Panniculus Carnosus Research Articles

Optimal skin regeneration after full thickness thermal burn injury in the spiny mouse, Acomys cahirinus

The spiny mouse, Acomys cahirinus, shows remarkable regenerative abilities after excisional skin wounding by regrowing hair, sebaceous glands, smooth muscle, skeletal muscle and dermis without scarring. We have asked here whether this same regeneration can be seen after full thickness thermal burn injuries. Using a brass rod thermal injury model we show that in contrast to the lab mouse, Mus musculus, which forms a thick scar covered by a hairless epidermis, the spiny mouse regenerates all the tissues injured — skeletal muscle, dermis, hairs, sebaceous glands such that the skin is externally indistinguishable from its original appearance. Re-epithelialization is faster in Acomys than in Mus but ingression and proliferation of dermal fibroblasts is the same in both species. After 3 weeks the wound epithelium of Acomys has developed a covering of new hair follicles in contrast to Mus. The skeletal muscle of the panniculus carnosus in Mus shows some regeneration but it is incomplete and fibrotic whereas the Acomys muscle is replaced perfectly. There are differences in the macrophage profiles which invade the damaged tissues such as the absence of F4/80 or MOMA-2 +ve cells in Acomys which likely reflect different cytokine profiles resulting from the same injury in these two species.

Utility of Adipocyte Fractions in Fat Grafting in an Athymic Rat Model.

Multiple processing and handling methods of autologous fat yield to variations in graft retention and viability, which results in unpredictable clinical outcomes. This study aims to understand the skin effects of fat graft preparations that contain a varying ratio of free-lipid and stem-cell-bearing stromal vascular fractions (SVF). Lipoaspirates from consenting patients were processed into emulsified fat and then SVF and adipocyte fractions (free-lipid). SVF enriched with 0%, 5%, and 15% free-lipid were grafted along the dorsum of athymic rats. The xenografts were collected 45 days after grafting and then prepped for immunostaining. Xenografts resulted in viable tissue mass under the panniculus carnosus of rats as confirmed with human specific markers. A low percentage of human cells was also detected in the lower reticular dermis. Although grafts with SVF formed adipocytes of normal architecture, grafts formed with free-lipid alone resulted in large lipid vacuoles in varying sizes. Among graft preparations, SVF with 10% free-lipid resulted in much-developed adipocyte architecture with collagen and elastin. Compared with SVF alone grafts, SVF with free-lipid had higher CD44 expression, suggesting a localized immune response of adipocytes. Current studies suggest that SVF enriched with approximately 10% free-lipid provides the best conditions for fat graft differentiation into viable fat tissue formation as well as collagen and elastin production to provide mechanical support for overlaying skin in an athymic rat model. Additionally, application of this therapeutic modality in a simple clinical setting may offer a practical way to concentrate SVF with free-lipid in a small volume for the improvement of clinical defects.

Synergistic Effect of Copper-Containing Mesoporous Bioactive Glass Coating on Stimulating Vascularization of Porous Hydroxyapatite Orbital Implants in Rabbits

Rapid and complete vascularization of the porous orbital implants after enucleation is vital for reducing postoperative complications, such as exposure and infection. In this study, the porous hydroxyapatite (pHA) scaffolds modified with the mesoporous bioactive glass with and without adding copper (MBG, Cu-MBG) were prepared by sol-gel technique and followed by evaporation induced self-assembly (EISA) process. The macro-/microstructure analysis of the modified scaffolds (i.e., MBG/pHA, Cu-MBG/pHA) showed highly interconnected macropores, and unique mesoporous structures in the pore wall with higher surface area. A primary angiogenic test in a panniculus carnosus muscle model in rabbit indicated that the Cu-MBG coating was significantly beneficial for the vascularization in the porous architecture of the scaffolds in the early stage. These results suggest that the Cu-MBG modification provides a simple and effective strategy to endow favorable biological performances with pHA implants and greater potential for future application in orbit reconstruction.

Botulinum toxin A increases allograft tolerance in an experimental transplantation model: a preliminary study.

