Bacterial bioburden of wounds: influence of debridement and negative-pressure wound therapy (NPWT).

OBJECTIVE: To clarify the role of microbiological swabs in surgical decision-making, we investigated the effect of negative-pressure wound therapy (NPWT) and serial surgical debridement on bacterial bioburden in hard-to-heal wounds and ultimately correlated them with the success of surgical closure. METHOD: All patients were treated with surgical debridement, jet lavage and NPWT before their wounds were finally closed. The treatment effect was assessed by correlating microbiological swabs obtained immediately after intervention with those obtained after removal of the dressings during the following surgical procedures. The result of the last microbiological swab taken before definitive surgical closure was correlated with the requirement for revision surgery. RESULTS: We included the results of 704 microbiological swabs from 97 patients in 110 wound localisations in this monocentric, retrospective study. NPWT did not improve bacterial bioburden in 77% of cases and the duration of NPWT did not affect the result. Furthermore, no significant effect of NPWT could be found for either anaerobic (p=0.96) or aerobic bacteria (p=0.43). In contrast, surgical debridement decreased bacterial load in approximately 60% of cases. If sterile wound swabs could be obtained at all, it was during the first four surgical debridements in 60% of patients; after that only 10% became sterile. CONCLUSIONS: Sterile microbiological wound swabs before surgical closure were associated with lower rates of revision surgery, while low or medium bacterial loads did not increase revision rates.

Common Rodent Flap Models in Experimental Surgery.

BACKGROUND: Flap procedures are widely used in clinical reconstructive surgery. Since ische-mia-associated complications, e.g., wound breakdown or tissue necrosis, are still a great challenge in flap surgery, experimental flap models are widely used to study flap physiology and to evaluate treatment strategies to prevent these complications. SUMMARY: Since rodents in general, and mice and rats in particular, are widely used in experimental flap models, we give an overview of the most common flap models in rodents, including the cremaster flap, the osteomyocutaneous flap, the McFarlane flap, the ear flap, and the dorsal skinfold chamber. Key Messages: Rodent flap models in experimental surgery are manifold and have a long history. These models play an important role in training surgical techniques, understanding flap physiology, defining flap anatomy and vascularity, and developing treatment regimens to prevent the necrosis of ischemically challenged tissue. However, it is important to be aware of the advantages and disadvantages of the single flap models concerning the possible time span of the experiment, the degree of difficulty, and the reproducibility and the translation of the results in humans.

Lipofilling of Fingertips for Volume Defects after Fingertip Injuries.

INTRODUCTION: Regardless of the good outcomes of conservatively treated fingertip injuries, many patients complain about volume defects and hypoesthesia. Injection of autologous fat into the defect zone may resolve the volume problem and stimulate digital nerve regeneration by adipose derived stem cell transplantation. METHODS: We analyzed 5 volume defects resulting from conservatively treated fingertip injuries in 4 patients (male to female ratio, 2:2), 6 months after the injection of autologous abdominal fat into the defect zone retrospectively. The fat transplantation was performed after complete wound healing was achieved (2.5-13.5 months; mean, 6.5 months). Assessment of 2-point discrimination; finger pulp circumference; the Disability of the Arm, Shoulder, and Hand score; visual analog scale score; and a questionnaire regarding the treatment satisfaction were carried out both preoperatively and at a 6 month follow-up according to the standard of our clinic. RESULTS: In 3 patients, one session of lipofilling was sufficient to correct the contour, whereas 1 patient with 2 fingertip injuries was treated a second time. There was no significant change in finger pulp circumference, in the 2-point discrimination values and the Disability of the Arm, Shoulder, and Hand score results. There was a significant improvement in the visual analog scale scores in 4 of 5 cases, and all patients were very satisfied with the results of the procedure regarding the improvement in hand function in sports, at work and their daily routine. CONCLUSIONS: Lipofilling can be performed with little operative risks, might alleviate the patient's symptoms and reduce pain after conservative treatment of fingertip injuries.

