The V-Y Latissimus Dorsi Musculocutaneous Flap in the Reconstruction of Large Posterior Chest Wall Defects

Posterior chest wall defects are frequently encountered after excision of tumors as a result of trauma or in the setting of wound dehiscence after spine surgery. Various pedicled fasciocutaneous and musculocutaneous flaps have been described for the coverage of these wounds. The advent of perforator flaps has allowed the preservation of muscle function but their bulk is limited. Musculocutaneous flaps remain widely employed. The trapezius and the latissimus dorsi (LD) flaps have been used extensively for upper and middle posterior chest wounds, respectively. Their bulk allows for obliteration of the dead space in deep wounds. The average width of the LD skin paddle is limited to 10-12cm if closure of the donor site is expected without skin grafting. In 2001 a modification of the skin paddle design was introduced in order to allow large flaps to be raised without requiring grafts or flaps for donor site closure. This V-Y pattern allows coverage of large anterior chest defects after mastectomy. We have modified this flap to allow its use for posterior chest wall defects. We describe the flap design, its indications, and its limitations with three clinical cases. Level of Evidence V This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors at www.springer.com/0026

Efficient decellularization of equine tendon with preserved biomechanical properties and cytocompatibility for human tendon surgery indications.

Chronic and acute tendon injuries are frequent afflictions, for which treatment is often long and unsatisfactory. When facing extended injuries, matrices and scaffolds with sufficient biomechanical properties are required for surgical repair and could additionally serve as supports for cellular therapies to improve healing. In this study, protocols of either commonly used detergents only (SDS 1%, Triton 1%, TBP 1%, and Tween-20 1%) or a combination of freeze/thaw (F/T) cycles with decellularization agents (NaCl 1M, ddH <sub>2</sub> O) were evaluated for the decellularization of horse equine superficial digital flexor tendon (SDFT) for hand flexor or extensor tendon reconstruction. Decellularization efficiency was assessed microscopically by histological staining (HE, DAPI) and DNA quantification. Macroscopical structure and biomechanical integrity of the tendon matrices were further assessed by gross observation, histological staining (SR), and mechanical testing (ultimate strain and stress, Young's modulus, energy to failure) for select protocols. Decellularization with hypertonic NaCl 1M in association with F/T cycles produced the most robust tendon matrices, which were nontoxic after 10 days for subsequent recellularization with human fetal progenitor tendon cells (hFPTs). This standardized protocol uses a less aggressive decellularization agent than current practice, which allows subsequent reseeding with allogenic cells, therefore making them very suitable and bioengineered tendon matrices for human tendon reconstruction in the clinic

Cell therapies for skin regeneration: an overview of 40 years of experience in burn units.

The earliest attempts at cell therapy can be attributed to Charles-Edward Brown-Séquard (1817–1894), who sought to treat senescence and aging by injecting animal gonad shreds into his contemporaries, a practice that was widespread in late 19th century. Since then, advances in science have enabled the development of biological substitutes to restore the function of various tissues. Skin was one of the first tissues to be regenerated. For severe burns, patient survival depends on the restoration of skin function as a barrier against pathogens and control of body temperature and fluid loss. We aim here to overview the different cell therapy techniques implemented at the University Hospital of Lausanne (CHUV), one of the two Swiss national centres of highly specialised medicine for burn care. In particular, we will describe the specific indications for each of the different therapies as well as future perspectives

Free Versus Pedicled Anterolateral Thigh Flap for Abdominal Wall Reconstruction.

Large full thickness abdominal wall defects following malignancies can be a reconstructive challenge. The purpose of this study was to analyze long-term outcomes and complications following abdominal wall reconstruction using composite antero-lateral thigh (ALT) flaps. The study retrospectively investigated 16 consecutive patients who underwent abdominal wall reconstruction with autologous flap between May 2003 and March 2018. Volumetric flap analysis was used to assess flap atrophy over time, evaluating the role of denervation and reinnervation. The long-term outcome was assessed to compare the two groups (free vs. pedicled ALT flap reconstructions). All flaps successfully covered the defects. We found a significant increase in flap resorption in free flaps when compared to pedicled ones. Abdominal bulging was seen in 3 out of 16 (19%) patients after more than 12 months follow-up, in close correlation with mesh absence. Free flaps were shown to be equally effective as their pedicled counterparts, without significant increase in complication rate

Optimized Manufacture of Lyophilized Dermal Fibroblasts for Next-Generation Off-the-Shelf Progenitor Biological Bandages in Topical Post-Burn Regenerative Medicine.

