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Surgical Angiogenesis in Porcine Tibial Allotransplantation: A New Large Animal Bone Vascularized Composite Allotransplantation Model

Segmental bone loss resulting from trauma, infection malignancy and congenital anomaly remains a major reconstructive challenge. Current therapeutic ...

Mayo Clinic

T-cell activation, particularly of CD8(+) cells, is invariably associated with viral infections. We now provide evidence for the activation of T cells in patients with localized bacterial soft tissue infections. During acute disease we detected in the peripheral blood of these patients, small though conspicuous populations of CD4(+) CD28(+) CD11b(+) and CD8(+) CD28(+) CD11b(+) cells, indicative of an expansion of effector T cells. Moreover, we identified CD4(+) and CD8(+) cells at the infected site, in addition to highly activated polymorphonuclear neutrophils (PMN). In keeping with their role as first-line defence, PMN were preponderant, but T cells amounted to 20% of the infiltrated cells. The majority of the infiltrated T cells expressed CXCR6, a homing receptor for non-lymphoid tissue. The infiltrated T cells produced interferon-gamma (IFN-gamma), while the peripheral blood cells obtained at the same time did not. In conclusion, in response to localized bacterial infections, T cells are activated and recruited to the infected site. We propose that these T cells, e.g. by producing IFN-gamma, enhance the efficiency of the infiltrated phagocytic cells, particularly of the PMN, thereby supporting the local host defence.

T lymphocytes in acute bacterial infection: increased prevalence of CD11b(+) cells in the peripheral blood and recruitment to the infected site.

T cell activation is invariably associated with virus infections, but activation of T cells is also noted, for example, in patients with persistent bacterial infections with intracellular pathogens or localised bacterial biofilms. The latter is characterised by a destructive inflammatory process. Massive infiltration of leukocytes, predominantly of polymorphonuclear neutrophils (PMNs) and of T lymphocytes, is seen. While PMN influx into sites of bacterial infection is in line with their role as "first-line defence" a role of T cells in bacterial infection has not yet been delineated. We now found evidence for activation and expansion of peripheral blood T cells and an upregulation of Toll-like receptors 1, 2, and 4 on small portions of T cells. T cells recovered from the infected site were terminally differentiated and produced interferon gamma, a cytokine known to enhance functions of phagocytic cells, leading to the conclusion that infiltrated T cells support the local immuner defence.

Activation of T Lymphocytes in Response to Persistent Bacterial Infection: Induction of CD11b and of Toll-Like Receptors on T Cells.

New very high-frequency ultrasound probes allow highly detailed imaging of superficial structures and thus are especially suitable for examination of the hand. For successful application, specific knowledge and experience as well as standardized examination techniques are required. Based on 11 determined sections of the flexor and extensor side of the hand, the authors present one approach to a standardized ultrasound examination allowing a quick view of all structures. An additional presentation of the most typical traumatic and degenerative disease patterns underlines the potency of this examination technique. With adequate equipment, training and expertise, ultrasound should be regarded as the first-line imaging modality for the assessment of a wide range of pathological conditions affecting the wrist and hand. An exact knowledge of the anatomical relation of the structures to each other gained from ultrasound experience is equally useful for following surgery of the cases.

Ultrasound in hand and wrist: approach for a standardized examination.

Biomechanical testing is an essential component of bone research. In order to test the metaphyseal region of long bones, a typical location for the nowadays increasing field of osteoporotic bone changes, three-point bending and breaking test devices are suitable and widely used. The aim of our study was to increase the effectiveness of this method by using a newly developed ball-mounted platform design. This new design eliminates the negative effects of friction, present in previous studies, caused by the lengthening of the distal tibia along its diaphyseal axis while sliding over the surface of a fixed aluminum block.

A novel device for resistance-free biomechanical testing of the metaphysis of long bones.