Microsurgical reconstruction in patients greater than 80 years old.

BACKGROUND: Demographic change implies that the human population is getting older and the elderly are living longer. Consequently, achieving good functional and aesthetic outcomes in microvascular procedures, especially in very old patients with higher incidence of atherosclerosis and vessel calcifications, constitutes a microsurgical challenge. This study evaluates the feasibility of microsurgical procedures in a very old patient cohort. PATIENTS AND METHODS: Between 2009 and 2015, 754 patients underwent 838 free flap reconstructions. The patients were divided into two groups according to age in "middle-aged" (<80 years old; n = 711) or "very old" (≥80 years old; n = 43). The series was retrospectively analyzed regarding potential influence of medical comorbidities, surgical and medical complications and outcomes. RESULTS: Between the groups, there was a significant difference regarding comorbidities with a higher prevalence of hypertension (P < 0.0001) and peripheral artery disease (P < 0.0001) in the very old group. However, there was no significant difference regarding the rate of surgical or medical complications, flap failure (middle aged group 43/791 flaps (5.44%) versus very old group 4/47 flaps (8.51%); P = 0.328), and revision rate (117/791 flaps (14.79%) versus 6/47 flaps (12.77%); P = 0.834) between the patient groups during our 3-months follow-up period. CONCLUSION: Our findings suggest that despite higher rates of patient comorbidities, successful free tissue transfer can also be achieved in a very old population with acceptable risk for complications.

Recurrence of Hypertrophic Abductor Digiti Minimi Muscle of the Foot After Subtotal Resection.

Soft tissue tumors of the foot are rare, and the diagnosis is often difficult. Surgery is indicated if pain, discomfort, or functional impairment is present or to rule out malignancy. We present the case of a 14-year-old female with a painless swelling at the lateral aspect of her right foot. After radiologic imaging, including ultrasonography and magnetic resonance imaging (MRI), we performed a subtotal resection of the abductor digiti minimi muscle, preserving its motor nerve. Four months later, recurrence of the soft tissue mass was observed. MRI revealed hypertrophy of the small muscles of the foot, including the abductor digiti minimi, quadratus plantae, and flexor digiti minimi brevis. Functional impairment resulted in complete excision of the remnant abductor digiti minimi muscle and partial excision of the flexor digiti minimi brevis muscle another 7 months later. Twelve months after the secondary surgery, neither clinical nor radiologic signs of a second recurrence were found. At the last follow-up visit, the patient was satisfied with the contour of her foot and not hindered at all during sporting activities. Our findings demonstrate that subtotal resection of a bulky muscle, preserving its motor nerve, can result in reactive hypertrophy of the remnant muscle part. The patient must be informed that partial excision of an innervated muscle could result in reactive hypertrophy and must be contrasted with radical muscle excision that might be more likely to result in functional impairment.

Microsurgeons do better--tactile training might prevent the age-dependent decline of the sensibility of the hand.

Recent data demonstrate that the normal sensibility of the hand seems to be age-dependent with the best values in the third decade and a consecutive deterioration afterwards. However, it is not clear if long-term tactile training might prevent this age-dependent decline. We evaluated sensibility of the hand in 125 surgeons aged between 26 and 75 years who perform microsurgical operations, thereby undergoing regular tactile training. We examined sensibility of the radial digital nerve of the index finger (N3) and the ulnar digital nerve of the small finger (N10) using static and moving two-point discrimination (2PD) tests and compared the results to 154 age-matched individuals without specific long-term tactile training. We found significantly lower static and moving 2PD values for the sixth, seventh, and eighth decade of life in the microsurgery group compared to the control group (p < 0.05). This study demonstrates that long-term tactile training might prevent the known age-dependent decline of the sensibility of the hand.