Identifying novel and safe immunosuppressants is of crucial importance. Recently, there have been several studies revealing that botulinum toxin A (BoTA) significantly alleviates ischemia–reperfusion injuries. Emerging evidence shows that ischemia–reperfusion injuries contribute to innate immune activation, promoting rejection, and inhibiting tolerance. Therefore, we hypothesized that a pretreatment with BoTA might decrease allograft rejection in a rat transplantation model. Twenty-four Lewis (LEW) rats were randomly assigned into two groups consisting of 12 rats each, depending on whether skin allograft was performed after pretreatment with BoTA (BoTA group) or with normal saline (control group). The experimental group was pretreated with a subcutaneous injection of BoTA (10 IU), while the control group was pretreated with normal saline 5 days prior to surgery. The donor Brown–Norway (BN) rat dorsal skin was subsequently grafted to the recipient LEW rats. The recipient wounds, measuring 2 cm × 2 cm, were made via dorsal skin excision through the panniculus carnosus. The donor skins of the same dimensions were obtained and transplanted on to the wounds and sutured with 4-0 nylon sutures. Mean graft survival time was measured in both groups. Quantitative reverse-transcriptase PCR and Western blotting were performed to evaluate the gene/protein expression of CD4 and VEGF. The mean graft survival time in the BoTA group was significantly longer than that of the control group (P=0.004). The relative mRNA and protein expression of CD4 was significantly lower in the BoTA group (P<0.001), while the relative mRNA and protein expression of VEGF was significantly higher in the BoTA group (P<0.001). In conclusion, our results show that BoTA prolongs the survival of skin allografts in a rat transplantation model.

A murine model of radiation-induced capsule-tissue reactions around smooth silicone implants

As the availability of breast reconstruction using implants is becoming widespread and many implant recipients undergo radiation therapy, there is an increasing interest in understanding the potential complications associated with capsule-tissue interactions in response to irradiation. Accordingly, our medical institution designed an animal experiment to investigate the effects of irradiation on capsular contracture. A total of 40 mice (C57BL6) were divided into four groups according to whether or not they received irradiation and the time from implantation to irradiation. After each mouse received a specially-fabricated, 1.5 cm semi-spherical silicone implant inserted into the area below the panniculus carnosus, half of the mice were irradiated using singe administration of a 10 Gy dose of radiation (6 MeV). Subsequently, data from gross inspection, histological analysis and immunohistochemical analysis were obtained at one and three months postoperatively and analyzed. Changes that occurred near the capsule led to the phenomenon of contracture subsequent to encapsulation. Our findings suggest that the inflammation reaction occurring near the implant becomes aggravated by ‘radiation toxicity’ and creates an environment conducive to capsular contracture. The present study demonstrated the process by which the complication of capsular contracture may occur during the treatment of human breast cancer via radiotherapy. These findings may serve as the basis for research and development of future treatments of capsular contracture.

Substance-P and transforming growth factor-β in chitosan microparticle-pluronic hydrogel accelerates regenerative wound repair of skin injury by local ionizing radiation.

Clinical irradiation therapy for cancer could increase the risk of localized wound complications. This study was conducted to evaluate the potential use of a chitosan microparticle-pluronic F127 (CSMP-PF) hydrogel complex containing bioactive molecules, substance P and transforming growth factor-β1, to regeneratively repair skin damaged by local ionizing radiation (IR). The BALB/c/bkl mice were locally irradiated to their limbs with a single 40Gy dose of Co-60 γ rays to induce a skin injury. The morphological characteristics of the chitosan microparticles were analysed by scanning electron microscopy. The amounts of bioactive molecules taken up and released by the CSMP-PF hydrogel complex were measured. Haematoxylin and eosin staining of IR-damaged skin showed acanthosis and hyperkeratosis in the epidermis; and damage to hair follicles/skin appendages and adipose tissue, as well as panniculus carnosus, in the dermis. Injection of the CSMP-PF hydrogel complex into IR-damaged skin resulted in skin repair, suggesting that the complex has potential for use in the regenerative repair of IR-damaged skin.

Skin regeneration with all accessory organs following ablation with irreversible electroporation.

