A new-generation, low-permeability flow diverting device for treatment of saccular aneurysms.

OBJECTIVES: We report a preclinical comparative study of a 96-strand braided flow diverter. METHODS: The 96-strand braided device was compared with the currently commercially available flow diverter with 48 strands. The devices were implanted across the neck of 12 elastase-induced aneurysms in New Zealand White rabbits and followed for 1 and 3 months (n = 6 respectively). Aneurysm occlusion rates, parent artery stenosis and patency of jailed branch occlusions were assessed by angiography, histology and scanning electron microscopy studies. RESULTS: It was feasible to navigate and implant the 96-strand device over the aneurysm orifice in all cases. At follow-up two aneurysms in the 48-strand vs. one in the 96-strand group were not occluded. This aneurysm from the 96-strand group however had a tracheal branch arising from the sac and showed a reverse remodelling of the vascular pouch at 3 months. In the occluded aneurysms, the parent artery was always completely reconstructed and the aneurysm orifice was sealed with neointimal tissue. No in-stent stenosis or jailed branch artery occlusion was observed. CONCLUSIONS: The 96-strand flow diverter proved to be safe, biocompatible and haemodynamically effective, induced stable occlusion of aneurysms and led to reverse remodelling of the parent artery. KEY POINTS: • Flow diversion has been introduced to improve endovascular treatment of cerebral aneurysms • A new low-permeability flow diverter is feasible for parent artery reconstruction. • The Silk 96 flow diverter appears effective at inducing aneurysm healing. • The covered branches remained patent at follow-up.

Flow diversion treatment: intra-aneurismal blood flow velocity and WSS reduction are parameters to predict aneurysm thrombosis.

BACKGROUND: To evaluate the haemodynamic changes induced by flow diversion treatment in cerebral aneurysms, resulting in thrombosis or persisting aneurysm patency over time. METHOD: Eight patients with aneurysms at the para-ophthalmic segment of the internal carotid artery were treated by flow diversion only. The clinical follow-up ranged between 6 days and 12 months. Computational fluid dynamics (CFD) analysis of pre- and post-treatment conditions was performed in all cases. True geometric models of the flow diverter were created and placed over the neck of the aneurysms by using a virtual stent-deployment technique, and the device was simulated as a true physical barrier. Pre- and post-treatment haemodynamics were compared, including mean and maximal velocities, wall-shear stress (WSS) and intra-aneurysmal flow patterns. The CFD study results were then correlated to angiographic follow-up studies. RESULTS: Mean intra-aneurysmal flow velocities and WSS were significantly reduced in all aneurysms. Changes in flow patterns were recorded in only one case. Seven of eight aneurysms showed complete occlusion during the follow-up. One aneurysm remaining patent after 1 year showed no change in flow patterns. One aneurysm rupturing 5 days after treatment showed also no change in flow pattern, and no change in the maximal inflow velocity. CONCLUSIONS: Relative flow velocity and WSS reduction in and of itself may result in aneurysm thrombosis in the majority of cases. Flow reductions under aneurysm-specific thresholds may, however, be the reason why some aneurysms remain completely or partially patent after flow diversion.

Injectable candidate sealants for fetal membrane repair: bonding and toxicity in vitro.

OBJECTIVE: This study was undertaken to test injectable surgical sealants that are biocompatible with fetal membranes and that are to be used eventually for the closure of iatrogenic membrane defects. STUDY DESIGN: Dermabond (Ethicon Inc, Norderstedt, Germany), Histoacryl (B. Braun GmbH, Tuttlingen, Germany), and Tissucol (Baxter AG, Volketwil, Switzerland) fibrin glue, and 3 types of in situ forming poly(ethylene glycol)-based polymer hydrogels were tested for acute toxicity on direct contact with fetal membranes for 24 hours. For the determination of elution toxicity, extracts of sealants were incubated on amnion cell cultures for 72 hours. Bonding and toxicity was assessed through morphologic and/or biochemical analysis. RESULTS: Extracts of all adhesives were nontoxic for cultured cells. However, only Tissucol and 1 type of poly(ethylene glycol)-based hydrogel, which is a mussel-mimetic tissue adhesive, showed efficient, nondisruptive, nontoxic bonding to fetal membranes. Mussel-mimetic tissue adhesive that was applied over membrane defects that were created with a 3.5-mm trocar accomplished leak-proof closure that withstood membrane stretch in an in vitro model. CONCLUSION: A synthetic hydrogel-type tissue adhesive that merits further evaluation in vivo emerged as a potential sealing modality for iatrogenic membrane defects.