The normal sensibility of the hand declines with age--a proclamation for the use of delta two-point discrimination values for sensibility assessment after nerve reconstruction.

The scores used to evaluate sensibility after digital nerve reconstruction do not take the patient's age into consideration, although there is evidence that the outcome after digital nerve reconstruction is age-dependent. However, it is not clear if the normal sensibility of the hand is also age-dependent, as the existing studies have major limitations. We evaluated the normal sensibility of the hand in 232 patients using static and moving two-point discrimination (2PD) tests and the Semmes-Weinstein-monofilament test. We found the climax of sensibility in the third decade with age-dependent deterioration afterwards in all three tests. Mean 2PD values of the radial digital nerve of the index finger (N3) showed to be significantly lower than values of the ulnar digital nerve of the small finger (N10). To overcome shortcomings of classification systems that do not consider the patient's age and inter-individual differences, we suggest using the difference of the static 2PD values of the injured to the uninjured contralateral nerve (delta 2PD) for assessment of sensibility after digital nerve reconstruction.

Is nerve regeneration after reconstruction with collagen nerve conduits terminated after 12 months? the long-term follow-up of two prospective clinical studies.

BACKGROUND: Long-term follow-up data of digital nerve reconstructions with nerve conduits are limited. Furthermore, it is not known whether nerve regeneration after tubulization is terminated after 12 months, or whether improvement can be expected after this period of time. Therefore, we present the long-term follow-up of two prospective clinical trials. PATIENTS AND METHODS: We invited 45 patients who were enrolled in two prospective clinical trials for long-term follow-up. All patients underwent digital nerve reconstruction with conduits made from bovine collagen I due to a gap length of < 26 mm. Sensibility was assessed using static and moving two-point discrimination and monofilament testing. Follow-up data of 1 week, 3, 6, and 12 months, and the current examination were available. Improvement of sensibility was investigated by comparison of the American Society for Surgery of the Hand classification score at 12-month follow-up with the score raised at current examination. RESULTS: We examined 20 reconstructed nerves in 16 patients with a mean follow-up of 58.1 months (range, 29.3-93.3 months). We found an improved sensibility at current follow-up compared with the 12-month follow-up in 13 cases. Three cases had the same values whereas four cases had worsened sensibility. Improvement of sensibility was associated with a significantly shorter nerve gap length with significantly better results if the gap length was < 10 mm. CONCLUSION: Our results provide evidence that the long-term recovery of sensibility after digital nerve tubulization depends on the nerve gap length with better results in those < 10 mm. Nerve regeneration after tubulization seems not to be terminated after 12 months.

Prospective clinical study on digital nerve repair with collagen nerve conduits and review of literature.

Little data are available concerning conduit repair of digital nerve lesions. We are presenting a prospective two-center cohort study on digital nerve reconstruction with collagen nerve conduits. The data are put into the context of a comprehensive review of existing literature. Over a period of 3 years, all consecutive digital nerve lesions that could not be repaired by tensionless coaptation with a gap length of less than 26 mm were reconstructed with nerve conduits made from bovine collagen I. Sensibility was assessed 1 week, 3, 6, and 12 months postoperatively by static and moving 2-point-discrimination (2PD) and monofilament testing. Forty-nine digital nerve lesions in 40 patients met the inclusion criteria. The mean nerve gap was 12.3 ± 2.3 mm (span 5-25 mm). Forty nerve reconstructions could be included in the 12-month follow-up. Three cases, assessed 12 months postoperatively, showed excellent sensibility (static 2PD <6 mm). Seventeen achieved good (2PD 6-10 mm), 5 fair (2PD 11-15 mm), 6 poor (2PD >15 mm, but protective sensibility), and 9 achieved no sensibility. Monofilament test results were significantly better if gap length was shorter than 12 mm. Our results confirm tubulization as one possible technique in nerve reconstruction for gap lengths of 5 to 25 mm.

Pyoderma gangrenosum following reduction mammoplasty: Systematic review of the literature and case report.