Skin scar formation is a complex process that results in the formation of dense extracellular matrix (ECM) without normal skin appendages such as hair and glands. The absence of a scarless healing model in adult mammals prevents the development of successful therapies. We show that irreversible electroporation of skin drives its regeneration with all accessory organs in normal adult rats. Pulsed electric fields at 500 V, with 70 μs pulse duration and 1000 pulses delivered at 3 Hz, applied through two electrodes separated by 2 mm lead to massive cell death. However, the ECM architecture of the skin was preserved. Six months after the ablation, the epidermis, sebaceous glands, panniculus carnosus, hair follicles, microvasculature and arrector pili muscle were altogether re-formed in the entire ablated area. These results suggest a key role of the ECM architecture in the differentiation, migration and signalling of cells during scarless wound healing. Copyright © 2016 John Wiley & Sons, Ltd.

A Model of Free Tissue Transfer: The Rat Epigastric Free Flap

Free tissue transfer has been increasingly used in clinical practice since the 1970s, allowing reconstruction of complex and otherwise untreatable defects resulting from tumor extirpation, trauma, infections, malformations or burns. Free flaps are particularly useful for reconstructing highly complex anatomical regions, like those of the head and neck, the hand, the foot and the perineum. Moreover, basic and translational research in the area of free tissue transfer is of great clinical potential. Notwithstanding, surgical trainees and researchers are frequently deterred from using microsurgical models of tissue transfer, due to lack of information regarding the technical aspects involved in the operative procedures. The aim of this paper is to present the steps required to transfer a fasciocutaneous epigastric free flap to the neck in the rat. This flap is based on the superficial epigastric artery and vein, which originates from and drain into the femoral artery and vein, respectively. On average the caliber of the superficial epigastric vein is 0.6 to 0.8 mm, contrasting with the 0.3 to 0.5 mm of the superficial epigastric artery. Histologically, the flap is a composite block of tissues, containing skin (epidermis and dermis), a layer of fat tissue (panniculus adiposus), a layer of striated muscle (panniculus carnosus), and a layer of loose areolar tissue. Succinctly, the epigastric flap is raised on its pedicle vessels that are then anastomosed to the external jugular vein and to the carotid artery on the ventral surface of the rat's neck. According to our experience, this model guarantees the complete survival of approximately 70 to 80% of epigastric flaps transferred to the neck region. The flap can be evaluated whenever needed by visual inspection. Hence, the authors believe this is a good experimental model for microsurgical research and training.

A Model of Free Tissue Transfer: The Rat Epigastric Free Flap.

Free tissue transfer has been increasingly used in clinical practice since the 1970s, allowing reconstruction of complex and otherwise untreatable defects resulting from tumor extirpation, trauma, infections, malformations or burns. Free flaps are particularly useful for reconstructing highly complex anatomical regions, like those of the head and neck, the hand, the foot and the perineum. Moreover, basic and translational research in the area of free tissue transfer is of great clinical potential. Notwithstanding, surgical trainees and researchers are frequently deterred from using microsurgical models of tissue transfer, due to lack of information regarding the technical aspects involved in the operative procedures. The aim of this paper is to present the steps required to transfer a fasciocutaneous epigastric free flap to the neck in the rat.This flap is based on the superficial epigastric artery and vein, which originates from and drain into the femoral artery and vein, respectively. On average the caliber of the superficial epigastric vein is 0.6 to 0.8 mm, contrasting with the 0.3 to 0.5 mm of the superficial epigastric artery. Histologically, the flap is a composite block of tissues, containing skin (epidermis and dermis), a layer of fat tissue (panniculus adiposus), a layer of striated muscle (panniculus carnosus), and a layer of loose areolar tissue.Succinctly, the epigastric flap is raised on its pedicle vessels that are then anastomosed to the external jugular vein and to the carotid artery on the ventral surface of the rat's neck. According to our experience, this model guarantees the complete survival of approximately 70 to 80% of epigastric flaps transferred to the neck region. The flap can be evaluated whenever needed by visual inspection. Hence, the authors believe this is a good experimental model for microsurgical research and training.