Current vascularized composite allotransplantation (VCA) transplantation protocols rely upon life-long immune modulation to maintain tissue perfusion. Alternatively, bone-only VCA viability may be maintained in small animal models using surgical angiogenesis from implanted autogenous vessels to develop a neoangiogenic bone circulation that will not be rejected. This study tests the method's efficacy in a large animal model as a bridge to clinical practice, quantifying the remodeling and mechanical properties of porcine tibial VCAs. A segmental tibial defect was reconstructed in Yucatan miniature swine by transplantation of a matched tibia segment from an immunologically mismatched donor. Microsurgical repair of nutrient vessels was performed in all pigs, with simultaneous intramedullary placement of an autogenous arteriovenous (AV) bundle in Group 2. Group 1 served as a no-angiogenesis control. All received 2 weeks of immunosuppression. After 16 weeks, micro-CT and histomorphometric analyses were used to evaluate healing and remodeling. Axial compression and nanoindentation studies evaluated bone mechanical properties. Micro-CT analysis demonstrated significantly more new bone formation and bone remodeling at the distal allotransplant/recipient junction and on the endosteal surfaces of Group 2 tibias (p = 0.03). Elastic modulus and hardness were not adversely affected by angiogenesis. The combination of 2 weeks of immunosuppression and autogenous AV-bundle implantation within a microsurgically transplanted tibial allotransplant permitted long-term allotransplant survival over the study period of 16 weeks in this large animal model. Angiogenesis increased bone formation and remodeling without adverse mechanical effects. The method may allow future composite-tissue allotransplantation of bone without the risks associated with long-term immunosuppression. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1242-1249, 2017.

Recipient-derived angiogenesis with short term immunosuppression increases bone remodeling in bone vascularized composite allotransplantation: A pilot study in a swine tibial defect model.

Three-dimensional (3D) high definition (HD) video systems are changing microsurgical practice by providing stereoscopic imaging not only for the surgeon and first assistant using the binocular microscope, but also for others involved in the surgery. The purpose of this study was to evaluate the potential to replace the binocular microscope for microarterial anastomoses and assess the rate of learning based on surgeons' experience. Two experienced and two novice microsurgeons performed a total of 88 rat femoral arterial anastomoses: 44 using a 3D HD video device ('Trenion', Carl Zeiss Meditech) and 44, a binocular microscope. We evaluated anastomosis time and modified OSATS scores as well as the subjects' preference for comfort, image adequacy and technical ease. Experienced microsurgeons showed a steep learning curve for anastomosis times with equivalent OSATS scores for both systems. However, prolonged anastomosis times were required when using the novel 3D-HD system rather than direct binocular vision. Comparable learning rates for anastomosis time were demonstrated for novice microsurgeons and modified OSATS scores did not differ between the different viewing technologies. All microsurgeons reported improved comfort for the 3D HD video system but found the image quality of the conventional microscope superior, facilitating technical ease. The present study demonstrates the potential of 3D HD video systems to replace current binocular microscopes, offering qualitatively-equivalent microvascular anastomosis with improved comfort for experienced microsurgeons. However, image quality was rated inferior with the 3D HD system resulting in prolonged anastomosis times. Microsurgical skill acquisition in novice microsurgeons was not influenced by the viewing system used.

The learning rate in three dimensional high definition video assisted microvascular anastomosis in a rat model.

Finger replantations demand technical excellence in microsurgery and hand trauma care. The objective of this study was to determine whether finger replantations constitute an appropriate and safe procedure for residency training. Additionally, the prognostic risk factors for the need to take a replanted finger back to the operation room and replant failure were analyzed.All patients who underwent finger replantation after complete amputation between 2007 and 2015 were included in a retrospective comparative study. These patients were either treated by an attending plastic surgeon (cohort 1) or by a postgraduate year 5 or 6 resident under supervision (cohort 2). Logistic regression analysis was used to identify the prognostic risk factors for emergent take backs and replant failures.A total of 109 completely amputated fingers were replanted in 89 patients. Fifty-seven digits were replanted in cohort 1, and 52 digits were replanted in cohort 2. Patient demographic data revealed an equal distribution between the two cohorts with an overall finger-replantation success rate of 67.0%. The prognostic risk factors related to increased take back and replant failure rates were fewer than two venous anastomoses (take back odds ratio [AOR], 0.27; confidence interval (CI), 0.12-0.63; and replant failure AOR, 0.21; 95% CI, 0.08-0.55) and intraoperative noticeable problems regarding the vascular anastomoses (take back AOR, 2.26; 95% CI, 0.96-5.33 and replant failure AOR, 2.45; 95% CI, 1.00-6.00). The type of surgeon did not exhibit an influence on the risk of take back (OR, 1.14; 95% CI, 0.53-2.41) or replant failure (OR, 1.03; 95% CI, 0.46-2.30). Similarly, after adjusting for all risk factors, the risks for take backs (AOR, 1.04; 95% CI, 0.46-2.36) and replant failures (AOR, 0.91; 95% CI, 0.38-2.19) did not differ between the 2 cohorts.Finger replantations can be applied as a safe procedure in residency training under standardized conditions and do not negatively affect quality of care. Technical proficiency in microsurgery and elective and trauma hand care as well as supervision by an experienced plastic or hand surgeon are mandatory. Regardless of the surgeons' experience, fewer than 2 venous anastomoses and the presence of intraoperative vascular anomalies represent significant prognostic risk factors for postoperative complications.

