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Summary: Patients with significant loss of abdominal wall soft tissue represent a reconstructive challenge. The purpose of this study was to describe the authors' experience using microvascular free tissue transfer to repair complex abdominal wall defects with insufficient overlying soft tissue. In this report, the authors highlight their techniques and experiences in performing microvascular free tissue transfer to the abdominal wall for these massive, complex defects. In total, 14 patients who underwent 16 free-flap reconstructions were included in the series. The patients' mean age was 50 ± 14 years, and mean body mass index was 27 ± 5 kg/m2. The mean hernia defect size was 412 ± 149 cm2. Ten flaps were fasciocutaneous anterolateral thigh flaps, one myocutaneous anterolateral thigh flap, two subtotal thigh flaps, one myocutaneous latissimus dorsi flap, one parascapular/latissimus dorsi flap, and one free filet of the lower leg. Five cases (36 percent) developed hernia recurrence, and seven developed surgical site complications. All flaps survived, with no total flap loss. This report highlights that microsurgical free tissue transfer in combination with mesh repair is a safe and reliable method for restoring complex, large, full-thickness abdominal wall defects. This case series illustrates a number of techniques and considerations that are of importance to achieve a favorable outcome when faced with these complex defects., Clinical Question/level of Evidence: Therapeutic, IV., (Copyright © 2021 by the American Society of Plastic Surgeons.)

Objectives/hypothesis: To evaluate the efficacy and reconstructive applications of angular vessel microvascular anastomosis in free-tissue transfer., Study Design: Retrospective cohort study., Methods: A study of patients treated from January 2010 to July 2017 was performed. Four hundred thirty patients undergoing free-tissue transfer at the Cleveland Clinic by a single reconstructive surgeon were reviewed. Patients in whom free-tissue transfer was performed using angular vessels were included. Patients in whom free-tissue transfer was performed using another vascular supply of the head and neck were excluded. Primary outcome was free-flap failure. Secondary outcomes included other postoperative complications and hospital length of stay., Results: Thirty-one patients underwent free-tissue transfer with microvascular anastomosis to the angular vessels during the study period. Seventy-one percent of patients underwent reconstruction immediately following tumor ablation. A variety of primary subsites were reconstructed; 58% underwent nasal reconstruction, 16% orbit/skull base reconstruction, 13% palatal reconstruction, 6% maxillary reconstruction, and 6% mandible reconstruction. Eighty-seven percent of patients underwent free-tissue transfer from an anterolateral thigh donor site. Ninety-seven percent of patients had successful free-tissue transfer with a viable flap during the follow-up period; only one patient experienced flap failure attributed to vascular insufficiency. Average length of stay was 4.7 days, and the most common length of stay was 3 days., Conclusions: The angular vessels provide excellent arterial supply and venous drainage to serve as a viable option for microvascular anastomosis during free-tissue transfer for head and neck reconstructive surgery. They are an ideal vascular source for central face and skull base reconstruction., Level of Evidence: NA Laryngoscope, 130:2589-2592, 2020., (© 2020 The American Laryngological, Rhinological and Otological Society, Inc.)

Background: Risk for venous thromboembolism formation and the relationship to postoperative free flap venous congestion and flap failure have not been adequately evaluated in a trauma population. The authors aim to use the Caprini Risk Assessment Model to evaluate the association between venous thromboembolism risk and postoperative flap venous congestion following lower extremity free tissue transfer., Methods: A retrospective analysis was conducted of all patients who underwent lower extremity free flap reconstruction of traumatic defects at a single institution between 2007 and 2016. A Wilcoxon rank sum test was used for nonparametric analysis of aggregate Caprini Risk Assessment Model scores and flap outcomes. Flap venous congestion and failure rates as associated with the categorical variables underlying the Caprini Risk Assessment Model were further studied. Logistic regression was used to evaluate each of these outcomes and other flap-related covariates relative to the Caprini Risk Assessment Model categorical variables that had the greatest effect on our patient sample., Results: One hundred twelve patients underwent lower extremity free flap reconstruction. One hundred eight free flaps were analyzed. Eight patients were excluded. The majority of patients were male (75.9 percent) and required reconstruction because of acute trauma (68.1 percent versus 31.9 percent for chronic wounds). There was no statistically significant association found between age, body mass index, or timing of trauma versus venous congestion, flap failure, or other flap-related covariates., Conclusion: In patients with significantly elevated Caprini Risk Assessment Model scores, there was no significant association between venous thromboembolism risk and flap failure following free tissue reconstruction of lower extremities., Clinical Question/level of Evidence: Risk, III.