Freeze-Dried Platelet Rich Plasma (PRP) Has Biological Activity in Acute Wound Healing of Animals, Inducing Significantly Angiogenesis

Background: Increasing prevalence of diabetes and obesity has registered a simultaneous increase in chronic wounds and defects in tissue repair. Recently PRP was described to be used in the treatment of chronic ulcers. PRP contains cytokines, chemokines and growth factors (GF) derived from platelets which induce molecular and cell mechanisms of natural wound healing. The possible use of GF derived from platelets, and the potential to prolong the shelf life of platelet concentrates, freeze-drying becomes one particularly suitable method to improve wound healing treatment. The use of lyophilized PRP appears to be interesting for greater convenience: only one blood collection, after hydration its soon ready for use, and also due to the highest concentration of bioactive molecules. This study aims to compare intra-lesional freeze-dried and fresh PRP for treatment of acute wound in a pre-clinic model.Methods: Fresh and freeze-dried PRP was prepared from two human platelet concentrate bags using double spin method. PRP characterization included platelet number and quantification of PDGF-AA, EGF, VEGF and TGF-β1 by Luminex (Millipore). Animal wound model was performed after shaving the dorsum of the rat, and a full-thickness excisional wound (1 cm2) was made to the level of the panniculus carnosus muscle. Thirty animals were divided according to the type o treatment in 3 groups: Fresh PRP (n=10), Freeze-dried PRP (FD-PRP) (n=10) and control saline (n=10). The animals received one perilesional application of 500 µL in the day of wound induction. The monitoring of wound closure was made through macroscopical analysis of wound size in days 3, 7 and 10 after wounding. Animals were sacrificed in the tenth day and the skin was removed for histology with hematoxilin-eosin and Masson´s Trichrome, and immunohistochemistry with α-actin smooth muscle for myofibroblasts and blood vessels, and quantified through image J.Results: The platelet number of PRP was 5714 x 103 cells / µL, presenting a high platelet recovery. The FD-PRP presented higher level of all GF when compared to fresh PRP from 1.64 to 3.72 folds. The application of PRP or FD-PRP did not induce significantly changes in wound healing kinetics compared to control during all evaluated days. The mean and standard deviation (SD) of area in D3 was 112.9 ± 16.6%, 107.9 ± 21.3 and 100.8 ± 30.2 for control, PRP and FD-PRP, respectively. In D7 it was 54.3 ± 28.9, 63.9 ± 22.8 and 61.6 ± 20.6 for control, PRP and FD-PRP, respectively. In D10 it was 9.9 ± 6.1, 13.9 ± 11.2, 7.7 ± 6.0 for control, PRP and FD-PRP, respectively. In immunohistochemistry of deep epidermis FD-PRP presented a significantly higher concentration of myofibroblasts in comparison with fresh PRP (16.61 ± 9.04 vs. 13.99 ± 14.07, p=0.0095). A significantly higher number of blood vessels was observed in the group treated with FD-PRP (in percentage of area) in comparison to the controls, both in superficial and deep regions of epidermis (0.43 ± 0.5 vs. 0.21 ± 0.22, P=0.01; 0.38 ± 0.44 vs. 0.24 ± 0.25, P=0.03, respectively).Discussion and conclusion: The most interesting result of this study was the increased number of blood vessels. VEGF plays a central role in promoting angiogenesis during wound repair. Previous studies demonstrated accelerated wound closure with collagen-binding VEGF topical treatment. However, the use of one growth factor has limited success and heterogeneity of clinical results, probably due to the need of multiple bioactive molecules that are necessary in the cascade of complexes events of healing. The use of multiples factors necessary to healing can orchestrated the physiological events resulting in chemotaxis, proliferation and differentiation of cells and the angiogenic process. The use of FD-PRP in this study of acute model of wounds showed positive results, especially in angiogenesis. The practicality and the improve in the shelf life of PRP have a great value in clinical practice and becomes very attractive, showing low cost, the possibility to increase the concentration of GF, various samples ready-to-use and a single blood collection. The investigation of FD-PRP in other clinical situations in which fresh PRP have been used is an interesting approach to be to evaluated to determine its effectiveness. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Critical role of tumor necrosis factor-α in the early process of wound healing in skin

