Decellularized Whole-Organ Pre-vascularization: A Novel Approach for Organogenesis

Introduction: Whole-organ decellularization is an attractive approach for three-dimensional (3D) organ engineering. However, progress with this approach is hindered by intra-vascular blood coagulation that occurs after in vivo implantation of the re-cellularized scaffold, resulting in a short-term graft survival. In this study, we explored an alternative approach for 3D organ engineering through an axial pre-vascularization approach and examined its suitability for pancreatic islet transplantation.

Methods: Whole livers from male Lewis rats were decellularized through sequential arterial perfusion of detergents. The decellularized liver scaffold was implanted into Lewis rats, and an arteriovenous bundle was passed through the scaffold. At the time of implantation, fresh bone marrow preparation (BM; n = 3), adipose-derived stem cells (ADSCs; n = 4), or HBSS (n = 4) was injected into the scaffold through the portal vein. After 5 weeks, around 2,600 islet equivalents (IEQs) were injected through the portal vein of the scaffold. The recipient rats were rendered diabetic by the injection of 65 mg/kg STZ intravenously 1 week before islet transplantation and were followed up after transplantation by measuring the blood glucose and body weight for 30 days. Intravenous glucose tolerance test was performed in the cured animals, and samples were collected for immunohistochemical (IHC) analyses. Micro-computed tomography (CT) images were obtained from one rat in each group for representation.

Results: Two rats in the BM group and one in the ADSC group showed normalization of blood glucose levels, while one rat from each group showed partial correction of blood glucose levels. In contrast, no rats were cured in the HBSS group. Micro-CT showed evidence of sprouting from the arteriovenous bundle inside the scaffold. IHC analyses showed insulin-positive cells in all three groups. The number of von-Willebrand factor-positive cells in the islet region was higher in the BM and ADSC groups than in the HBSS group. The number of 5-bromo-2′-deoxyuridine-positive cells was significantly lower in the BM group than in the other two groups.

Conclusions: Despite the limited numbers, the study showed the promising potential of the pre-vascularized whole-organ scaffold as a novel approach for islet transplantation. Both BM- and ADSCs-seeded scaffolds were superior to the acellular scaffold.

Disfiguring high-flow cervicofacial arteriovenous malformations

Arteriovenous malformations (AVMs) are congenital vascular anomalies resulting from defects in angiogenesis. Approximately 40% of AVMs go undetected after birth and only experience the delayed clinical onset of symptoms in adulthood. AVMs are rare, representing only 1.5% of all vascular anomalies. The most common sites for the aberrant vascular nidus are the oral cavity and maxillofacial region, which represent 50% of the cases. AVMs are the most challenging and life-threatening form of vascular malformation. Exsanguination, thrombus detachment and embolization are the most hazardous operative risks. Small case series revealed a 75% recurrence rate during a 5-year follow-up, which adds another layer of complexity to their management. Large lesions in the head and neck cause deformation to the patient and present a challenge to the surgeon during their excision among vital structures and reconstruction of the 3D complex defects.

Rapid hepatic perfusion decellularization: technique and critique

BACKGROUND

Organ shortage facing the increasing success of liver transplantation has provoked research into the utilization of animal organs for clinical transplantation. The technique of whole-organ decellularization aims at the removal of the antigenic cellular content, thus evading the immune rejection cascade and the production of complex three-dimensional extracellular matrices of the entire organs with preservation of their intrinsic vascular networks rendering them transplantable. The aim of this study was the production of decellularized rabbit liver matrices by applying a simple, rapid perfusion decellularization technique and their characterization (both qualitatively and quantitatively).

MATERIALS AND METHODS

Decellularization of the caudate hepatic lobes of New Zealand white rabbits (n = 22) was achieved through sequential perfusion of the portal venous system with deionized water, 0.8% Triton X-100 and 0.8% sodium dodecyl sulphate (SDS). Decellularized specimens were characterized both qualitatively (histology, fluoroscopy, corrosion casting and scanning electron microscopy) and quantitatively (total collagen assay [colorimetric] and total DNA assay [Hoechst 33258]). A Student's t-test was used to compare quantitative laboratory results before and after decellularization. A probability (P) value of <0.05 was considered significant.

RESULTS

Effective decellularization was achieved as proven by histology and quantitative assessment (DNA remnants <1.5%, P = 0.0009), while preserving 68% of the total collagen content (P = 0.003). Portal vascular network integrity was confirmed by fluoroscopy and corrosion casting. Scanning electron microscopy also confirmed the preservation of the three-dimensional architecture.