Hemophilia A (HA) is a bleeding disorder caused by mutations in the F8 gene encoding coagulation factor VIII (FVIII). Current treatments are based on regular infusions of FVIII concentrates throughout a patient's life. Alternatively, viral gene therapies that directly deliver F8 in vivo have shown preliminary successes. However, hurdles remain, including lack of infection specificity and the inability to deliver the full-length version of F8 due to restricted viral cargo sizes. Here, we developed an alternative nonviral ex vivo gene-therapy approach that enables the overexpression of full-length F8 in patients' endothelial cells (ECs). We first generated HA patient-specific induced pluripotent stem cells (HA-iPSCs) from urine epithelial cells and genetically modified them using a piggyBac DNA transposon system to insert multiple copies of full-length F8. We subsequently differentiated the modified HA-iPSCs into competent ECs with high efficiency, and demonstrated that the cells (termed HA-FLF8-iECs) were capable of producing high levels of FVIII. Importantly, following subcutaneous implantation into immunodeficient hemophilic (SCID-f8ko) mice, we demonstrated that HA-FLF8-iECs were able to self-assemble into vascular networks, and that the newly formed microvessels had the capacity to deliver functional FVIII directly into the bloodstream of the mice, effectively correcting the clotting deficiency. Moreover, our implant maintains cellular confinement, which reduces potential safety concerns and allows effective monitoring and reversibility. We envision that this proof-of-concept study could become the basis for a novel autologous ex vivo gene-therapy approach to treat HA., (© 2019 by The American Society of Hematology.)

Tissue engineering may address organ shortages currently limiting clinical transplantation. Off-the-shelf engineered vascularized organs will likely use allogeneic endothelial cells (ECs) to construct microvessels required for graft perfusion. Vasculogenic ECs can be differentiated from committed progenitors (human endothelial colony-forming cells or HECFCs) without risk of mutation or teratoma formation associated with reprogrammed stem cells. Like other ECs, these cells can express both class I and class II major histocompatibility complex (MHC) molecules, bind donor-specific antibody (DSA), activate alloreactive T effector memory cells, and initiate rejection in the absence of donor leukocytes. CRISPR/Cas9-mediated dual ablation of β2-microglobulin and class II transactivator (CIITA) in HECFC-derived ECs eliminates both class I and II MHC expression while retaining EC functions and vasculogenic potential. Importantly, dually ablated ECs no longer bind human DSA or activate allogeneic CD4+ effector memory T cells and are resistant to killing by CD8+ alloreactive cytotoxic T lymphocytes in vitro and in vivo. Despite absent class I MHC molecules, these ECs do not activate or elicit cytotoxic activity from allogeneic natural killer cells. These data suggest that HECFC-derived ECs lacking MHC molecule expression can be utilized for engineering vascularized grafts that evade allorejection.

Large and deep defects resulting from lateral skull base surgery represent a challenge to the head and neck surgeon. Different microvascular free flaps have specific advantages and disadvantages. While the pedicled pectoralis major flap is considered a "work horse," it comes with a rather short pedicle. The aim of this study was to analyze the vascular anatomy of the pectoralis major flap and assess its suitability for microvascular transfer. Anatomical studies have been performed on 6 Thiel-fixed cadavers allowing a harvest of 12 flaps by the same surgeon. Measurements of the pedicle's length and vessel diameters have been taken with a ruler and caliper. The mean pedicle length and mean diameters (Ø) of the thoracoacromial artery and concomitant vein were found to be 9.8 cm, Ø 4.2 mm, and Ø 4.9 mm, respectively. These results suggest the potential utility of a free pectoralis major flap with microvascular anastomosis.