Tumor necrosis factor (TNF)-α is quickly released and initiates inflammation at wound tissues, but its precise role in wound healing is not fully understood. We examined the contribution of this cytokine to the early process of healing using a mouse model with full-thickness wounds in skin. TNF-α synthesis was detected just after wound creation, increased during the first several hours, reached a peak level on day 1, and then decreased to the basal level. In mice treated with anti-TNF-α mAb, wound closure was significantly delayed, and distances between the panniculus carnosus edges were significantly longer on day 3, compared with control. Inflammatory cell and fibroblast density were markedly decreased on day 3 in the anti-TNF-α mAb-treated mice compared with control. In contrast, wound healing was accelerated on day 3 when mice were treated with bioactive TNF-α. These results indicate that TNF-α is involved in the early process of wound healing.

Identification and Characterization of the Dermal Panniculus Carnosus Muscle Stem Cells.

SummaryThe dermal Panniculus carnosus (PC) muscle is important for wound contraction in lower mammals and represents an interesting model of muscle regeneration due to its high cell turnover. The resident satellite cells (the bona fide muscle stem cells) remain poorly characterized. Here we analyzed PC satellite cells with regard to developmental origin and purported function. Lineage tracing shows that they originate in Myf5+, Pax3/Pax7+ cell populations. Skin and muscle wounding increased PC myofiber turnover, with the satellite cell progeny being involved in muscle regeneration but with no detectable contribution to the wound-bed myofibroblasts. Since hematopoietic stem cells fuse to PC myofibers in the absence of injury, we also studied the contribution of bone marrow-derived cells to the PC satellite cell compartment, demonstrating that cells of donor origin are capable of repopulating the PC muscle stem cell niche after irradiation and bone marrow transplantation but may not fully acquire the relevant myogenic commitment.

Rational Design and Fabrication of Porous Calcium-Magnesium Silicate Constructs That Enhance Angiogenesis and Improve Orbital Implantation.

Tissue integration of orbital implants, following orbital enucleation treatment, represents a challenge for rapid fibrovascularization, long-time stability, anti-infection, and even induction of vascule regeneration. The objective of this study was to develop porous calcium-magnesium silicate materials, with good stability, bioactivity, and antibacterial potential as new orbital fillers. Three-dimensional (3D) diopside scaffolds (low dissolvability) were fabricated by direct ceramic ink writing assembly and then followed by one-step sintering at 1150 °C for 3 h. The pore wall of the scaffold was modified by another calcium-magnesium silicate, such as bredigite or akermanite, which dissolves quickly but shows greater angiogenic potential. These two Ca-Mg-silicates can be coated onto the pore strut, and the coating layers were observed to slowly dissolve in Tris buffer. The vascularization-favorable Cu ions, which had been doped into the bredigite or akermanite coating, could also be measured in the immersion medium. A primary angiogenic test in a panniculus carnosus muscle model in rabbit indicated that the Cu-doped bredigite and akermanite coatings were significantly beneficial for the neovascularization in the early stages. These results suggest that the diopside-based porous materials modified with functional coatings hold great potential for application in orbital reconstruction.

Saphenous artery-based flap models in rats: new flap designs for experimental studies

BackgroundExperimental research using laboratory animals provides substantial data about reconstructive surgery. However, the literature does not include any experimental studies that have used flap models on the hind limbs of rats. To gain an understanding of the physiology of lower-extremity flaps and of flap failures, this study assessed the cutaneous perforators of the saphenous artery, and new flap models were designed for the hind limbs of rats. Materials and methodsThe experiment was designed to include three stages and used 35 rats. The first stage involved mapping the perforators of the saphenous artery. In the second stage, the contents and structures of McFarlane, epigastric, and anterior hind limb flap tissues were compared histologically. The third stage of the study involved designing and comparing different flaps for the hind limbs of the rats and included random flaps, perforator-based peninsular flaps, perforator-based island flaps, and perforator-based flaps with rotated pedicles. Postoperative necrosis ratios were evaluated using computer-based software. ResultsMapping of the saphenous artery perforators revealed an average of 2.2 septocutaneous arteries in each hind limb. Histologic studies showed thick dermis and panniculus carnosus in the McFarlane flaps, thick dermis, and thin panniculus carnosus layers in the epigastric flaps, and thin subcutaneous tissue with no panniculus carnosus tissue in the skin of the hind limbs. The results of the flap studies that used random flaps showed a 52.4% necrosis, while there was no necrosis when perforator-based peninsular flaps, island flaps, and flaps with rotated pedicles were used. ConclusionsNew flap models used on the saphenous artery perforators of the hind limbs of rats can provide valuable information about the physiology of lower-extremity flaps. New studies can also be designed based on these flap models to acquire more knowledge about pathologic conditions such as ischemia and venous insufficiency.