CONCLUSIONS

Liver perfusion decellularization technique using both 0.8% Triton X-100 and 0.8% SDS is a simple and rapid technique, yielding efficiently decellularized liver matrices preserving their vascular integrity, 3D architecture and 68% of total collagen content.

The extended latissimus dorsi flap option in autologous breast reconstruction: A report of 14 cases and review of the literature

Background:

Autologous breast reconstruction using the extended latissimus dorsi flap has been infrequently reported. In the current study, the authors are reporting their own clinical experience with this method. A review of the literature is also discussed.

Materials and Methods:

Over a three year period, 14 patients underwent breast reconstruction using the extended latissimus dorsi (LD) flap. Patients with small to medium sized breasts were selected. The age of the patients ranged from 29 to 42 years with a follow-up period ranging from six to 18 months. The indications, flap-related complications and donor site morbidity and aesthetic results were evaluated.

Results:

The main indication to use the flap was dorsal donor site preference by patients. The remaining patients were either not suitable for a flap from the abdomen or wished to get pregnant and were offered the dorsal donor site. Neither total nor partial flap loss was recorded but donor site morbidity was mainly due to seroma, which was treated conservatively in all patients, except for one who required surgery. Another two patients suffered from wound breakdown and distal necrosis of the back flaps. Mild contour deformity was also noted on the back of all patients but caused no major concern. Indeed, the overall patient satisfaction was very high.

Conclusion:

The extended LD flap proved to be a good option for autologous breast reconstruction in selected patients. Patients should be warned of the potential for seroma and mild contour back deformity.

The extended latissimus dorsi flap option in autologous breast reconstruction: A report of 14 cases and review of the literature

Background: Autologous breast reconstruction using the extended latissimus dorsi flap has been infrequently reported. in the current study, the authors are reporting their own clinical experience with this method. a review of the literature is also discussed.Materials and methods: Over a three year period, 14 patients underwent breast reconstruction using the extended latissimus dorsi (ld) flap. patients with small to medium sized breasts were selected. the age of the patients ranged from 29 to 42 years with a follow-up period ranging from six to 18 months. the indications, flap-related complications and donor site morbidity and aesthetic results were evaluated.Results: The main indication to use the flap was dorsal donor site preference by patients. the remaining patients were either not suitable for a flap from the abdomen or wished to get pregnant and were offered the dorsal donor site. neither total nor partial flap loss was recorded but donor site morbidity was mainly due to seroma, which was treated conservatively in all patients, except for one who required surgery. another two patients suffered from wound breakdown and distal necrosis of the back flaps. mild contour deformity was also noted on the back of all patients but caused no major concern. indeed, the overall patient satisfaction was very high.Conclusion: The extended ld flap proved to be a good option for autologous breast reconstruction in selected patients. patients should be warned of the potential for seroma and mild contour back deformity.

Measurement of blood flow and oxygen tension in adjacent tissues in pedicled and free flap head and neck reconstruction

The purpose of this study was to evaluate blood flow and transcutaneous partial oxygen pressure (TcPO(2)) in adjacent tissues to free and pedicled flaps following reconstructive procedures used in conjunction with radical surgery for head and neck cancers. Fifty patients were included. Fourteen patients had reconstruction with pedicled flaps and 36 with free flaps. For each patient, TcPO(2) and laser Doppler flow measurements were taken at the center of the flap, in adjacent tissue, and in a corresponding contralateral site. Three laser Doppler measurements were performed at each site and a mean value recorded. All patients had undergone reconstruction up to 6 months prior to the time of the measurements. The collected data were analyzed using a Wilcoxon signed rank test. There were no statistically significant differences in partial oxygen tension or laser Doppler values between tissues adjacent to free compared to pedicled flaps. Although there is strong evidence to support that free flaps have improved blood flow and partial oxygen tension over pedicled flaps, further study is required to evaluate adjacent tissues. Flap choice may assist with alteration in blood flow in less favorable defects such as those in previously irradiated fields and those resulting from burn scars or chronic infections.