Aim: Adipose tissue-derived microvascular fragments (ad-MVF) are vascularization units for regenerative medicine. We investigated whether University of Wisconsin (UW) solution is suitable for their xeno-free storage. Materials & methods: Murine ad-MVF were cultivated for 24 h in 4°C or 20°C UW solution and 20°C endothelial cell growth medium (control). The ad-MVF were seeded onto collagen-glycosaminoglycan scaffolds, which were analyzed in dorsal skinfold chambers by intravital fluorescence microscopy and histology. Results: All implants exhibited microvascular networks on day 14 with the highest functional microvessel density in controls. Ad-MVF cultivation in UW solution at 4°C resulted in an improved scaffold vascularization compared with cultivation at 20°C. Conclusion: UW solution is suitable for the hypothermic storage of ad-MVF.

Traumatic composite bone-muscle injuries, such as open fractures, often require multiple surgical interventions and still typically result in long-term disability. Clinically, a critical indicator of composite injury severity is vascular integrity; vascular damage alone is sufficient to assign an open fracture to the most severe category. Challenging bone injuries are often treated with bone morphogenetic protein 2 (BMP-2), an osteoinductive growth factor, delivered on collagen sponge. Previous studies in a composite defect model found that a minimally bridging dose in the segmental defect model was unable to overcome concomitant muscle damage, but the effect of BMP dose on composite injuries has not yet been studied. Here, we test the hypotheses that BMP-2-mediated functional regeneration of composite extremity injuries is dose dependent and can be further enhanced via co-delivery of adipose-derived microvascular fragments (MVF), which have been previously shown to increase tissue vascular volume. Although MVF did not improve healing outcomes, we observed a significant BMP-2 dose-dependent increase in regenerated bone volume and biomechanical properties. This is the first known report of an increased BMP-2 dose improving bone healing with concomitant muscle damage. While high dose BMP-2 delivery can induce heterotopic ossification (HO) and increased inflammation, the maximum 10 μg dose used in this study did not result in HO and was associated with a lower circulating inflammatory cytokine profile than the low dose (2.5 μg) group. These data support the potential benefits of an increased, though still moderate, BMP-2 dose for treatment of bone defects with concomitant muscle damage. Published 2019. This article is a U.S. Government work and is in the public domain in the USA. J Orthop Res., (Published 2019. This article is a U.S. Government work and is in the public domain in the USA.)

Background: Hypoxia-inducible factors (HIFs), especially HIF-1α and HIF-2α, are key mediators of the adaptive response to hypoxic stress and play essential roles in maintaining lung homeostasis. Human and animal genetics studies confirm that abnormal HIF correlates with pulmonary vascular pathology and chronic lung diseases, but it remains unclear whether endothelial cell HIF production is essential for microvascular health. The large airway has an ideal circulatory bed for evaluating histological changes and physiology in genetically modified rodents., Methods: The tracheal microvasculature of mice, with conditionally deleted or overexpressed HIF-1α or HIF-2α, was evaluated for anatomy, perfusion, and permeability. Angiogenic signaling studies assessed vascular changes attributable to dysregulated HIF expression. An orthotopic tracheal transplantation model further evaluated the contribution of individual HIF isoforms in airway endothelial cells., Results: The genetic deletion of Hif-2α but not Hif-1α caused tracheal endothelial cell apoptosis, diminished pericyte coverage, reduced vascular perfusion, defective barrier function, overlying epithelial abnormalities, and subepithelial fibrotic remodeling. HIF-2α promoted microvascular integrity in airways through endothelial angiopoietin-1/TIE2 signaling and Notch activity. In functional tracheal transplants, HIF-2α deficiency in airway donors accelerated graft microvascular loss, whereas HIF-2α or angiopoietin-1 overexpression prolonged transplant microvascular perfusion. Augmented endothelial HIF-2α in transplant donors promoted airway microvascular integrity and diminished alloimmune inflammation., Conclusions: Our findings reveal that the constitutive expression of endothelial HIF-2α is required for airway microvascular health.