Efficacy of the Quorum Sensing Inhibitor FS10 Alone and in Combination with Tigecycline in an Animal Model of Staphylococcal Infected Wound.

In staphylococci, quorum sensing regulates both biofilm formation and toxin production, moreover it has been demonstrated to be inhibited by RNAIII inhibiting peptide (RIP). Aim our study was to evaluate the in vitro activity and its in vivo efficacy of the combined administration of FS10, a novel RIP derivative, and tigecycline in an animal model of methicillin-resistant (MR) and methicillin-sensitive (MS) Staphylococcus aureus wound infection. Using a 1.x2 cm template, one full thickness wound was established through the panniculus carnosus on the back subcutaneous tissue of each animal. Infection was determined by inoculation of 5x107 CFU/ml of bacteria, that produced an abscess within 24 h, after this, treatment was initiated. The study included, for each strain, a control group without infection, a control infected group that did not receive any treatment and a control infected group with drug-free foam dressing, and three infected groups treated, respectively, with: FS10-soaked foam dressing (containing 20 μg FS10), daily intraperitoneal tigecycline (7 mg/Kg), FS10-soaked foam dressing (containing 20 μg FS10) and daily intraperitoneal injections of tigecycline (7 mg/Kg). The main outcome measures were quantitative culture and histological examination of tissue repair. The highest inhibition of infection was achieved in the group that received FS10-soaked and parenteral tigecycline reducing the bacterial load from 107 CFU/ml to about 103 CFU/g for MSSA and to about 104 CFU/g for MRSA. The group treated with FS10-soaked foam dressing associated with parenteral tigecycline showed, histologically, better overall healing with epithelialization and collagen scores significantly higher than those of the other groups in both strains. In conclusion, the combined use of topical FS10 with i.p. tigecycline induced positive interaction in vivo, resulting in an enhanced therapeutic benefit versus staphylococcal infections in murine wound models.

Effects of ozone gas on skin flaps viability in rats: an experimental study

Background: The main purpose of this study was to assess the effects of ozone gas on the viability of flaps for reconstruction and to determine the optimum application method. The antioxidant, immunomodulatory, and reperfusion effects of ozone gas have been previously assessed, and successful results have been reported. However, only one study has investigated the effect of ozone gas on flap viability. In the present study, it was hypothesised that the antioxidant and reperfusion effects of ozone gas would enhance flap viability.Methods: Forty female Wistar rats were randomly divided into four groups of 10 rats each. A cranial-based, 3 × 11 cm modified McFarlane flap including the panniculus carnosus was raised from the dorsum of a rat and re-sutured to its own bed using 3/0 sharp propylene. Group 1 (n = 10): no pharmacological agent was used after the operation. Group 2 (n = 10): vegetable (olive) oil group; vegetable-oil-impregnated gauze was used as a dressing for 7 days. Group 3 (n = 10): Vegetable (olive) oil with ozone peroxide group; vegetable oil with ozone peroxide-impregnated gauze was used as a dressing for 7 days. Group 4 (n = 10): Hemo-ozone therapy group; hemo-ozone therapy was applied rectally once every day for 7 days. All rats were sacrificed at the end of week 1 and assessed macroscopically and histopathologically.Results: The proportion of substantive necrosis was less in group 4 than in the other three groups. Survival area ratios were better in groups 2 and 3 than in group 1; however, there was no significant difference between groups 2 and 3. No significant differences in the histopathological scores were observed among the groups.Conclusion: Ozone gas enhanced flap viability. No differences in flap viability were observed between the vegetable oil and vegetable oil with ozone peroxide groups. The greatest benefit ratios were found in the hemo-ozone therapy group.