Comparative characterization of cultured human term amnion epithelial and mesenchymal stromal cells for application in cell therapy.

Emerging evidence suggests human amnion tissue as a valuable source of two distinct types of pluripotent cells, amnion epithelial cells (hAECs) and mesenchymal stromal cells (hAMSCs), for applications in cell replacement therapy. For some approaches, it may be necessary to culture and differentiate these cells before they can be transplanted. No systematic attempt has been yet made to determine the quantity and quality of amnion cells after isolation and culture. We looked at amnion cell isolates from 27 term placentas. Following our optimized protocol, primary yields were 6.3 x 10(6) hAECs and 1.7 x 10(6) hAMSCs per gram amnion. All 27 cases gave vital cultures of hAMSCs, while one third of cases (9 of 27) failed to give adherent cultures of hAECs. Primary cultures contained significantly more proliferating than apoptotic cells (hAECs: 16.4% vs. 4.0%; hAMSCs: 9.5% vs. 2.4%). Neither hAECs nor hAMSCs were clonogenic. They showed slow proliferation that almost stopped beyond passage 5. Microscopic follow-up revealed that hAEC morphology gradually changed towards mesenchymal phenotype over several passages. Flow cytometric characterization of primary cultures showed expression of mesenchymal progenitor markers CD73, CD90, CD105, and CD166, as well as the embryonic stem cell markers SSEA-3 and -4 on both amnion cell types. These profiles were grossly maintained in secondary cultures. Reverse transcriptase-PCR analysis exhibited transcripts of Oct-3/4 and stem cell factor in primary and secondary cultures of all cases, but no telomerase reverse transcriptase. Immunocytochemistry confirmed translation into Oct-3/4 protein in part of hAEC cultures, but not in hAMSCs. Further, both amnion cell types stained for CD90 and SSEA-4. Osteogenic induction studies with amnion cells from four cases showed significantly stronger differentiation of hAECs than hAMSCs; this capacity to differentiate greatly varied between cases. In conclusion, hAECs and hAMSCs in culture exhibit and maintain a similar marker profile of mesenchymal progenitors. hAECs were found as a less reliable source than hAMSCs and altered morphology during subculture.

Fetoscopic closure of punctured fetal membranes with acellular human amnion plugs in a rabbit model.

OBJECTIVE: To explore a surgical plug formed from decellularized term human amnion membrane for fetoscopic closure of iatrogenic defects in fetal membranes in a rabbit model. METHODS: The study was performed in eight rabbit does. Punctures were created at midgestational day 23 by 14-gauge needle fetoscopy on surgically exposed rabbit amniotic sacs. The entry sites were fetoscopically plugged either with decellularized term human amnion membrane (n=10) or previously successful commercial collagen matrix foil (n=10), followed by their primary fixation with fibrin glue and myometrial suturing. Seven punctured sacs without any plugging and 31 sacs without any manipulation served as two reference groups. Amniotic integrity and fetal parameters were assessed at gestational day 30. RESULTS: We established a facile method to prepare sheets of decellularized term human amnion membrane and verified its nontoxicity and cell compatibility in vitro. Decellularized term human amnion membrane sheets could be delivered precisely and controlled by fetoscopy as compact plugs into amniotic defects. The surgical handling characteristics of decellularized term human amnion membrane were better than the commercial collagen matrix foil. Treatment with human decellularized term human amnion membrane was comparable to treatment with the collagen matrix with regard to efficiency in restoring amniotic integrity. Seventy-five percent and 71.4% of amniotic sacs treated with decellularized term human amnion membrane or the commercial collagen matrix foil, respectively, showed amniotic integrity, compared with 25% in the left-open study group. Histology at the 1 week experimental endpoint showed no evidence for inflammation or beginning of anatomic healing of grafted, decellularized term human amnion membrane. CONCLUSION: Fetoscopic delivery of plugs made of decellularized term human amnion membrane presents a potentially practical surgical method to restore amniotic integrity of punctured fetal membranes. LEVEL OF EVIDENCE: III.