Manipulation of human T cell functioning by delivery of macromolecules such as DNA, RNA, or protein is limited, unless the human T cells have been stimulated or electropermeabilized. To achieve successful adaptation and survival of a grafted organ, the alloreactive T cells that induce graft rejection must be regulated. Corticosteroids, calcineurin inhibitors, and mTOR inhibitors, which are systemic immunosuppressants, are currently used for transplantation, with significant side effects. In this study, we demonstrated that a cell-permeable peptide (CPP), dNP2, could efficiently deliver proteins into human CD4 and CD8 T cells. We confirmed regulatory functioning of the cytoplasmic domain of CTLA-4 conjugated with dNP2 (dNP2-ctCTLA-4) in human T cell activation, proliferation, and chemokine receptor expression. We utilized a human skin allograft system in SCID/beige mice to examine whether dNP2-ctCTLA-4 could inhibit allograft rejection by controlling T cell responses. The grafted skin tissue inflammation, allogeneic T cell infiltration, and blood cytokine level was markedly reduced by dNP2-ctCTLA-4, resulting in successful transplantation. In addition, it also inhibited T cell alloresponses against microvessels formed form Bcl-2-transduced human umbilical vein endothelial cells implanted into Balb/c Rag1 -/- /IL-2Rγ -/- double knockout (DKO) mice, assessed as reduced T cell infiltration and granzyme B expression. These results collectively suggest that dNP2 peptide conjugation offers a valuable tool for delivering macromolecules like proteins into human T cells, and dNP2-ctCTLA-4 is a novel agent that shows potential in controlling human T cell responses to allow successful adaptation of grafted tissues., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Split-thickness skin grafts (STSG) are still the gold standard for the treatment of most skin defects. Hence, there is an ongoing need to improve this procedure. For this purpose, we herein analyzed dermal matrices seeded with adipose tissue-derived microvascular fragments (ad-MVF) in a bradythrophic wound model. In additional experiments, the matrices were covered with autologous STSG 10 days after implantation. Green fluorescence protein (GFP) + ad-MVF were isolated from C57BL/6-Tg(CAG-EGFP)1Osb/J mice and seeded onto collagen-glycosaminoglycan matrices. Non-seeded and prevascularized matrices were implanted into full-thickness skin defects on the skull of CD1 nu/nu mice for 21 days. Vascularization, lymphangiogenesis and incorporation of the matrices were analyzed using photo-acoustic imaging, trans-illumination stereomicroscopy, histology, and immunohistochemistry. The survival rate of STSG was assessed by planimetry. After 21 days, the density of microvascular and lymphatic networks was significantly higher in prevascularized matrices when compared to controls. This was associated with an improved implant integration. Moreover, prevascularization with ad-MVF allowed successful autologous skin grafting already at day 10, while coverage of non-seeded controls at day 10 resulted in STSG necrosis. In conclusion, ad-MVF represent powerful vascularization units. Seeded on dermal substitutes, they accelerate and enhance the healing of full-thickness skin defects and allow early coverage with STSG.

The seeding of tissue constructs with adipose tissue-derived microvascular fragments (ad-MVF) is an emerging pre-vascularisation strategy. Ad-MVF rapidly reassemble into new microvascular networks after in vivo implantation. Herein it was analysed whether this process was improved by erythropoietin (EPO). Ad-MVF were isolated from green fluorescent protein (GFP)+ as well as wild-type C57BL/6 mice and cultivated for 24 h in medium supplemented with EPO (20 IU/mL) or vehicle. Freshly isolated, non-cultivated ad-MVF served as controls. Protein expression, cell viability and proliferation of ad-MVF were assessed by proteome profiler array and fluorescence microscopy. GFP+ ad-MVF were seeded on collagen-glycosaminoglycan matrices, which were implanted into dorsal skinfold chambers of C57BL/6 mice, to analyse their vascularisation over 14 d by intravital fluorescence microscopy, histology and immunohistochemistry. Cultivation up-regulated the expression of pro- and anti-angiogenic factors within both vehicle- and EPO-treated ad-MVF when compared with non-cultivated controls. Moreover, EPO treatment suppressed cultivation-associated apoptosis and significantly increased the number of proliferating endothelial cells in ad-MVF when compared with vehicle-treated and non-cultivated ad-MVF. Accordingly, implanted matrices seeded with EPO-treated ad-MVF exhibited an improved vascularisation, as indicated by a significantly higher functional microvessel density. The matrices of the three groups contained a comparably large fraction of GFP+ microvessels originating from the ad-MVF, whereas the tissue surrounding the matrices seeded with EPO-treated ad-MVF exhibited a significantly increased microvessel density when compared with the other two groups. These findings indicated that EPO represents a promising cytokine to further boost the excellent vascularisation properties of ad-MVF in tissue-engineering applications.