BACKGROUND: Pyoderma gangrenosum (PG) is a rare inflammatory neutrophilic dermatosis that can develop at a surgical site. Diagnosis can be challenging at its presentation causing delays in appropriate treatment. The aim of this study is to review the current literature as well as to describe the clinical presentation, diagnostic pathway, and treatment of PG after reduction mammaplasty in order to define a standardized multidisciplinary diagnostic and therapeutic approach. In the future, this may ease early identification and prompt treatment, and eventually minimize severe morbidity and long-term sequelae. METHODS: The entire PubMed/Medline database was screened following the PRISMA guidelines to identify studies describing PG that have occurred after reduction mammoplasty. RESULTS: Twenty-eight articles including 31 patients reported a PG after breast reduction surgery between January 1988 and March 2022. Twenty-one (68%) patients presented with skin ulcerations, 14 (45%) with erythema, and 5 (16%) with vesicles. Out of the 30 cases that underwent bilateral surgery, 18 (60%) developed PG bilaterally. In 12 out of 31 patients, nipple-areolar complex (NAC) involvement was evaluated, though in 10 patients (83%) the NAC was spared. Of the 20 patients (65%) who underwent skin biopsies for histopathological examination, 18 (90%) showed neutrophilic infiltration of the dermal layers. All 31 patients (100%) showed rapid clinical improvement after the introduction of immunosuppressive therapy. CONCLUSIONS: PG can result in devastating skin alterations also after reduction mammoplasty, if misdiagnosed. However, it presents with constant yet unspecific local and general signs and symptoms that can be recognized to early initiate an appropriate pharmacological treatment.

Microvascular Fragments Protect Ischemic Musculocutaneous Flap Tissue from Necrosis by Improving Nutritive Tissue Perfusion and Suppressing Apoptosis.

Microvascular fragments (MVF) derived from enzymatically digested adipose tissue are functional vessel segments that have been shown to increase the survival rate of surgical flaps. However, the underlying mechanisms have not been clarified so far. To achieve this, we raised random-pattern musculocutaneous flaps on the back of wild-type mice and mounted them into dorsal skinfold chambers. The flaps were injected with MVF that were freshly isolated from green fluorescent protein-positive (GFP+) donor mice or saline solution (control). On days 1, 3, 5, 7, and 10 after surgery, intravital fluorescence microscopy was performed for the quantitative assessment of angiogenesis, nutritive blood perfusion, and flap necrosis. Subsequently, the flaps were analyzed by histology and immunohistochemistry. The injection of MVF reduced necrosis of the ischemic flap tissue by ~20%. When compared to controls, MVF-injected flaps also displayed a significantly higher functional capillary density and number of newly formed microvessels in the transition zone, where vital tissue bordered on necrotic tissue. Immunohistochemical analyses revealed a markedly lower number of cleaved caspase-3+ apoptotic cells in the transition zone of MVF-injected flaps and a significantly increased number of CD31+ microvessels in both the flaps' base and transition zone. Up to ~10% of these microvessels were GFP+, proving their origin from injected MVF. These findings demonstrate that MVF reduce flap necrosis by increasing angiogenesis, improving nutritive tissue perfusion, and suppressing apoptosis. Hence, the injection of MVF may represent a promising strategy to reduce ischemia-induced flap necrosis in future clinical practice.

Aesthetic training concept during plastic surgery residency - Opportunity or risk?

