Radu Olariu

A single localized dose of enzyme-responsive hydrogel improves long-term survival of a vascularized composite allograft

Tacrolimus-encapsulated hydrogels improve long-term survival of a vascularized composite allograft. A Leg Up for Transplant A one-shot delivery can enhance transplant survival in rats. Gajanayake et al. report that tacrolimus-encapsulated hydrogels improve long-term survival of a vascularized composite allograft (VCA). VCA is a promising alternative to reconstructive surgery or prosthesis use. However, transplant recipients must undergo systemic long-term immunosuppression, which increases their susceptibility to infection, kidney disease, and certain cancers. The authors encapsulated the immunosuppressive tacrolimus in a hydrogel composed of a material FDA classified as generally recognized as safe that was degraded by inflammatory enzymes. The tacrolimus-laden hydrogel increased graft survival time with one injection in a rat hindlimb transplant model. If reproduced in people, this delivery method could increase patient compliance and potentially decrease toxicity in transplant recipients. Currently, systemic immunosuppression is used in vascularized composite allotransplantation (VCA). This treatment has considerable side effects and reduces the quality of life of VCA recipients. We loaded the immunosuppressive drug tacrolimus into a self-assembled hydrogel, which releases the drug in response to proteolytic enzymes that are overexpressed during inflammation. A one-time local injection of the tacrolimus-laden hydrogel significantly prolonged graft survival in a Brown Norway–to–Lewis rat hindlimb transplantation model, leading to a median graft survival of >100 days compared to 33.5 days in tacrolimus only–treated recipients. Control groups with no treatment or hydrogel only showed a graft survival of 11 days. Histopathological evaluation, including anti-graft antibodies and complement C3, revealed significantly reduced immune responses in the tacrolimus-hydrogel group compared with tacrolimus only. In conclusion, a single-dose local injection of an enzyme-responsive tacrolimus-hydrogel is capable of preventing VCA rejection for >100 days in a rat model and may offer a new approach for immunosuppression in VCA.

Development and Implementation of a Web-Enabled 3D Consultation Tool for Breast Augmentation Surgery Based on 3D-Image Reconstruction of 2D Pictures

Background Producing a rich, personalized Web-based consultation tool for plastic surgeons and patients is challenging. Objective (1) To develop a computer tool that allows individual reconstruction and simulation of 3-dimensional (3D) soft tissue from ordinary digital photos of breasts, (2) to implement a Web-based, worldwide-accessible preoperative surgical planning platform for plastic surgeons, and (3) to validate this tool through a quality control analysis by comparing 3D laser scans of the patients with the 3D reconstructions with this tool from original 2-dimensional (2D) pictures of the same patients. Methods The proposed system uses well-established 2D digital photos for reconstruction into a 3D torso, which is then available to the user for interactive planning. The simulation is performed on dedicated servers, accessible via Internet. It allows the surgeon, together with the patient, to previsualize the impact of the proposed breast augmentation directly during the consultation before a surgery is decided upon. We retrospectively conduced a quality control assessment of available anonymized pre- and postoperative 2D digital photographs of patients undergoing breast augmentation procedures. The method presented above was used to reconstruct 3D pictures from 2D digital pictures. We used a laser scanner capable of generating a highly accurate surface model of the patient’s anatomy to acquire ground truth data. The quality of the computed 3D reconstructions was compared with the ground truth data used to perform both qualitative and quantitative evaluations. Results We evaluated the system on 11 clinical cases for surface reconstructions and 4 clinical cases of postoperative simulations, using laser surface scan technologies showing a mean reconstruction error between 2 and 4 mm and a maximum outlier error of 16 mm. Qualitative and quantitative analyses from plastic surgeons demonstrate the potential of these new emerging technologies. Conclusions We tested our tool for 3D, Web-based, patient-specific consultation in the clinical scenario of breast augmentation. This example shows that the current state of development allows for creation of responsive and effective Web-based, 3D medical tools, even with highly complex and time-consuming computation, by off-loading them to a dedicated high-performance data center. The efficient combination of advanced technologies, based on analysis and understanding of human anatomy and physiology, will allow the development of further Web-based reconstruction and predictive interfaces at different scales of the human body. The consultation tool presented herein exemplifies the potential of combining advancements in the core areas of computer science and biomedical engineering with the evolving areas of Web technologies. We are confident that future developments based on a multidisciplinary approach will further pave the way toward personalized Web-enabled medicine.