Background/aim: Due to increased average life expectancy, the number of elderly patients requiring complex reconstructive microsurgical procedures is rising. Age, comorbid conditions, and location of operation are all possible risk factors. The aim of this study is to evaluate surgical outcomes to set the right criteria., Materials and Methods: Between 1996 and 2014, the data of 30 patients over the age of 70, who were treated with microsurgical techniques in our clinic, were extracted from patient records and analyzed retrospectively., Results: In this patient population, flap success rate was 94%. Systemic and surgical complication rates were 40% and 48%, respectively. Complication rates were higher in head and neck cases but there was no statistically significant difference compared to reconstructions in other areas. Loss of oral lining, as a serious complication, had no effect on complications in head and neck reconstruction patients in our series. Conclusions: Flap success is comparable to younger age groups but procedures are associated with a high rate of complications Evaluating and controlling comorbid conditions is important. The American Society of Anesthesiologists scoring system is reliable in this patient population. Although complications are more common, these procedures can be performed safely in elderly populations with careful patient selection.

Background: In young women, ovarian cortex cryopreservation before gonadotoxic chemotherapy and its avascular grafting after cancer healing permitted fertility restoration. However, ischemia reduced the grafts' lifespan. Microvascular transplantation of cryopreserved whole ovary may allow immediate revascularization, ensuring better fertility preservation, but the best cryopreservation method is unknown. We aimed to compare slow freezing and vitrification of whole ovary for fertility preservation purposes, in an ewe model., Methods: Twelve ewes were allocated at random to slow freezing (n = 6) or vitrification group (n = 6). Ewes' left ovary was removed and cryopreserved. Dimethyl sulfoxide 2 M was used as cryoprotector for slow freezing. Vitrification was obtained using increasing concentrations of a vitrification solution of the latest generation (VM3) and gradual temperature lowering to minimize toxicity. After a month, the right ovary was removed, the left ovary was thawed/warmed, and its vessels were anastomosed to the right pedicle. Fertility and ovarian function were assessed for 3 years. Ovarian follicles in native and transplanted ovaries were counted and compared at study completion., Results: Hormonal secretion resumed in all ewes of both groups. One ewe of the slow-freezing group delivered healthy twins 1 year 9 months and 12 days after transplantation. Estimated whole follicle survival was very low in both groups but significantly higher after vitrification than after slow freezing (0.3% ± 0.5% vs 0.017% ± 0.019%, respectively; p < 0.05)., Conclusions: Further progress is needed before whole-ovary cryopreservation can be considered an option for safeguarding fertility. Whole ovary vitrification provides better follicular survival compared to slow freezing and may be a valuable cryopreservation option.

We previously showed that transplantation of brain microvascular endothelial cells (MVECs) greatly stimulated remyelination in the white matter infarct of the internal capsule (IC) induced by endothelin-1 injection and improved the behavioral outcome. In the present study, we examined the effect of MVEC transplantation on the infarct volume using intermittent magnetic resonance image and on the behavior of oligodendrocyte lineage cells histochemically. Our results in vivo show that MVEC transplantation reduced the infarct volume in IC and apoptotic death of oligodendrocyte precursor cells (OPCs). These results indicate that MVECs have a survival effect on OPCs, and this effect might contribute to the recovery of the white matter infarct. The conditioned-medium from cultured MVECs reduced apoptosis of cultured OPCs, while the conditioned medium from cultured fibroblasts did not show such effect. These results suggest a possibility that transplanted MVECs increased the number of OPCs through the release of humoral factors that prevent their apoptotic death. Identification of such humoral factors may lead to the new therapeutic strategy against ischemic demyelinating diseases., (© 2015 International Society for Neurochemistry.)