Background: Aesthetic surgery training renders to be challenging to acquire sufficient hands-on experience during residency. To resolve this problem, the "Munich Model" was established in our clinic: Senior residents perform aesthetic surgeries, supervised by an experienced plastic surgeon while patients benefit from reduced surgery costs. With this model, we hypothesize no significant differences in the postoperative outcome between procedures performed by residents and plastic surgeons. Methods: Between August 2012 and December 2017, 481 aesthetic surgeries were included in this retrospective single-center study, of which 283 were performed by residents and 198 by plastic surgeons. Procedures included mastopexy, abdominoplasty, extremity lift, breast reduction, breast augmentation, facial surgery, aesthetic liposuction and lipedema liposuction. Postoperative outcomes were compared regarding surgery time, time of drain removal, inpatient length of stay, duration of wound healing, perioperative blood loss and occurrence of major (surgical revision needed) and minor complications (no surgery needed). Results: We found no significant differences in aesthetic surgical procedures between residents and board-certified plastic surgeons in the outcome measures of surgery duration, time of drain removal, inpatient length of stay, perioperative blood loss and complication rate, including major and minor complications. Only the inpatient stay was prolonged in aesthetic liposuctions performed by residents. Conclusion: This study demonstrates comparatively that supervised aesthetic surgeries at a university hospital utilizing the "Munich Model" widely meet the specialist surgeons' standards.

[The Value of Synthetic and Biologic Meshes in Implant-Based Breast Reconstruction]. / Der Stellenwert von synthetischen Netzen und biologischen Matrices in der Implantat-basierten Brustrekonstruktion.

Implant based breast reconstruction (IBBR) keeps evolving and has been influenced heavily by the use of synthetic and biologic meshes in the last years. In both, subpectoral as well as prepectoral approaches the use of synthetic and biologic meshes has made it possible to place implants precisely according to the breast's footprint and strengthen soft-tissue coverage, particularly in the lower pole of the breast with lower complication rates and better cosmesis. Various mesh options that differ in material, processing, size and cost are currently in clinical use. This review aims to define the role of biologic and synthetic meshes in IBBR regarding the advantages and disadvantages of their use.

[The Significance of Oncoplastic Breast Reconstruction After Tumorectomy in Surgical Breast Cancer Therapy]. / Der Stellenwert der onkoplastischen Brustrekonstruktion nach Tumorektomie in der chirurgischen Brustkrebs-Behandlung.

Breast-conserving therapy (BCT), meaning tumorectomy in combination with systemic therapy and locoregional radiation therapy has become the preferred method to treat early-stage breast cancer. With excellent long-term recurrence-free and overall survival rates, breast surgeons today must deliver du- rable and aesthetically appealing results that guarantee a good quality of life to meet the high patient expectations. Oncoplas- tic breast surgery (OPBS) is an innovative approach to improve the overall results of BCT. Often carried out by a team of a plastic surgeon and an oncologic breast surgeon, OPBS can actively prevent breast deformities without compromising oncological safety. In the following, an overview of the principles and techniques of oncoplastic breast surgery will be given due to its ever-increasing significance and its advantages and dis- advantages will be discussed in the context of reconstructive breast surgery.

Implant-Based Breast Reconstruction after Mastectomy, from the Subpectoral to the Prepectoral Approach: An Evidence-Based Change of Mind?

Over the last years, prepectoral implant-based breast reconstruction has undergone a renaissance due to several technical advancements regarding mastectomy techniques and surgical approaches for the placement and soft tissue coverage of silicone implants. Initially abandoned due to the high incidence of complications, such as capsular contraction, implant extrusion, and poor aesthetic outcome, the effective prevention of these types of complications led to the prepectoral technique coming back in style for the ease of implant placement and the conservation of the pectoralis muscle function. Additional advantages such as a decrease of postoperative pain, animation deformity, and operative time contribute to the steady gain in popularity. This review aims to summarize the factors influencing the trend towards prepectoral implant-based breast reconstruction and to discuss the challenges and prospects related to this operative approach.

Relevance of the Scaphoid Shift Test for the Investigation of Scapholunate Ligament Injuries.

