Automatic quantification of angiogenesis in 2D sections: a precise and timesaving approach.

INTRODUCTION: The standardized characterization of angiogenesis is crucial in the field of tissue engineering as sufficient blood supply is the limiting factor of mass transfer. However, reliable algorithms that provide a straight forward and observer-independent assessment of new vessel formation are still lacking. We propose an automatic observer-independent quantitative method (including downloadable source code) to analyze vascularization using two-dimensional microscopic images of histological cross-sections and advanced postprocessing, based on a 'positive- and negative-experts' model and a (corrected) nearest neighbour classification, in a vascularized tissue engineering model. MATERIALS AND METHODS: An established angioinductive rat arteriovenous loop model was used to compare the new automatic analysis with a common 2D method and a µCT algorithm. Angiogenesis was observed at three different time points (5, 10 and 15 days). RESULTS: In line with previous results, formation of functional new vessels that arose from the venous graft was evident within the three-dimensional construct and a significant (p < 0.05) increase in vessel count and area was observed over time. The proposed automatic analysis obtained precise values for vessel count and vessel area that were similar to the manually gained data. The algorithm further provided vectorized parameterization of the newly formed vessels for advanced statistical analysis. Compared to the µCT-based three-dimensional analyses, the presented two-dimensional algorithm was superior in terms of small vessel detection as well as cost and time efficiency. CONCLUSIONS: The quantitative evaluation method, using microscopic images of stained histological sections, 'positive- and negative-experts'-based vessel segmentation, and nearest neighbour classification, provides a user-independent and precise but also time- and cost-effective tool for the analysis of vascularized constructs. Our algorithm, which is freely available to the public, outperforms previous approaches especially in terms of unambiguous vessel classification and statistical analyses.

The impact of VEGF and bFGF on vascular stereomorphology in the context of angiogenic neo-arborisation after vascular induction.

The aim of this in vivo study was to gather quantitative information on the three-dimensional morphology of a new vascular network under the influence of angioactive growth factors. For this purpose, the arteriovenous loop model was used in 10 Lewis rats to generate a bioartificial vascular assembly by means of vascular induction. In this model, an isolated organoid is created in the medial thigh of the animal by methods of tissue engineering. A fibrin gel containing vascular endothelial growth factor (VEGF(165)) and basic fibroblastic growth factor (bFGF) was used as a matrix in the effect group (GF+). Fibrin matrices devoid of growth factors were used as controls (GF-). A microvascular replica of the organoid was created by means of corrosion casting and the network was investigated on stereo-paired images obtained by scanning electron microscopy. Vectors of intercapillary and interbranching distances as well as the diameter of the pores in the intussusceptive events diameter and the ratio of sprouting versus intussusceptive angiogenic events were compared in the two groups. The results were highly significant. In the GF+ group there were more profound three-dimensional morphological traits of angiogenesis, whereas advanced neovascularisation in the phase of remodelling was demonstrated by a higher incidence of intussusception, compared to control. These results illustrate the importance of morphological studies with focus on the generation of three-dimensional vascular networks.

Random-pattern versus perforator-based adipocutaneous skin paddles for postoperative monitoring of free muscle flaps-a comparative retrospective cohort study.

INTRODUCTION: Free microvascular muscle flaps represent well-established reconstructive options for complex soft tissue defects. However, due to their lack of cutaneous capillary beds, they are difficult to monitor postoperatively. To this end, random and axial-pattern adipocutaneous skin paddles are often included. The objective of the study was to compare the impact of random-pattern versus perforator-based adipocutaneous skin paddles on operative efficacy and muscle flap safety. METHODS: Between August 2014 and July 2016, a total of 120 free muscle flaps were included in this retrospective monocentric cohort study. Based on their skin-paddle type, they were either grouped into a 'perforator-based' (group Pb) or 'random-pattern' (group Rp) cohort. The electronic medical records and operative reports of all patients were subsequently reviewed and patient, defect, and flap characteristics of both groups were compared. The effect of the competing skin paddle types on the overall operative time, incidences of flap loss or microvascular complications, and total length of hospital stay were then assessed. RESULTS: Group Pb comprised 72 flaps, whereas 48 flaps constituted group Rp. Patient, defect, and flap characteristics were similar between both groups. Groups Pb and Rp were comparable regarding patient age (group Pb: 61 (10-90) vs. Rp: 59 (13-81), p = 0.556), ASA (American Society of Anesthesiologists) class (group Pb: 3 (1-4) vs. Rp 3 (1-3), p = 0.977), and comorbidities, summarized by the Charlson comorbidity index (CCI; group Pb: 1 (0-4 vs. Rp: 1 (0-5), p = 0.295). Both types of monitoring skin paddles were equally reliable. There was no significant difference in the mean operation time between both groups (group Pb: 373 ±â€¯122 min vs. Rp: 342 ±â€¯84 min, p = 0.124). In-patient treatment after flap surgery and total length of hospital stay were significantly shorter in group Pb (group Pb: 24 ±â€¯10 days vs. Rp: 32 ±â€¯17 days, p = 0.002 and group Pb: 39 ±â€¯15 vs. Rp: 48 ±â€¯24, p = 0.022). CONCLUSION: Perforator-based skin paddles are a reliable tool for postoperative perfusion monitoring of free muscle flaps and help avoid additional surgical interventions as opposed to their random-pattern counterparts. Thus, the overall and postoperative length of hospital stay is significantly reduced.

