Christian A. Schmidt

Sustaining Neovascularization of a Scaffold Through Staged Release of Vascular Endothelial Growth Factor-A and Platelet-Derived Growth Factor-BB

Tissue regeneration into a three-dimensional scaffold requires the stimulation of blood vessel ingrowth. We have employed a freely interconnecting porous scaffold developed by us to determine the utility of a covalently bound heparin surface coating for the delivery of vascular endothelial growth factor (VEGF) and platelet-derived growth factor BB (PDGF-BB) in vivo. The heparin surface was shown to release VEGF far more rapidly than PDGF-BB in vitro (VEGF: 75 ng/h for 24 h; PDGF-BB: 86 pg/h for >7 days). In rat subcutaneous implants, at 10 days the heparin surface alone increased vessel ingrowth substantially (p<0.05 vs. unmodified scaffold), release of VEGF resulted in a further increase (p<0.05 vs. heparinized scaffold), whereas PDGF-BB had no additional effect. The increase induced by the combination of growth factors was similar to VEGF alone. After 2 months, PDGF-BB, but not VEGF delivery, resulted in a substantial increase in vascularization above that induced by heparin (p<0.05). At the longer time point the combination of growth factors was similar to PDGF-BB. However, only the combination of growth factors significantly elevated the number of ingrowing arterioles (p<0.05 vs. heparinized scaffold). Thus, the covalent modification of a porous scaffold with heparin allows for the differential release of VEGF and PDGF-BB that results in both a rapid and sustained increase in scaffold vascularization.

Temporary angiogenic transformation of the skin graft vasculature after reperfusion.

Background: In the era of tissue engineering, the physiologic process of skin graft revascularization remains unclear, preventing the successful development of skin substitutes. Therefore, the authors developed a new in vivo model with which to visualize the process of engraftment and its microvascular architecture. The aim of this study was to specifically investigate the vascular transformations within the skin graft to gain applicable knowledge on how vascular processes during engraftment occur. Methods: Microsurgical preparation of the modified dorsal skinfold chamber including autologous skin grafting was performed in male C57BL/6J mice (n = 10). In addition, immunohistochemistry of angiogenic factors, endothelial cells, and pericytes, and corrosion casting were performed to further characterize the specific mechanisms. Results: The graft exhibited capillary widening starting at day 3, resulting in the temporary formation of spherical protrusions at the graft capillary divisions starting in the center of the graft 24 to 48 hours after revascularization. Confocal microscopy showed the simultaneous expression of CD31 and desmin. Corrosion casting and evaluation by light microscopy and scanning electron microscopy showed the three-dimensional formation of capillaries in the wound bed that connected to the preexisting capillary loops of the skin graft. Conclusions: The authors were able to show for the first time a temporary angiogenic response within the capillaries of the skin graft. This most likely represents a reaction to reperfusion allowing the supply of proangiogenic factors to the hypoxic skin graft. The detection of an angiogenic response within the graft capillaries is for the first time made possible in the newly developed model and is therefore completely novel.

Paraincisional Subcutaneous Infusion of Ropivacaine after Open Abdominal Vascular Surgery Shows Significant Advantages