“Dinosaur spine” in ankylosing spondylitis: case illustration

An 89-year old man with known ankylosing spondylitis (AS) had undergone ventral corpectomy, implantation of a PEEK (polyetheretherketone) cage, and ventral fusion after suffering a dislocated compression fracture of C-7 (Fig. 1A); stabilization was subsequently achieved by dorsal C5–6 and T1–2 fusion (Fig. 1B). The patient had no neurological deficits. Eighteen months later the man presented with massive atrophy of paraspinal muscles and protrusion of spinous processes (Fig. 1C and D). Open resection of the C-7, T-1, and T-2 spinous processes was performed. The overlying skin and atrophic scar tissue were removed (Fig. 1E and F). Adaptation to the bone of paraspinal muscles was not possible due to atrophy. Six weeks after surgery, efficient wound healing was observed (Fig. 1G). Satisfactory cosmesis was achieved, and no infection developed. Neither complications of wound healing nor related to the fracture occurred within the 6-month follow-up period. The patient died 8 months after surgery, with no causal relation between the procedure and death. Atrophic changes leading to paraspinal muscle fibrosis in AS1 appeared to arise from disuse of or neurogenic damage to the posterior branches of the spinal nerves due to bony facet joint encroachment in the neural foramina. This patient with an AS-induced rigid spine had extreme atrophy of the paraspinal muscles that led to direct mechanical exposure of spinous processes. We describe a safe and simple surgical approach—so far lacking in the literature—that prevents potential complications due to wound perforation or skin infection. As ours was a single case, recommendations to prevent this condition are limited.

3D Face Reconstruction from Video Using 3D Morphable Model and Silhouette

Capitalizing on the advances of 3D face reconstruction from computer graphics and computer vision, this work presents a system to enable precise and robust 3D facial reconstruction from video in order to improve current approaches for doctor-patient communication tools. The reconstructed face can be used for emulation of aesthetic procedures in 3D. The proposed 3D face reconstruction algorithm uses a statistical shape model as well as information from facial landmarks and silhouette to iteratively model the face of a subject moving the face from front to left. The presented 3D active shape model approach enables the spatio-temporal tracking of facial landmarks and pose estimation based on a few initial facial landmarks defined in the first frame. Silhouette information extracted from key frames allows for better face reconstruction. The proposed methods were rigorously evaluated with experiments using real and artificial data. Results showed that the proposed method can detect facial landmarks with an approximate median error of 5% intraocular distance, can estimate pose with a median error below 5 degrees, and that silhouette information can improve reconstruction accuracy in all facial regions, specially on the cheeks.

Dimethyloxalylglycine stabilizes HIF-1α in cultured human endothelial cells and increases random-pattern skin flap survival in vivo.

Background: The goal of this study was to evaluate in vitro and in vivo the effects of up-regulation of the proangiogenic hypoxia inducible factor (HIF)-1&agr; induced by dimethyloxalylglycine on endothelial cell cultures and on skin flap survival. Methods: Human umbilical vein endothelial cell cultures were exposed to hypoxic conditions, to dimethyloxalylglycine, and to cobalt chloride for up to 24 hours. Expression of HIF-1&agr; and vascular endothelial growth factor (VEGF) in cell culture media was analyzed. In vivo, 20 male Wistar rats were assigned randomly to either the treatment group (dimethyloxalylglycine intraperitoneal injection, n = 10) or the control group (saline intraperitoneal injection, n = 10). A dorsal skin flap was raised in all animals and sutured back into place. Flap survival was evaluated on postoperative day 7 by laser Doppler and digital planimetry. Results: In vitro treatment of human umbilical vein endothelial cells during a 24-hour period showed a significant elevation of VEGF expression with dimethyloxalylglycine exposure (92 ± 35 pg/mg total cellular protein) or hypoxia exposure (88 ± 21 pg/mg total cellular protein) compared with controls (23 ± 10 pg/mg total cellular protein) (p < 0.05 for both). In vivo experiments showed a significant decrease of flap necrosis in the treatment group animals versus controls (35.95 ± 5.03 percent versus 44.42 ± 5.18 percent, p < 0.05). The laser Doppler evaluation revealed significantly increased blood flow in the proximal two-thirds of the flap in the treatment group compared with the control group (p < 0.05). Conclusion: Dimethyloxalylglycine treatment significantly increases VEGF and HIF-1&agr; expression in endothelial cell cultures and enhances skin flap survival in vivo in a rat model.