[Establishing and evaluating a multinational Science Academy: A new tool for fostering scientific young talents in microsurgical research - a Consensus Statement of the DAM]. / Etablierung und Evaluation einer multinationalen Wissenschaftsakademie: Ein neues Modell zur Stärkung des wissenschaftlichen Nachwuchses in der mikrochirurgischen Forschung ­ Ein Konsensus Papier der DAM.

BACKGROUND: The formation of professional networks and cooperations - in addition to any qualified good education - seems fundamental for a successful career. In a number of disciplines, various symposia or conferences exist. In the field of microsurgery, however, a specific, guided and designated opportunity for junior scientists to network with one another has been missing so far. METHODS: In 2017, a science academy was initiated for the first time by the German-speaking Association for Nerves and Vessels (DAM) with the goal of bringing together and networking microsurgically researching young physicians and scientists. This was intended to happen on a small scale once a year in order to develop synergies for joint research projects. For this purpose, motivated junior researchers were individually selected by their mentors and sent to the academy by the boards of research institutions that are organized in the DAM. After getting to know each other in a relaxed atmosphere, the participants were given the opportunity to present their respective research project within the framework of thematic blocks and moderated by experienced mentors. Each presentation was followed by a round table discussion and small group work, in which knowledge and methods were exchanged and points of contact for possible later cooperation were identified. RESULTS: In the past 3 years, the DAM Science Academy proved to be an optimal format to initiate and promote networks of young researchers comprising microsurgically interested physicians and scientists. There were many lively and in-depth discussions, which were mainly due to the open working atmosphere and the obligation to confidentiality. Most of the synergies were shown i. a. in the field of angiogenesis, bioreactor, carcinoma-ADSC interactions, stem cells, AV loop model, ischemia/reperfusion, and nerve regeneration. The participants consistently gave a very positive feedback in the final evaluation with the wish to continue this academy. CONCLUSION: The DAM Science Academy can be considered a highly suitable complemental platform to the existing networking opportunities among microsurgical researchers. Experience so far suggests that this will hopefully result in long-term cooperations and a permanent transfer of knowledge among the participants.

[The "safe" flap - Preoperative perforator-mapping and intraoperative perfusion assessment to reduce flap-associated morbidity - Consensus statement of the German Speaking Working Group for Microsurgery of the Peripheral Nerves and Vessels]. / Der sichere Lappen ­ Präoperatives Gefäß-Mapping und intraoperative Perfusionsmessung zur Reduktion der lappenbedingten Morbidität.

Reconstructive microsurgery using free and pedicled flaps has become a reliable method with a high success rate. Preoperative perforator mapping and intraoperative assessment of perfusion might further reduce flap-associated morbidity.There are various techniques for perforator mapping and perfusion measurement, but no guidelines regarding their use. Therefore, an expert panel at the 40th Annual Meeting of the German-Speaking Working Group for Microsurgery of the Peripheral Nerves and Vessels (DAM) discussed and critically reviewed the current literature. The consensus statement represents the expert opinion based on the available literature and provides recommendations regarding the use of preoperative perforator mapping and intraoperative perfusion measurement.

[Bioreactors in regenerative medicine--from a technical device to a reconstructive alternative?]. / Bioreaktoren in der Regenerativen Medizin--Vom technischen Apparat zur rekonstruktiven Alternative?

With the advent of the era of tissue engineering (TE), experimental settings have been developed that allow for a defined environment with optimised cell growth conditions and/or the production of specific substitutes. These isolated systems have been termed "bioreactors". By translating the principles of bioreactors into an in vivo context, advances in biomaterial sciences and cell biology have been merged into an integrative research concept. Even today, in the age of regenerative Medicine (RegMed) the transfer of experimental in vitro findings into a clinical in vivo approach still remains a vast challenge. In order to fulfil these specific requirements bioreactors had to be defined anew. Latest advances in areas like reconstructive medicine (the arteriovenous loop as a means of organogenesis) or modern wound management (topical negative pressure therapy as a perfusion bioreactor) give new impulses towards the translation of Reg-Med concepts into the clinical routine.