INTRINSIC INCREASED ACE2 EXPRESSION PROTECTS SPINY MOUSE ACOMYS CAHIRINUS AGAINST ISCHEMIC‐INDUCED CARDIAC DYSFUNCTION

Angiotensin converting enzyme 2 (ACE2), a key component of the renin angiotensin system (RAS), is a potential therapeutic target for ischemic heart disease as it protects cardiovascular function. Recently, extensive evidence points to a significant role of ACE2 in regulation of hematopoiesis and vasculogenesis via correction of endothelial progenitor cell dysfunction and increases in the number of cardiac and endothelial progenitor cells after ischemic injury. Spiny mice (Acomys cahirinus, SM) possess lizard‐like abilities when a large portion of skin is “torn away” the deep tissue injury heals rapidly by regenerating complete hair follicles, dermis, epidermis, sebaceous glands, adipose tissue, microvessels, smooth muscle and skeletal muscle of the panniculus carnosus without scaring (Nature 2013). This skin auto to my provides an effective defense against predators. We tested the cardiac regenerative capacity of SM using a myocardial infarction (MI) model. Following ligation of left anterior descending coronary artery, the SM exhibited smaller infarct size (SM‐MI 20% of left ventricular free wall vs CD1‐MI 50%, p&lt;0.05) with preserved ejection fraction vs CD1 mice (SM‐MI 62 ± 2% vs CD1‐MI 32± 7%, p&lt;0.05). At baseline ACE2 activity in SM sham was elevated 12% in myocardial tissue and 23% in plasma vs CDl sham (both, p&lt;0.05). MI resulted in a 37% decrease in ACE2 activity in CD1 mice (p&lt;0.05 vs baseline and vs SM‐MI). Interestingly, SM exhibited further elevation of ACE2 activity (7%) in myocardial tissue following MI, while plasma ACE2 activity remained unchanged after MI. Collectively, our findings suggest that ACE2 is likely to be modulating, at least in part, the myocardial preservation/regeneration process in the SM.Support or Funding Information2 UM1 HL087366‐06, R01 HL056921, HL033610, and UL1 TR000064 from the National Institutes of Health

The Dorsal Skin Fold Chamber as new model of delayed wound healing to monitor the impact of pro-angiogenic starPEG-heparin hydrogels on angiogenesis and wound healing outcome during skin regeneration

Event Abstract Back to Event The Dorsal Skin Fold Chamber as new model of delayed wound healing to monitor the impact of pro-angiogenic starPEG-heparin hydrogels on angiogenesis and wound healing outcome during skin regeneration Christian Beescho1, Teresa Schöpfer2, Lucas Schirmer3, Passant Atallah3, Uwe Freudenberg3, Carsten Werner3, Jan Christoph Simon2, Stefan Langer1 and Sandra Franz2 1 University Hospital Leipzig, Plastic and Reconstructive Surgery, Germany 2 University Hospital Leipzig, Dermatology and Venerology, Germany 3 Max Bergmann Center of Biomaterials, Leibniz Institute of Biofunctinoal Polymer Materials, Germany The Dorsal Skin Fold Chamber (DSFC) model is a useful tool that allows in vivo monitoring of vascularization of biomaterials. Angiogenesis is indispensable in wound healing. Delayed wound healing is associated with impaired new blood vessel formation, which calls for the development of pro-angiogenic wound dressings. We have recently shown that poly(ethylene glycol) (starPEG)-heparin hydrogels can deliver the angiogenic factors FGF-2 and VEGF and encourage angiogenesis in a CAM assay[1]. However, whether these hydrogels promote angiogenesis during wound healing and improve the wound healing outcome needs to be shown. We have therefore established the DSFC as a wound healing model that allows real-time in vivo imaging of angiogenesis and a dynamic characterization of inflammation and re-epithelialization. Dorsal skin of C57BL6 mice was shaved and depilated prior to DSFC implantation. Within the microscopy window, a 5 mm full-thickness wound was created. The chamber was filled with NaCl and closed with a transparent coverslip. At day 1, exudate was gently removed to receive a clear observation window for intravital microscopy (IVM). A starPEG-heparin hydrogel was applied onto the wound and the chamber was closed again. IVM was performed on day 1, 3, 6, 8, 10, 13, and 19 after wounding using FITC/dextran (i.v. injection) to visualize vessels in the wound area. Angiogenesis was analyzed with ZEN software (Zeiss), measuring the functional vessel density (defined as total blood vessel length per area) in the wound and wound edges. To correlate angiogenic events with the wound healing outcome inflammation, granulation tissue formation and re-epithelialization were analyzed in wound biopsies post mortem in the same kinetic as IVM using qRT-PCR and immunohistochemistry. Wound healing in the DSFC is delayed as seen by a late wound closure at day 13. The DSFC impairs the contraction of the M. panniculus carnosus that mediates murine wound closure. Instead, wounds close with new tissue formed by proliferating myofibroblasts and keratinocytes. Delayed wound healing in the DSFC is characterized by prolonged inflammation with a slow increase on infiltrating immune cells, reaching a peak at day 13 and resolving till day 19. Using IVM, angiogenesis could be observed during the whole study. New capillaries resulted in formation of tubular-structured blood vessels. The application of hydrogels onto wounds does not impair the wound healing process. We have adapted the DSFC as a useful model for standardized testing of angiogenic biomaterials during wound healing. Advantages of this model imply in vivo imaging of angiogenesis up to 3 weeks in a human-like wound healing model without muscle induced wound contraction that allows direct correlation of angiogenic effects with wound healing events. We are currently analyzing the impact of star-PEG-heparin hydrogels loaded with pro-angiogenic factors on angiogenesis and wound healing outcome using our DSFC wound healing model.