Fibular hemimelia, or fibular hypoplasia-aplasia, is the most frequent congenital long-bone deficiency. There is still some debate on reconstruction versus amputation for the severe type Ib and type II cases. Limb-length discrepancy can be corrected with Ilizarov methods, but ankle stability remains a problem. The absence of the lateral malleolus destabilizes the mortise in valgus and ankle fusion is usually needed. A case of lateral malleolus reconstruction in a teenage patient with severe type-Ib fibular hemimelia using a contralateral free proximal fibular epiphyseal transfer is reported.

Background: Although perforator-to-perforator anastomosis in supermicrosurgery may be used in transferring free flaps with small vessels, it is still difficult in certain situations that include potentially infected wounds. Moreover, it is limited to smaller flaps. Anastomosis of large vessels is still safer for transfer of a large flap for most surgeons. The harvesting of a patch of the parent artery together with the perforator supplying the flap allows the surgeon to perform an anastomosis between the vessel ends of larger caliber, and possibly with greater anastomotic success., Method: When the vascular pedicle of a free flap is < 0.8 mm, an option is to take a cuff of the major artery for an end-to-patch anastomosis. From 1983 to 2013, this method was applied to the anteromedial thigh (AMT) flap (seven cases), the groin flap (81 cases), and the free Becker's flap (five cases). When a patch was taken from the femoral artery, direct anastomosis for the major artery was performed using 5/0 Prolene sutures, followed by coverage with local soft tissue. When a patch was taken from the ulnar artery, a patch of vein graft was used for repair of the ulnar artery. In one case, a segment of the femoral artery was harvested with an AMT flap and a segment of a sartorius muscle flap; the compound tissue was transferred to the neck with the femoral artery to replace the left carotid artery. In the donor site, the defect of the femoral artery was reconstructed with an artificial graft., Results: The flaps had no failure or partial necrosis, but one patient developed bleeding from the femoral artery 2 days postoperatively. It was treated by adding one more suture for the femoral artery and coverage with the sartorius muscle. In the ulnar artery, the patients did not complain of cold intolerance and the postoperative angiogram showed good patency of the ulnar artery after an average follow-up of 1 year., Conclusion: For the majority of plastic surgeons, this method provides a reliable and comfortable anastomosis when transferring a flap with small vessels. The only concern is to repair the donor artery carefully and ensure coverage of the repair site with local tissue., (Copyright © 2014 British Association of Plastic, Reconstructive and Aesthetic Surgeons. Published by Elsevier Ltd. All rights reserved.)

Adipose tissue-derived microvascular fragments represent promising vascularisation units for implanted tissue constructs. However, their reassembly into functional microvascular networks takes several days, during which the cells inside the implants are exposed to hypoxia. In the present study, we analysed whether this critical phase may be overcome by pre-cultivation of fragment-seeded scaffolds prior to their implantation. Green fluorescent protein (GFP)-positive microvascular fragments were isolated from epididymal fat pads of male C57BL/6-TgN (ACTB-EGFP) 1Osb/J mice. Nano-size hydroxyapatite particles/poly (ester-urethane) scaffolds were seeded with these fragments and cultivated for 28 days. Subsequently, these scaffolds or control scaffolds, which were freshly seeded with GFP-positive microvascular fragments, were implanted into the dorsal skinfold chamber of C57BL/6 wild-type mice to study their vascularisation and incorporation by means of intravital fluorescence microscopy, histology and immunohistochemistry over 2 weeks. Pre-cultivation of microvascular fragments resulted in the loss of their native vessel morphology. Accordingly, pre-cultivated scaffolds contained a network of individual CD31/GFP-positive endothelial cells with filigrane cell protuberances. After implantation into the dorsal skinfold chamber, these scaffolds exhibited an impaired vascularisation, as indicated by a significantly reduced functional microvessel density and lower fraction of GFP-positive microvessels in their centre when compared to freshly seeded control implants. This was associated with a deteriorated incorporation into the surrounding host tissue. These findings indicate that freshly isolated, non-cultivated microvascular fragments should be preferred as vascularisation units. This would also facilitate their use in clinical practice during intra-operative one-step procedures.