RETRACTED: Successful tissue engineering of competent allogeneic venous valves

ObjectiveThe purpose of this study was to evaluate whether tissue-engineered human allogeneic vein valves have a normal closure time (competency) and tolerate reflux pressure in vitro.MethodsFifteen human allogeneic femoral vein segments containing valves were harvested from cadavers. Valve closure time and resistance to reflux pressure (100 mm Hg) were assessed in an in vitro model to verify competency of the vein valves. The segments were tissue engineered using the technology of decellularization (DC) and recellularization (RC). The decellularized and recellularized vein segments were characterized biochemically, immunohistochemically, and biomechanically.ResultsFour of 15 veins with valves were found to be incompetent immediately after harvest. In total, 2 of 4 segments with incompetent valves and 10 of 11 segments with competent valves were further decellularized using detergents and DNAse. DC resulted in significant decrease in host DNA compared with controls. DC scaffolds, however, retained major extracellular matrix proteins and mechanical integrity. RC resulted in successful repopulation of the lumen and valves of the scaffold with endothelial and smooth muscle cells. Valve mechanical parameters were similar to the native tissue even after DC. Eight of 10 veins with competent valves remained competent even after DC and RC, whereas the two incompetent valves remained incompetent even after DC and RC. The valve closure time to reflux pressure of the tissue-engineered veins was <0.5 second.ConclusionsTissue-engineered veins with valves provide a valid template for future preclinical studies and eventual clinical applications. This technique may enable replacement of diseased incompetent or damaged deep veins to treat axial reflux and thus reduce ambulatory venous hypertension.Clinical RelevanceThe use of natural, human scaffolds to produce tissue-engineered venous segments containing functioning valves will revolutionize the surgical correction of deep venous reflux in patients with chronic venous insufficiency and leg ulcer. Reconstructive deep venous surgery in the form of valvuloplasty, transplantation, and neovalve construction has met limitations in the rare availability of valves to be repaired, lack of donor sites, and inadequate conditions to create new valves. This tissue-engineered procedure produces the functioning unit “valve-conduit,” and surgery will be used only to implant it

The acute effects of lower limb intermittent negative pressure on foot macro- and microcirculation in patients with peripheral arterial disease

<div><p>Background</p><p>Intermittent negative pressure (INP) applied to the lower leg and foot increases foot perfusion in healthy volunteers. The aim of the present study was to describe the effects of INP to the lower leg and foot on foot macro- and microcirculation in patients with lower extremity peripheral arterial disease (PAD).</p><p>Methods</p><p>In this experimental study, we analyzed foot circulation during INP in 20 patients [median (range): 75 (63-84yrs)] with PAD. One leg was placed inside an air-tight vacuum chamber connected to an INP-generator. During application of INP (alternating 10s of -40mmHg/7s of atmospheric pressure), we continuously recorded blood flow velocity in a distal foot artery (ultrasound Doppler), skin blood flow on the pulp of the first toes (laser Doppler), heart rate (ECG), and systemic blood pressure (Finometer). After a 5-min baseline sequence (no pressure), a 10-min INP sequence was applied, followed by 5-min post-INP (no pressure). To compare and quantify blood flow fluctuations between sequences, we calculated cumulative up-and-down fluctuations in arterial blood flow velocity per minute.</p><p>Results</p><p>Onset of INP induced an increase in arterial flow velocity and skin blood flow. Peak blood flow velocity was reached 3s after the onset of negative pressure, and increased 46% [(95% CI 36–57), <i>P</i><0.001] above baseline. Peak skin blood flow was reached 2s after the onset of negative pressure, and increased 89% (95% CI 48–130), <i>P</i><0.001) above baseline. Cumulative fluctuations per minute were significantly higher during INP-sequences compared to baseline [21 (95% CI 12–30)cm/s/min to 41 (95% CI 32–51)cm/s/min, <i>P</i><0.001]. Mean INP blood flow velocity increased significantly ~12% above mean baseline blood flow velocity [(6.7 (95% CI 5.2–8.3)cm/s to 7.5 (95% CI 5.9–9.1)cm/s, <i>P</i> = 0.03)].</p><p>Conclusion</p><p>INP increases foot macro- and microcirculatory flow pulsatility in patients with PAD. Additionally, application of INP resulted in increased mean arterial blood flow velocity.</p></div

Arterial blood flow velocities (cm/s) for each second relative to each subject′s mean baseline value.

<p>Black lines are mean values with 95% confidence intervals for each second as grey lines. Panel A shows the whole 20-min experiment. Panel B shows a section at the end of baseline and beginning of INP.</p

The effects of time for the first 17s (one pressure cycle) after onset of negative pressure.

<p>Effect estimates are for all the INP-cycles aggregated within and between subjects relative to each subject′s mean baseline value. Blood flow velocity (cm/s), Laser Doppler Flux, LDF (AU) measured in test leg and control leg (shown as dashed line); Vacuum chamber pressure (mmHg, right y-axis).</p

The effects of time for the first 17s (one pressure cycle) after onset of negative pressure.

<p>Effect estimates are for all the INP-cycles aggregated within and between subjects relative to each subject′s mean baseline value. Blood flow velocity (cm/s), Laser Doppler Flux, LDF (AU) measured in test leg and control leg (shown as dashed line); Vacuum chamber pressure (mmHg, right y-axis).</p

Physiological parameters for all the PAD patients (n = 20) during baseline, INP, and post-INP.

<p>Estimates are mean and 95% CI.</p

An example of blood flow velocity and laser Doppler flux responses in one of the patients (age: 64 years; Fontaine stage IIB; ABPI test leg: 0.21, ABPI control leg: 0.29, PVR test leg: 1mm, PVR control leg: 4mm) during the 20 minute experiment: 5 min baseline (atmospheric pressure), 10 min INP, and 5 min post-INP (atmospheric pressure) sequences.

<p>Panel A: Pressure within the vacuum chamber; Panel B: Blood flow velocity (ultrasound Doppler); Panel C: Laser Doppler flux in the test foot; Panel D: Laser Doppler flux in the control foot not exposed to INP. All panels’ timelines are from 0 to 1200s (x-axis).</p

Description of the study sequences and the intermittent negative pressure (INP) applied.

<p>The three sequences were as follows: (i) 5-min baseline (no pressure), (ii) 10-min INP, followed by (iii) 5-min post-INP (no pressure). One pressure cycle equals 10s -40mmHg negative pressure and 7s atmospheric pressure. INP = intermittent negative pressure.</p

Patients’ characteristics, n = 20^†.

<p>Patients’ characteristics, n = 20<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0179001#t001fn004" target="_blank">^†</a>.</p