Pietro G. di Summa

Effect of controlled co-delivery of synergistic neurotrophic factors on early nerve regeneration in rats

Present interventions to repair severed peripheral nerves provide slow and poor early axonal regeneration, which may cause unsatisfactory functional reinnervation. To improve early axonal regeneration in a 10 mm rat sciatic nerve gap model, we developed collagen nerve conduits loaded with the synergistically acting glial cell line-derived neurotrophic factor (GDNF) and nerve growth factor (NGF). For controlling the concomitant GDNF and NGF release, the collagen tubes were cross-linked by a dehydro-thermal treatment (110 degrees C; 20 mbar; 5 days) prior to impregnating the tubes with GDNF and NGF and by coating drug-loaded tubes with layers of poly(lactide-co-glycolide). The conduits made of cross-linked collagen released low initial amounts of GDNF and NGF (2% of both during first 3 days) and enhanced significantly the early (2 weeks) nerve regeneration in terms of axonal outgrowth and Schwann cell migration in a 10 mm rat sciatic nerve gap model, as compared to the conduits made of non-cross-linked collagen releasing higher initial amounts of GDNF and NGF (12-16% within 3 days), or those releasing GDNF alone. The enhancement of early axonal regeneration using controlled co-delivery of multiple synergistic neurotrophic factors is an important requisite for eventually establishing functional connections with the target organ.

Collagen (NeuraGen®) nerve conduits and stem cells for peripheral nerve gap repair

Collagen nerve guides are used clinically for peripheral nerve defects, but their use is generally limited to lesions up to 3 cm. In this study we combined collagen conduits with cells as an alternative strategy to support nerve regeneration over longer gaps. In vitro cell adherence to collagen conduits (NeuraGen(®) nerve guides) was assessed by scanning electron microscopy. For in vivo experiments, conduits were seeded with either Schwann cells (SC), SC-like differentiated bone marrow-derived mesenchymal stem cells (dMSC), SC-like differentiated adipose-derived stem cells (dASC) or left empty (control group), conduits were used to bridge a 1cm gap in the rat sciatic nerve and after 2-weeks immunohistochemical analysis was performed to assess axonal regeneration and SC infiltration. The regenerative cells showed good adherence to the collagen walls. Primary SC showed significant improvement in distal stump sprouting. No significant differences in proximal regeneration distances were noticed among experimental groups. dMSC and dASC-loaded conduits showed a diffuse sprouting pattern, while SC-loaded showed an enhanced cone pattern and a typical sprouting along the conduits walls, suggesting an increased affinity for the collagen type I fibrillar structure. NeuraGen(®) guides showed high affinity of regenerative cells and could be used as efficient vehicle for cell delivery. However, surface modifications (e.g. with extracellular matrix molecule peptides) of NeuraGen(®) guides could be used in future tissue-engineering applications to better exploit the cell potential.

Harvest site influences the growth properties of adipose derived stem cells.

The therapeutic potential of adult stem cells may become a relevant option in clinical care in the future. In hand and plastic surgery, cell therapy might be used to enhance nerve regeneration and help surgeons and clinicians to repair debilitating nerve injuries. Adipose-derived stem cells (ASCs) are found in abundant quantities and can be harvested with a low morbidity. In order to define the optimal fat harvest location and detect any potential differences in ASC proliferation properties, we compared biopsies from different anatomical sites (inguinal, flank, pericardiac, omentum, neck) in Sprague–Dawley rats. ASCs were expanded from each biopsy and a proliferation assay using different mitogenic factors, basic fibroblast growth factor (bFGF) and platelet-derived growth factor (PDGF) was performed. Our results show that when compared with the pericardiac region, cells isolated from the inguinal, flank, omental and neck regions grow significantly better in growth medium alone. bFGF significantly enhanced the growth rate of ASCs isolated from all regions except the omentum. PDGF had minimal effect on ASC proliferation rate but increases the growth of ASCs from the neck region. Analysis of all the data suggests that ASCs from the neck region may be the ideal stem cell sources for tissue engineering approaches for the regeneration of nervous tissue.

Extracellular matrix components in peripheral nerve repair: how to affect neural cellular response and nerve regeneration?