BACKGROUND Opiates are widely used for postoperative pain relief. Unfortunately, their side effects such as inhibited gastrointestinal motility and respiratory depression may compromise or delay postoperative recovery after laparotomy. We used paraincisional subcutaneous catheters (PSCs) and applied 0.25% ropivacaine infusion to improve pain relief and decrease postoperative morphine consumption in patients after open surgery for aortic aneurysm. METHODS A retrospective single-center study including 58 patients treated by open surgery for aortic aneurysm between October 2006 and June 2012. Overall, 28 patients (control group) received standard postoperative pain management including opiates, and 30 patients (PSC group) were treated with paraincisional continuous local analgesia with 0.25% ropivacaine administrated via bilateral subcutaneous catheters along with additional ad libitum opiates administration, at first intravenously and then orally. RESULTS Patients characteristics as well as perioperative and postoperative outcomes were comparable between the groups during the first 5 days after surgery. Patients of the PSC group received significantly less morphine, although the patients in both groups reported a similar pain intensity. Neither wound-healing disorder nor catheter-associated subcutaneous infection was reported. High serum concentration of ropivacaine was detected in 2 patients (6%) with end-stage renal disease, who developed temporary neurologic symptoms. Length of intensive care unit (ICU) stay was significantly shorter in the PSC group (2 [0-23] vs. 4.5 [0-32] ICU days). CONCLUSIONS This is the first report about PSCs for analgesia after laparotomy. This case/control study shows that continuous paraincisional subcutaneous infusion of 0.25% ropivacaine after open surgery for aortic aneurysm repair is a feasible method of postoperative analgesia. This technique allows sustained pain relief with significant reduction of opiate requirement and faster recovery after surgery. Prospective randomized controlled trial is necessary for the assessment of safety and efficacy of this method.

EPO reverses defective wound repair in hypercholesterolaemic mice by increasing functional angiogenesis

This study aims to elucidate the effect of erythropoietin (EPO) on the microcirculation during wound healing in mice genetically depleted of apolipoprotein E (ApoE(-/-)). The skinfold chamber in mice was used for intravital microscopy, whereby an incisional wound was created within the chamber. Animals received Recormon(®) 1000 U kg(-1) body weight (BW) intra-peritoneally (i.p.) at day 1, 3, 5, 7, 9 and 11 post-wounding at a concentration of 100 Uml(-1) (n=42). Normal healing and vehicle-treated wild type animals (WT) served as controls. The microcirculation of the wound was analysed quantitatively in vivo using epi-illumination intravital fluorescence microscopy. Microtomography (micro-CT) analysis of casted wound microvessels was performed allowing three-dimensional (3D) histomorphometric analysis. Tissue samples were examined ex vivo for wound scoring and for expression analysis of EPO-Receptor (Epo-R) and endothelial nitric oxide synthase (eNOS). Upon EPO treatment, the total wound score in ApoE(-/-) mice was increased by 23% on day 3, by 26% on day 7 and by 18% on day 13 when compared to untreated ApoE(-/-) mice (all P<0.05 vs. vehicle). Improved wound healing was accompanied with a significant increase of functional angiogenetic density and angiogenetic red blood cell perfusion on days 5, 7, 9 and 11 post-wounding. 3D histomorphometric analysis revealed an increase of vessel thickness (1.7-fold), vessel volume (2.4-fold) and vessel surface (1.7-fold) (all P<0.05 vs. vehicle). In addition, improved wound healing was associated with enhanced Epo-R expression (4.6-fold on day 3 and 13.5-fold on day 7) and eNOS expression (2.4-fold on day 7) (all P<0.05 vs. vehicle). Our data demonstrate that repetitive systemic EPO treatment reverses microvascular dysfunction during wound healing in hypercholesterolaemic mice by inducing new vessel formation and by providing the wound with more oxygen.

Hypothermic, initially oxygen-free, controlled limb reperfusion for acute limb ischemia