Cultured fibroblast progenitor cells (FPC) have been studied in Swiss translational regenerative medicine for over two decades, wherein clinical experience was gathered for safely managing burns and refractory cutaneous ulcers. Inherent FPC advantages include high robustness, optimal adaptability to industrial manufacture, and potential for effective repair stimulation of wounded tissues. Major technical bottlenecks in cell therapy development comprise sustainability, stability, and logistics of biological material sources. Herein, we report stringently optimized and up-scaled processing (i.e., cell biobanking and stabilization by lyophilization) of dermal FPCs, with the objective of addressing potential cell source sustainability and stability issues with regard to active substance manufacturing in cutaneous regenerative medicine. Firstly, multi-tiered FPC banking was optimized in terms of overall quality and efficiency by benchmarking key reagents (e.g., medium supplement source, dissociation reagent), consumables (e.g., culture vessels), and technical specifications. Therein, fetal bovine serum batch identity and culture vessel surface were confirmed, among other parameters, to largely impact harvest cell yields. Secondly, FPC stabilization by lyophilization was undertaken and shown to maintain critical functions for devitalized cells in vitro, potentially enabling high logistical gains. Overall, this study provides the technical basis for the elaboration of next-generation off-the-shelf topical regenerative medicine therapeutic products for wound healing and post-burn care

Bio-Enhanced Neoligaments Graft Bearing FE002 Primary Progenitor Tenocytes: Allogeneic Tissue Engineering & Surgical Proofs-of-Concept for Hand Ligament Regenerative Medicine.

Hand tendon/ligament structural ruptures (tears, lacerations) often require surgical reconstruction and grafting, for the restauration of finger mechanical functions. Clinical-grade human primary progenitor tenocytes (FE002 cryopreserved progenitor cell source) have been previously proposed for diversified therapeutic uses within allogeneic tissue engineering and regenerative medicine applications. The aim of this study was to establish bioengineering and surgical proofs-of-concept for an artificial graft (Neoligaments Infinity-Lock 3 device) bearing cultured and viable FE002 primary progenitor tenocytes. Technical optimization and in vitro validation work showed that the combined preparations could be rapidly obtained (dynamic cell seeding of 10 <sup>5</sup> cells/cm of scaffold, 7 days of co-culture). The studied standardized transplants presented homogeneous cellular colonization in vitro (cellular alignment/coating along the scaffold fibers) and other critical functional attributes (tendon extracellular matrix component such as collagen I and aggrecan synthesis/deposition along the scaffold fibers). Notably, major safety- and functionality-related parameters/attributes of the FE002 cells/finished combination products were compiled and set forth (telomerase activity, adhesion and biological coating potentials). A two-part human cadaveric study enabled to establish clinical protocols for hand ligament cell-assisted surgery (ligamento-suspension plasty after trapeziectomy, thumb metacarpo-phalangeal ulnar collateral ligamentoplasty). Importantly, the aggregated experimental results clearly confirmed that functional and clinically usable allogeneic cell-scaffold combination products could be rapidly and robustly prepared for bio-enhanced hand ligament reconstruction. Major advantages of the considered bioengineered graft were discussed in light of existing clinical protocols based on autologous tenocyte transplantation. Overall, this study established proofs-of-concept for the translational development of a functional tissue engineering protocol in allogeneic musculoskeletal regenerative medicine, in view of a pilot clinical trial

Burn Center Organization and Cellular Therapy Integration: Managing Risks and Costs.