Peripheral nerve injury is a serious problem affecting significantly patients’ life. Autografts are the “gold standard” used to repair the injury gap, however, only 50% of patients fully recover from the trauma. Artificial conduits are a valid alternative to repairing peripheral nerve. They aim at confining the nerve environment throughout the regeneration process, and providing guidance to axon outgrowth. Biocompatible materials have been carefully designed to reduce inflammation and scar tissue formation, but modifications of the inner lumen are still required in order to optimise the scaffolds. Biomicking the native neural tissue with extracellular matrix fillers or coatings showed great promises in repairing longer gaps and extending cell survival. In addition, extracellular matrix molecules provide a platform to further bind growth factors that can be released in the system over time. Alternatively, conduit fillers can be used for cell transplantation at the injury site, reducing the lag time required for endogenous Schwann cells to proliferate and take part in the regeneration process. This review provides an overview on the importance of extracellular matrix molecules in peripheral nerve repair.

Peripheral Nerve Repair: Multimodal Comparison of the Long-Term Regenerative Potential of Adipose Tissue-Derived Cells in a Biodegradable Conduit

Tissue engineering is a popular topic in peripheral nerve repair. Combining a nerve conduit with supporting adipose-derived cells could offer an opportunity to prevent time-consuming Schwann cell culture or the use of an autograft with its donor site morbidity and eventually improve clinical outcome. The aim of this study was to provide a broad overview over promising transplantable cells under equal experimental conditions over a long-term period. A 10-mm gap in the sciatic nerve of female Sprague-Dawley rats (7 groups of 7 animals, 8 weeks old) was bridged through a biodegradable fibrin conduit filled with rat adipose-derived stem cells (rASCs), differentiated rASCs (drASCs), human (h)ASCs from the superficial and deep abdominal layer, human stromal vascular fraction (SVF), or rat Schwann cells, respectively. As a control, we resutured a nerve segment as an autograft. Long-term evaluation was carried out after 12 weeks comprising walking track, morphometric, and MRI analyses. The sciatic functional index was calculated. Cross sections of the nerve, proximal, distal, and in between the two sutures, were analyzed for re-/myelination and axon count. Gastrocnemius muscle weights were compared. MRI proved biodegradation of the conduit. Differentiated rat ASCs performed significantly better than undifferentiated rASCs with less muscle atrophy and superior functional results. Superficial hASCs supported regeneration better than deep hASCs, in line with published in vitro data. The best regeneration potential was achieved by the drASC group when compared with other adipose tissue-derived cells. Considering the ease of procedure from harvesting to transplanting, we conclude that comparison of promising cells for nerve regeneration revealed that particularly differentiated ASCs could be a clinically translatable route toward new methods to enhance peripheral nerve repair.

Fibrin sealant for fasciocutaneous flaps

Fibrin sealant is used in many areas of surgery. We present a novel aspect of flap insetting in the ischial region using fibrin spray to seal the transferred tissue. We analyzed 10 patients suffering from decubital ulcers and assessed drainage output, time of drain removal, as well as complications following fasciocutaneous flap surgery. Patients were randomized to receive sprayed fibrin glue (study group) or not (control group) before wound closure. The mean drainage time was 4 +/- 1 days in the study group and 6 +/- 1 days in the control group ( P = 0.06). The mean drainage volume was 100 +/- 20 mL in the study group and 168 +/- 30 mL in the control group ( P < 0.01). Fibrin sealant led to reduced drainage volumes and duration of drainage, indicating a beneficial effect of the application of fibrin glue in fasciocutaneous flap surgery for pressure sore coverage.

The Combined Pedicled Anterolateral Thigh and Vastus Lateralis Flap as Filler for Complex Perineal Defects.

