial aneurysms

BACKGROUND

Endovascular therapy with Guglielmi detachable coils is an accepted treatment option for patients with intracranial aneurysms. However, an emerging technology in the realm of endovascular tools is the use of traditional Guglielmi detachable coils with biologically active substances complexed to the coil surface to enhance aneurysm occlusion.

METHODS

We review the literature and current trends in modified Guglielmi detachable coils. Surface modifications with extracellular matrix proteins, growth factors, ion impregnation, and genetically altered cells have been used in animal studies to improve the cellular response of Guglielmi detachable coils. Similarly, coronary artery stents have been modified in several different ways to maintain vessel patency, contrary to the goal of endovascular therapy. We comparatively reviewed this literature to add insight into the evolution of the research on modified Guglielmi detachable coils.

CONCLUSIONS

Guglielmi detachable coil modifications have the potential to enhance aneurysm obliteration with directed cellular responses. This may allow aneurysm occlusion with coils in less time than untreated coils, thus decreasing the risks of aneurysm enlargement and hemorrhage.

1999 ARRS Executive Council Award. Creation of saccular aneurysms in the rabbit: a model suitable for testing endovascular devices. American Roentgen Ray Society

OBJECTIVE

This study developed an animal model of intracranial aneurysms suitable for evaluating emerging endovascular devices for aneurysmal therapy. We characterized the short-, medium-, and long-term attributes of this endovascular technique for saccular aneurysmal creation in the rabbit.

MATERIALS AND METHODS

The right common carotid artery was surgically exposed in nine New Zealand white rabbits. Using endovascular techniques, we occluded the origin of the right common carotid artery with a pliable balloon. Elastase was incubated endoluminally in the proximal common carotid artery above the balloon. The common carotid artery was ligated distally. Animals were studied angiographically and sacrificed at 2 weeks (n = 3), 10 weeks (n = 3), and 24 weeks (n = 3) after aneurysm creation. Histology was obtained.

RESULTS

Saccular aneurysms formed in eight of the nine rabbits. The aneurysm projected from the apex of an approximately 90 degree curve of the parent vessel, the brachiocephalic artery. Mean aneurysm diameter was 4.5 mm (SD, 1.2 mm), and mean height was 7.5 mm (SD, 1.6 mm). All samples showed thinned elastic lamina and no evidence of inflammation. In four of eight aneurysms, unorganized thrombus was present in the dome of the aneurysm.

CONCLUSION

Arterial aneurysms with intact endothelium and deficient elastic lamina were reliably created in an area of high shear stress in New Zealand white rabbits. Three of these aneurysms remained patent for at least 6 months. We found a simple procedure that can be readily applied to the testing of new endovascular devices for a reliable creation of aneurysms in rabbits.

Histologic evaluation of platinum coil embolization in an aneurysm model in rabbits

PURPOSE

To characterize the histologic response to platinum coil embolization by using a rabbit aneurysm model.

MATERIALS AND METHODS

Saccular aneurysms were created in New Zealand White rabbits by using vessel ligation with intraluminal elastase incubation. Aneurysms were subsequently embolized by using platinum coils. Subjects were sacrificed at various intervals up to 12 weeks following coil embolization. The aneurysm cavities and adjacent vessels were embedded in methylmethacrylate, were sectioned, and were stained for histologic examination.

RESULTS

Two weeks following coil implantation, aneurysms were filled predominantly with unorganized thrombus. Six weeks following coil implantation, histologic features included complete filling of the aneurysm lumen with either prominent laminated but unorganized thrombus or areas of unorganized thrombus interspersed among areas of cellular infiltration. At 12 weeks following coil implantation, aneurysms were filled with the loosely packed, disordered cells contained within the extracellular matrix. Fibrosis or smooth muscle cell infiltration was not present in any of the 6- or 12-week samples.

CONCLUSION

Platinum coils placed into experimental saccular aneurysms in New Zealand White rabbits failed to elicit a fibrotic response. This model can be used for the testing of biologic modifications of platinum coils aimed at increasing intra-aneurysmal fibrosis.