Novel Polydioxanone Multifilament Scaffold Device for Tissue Regeneration.

Facial aging is the result of intrinsic and extrinsic factors that lead to gradual reduction of dermal extracellular components and skin elasticity and wrinkle formation. A novel stent-shaped biodegradable and biocompatible scaffold device braided with absorbable polydioxanone (PDO) multifilaments was recently marketed for tissue suturing and augmentation. To explore tissue regeneration profiles following implantation of the stent-shaped hollow scaffold in rats and mini-pigs. The scaffold device was implanted under the panniculus carnosus of rat dorsal skin and in the subcutaneous layer of mini-pig dorsal skin. Tissue samples were harvested and histologically evaluated after 3 days and 1, 2, 4, and 12 weeks for rats and after 1, 2, 4, 8, and 12 weeks for mini-pigs. Type III collagen was slowly replaced by Type I collagen in the scaffold. Cells from the surrounding tissue infiltrated the hollow space of the scaffold, which induced de novo tissue regeneration in this space. The novel stent-shaped scaffold used here may be useful for stimulated tissue remodeling of aged skin, collagen synthesis, and partial restoration of dermal matrix components. The cosmetic purpose of this novel soft tissue augmentation device should be clinically investigated in long-term studies.

Abstract 14166: Cardiac Function is Protected From Ischemic Injury in African Spiny Mice

Tissue regeneration is common in crustaceans, insects, reptiles and amphibians. African spiny mice (ASM) evolve to shed a large portion of skin to escape from predators. They have been recently reported as the first mammal to regenerate complete hair follicles, dermis, epidermis, sebaceous glands, adipose tissue, microvessels, smooth muscle, skeletal muscle of the panniculus carnosus and cartilage ( Seifert et al. Nature 2012 ). However, the extent of regenerative ability of ASM with regard to their heart has not been investigated. The objective of this project is to determine the cardiac regenerative potential of ASM relative to another murine species (CD1 mouse) in a coronary artery ligation model. CD1 and ASM were divided into four groups (see table below). Similar ischemic area was induced for group 2 and 4. Cardiac function was assessed using echocardiography and MRI. Briefly, MI led to a 51% decrease in left ventricle ejection fraction (LVEF, 31.9±6.5 vs 64.5±3.7%) in CD1 mice following MI. Whereas, EF was preserved in ASM following MI (78.4±6.5 vs 61.71±1.8%). Collectively, it appears that ASM may be able to preserve and/or regenerate myocardium after ischemic injury. Our findings warrant additional studies to identify molecular pathways and genetic circuits that promote myocardial preservation/regeneration processes.