BACKGROUND Controlled limb reperfusion has been shown to prevent the deleterious effects of ischemia-reperfusion (IR) syndrome following revascularization of acute limb ischemia (ALI). To reduce the production of cell-toxic oxygen-free radicals, we have established a new initially oxygen-free, hypothermic, heparin-coated perfusion and hemofiltration system and report on our first results. METHODS In a retrospective single-center study, controlled limb reperfusion was applied in 36 patients (64.7 ± 15 years) with ALI of category IIA to III (33.7 ± 20.7 hr ischemic time). 52.8% had central (aortic and bifurcation) and 47.2% had peripheral (common iliac artery and distal) vascular occlusions. The common femoral artery and vein were cannulated, and a hypothermic (22°C), initially oxygen-free, potassium-free ringers solution was perfused using a heparin-coated extracorporeal membrane oxygenation (ECMO) and hemofiltration system with low-dose heparinization. Thirty-day mortality, clinical recovery of neurological dysfunction, limb amputation, and fasciotomy rate were analyzed. Laboratory parameters associated with ischemia and IR injury were determined. RESULTS Average perfusion time was 94 ± 35 min. Thirty-day mortality was 27.8%. 55.5% of patients showed complete recovery of motor and sensory dysfunction. A total of 27.8% of patients developed a compartment syndrome and required fasciotomy. Lower leg amputation was necessary in 11.1% of patients. Lactate levels were reduced in ischemic limbs by 25.3% within 60 min (P < 0.05). Preoperative negative base excess of -1.96 ± 0.96 mmol/L was equalized after 12 hr (P < 0.05), while pH stayed balanced at 7.4. Serum potassium stayed within normal limits throughout 24 hr, and therefore systemic hyperkalemia was prevented and imminent metabolic acidosis was corrected. CONCLUSIONS An initially oxygen-free, hypothermic, heparin-coated ECMO counteracts local and systemic effects of IR injury. Reduced mortality and morbidity might result from this new treatment, although this could not be conclusively proven in our study. A prospective, randomized controlled trial is needed to prove superiority of this new concept.

Teleconsultation in vascular surgery: a 13 year single centre experience

The University Hospital of Zurich has provided an email-based medical consultation service for the general public since 1999. We examined the enquiries in a 13-year period to identify those related to vascular surgery (based on 22 ICD-10 codes specific for vascular surgery). There were 40,062 questions, of which 643 (2%) were selected by ICD-10 codes. After exclusion of diagnoses not relevant to vascular surgery, 139 questions remained, i.e. an average rate of about one per month. The mean age of the users was 43 years (range 19–88). Most users (61%) were women. The majority of users asked questions about their own health problems (79%) with varicose veins and spider veins accounting for 63% of all questions. Arterial diseases accounted for 30%. The patient’s intention in contacting the service was to obtain advice on treatment options (37%), information about a diagnosis or symptoms (27%), or a second opinion (15%). The online service responded with detailed information and advice (87%) and suggested a referral to the family doctor or a specialist in 75%. Most patients (82%) rated the service overall as good or very good. It appears likely that telemedicine and in particular email teleconsultations will increase in vascular surgery in the future.

In Vivo Evaluation of Wound Bed Reaction and Graft Performance After Cold Skin Graft Storage: New Targets for Skin Tissue Engineering

Surplus harvested skin grafts are routinely stored at 4 to 6°C in saline for several days in plastic surgery. The purpose of this study was to evaluate the influence of storage on human skin graft performance in an in vivo intravital microscopic setting after transplantation. Freshly harvested human full-thickness skin grafts and split-thickness skin grafts (STSGs) after storage of 0, 3, or 7 days in moist saline at 4 to 6°C were transplanted into the modified dorsal skinfold chamber, and intravital microscopy was performed to evaluate vessel morphology and angiogenic change of the wound bed. The chamber tissue was harvested 10 days after transplantation for evaluation of tissue integrity and inflammation (hematoxylin and eosin) as well as for immunohistochemistry (human CD31, murine CD31, Ki67, Tdt-mediated dUTP-biotin nick-end labelling). Intravital microscopy results showed no differences in the host angiogenic response between fresh and preserved grafts. However, STSGs and full-thickness skin grafts exhibited a trend toward different timing and strength in capillary widening and capillary bud formation. Preservation had no influence on graft quality before transplantation, but fresh STSGs showed better quality 10 days after transplantation than 7-day preserved grafts. Proliferation and apoptosis as well as host capillary in-growth and graft capillary degeneration were equal in all groups. These results indicate that cells may activate protective mechanisms under cold conditions, allowing them to maintain function and morphology. However, rewarming may disclose underlying tissue damage. These findings could be translated to a new approach for the design of full-thickness skin substitutes.

["Doc2Patient" -16 years' experience of the Medical Online Consultation Service at the University Hospital Zurich].