Background: Although it is part of the common clinical examination of scapholunate ligament pathologies, there are only little data on the diagnostic value of the scaphoid shift test. The aim of this study was to evaluate the scaphoid shift test in a large cohort of patients. Materials and Methods: We retrospectively analysed 447 patients who underwent the scaphoid shift test and wrist arthroscopy because of various suspected injuries of the wrist, correlating the results of clinical examination with data obtained during the wrist arthroscopy. Sensitivity, specificity, and positive and negative predictive values were calculated and evaluated. Results: The sensitivity of the scaphoid shift test was low (0.50) when examining the whole cohort. In a subgroup of patients specifically referred for suspected scapholunate ligament injury, the sensitivity was higher (0.61), but the specificity was low (0.62). In detecting more serious lesions (Geissler 3 + 4), the scaphoid shift test demonstrated higher sensitivity (0.66). Conclusions: An isolated scaphoid shift test may only be of limited value in the diagnosis of scapholunate ligament lesions and should, therefore, be viewed as a useful tool for a preliminary assessment, but a negative test should not prevent the surgeon from indicating a more extensive diagnostic workup.

Bromelain Protects Critically Perfused Musculocutaneous Flap Tissue from Necrosis.

Bromelain has previously been shown to prevent ischemia-induced necrosis in different types of tissues. In the present study, we, therefore, evaluated for the first time, the tissue-protective effects of bromelain in musculocutaneous flaps in mice. Adult C57BL/6N mice were randomly assigned to a bromelain treatment group and a control group. The animals were treated daily with intraperitoneal injections of 20 mg/kg bromelain or saline (control), starting 1 h before the flap elevation throughout a 10-day observation period. The random-pattern musculocutaneous flaps were raised on the backs of the animals and mounted into a dorsal skinfold chamber. Angiogenesis, nutritive blood perfusion and flap necrosis were quantitatively analyzed by means of repeated intravital fluorescence microscopy over 10 days after surgery. After the last microscopy, the flaps were harvested for additional histological and immunohistochemical analyses. Bromelain reduced necrosis of the critically perfused flap tissue by ~25%. The bromelain-treated flaps also exhibited a significantly higher functional microvessel density and an elevated formation of newly developed microvessels in the transition zone between the vital and necrotic tissues when compared to the controls. Immunohistochemical analyses demonstrated a markedly lower invasion of the myeloperoxidase-positive neutrophilic granulocytes and a significantly reduced number of cleaved caspase 3-positive apoptotic cells in the transition zone of bromelain-treated musculocutaneous flaps. These findings indicate that bromelain prevents flap necrosis by maintaining nutritive tissue perfusion and by suppressing ischemia-induced inflammation and apoptosis. Hence, bromelain may represent a promising compound to prevent ischemia-induced flap necrosis in clinical practice.

Boosting Tissue Vascularization: Nanofat as a Potential Source of Functional Microvessel Segments.

Nanofat is increasingly applied in plastic surgery for the improvement of scar quality and skin rejuvenation. However, little is known about the underlying regenerative mechanisms. Therefore, we herein investigated nanofat grafts in a murine dorsal skinfold chamber model. Nanofat generated from subcutaneous, inguinal adipose tissue of green fluorescent protein (GFP)+ C57BL/6 male and female donor mice was injected intracutaneously into dorsal skinfold chambers of gender-matched GFP- wild-type mice. The vascularization and tissue composition of the grafted nanofat were analyzed by means of intravital fluorescence microscopy, histology and immunohistochemistry over an observation period of 14 days. The freshly generated nanofat consisted of small fragments of perilipin+ adipocytes surrounded by Sirius red+ collagen fibers and still contained intact CD31+/GFP+ vessel segments. After transplantation into the dorsal skinfold chamber, these vessel segments survived and developed interconnections to the surrounding CD31+/GFP- host microvasculature. Accordingly, the grafted nanofat rapidly vascularized and formed new microvascular networks with a high functional microvessel density on day 14 without marked differences between male and female mice. Even though further research is needed to confirm these findings, the present study suggests that nanofat boosts tissue vascularization. Thus, nanofat may represent a versatile resource for many applications in tissue engineering and regenerative medicine.