LONG-TERM RESULTS AFTER MUSCLE-RIB FLAP TRANSFER FOR RECONSTRUCTION OF COMPOSITE LIMB DEFECTS

The authors present the long‐term results in a series of 44 cases with post‐traumatic bone defects solved with muscle‐rib flaps, between March 1997 and December 2007. In these cases, we performed 21 serratus anterior‐rib flaps (SA‐R), 10 latissimus dorsi‐rib flaps (LD‐R), and 13 LD‐SA‐R. The flaps were used in upper limb in 18 cases and in lower limb in 26 cases. With an overall immediate success rate of 95.4% (42 of 44 cases) and a primary bone union rate of 97.7% (43 of 44 cases), and despite the few partisans of this method, we consider that this procedure still remains very usefully for small and medium bone defects accompanied by large soft tissue defects.

Local injections of tacrolimus-loaded hydrogel reduce systemic immunosuppression-related toxicity in vascularized composite allotransplantation.

Background Routine application of vascularized composite allotransplantation is hampered by immunosuppression-related health comorbidities. To mitigate these, we developed an inflammation-responsive hydrogel for local immunosuppression. Here, we report on its long-term effect on graft survival, immunological, and toxicological impact. Methods Brown Norway-to-Lewis rat hindlimb transplantations were treated either systemically with daily injections of 1 mg/kg tacrolimus (TAC) or with subcutaneous intragraft injections of hydrogel containing 7 mg TAC, every 70 days. Animals were monitored for rejection or other pathology for 280 days. Systemic and graft TAC levels, regulatory T cells, and donor cell chimerism were measured periodically. At endpoint, markers for kidney, liver, and metabolic state were compared to naive age-matched rats. Results Both daily systemic TAC and subcutaneous intragraft TAC hydrogel at 70-day intervals were able to sustain graft survival longer than 280 days in 5 of 6 recipients. In the hydrogel group, 1 graft progressed to grade 3 rejection at postoperative day 149. In systemic TAC group, 1 animal was euthanized due to lymphoma on postoperative day 275. Hydrogel treatment provided stable graft and reduced systemic TAC levels, and a 4 times smaller total TAC dose compared with systemic immunosuppression. Hydrogel-treated animals showed preserved kidney function, absence of malignancies or opportunistic infections and increased hematopoietic chimerism compared with systemic immunosuppression. Conclusions Our findings demonstrate that localized immunosuppression with TAC hydrogel is a long-term safe and reliable treatment. It may reduce the burden of systemic immunosuppression in vascularized composite allotransplantation, potentially boosting the clinical application of this surgical intervention.

The influence of diabetes mellitus on survival of abdominal perforator flaps: an experimental study in rats with slowly induced diabetes mellitus.

BACKGROUND Lower limb ulcers are a major source of morbidity and mortality in diabetic patients. Surgical coverage of these wounds is fraught with a high complication rate. Although clinically perforator flaps lead to good results in diabetic patients, there is little experimental data to support this finding. METHODS A total of 60 Wistar rats were randomly assigned either to the diabetic (n = 30) or control (n = 30) group. Diabetes was induced by streptozotocin injection at 50 mg/kg body weight and was confirmed by blood glucose levels > 180 mg/dL preoperatively. In all rats, a cranial epigastric artery perforator flap was raised. At postoperative day 7, all flaps were raised, photographed by digital planimetry, and analyzed histologically. RESULTS Mean glycemic levels preoperatively were 207.8 ± 16 in the diabetic group and 82.8 ± 5.1 in the control group (p < 0.05). Ninety percent of the flaps survived completely in the control group, compared with 66.7% in the diabetic group (p < 0.05). The mean flap survival area was lower in the diabetic group (83.3 ± 16.5%) than in the control group (96 ± 4%). There were significantly more perioperative complications in the diabetic group (46.7%) than in the control group (16.7%), but these did not affect flap survival. Superficial ulceration appeared only in the diabetic group as a complication. CONCLUSION Perforator flaps can be successfully used for coverage of cutaneous defects in a rat diabetic model. These flaps show higher complication rates in diabetic versus nondiabetic animals; however, this complication rate has little influence on flap survival.