AbstractExtensive defects of the pelvis and genitoperineal region are a reconstructive challenge. We discuss a consecutive series of 25 reconstructions with the pedicled anterolateral thigh (ALT) flap including muscle part of the vastus lateralis (VL) in 23 patients from October 1999 to September 2012.Only surface defects larger than 100 cm2 and reconstructions by composite ALT + VL were included in this retrospective analysis. Of the 23 patients, 19 underwent oncologic resection, whereas 4 cases presented Fournier gangrene. Three patients did not reach 6 months of follow-up and were excluded from further data analysis. Among the remaining 20 patients (22 reconstructions), average follow-up period was 14 months (range, 10–18 months). Patient’s average age was 60 years. Average size of the defect was 182 cm2.Postoperative complications included 1 (4.5%) flap necrosis out of 22 raised flaps, 1 partial flap necrosis after venous congestion, and 2 cases where a complementary reconstructive procedure was performed due to remaining defect or partial flap failure. In 6 cases, peripheral wound dehiscence (27%) was treated by debridement followed by split-thickness skin graft or advancement local flaps. Defect size was significantly related to postoperative complications and increased hospital stay, especially in those patients who underwent preoperative radiotherapy. At the end of the follow-up period, a long-term and satisfactory coverage was obtained in all patients without functional deficits.This consecutive series of composite ALT + VL flap shows that, in case of extended defects, the flap provides an excellent and adjustable muscle mass, is reliable with minimal donor-site morbidity, and can even be designed as a sensate flap.

The Unresolved Case of Sacral Chordoma: From Misdiagnosis to Challenging Surgery and Medical Therapy Resistance

Purpose A sacral chordoma is a rare, slow-growing, primary bone tumor, arising from embryonic notochordal remnants. Radical surgery is the only hope for cure. The aim of our present study is to analyse our experience with the challenging treatment of this rare tumor, to review current treatment modalities and to assess the outcome based on R status. Methods Eight patients were treated in our institution between 2001 and 2011. All patients were discussed by a multidisciplinary tumor board, and an en bloc surgical resection by posterior perineal access only or by combined anterior/posterior accesses was planned based on tumor extension. Results Seven patients underwent radical surgery, and one was treated by using local cryotherapy alone due to low performance status. Three misdiagnosed patients had primary surgery at another hospital with R1 margins. Reresection margins in our institution were R1 in two and R0 in one, and all three recurred. Four patients were primarily operated on at our institution and had en bloc surgery with R0 resection margins. One had local recurrence after 18 months. The overall morbidity rate was 86% (6/7 patients) and was mostly related to the perineal wound. Overall, 3 out of 7 resected patients were disease-free at a median follow-up of 2.9 years (range, 1.6-8.0 years). Conclusion Our experience confirms the importance of early correct diagnosis and of an R0 resection for a sacral chordoma invading pelvic structures. It is a rare disease that requires a challenging multidisciplinary treatment, which should ideally be performed in a tertiary referral center.

Propionibacterium avidum infection following breast reduction: high morbidity from a low-virulence pathogen

Propionibacterium avidum is a common inhabitant of sebaceous glands, traditionally considered to be of low virulence and generally found on implanted foreign material. We report a rare case of P. avidum breast abscess, causing severe morbidity following breast reduction surgery. A 36-year-old woman presented with a non-painful wound discharge 3 weeks postoperatively, and was treated conservatively. She was readmitted 7 weeks postoperatively with a red and tender breast. A purulent discharging abscess was drained under ultrasound guidance. A 2-week intravenous course of amoxicillin–clavulanic acid, followed by oral replacement for a month resulted effective. Serial ultrasound imaging was useful in treatment decision-making. The infective potential of P. avidum may be underappreciated. Proximity of sutures to the axilla, tobacco smoking and the potential for resorbable sutures to host bacteria may predispose to infection, and should raise the clinicians awareness.

Multidisciplinary approach of lumbo‐sacral chordoma: From oncological treatment to reconstructive surgery

Lumbo‐sacral chordoma is a rare, slow‐growing tumor, arising from embryonic nothocordal remnants. Wide en bloc excision with clear margins remains mandatory to achieve satisfactory recurrence rates and disease‐free survival. No chemotherapy has been demonstrated to be effective and radiotherapy is only marginally effective. Tyrosine kinase receptor inhibitors have showed encouraging results in locally advanced and metastatic chordoma. Reconstructive surgery may become very complex. Multidisciplinary approach in tertiary hospitals is always necessary. J. Surg. Oncol. 2015; 112:544–554.