Safety and Suitability of Finger Replantations as a Residency Training Procedure: A Retrospective Cohort Study With Analysis of the Initial Postoperative Outcomes.

OBJECTIVE Commercially available processed nerve allografts have been shown to be inferior to autografts in previous animal studies. The authors hypothesized that combining different processing and storage techniques will result in improved nerve ultrastructure preservation, lower immunogenicity, and minimized cellular debris. Different processing protocols were evaluated using chemical detergents, enzymes, and irradiation, with the addition the of enzyme elastase, were used. Additionally, the difference between cold and frozen storage was investigated. The goal of this study was to create an optimized nerve allograft. METHODS Fifty rat nerves were decellularized with modifications of previous protocols and the addition of elastase. Subsequently, the nerve segments were stored at either 4°C or -80°C. Both processed and fresh control nerves were analyzed with confocal microscopy using immunohistochemical staining on the basal lamina (laminin γ-1), Schwann cells (S100 protein), and immunogenicity using major histocompatibility complex-I (MHCI) staining. Morphology of the ultrastructure and amount of cellular debris were analyzed on cross-sections of the nerves stained with toluidine blue and H & E, and by using electron microscopy. RESULTS Nerve ultrastructure was preserved with all decellularization protocols. Storage at -80°C severely altered nerve ultrastructure after any decellularization method. Elastase was found to significantly reduce the immunogenicity and amount of Schwann cells, while maintaining good structural properties. CONCLUSIONS Reduced immunogenicity, diminished cellular debris, and the elimination of Schwann cells was observed when elastase was added to the nerve processing while maintaining ultrastructure. Storage at -80°C after the decellularization process heavily damaged the nerve ultrastructure as compared with cold storage. Further in vivo studies are needed to prove the nerve regenerative capacity of these optimized allografts.

Article	Year
T lymphocytes in acute bacterial infection: increased prevalence of CD11b(+) cells in the peripheral blood and recruitment to the infected site. Immunology\| PubMed ID: 18479349	2008
Activation of T Lymphocytes in Response to Persistent Bacterial Infection: Induction of CD11b and of Toll-Like Receptors on T Cells. International journal of inflammation\| PubMed ID: 21151520	2010
Ultrasound in hand and wrist: approach for a standardized examination. Expert review of medical devices\| PubMed ID: 23895074	2013
A novel device for resistance-free biomechanical testing of the metaphysis of long bones. BMC musculoskeletal disorders\| PubMed ID: 25048639	2014
Recipient-derived angiogenesis with short term immunosuppression increases bone remodeling in bone vascularized composite allotransplantation: A pilot study in a swine tibial defect model. Journal of orthopaedic research : official publication of the Orthopaedic Research Society\| PubMed ID: 27471833	2017
The learning rate in three dimensional high definition video assisted microvascular anastomosis in a rat model. Journal of plastic, reconstructive & aesthetic surgery : JPRAS\| PubMed ID: 27650118	2016
Safety and Suitability of Finger Replantations as a Residency Training Procedure: A Retrospective Cohort Study With Analysis of the Initial Postoperative Outcomes. Annals of plastic surgery\| PubMed ID: 27893542	2017
Optimizing decellularization techniques to create a new nerve allograft: an in vitro study using rodent nerve segments. Neurosurgical focus\| PubMed ID: 28245670	2017

Dimitra Kotsougiani

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