The effects of cisplatinum and vincristine on peripheral nerve regeneration

Current treatment modalities for extremity sarcoma often include tumor extirpation plus neoadjuvant therapy. Limb-sparing surgery may require reconstruction of critical nerve defects. Neurotoxic side effects from adjuvant chemotherapy have been reported and raise concerns regarding the effects of chemotherapy on nerve regeneration. In an attempt to define the effects of adjuvant chemotherapy on peripheral nerve regeneration, cisplatin and vincristine were administered to rats following isografting of the posterior tibial nerve. Parameters used to assess peripheral nerve regeneration included walking track analysis and histomorphology. Sixty 250-g Sprague-Dawley rats were randomly allocated into one of three treatment groups. Each animal underwent a 15-mm reversed interposition nerve isograft from 30 donor rats into the right posterior tibial nerve. Ten animals served as control. The remaining animals were divided into two groups of 25 animals each. One group received cisplatin (75 mg/m2) and the other group received vincristine (1 mg/m2). Chemotherapy was administered at 4-week cycles for a total of six cycles (24 weeks). Walking track analysis was performed monthly. Nerve specimens were harvested from the grafted segment and the distal posterior tibial nerve for histomorphology. Walking track analysis demonstrated no statistical difference in print length between the control and chemotherapeutic groups at the conclusion of the study. The number of axons per square millimeter and nerve fiber density were not statistically different between control and chemotherapeutic groups. In the rodent posterior tibial nerve model, postoperative adjuvant therapy does not significantly alter functional outcome in peripheral nerve regeneration. The practice of immediate nerve grafting after tumor extirpation, despite planned postoperative chemotherapy, is supported.

In vivo evaluation of poly(L-lactic acid) porous conduits for peripheral nerve regeneration

The present study provides in vivo trials of poly(L-lactic acid) (PLLA) as a porous biodegradable nerve conduit using a 10 mm sciatic nerve defect model in rats. The PLLA conduits, fabricated by an extrusion technique, had an inner diameter of 1.6 mm, an outer diameter of 3.2 mm, and a length of 12 mm. They were highly porous with an interconnected pore structure (of 83.5% porosity and 12.1 microm mean pore size). The conduits were interposed into the right sciatic nerve defect of Sprague Dawley rats using microsurgical techniques; nerve isografts served as controls. Walking track analysis was performed after conduit placement monthly through 16 weeks. At the conclusion of 6 and 16 weeks, sections from the isograft/conduit and distal nerve were harvested for histomorphometric analysis. The right gastrocnemius muscle was also harvested and its weight was determined. All conduits remained intact without breakage. Moreover, no conduit elongated during the 16 weeks of placement. Walking track analysis and gastrocnemius muscle weight demonstrated increasing regeneration over the 16 weeks in both the conduit and isograft control groups, with control values significantly greater. The nerve fiber density in the distal sciatic nerve for the PLLA conduits (0.16+/-0.07) was similar to that for the control isografts (0.19+/-0.05) at 16 weeks. The number of axons/mm2 in the distal sciatic nerve for the PLLA conduits was lower than that for the isografts (13 800+/-2500 vs. 10700+/-4700) at 16 weeks. The results for PLLA were significantly improved over those for 75:25 poly(DL-lactic-co-glycolic acid) of a previous study and suggest that PLLA porous conduits may serve as a scaffold for peripheral nerve regeneration.

The effects of preoperative irradiation on peripheral nerve regeneration

The purpose of this study was to evaluate the effects of preoperative external cobalt60 beam irradiation on nerve regeneration. Ninety 250-g male Sprague-Dawley rats were studied. Peripheral nerve regeneration was measured by walking track analysis and histomorphology of the proximal, grafted, and distal nerve segments. Ninety animals were randomly assigned to one of five treatment groups, receiving a total fractionated dose of 30, 50, 70, and 90 Gy. Each animal received a 15-mm interposition nerve graft into the right posterior tibial nerve 6 weeks following completion of radiation therapy. The left leg served as a control. The remaining 10 animals received a nerve isograft subjected to a single dose of 30 Gy prior to placement (group 5). Walking track analysis was performed monthly through 8 months. At the conclusion of 120 and 240 days, sections of the proximal, grafted, and distal nerve were harvested, stained, and examined histomorphologically. Evaluation of the print length index demonstrated no statistical difference between our previously established nonirradiated controls, the irradiated groups, and the irradiated isograft group (group 5). The total number of axons per square millimeter was significantly decreased in the distal segment of all irradiated groups when compared with the controls. No statistical difference in number of axons per square millimeter was noted in the irradiated isograft group. Furthermore, no statistical difference was noted in the nerve fiber density between the control group, the preoperative irradiated groups, or the irradiated isograft group (group 5). Despite the reduction in myelinated regenerating fibers, no reduction in function was observed as measured by walking track analysis. Thus, immediate reconstruction of peripheral nerve defects in the face of preoperative irradiation may not be contraindicated.