The increasing availability of telemedicine services and the transition to an information society allow the increased use of telemedicine in everyday medical practice. This requires acceptance of telemedicine as a powerful, additional pillar in the overall architecture of the health system. The implementation is still between the poles of the large variety of telemedicine applications and their realization. The University Hospital of Zurich looks back on 16 years of experience in the field of online medical advice. The quality of advice is continuously monitored and evaluated. Scientific evaluations analyze the profile of the questioner and their requests in order to optimize the services. Medical online advice conducted ethically correct can improve health literacy and increase the autonomy of medica/laypersons.

High heparin content surface‐modified polyurethane discs promote rapid and stable angiogenesis in full thickness skin defects through VEGF immobilization

Three-dimensional scaffolds have the capacity to serve as an architectural framework to guide and promote tissue regeneration. Parameters such as the type of material, growth factors, and pore dimensions are therefore critical in the scaffolds success. In this study, heparin has been covalently bound to the surface of macroporous polyurethane (PU) discs via two different loading methods to determine if the amount of heparin content had an influence on the therapeutic affinity loading and release of (VEGF165 ) in full thickness skin defects. PU discs (5.4 mm diameter, 300 µm thickness, and interconnected pore size of 150 µm) were produced with either a low (2.5 mg/g) or high (6.6 mg/g) heparin content (LC and HC respectively), and were implanted into the modified dorsal skin chamber (MDSC) of C57BL/6 J mice with and without VEGF. Both low- and high-content discs with immobilized VEGF165 (LCV and HCV, respectively) presented accelerated neovascularization and tissue repair in comparison to heparin discs alone. However, the highest angiogenetic peak was on day 7 with subsequent stabilization for HCV, whereas other groups displayed a delayed peak on day 14. We therefore attribute the superior performance of HCV due to its ability to hold more VEGF165, based on its increased heparin surface coverage, as also demonstrated in VEGF elution dynamics.

Veno-venous perfusion to cool and rewarm in thoracic and thoracoabdominal aortic aneurysm repair

BACKGROUND Femoro-femoral veno-arterial perfusion is an established circulatory support and cooling method for thoracic- and/or thoracoabdominal aortic aneurysm repair. However, retrograde perfusion through femoral arteries can lead to retrograde cerebral embolization and neurologic dysfunction after surgery. To avoid these complications, we have established a femoro-femoral veno-venous perfusion technique and evaluated its safety and effectiveness in elective and nonelective patients. METHODS Common femoral veins were cannulated bilaterally percutaneously following systemic low-dose heparinization (100 IU/kg body weight). Venous blood was drained from drainage of the inferior vena cava, and venous return followed through the superior vena cava. After proximal aortic cross-clamping, veno-venous perfusion was switched to veno-arterial antegrade perfusion through the distal descending thoracic aorta to achieve spinal and visceral perfusion or through iliac arteries for distal perfusion combined with selective renovisceral blood perfusion. After completion of aortic repair, the arterial cannula was removed and the patient rewarmed just by switching back to veno-venous perfusion. Gas and temperature exchange as well as relevant hemodynamic parameters were recorded prospectively and analyzed retrospectively in 25 consecutive patients including 15 nonelective cases. RESULTS Percutaneous insertion of outflow (28F cannula) and inflow (18F cannula) venous cannulae was complication-free and allowed unrestricted perfusion in all 25 patients. Veno-venous perfusion allowed effective cooling (mean body temperature 36.6 ± 0.6°C to 31.6 ± 2.1°C, P = .001 compared with start of cooling) and re-warming (mean body temperature 30.5 ± 3°C to 36.3 ± 0.8°C, P = .03 compared with start of re-warming). Hemodynamic as well as pulmonary parameters remained remarkably stable during surgical dissection and single lung ventilation even in nonelective cases. There was no complication associated with the perfusion technique during surgery. CONCLUSIONS Transfemoral veno-venous cooling and re-warming results in remarkable hemodynamic stability during open repair of thoracic- and/or thoracoabdominal aortic aneurysms and eliminates the need for retrograde arterial perfusion and its inherent risks.