Local release of tacrolimus from hydrogel-based drug delivery system is controlled by inflammatory enzymes in vivo and can be monitored non-invasively using in vivo imaging.

Background Local drug delivery systems that adjust the release of immunosuppressive drug in response to the nature and intensity of inflammation represent a promising approach to reduce systemic immunosuppression and its side effects in allotransplantation. Here we aimed to demonstrate that release of tacrolimus from triglycerol monostearate hydrogel is inflammation-dependent in vivo. We further report that by loading the hydrogel with a near-infrared dye, it is possible to monitor drug release non-invasively in an in vivo model of vascularized composite allotransplantation. Materials and methods Inflammation was induced by local challenge with lipopolysaccharides in naïve rats 7 days after injection of tacrolimus-loaded hydrogel in the hind limb. Tacrolimus levels in blood and tissues were measured at selected time points. A near-infrared dye was encapsulated in the hydrogel together with tacrolimus in order to monitor hydrogel deposits and drug release in vitro and in vivo in a model of vascularized composite allotransplantation. Results Injection of lipopolysaccharides led to increased blood and skin tacrolimus levels (p = 0.0076, day 7 vs. day 12 in blood, and p = 0.0007 in treated limbs, 48 h after injection compared to controls). Moreover, lipopolysaccharides-injected animals had higher tacrolimus levels in treated limbs compared to contralateral limbs (p = 0.0003 for skin and p = 0.0053 for muscle). Imaging of hydrogel deposits and tacrolimus release was achieved by encapsulating near-infrared dye in the hydrogel for 160 days. The correlation of tacrolimus and near-infrared dye release from hydrogel was R2 = 0.6297 and R2 = 0.5619 in blood and grafts of transplanted animals respectively and R2 = 0.6066 in vitro. Conclusions Here we demonstrate the inflammation-responsiveness of a tacrolimus-loaded hydrogel in vivo. Moreover, we show that encapsulating a near-infrared dye in the hydrogel provides a reliable correlation of tacrolimus and dye release from the hydrogel, and an accessible non-invasive method for monitoring drug release from hydrogel deposits.

Biochemical re-programming of human dermal stem cells to neurons by increasing mitochondrial membrane potential

Stem cells are generally believed to contain a small number of mitochondria, thus accounting for their glycolytic phenotype. We demonstrate here, however, that despite an indispensable glucose dependency, human dermal stem cells (hDSCs) contain very numerous mitochondria. Interestingly, these stem cells segregate into two distinct subpopulations. One exhibits high, the other low-mitochondrial membrane potentials (Δψm). We have made the same observations with mouse neural stem cells (mNSCs) which serve here as a complementary model to hDSCs. Strikingly, pharmacologic inhibition of phosphoinositide 3-kinase (PI3K) increased the overall Δψm, decreased the dependency on glycolysis and led to formation of TUJ1 positive, electrophysiologically functional neuron-like cells in both mNSCs and hDSCs, even in the absence of any neuronal growth factors. Furthermore, of the two, it was the Δψm-high subpopulation which produced more mitochondrial reactive oxygen species (ROS) and showed an enhanced neuronal differentiation capacity as compared to the Δψm-low subpopulation. These data suggest that the Δψm-low stem cells may function as the dormant stem cell population to sustain future neuronal differentiation by avoiding excessive ROS production. Thus, chemical modulation of PI3K activity, switching the metabotype of hDSCs to neurons, may have potential as an autologous transplantation strategy for neurodegenerative diseases.