The effect of a myocardial infarction on the normalized time-varying elastance curve.

It has been suggested that the shape of the normalized time-varying elastance curve [E(n)(t(n))] is conserved in different cardiac pathologies. We hypothesize, however, that the E(n)(t(n)) differs quantitatively after myocardial infarction (MI). Sprague-Dawley rats (n = 9) were anesthetized, and the left anterior descending coronary artery was ligated to provoke the MI. A sham-operated control group (CTRL) (n = 10) was treated without the MI. Two months later, a conductance catheter was inserted into the left ventricle (LV). The LV pressure and volume were measured and the E(n)(t(n)) derived. Slopes of E(n)(t(n)) during the preejection period (alpha(PEP)), ejection period (alpha(EP)), and their ratio (beta = alpha(EP)/alpha(PEP)) were calculated, together with the characteristic decay time during isovolumic relaxation (tau) and the normalized elastance at end diastole (E(min)(n)). MI provoked significant LV chamber dilatation, thus a loss in cardiac output (-33%), ejection fraction (-40%), and stroke volume (-30%) (P < 0.05). Also, it caused significant calcium increase (17-fold), fibrosis (2-fold), and LV hypertrophy. End-systolic elastance dropped from 0.66 +/- 0.31 mmHg/microl (CTRL) to 0.34 +/- 0.11 mmHg/microl (MI) (P < 0.05). Normalized elastance was significantly reduced in the MI group during the preejection, ejection, and diastolic periods (P < 0.05). The slope of E(n)(t(n)) during the alpha(PEP) and beta were significantly altered after MI (P < 0.05). Furthermore, tau and end-diastolic E(min)(n) were both significantly augmented in the MI group. We conclude that the E(n)(t(n)) differs quantitatively in all phases of the heart cycle, between normal and hearts post-MI. This should be considered when utilizing the single-beat concept.

Effects of protein and gene transfer of the angiopoietin-1 fibrinogen-like receptor-binding domain on endothelial and vessel organization.

The vessel-stabilizing effect of angiopoietin-1 (Ang1)/Tie2 receptor signaling is a potential target for pro-angiogenic therapies as well as anti-angiogenic inhibition of tumor growth. We explored the endothelial and vascular specific activities of the Ang1 monomer, i.e. dissociated from its state as an oligomer. A truncated monomeric Ang1 variant (i.e. DeltaAng1) containing the isolated fibrinogen-like receptor-binding domain of Ang1 was created and recombinantly produced in insect cells. DeltaAng1 ligated the Tie2 receptor without triggering its phosphorylation. Moreover, monomeric DeltaAng1 was observed to bind alpha(5)beta(1) integrin with similar affinity compared with Tie2. Unexpectedly, in vitro treatment of endothelial cells with DeltaAng1 showed some of the known effects of full-length Ang1, including inhibition of basal endothelial cell permeability and stimulation of cell adhesion as well as activation of MAPKs. Local treatment of the microvasculature of the developing chicken chorioallantoic membrane with the DeltaAng1 protein led to profound reduction of the mean vascular length density, thinning of vessels, and reduction of the number of vessel branching points. Similar effects were observed in side-by-side experiments with the recombinant full-length Ang1 protein. These effects of simplification of the vessel branching pattern were confirmed through local gene transfer with lentiviral particles encoding DeltaAng1 or full-length Ang1. Together, our findings suggest a potential use for exogenous Ang1 in reducing rather than increasing vascular density. Furthermore, we show that the isolated receptor-binding domain of Ang1 is capable of mediating some effects of full-length Ang1 independently of Tie2 phosphorylation, possibly through integrin ligation.