The complex management of severe burn victims requires an integrative collaboration of multidisciplinary specialists in order to ensure quality and excellence in healthcare. This multidisciplinary care has quickly led to the integration of cell therapies in clinical care of burn patients. Specific advances in cellular therapy together with medical care have allowed for rapid treatment, shorter residence in hospitals and intensive care units, shorter durations of mechanical ventilation, lower complications and surgery interventions, and decreasing mortality rates. However, naturally fluctuating patient admission rates increase pressure toward optimized resource utilization. Besides, European translational developments of cellular therapies currently face potentially jeopardizing challenges on the policy front. The aim of the present work is to provide key considerations in burn care with focus on architectural and organizational aspects of burn centers, management of cellular therapy products, and guidelines in evolving restrictive regulations relative to standardized cell therapies. Thus, based on our experience, we present herein integrated management of risks and costs for preserving and optimizing clinical care and cellular therapies for patients in dire need

The p21-Dependent Radiosensitization of Human Breast Cancer Cells by MLN4924, an Investigational Inhibitor of NEDD8 Activating Enzyme

Radiotherapy is a treatment choice for local control of breast cancer. However, intrinsic radioresistance of cancer cells limits therapeutic efficacy. We have recently validated that SCF (SKP1, Cullins, and F-box protein) E3 ubiquitin ligase is an attractive radiosensitizing target. Here we tested our hypothesis that MLN4924, a newly discovered investigational small molecule inhibitor of NAE (NEDD8 Activating Enzyme) that inactivates SCF E3 ligase, could act as a novel radiosensitizing agent in breast cancer cells. Indeed, we found that MLN4924 effectively inhibited cullin neddylation, and sensitized breast cancer cells to radiation with a sensitivity enhancement ratio (SER) of 1.75 for SK-BR-3 cells and 1.32 for MCF7 cells, respectively. Mechanistically, MLN4924 significantly enhanced radiation-induced G2/M arrest in SK-BR-3 cells, but not in MCF7 cells at early time point, and enhanced radiation-induced apoptosis in both lines at later time point. However, blockage of apoptosis by Z-VAD failed to abrogate MLN4924 radiosensitization, suggesting that apoptosis was not causally related. We further showed that MLN4924 failed to enhance radiation-induced DNA damage response, but did cause minor delay in DNA damage repair. Among a number of tested SCF E3 substrates known to regulate growth arrest, apoptosis and DNA damage response, p21 was the only one showing an enhanced accumulation in MLN4924-radiation combination group, as compared to the single treatment groups. Importantly, p21 knockdown via siRNA partialy inhibited MLN4924-induced G2/M arrest and radiosensitization, indicating a causal role played by p21. Our study suggested that MLN4924 could be further developed as a novel class of radiosensitizer for the treatment of breast cancer

Cancer Biomarker Discovery: The Entropic Hallmark

Background: It is a commonly accepted belief that cancer cells modify their transcriptional state during the progression of the disease. We propose that the progression of cancer cells towards malignant phenotypes can be efficiently tracked using high-throughput technologies that follow the gradual changes observed in the gene expression profiles by employing Shannon's mathematical theory of communication. Methods based on Information Theory can then quantify the divergence of cancer cells' transcriptional profiles from those of normally appearing cells of the originating tissues. The relevance of the proposed methods can be evaluated using microarray datasets available in the public domain but the method is in principle applicable to other high-throughput methods. Methodology/Principal Findings: Using melanoma and prostate cancer datasets we illustrate how it is possible to employ Shannon Entropy and the Jensen-Shannon divergence to trace the transcriptional changes progression of the disease. We establish how the variations of these two measures correlate with established biomarkers of cancer progression. The Information Theory measures allow us to identify novel biomarkers for both progressive and relatively more sudden transcriptional changes leading to malignant phenotypes. At the same time, the methodology was able to validate a large number of genes and processes that seem to be implicated in the progression of melanoma and prostate cancer. Conclusions/Significance: We thus present a quantitative guiding rule, a new unifying hallmark of cancer: the cancer cell's transcriptome changes lead to measurable observed transitions of Normalized Shannon Entropy values (as measured by high-throughput technologies). At the same time, tumor cells increment their divergence from the normal tissue profile increasing their disorder via creation of states that we might not directly measure. This unifying hallmark allows, via the the Jensen-Shannon divergence, to identify the arrow of time of the processes from the gene expression profiles, and helps to map the phenotypical and molecular hallmarks of specific cancer subtypes. The deep mathematical basis of the approach allows us to suggest that this principle is, hopefully, of general applicability for other diseases

Exponential stability of dynamic equations on time scales

We investigate the exponential stability of the zero solution to a system of dynamic equations on time scales. We do this by defining appropriate Lyapunov-type functions and then formulate certain inequalities on these functions. Several examples are given