A Modified Burn Comb Model With a New Dorsal Frame That Allows for Local Treatment in Partial-Thickness Burns in Rats.

Burn wound progression (BWP) leads to vertical and horizontal injury extension. The "burn comb model" is commonly used, in which a full-thickness burn with intercalated unburned interspaces is induced. We aimed to establish an injury progressing to the intermediate dermis, allowing repeated wound evaluation. Furthermore, we present a new dorsal frame that enables topical drug application. Eight burn fields and six interspaces were induced on each of 17 rats' dorsa with a 10-second burn comb application. A developed 8-panel aluminum frame was sutured onto 12 animals and combined with an Elizabethan collar. Over 14 days, macroscopic and histologic wound assessment and laser speckle contrast imaging (LSCI) were performed besides evaluation of frame durability. The 10-second group was compared with nine animals injured with a full-thickness 60-second model. Frame durability was sufficient up to day 4 with 8 of the 12 frames (67%) still mounted. The 60-second burn led to an increased extent of interspace necrosis (P = .002). The extent of necrosis increased between days 1 and 2 (P = .001), following the 10-second burn (24% ± SEM 8% to 40% ± SEM 6%) and the 60-second burn (57% ± SEM 6% to 76% ± SEM 4%). Interspace LSCI perfusion was higher than burn field perfusion. It earlier reached baseline levels in the 10-second group (on day 1: 142% ± SEM 9% vs 60% ± SEM 5%; P < .001). Within day 1, the 10-second burn showed histological progression to the intermediate dermis, both in interspaces and burn fields. This burn comb model with its newly developed fixed dorsal frame allows investigation of topical agents to treat BWP in partial-thickness burns.

Immunoregulatory effects of the flavonol quercetin in vitro and in vivo.

PURPOSE: Atherosclerosis is known to be an inflammatory disease. Dendritic cells (DCs) are essential for the regulation of the immune system. Up to 10% of the cells in atherosclerotic plaques are DCs. The cardiovascular protective effects of flavonoids (tea, wine) may be mediated by anti-inflammatory mechanisms that affect DC regulation. We aimed to characterize the impact of the flavonol quercetin on DC activity and differentiation in vitro and in vivo. METHODS: For the in vitro experiments, we used murine DCs and endothelial cells to study adhesion properties. For all other experiments (DC phagocytosis capacity, DC maturation, DC differentiation (BDCA-1/-2) and NF-kB-activation), human monocyte-derived DCs were used. The cells were incubated with quercetin (10 µmol/L) ± oxLDL (10 µg/mL) between 24 and 48 h. For in vivo experiments, eight healthy male volunteers took 500 mg of quercetin twice daily over 4 weeks, five healthy male volunteers served as control. Before and after intake, blood samples were collected. Peripheral blood leukocytes were isolated (analyses of DC differentiation), and plasma was immediately frozen. RESULTS: Quercetin reduced DC adhesion (-42%; p < 0.05) and expression of CD11a (-21%; p < 0.05). OxLDL-induced DC differentiation was partially inhibited by quercetin (BDCA-1-29%; BDCA-2-33%; p < 0.05). These effects were achieved by compensation of oxLDL-induced up-regulation of NF-kB by quercetin. The 4-week treatment with quercetin resulted in relevant plasma levels (2.47 µmol/L) and reduced BDCA-2 + DCs in the peripheral blood by 42% (p < 0.05) as well as systemic levels of the NO-synthase inhibitor asymmetric dimethylarginine (-31%, p < 0.05). CONCLUSION: In vitro, quercetin reduced DC adhesion and oxLDL-induced DC differentiation. In vivo, quercetin reduced circulating plasmacytoid DCs and systemic ADMA-levels. The immunoregulatory effects of quercetin may contribute to the anti-atherosclerotic potential of flavonols.