Intravital insights in skin wound healing using the mouse dorsal skin fold chamber

The skin fold chamber is one of the most accepted animal models for studying the microcirculation both in health and disease. Here we describe for the first time the alternative use of the skin fold chamber in mice for intravital microscopic investigation of skin regeneration after creating a full dermal thickness wound. The dorsal skin fold chamber was implanted in hairless SKH1-hr mice and a full dermal thickness wound (area approximately 4 mm2) was created. By means of intravital fluorescence microscopy, the kinetics of wound healing were analyzed for 12 days post wounding with assessment of epithelialization and nutritive perfusion. The morphology of the regenerating skin was characterized by hematoxylin-eosin histology and immunohistochemistry for proliferation and microvessel density. The model allows the continuous visualization of wound closure with complete epithelialization at day 12. Furthermore, a sola cutis se reficientis could be described by an inner circular ring of vessels at the wound margin surrounded by outer radial passing vessels. Inner circular vessels presented initially with large diameters and matured towards diameters of less than 15 microm for conversion into radial spreading outer vessels. Furthermore, wound healing showed all diverse core issues of skin repair. In summary, we were able to establish a model for the analysis of microcirculation in the healing skin of the mouse. This versatile model allows distinct analysis of new vessel formation and maturation in regenerating skin as well as evaluation of skin healing under different pathologic conditions.     

Depletion of neuropeptides during wound healing in rat skin

The peptides substance P, calcitonin gene-related peptide and somatostatin are present in nerve fibres in mammalian, including human, skin. There is evidence that in addition to having a putative neurotransmitter role, they may be trophic agents: a study was therefore undertaken of peptide changes during wound healing in rat skin. A significant depletion of the neuropeptides was found in the region of the wound within two days, and this persisted for two weeks. A smaller and delayed depletion also occurred in intact skin of the same dermatome, but not in an adjacent dermatome.     

Evaluation of fibrin sealants in cutaneous wound closure.

Human fibrin sealant (HFS) and bovine fibrin sealant (BFS) were delivered as preformulated fibrinogen-thrombin mixtures that are light activated. These formulations were evaluated in the healing of incised cutaneous wounds in beagle dogs. Four groups were differentiated by sealant type and study duration with group: BFS for 10 days, HFS for 10 days, BFS for 30 days, and HFS for 30 days. Healing was evaluated by noting incidences of open wounds, laser Doppler perfusion imaging (LDPI), planimetry, breaking strength, and histopathology. In the absence of tension, both sealants tended to hold wound edges together; however, HFS tended to be better than its controls and BFS. Both sealants augmented suture closure, necessitating fewer sutures for wound closure. At 5 and 30 days BFS wounds had more perfusion than HFS wounds, indicating more inflammation. At 10 and 30 days BFS wounds had larger scar areas than their controls, while scar areas of HFS wounds were smaller than either BFS wounds or controls. Breaking strengths indicated that HFS wounds were stronger than their controls and BFS wounds. Histologically, mild to moderate chronic-active inflammation was observed in wounds receiving either sealant, and this persisted longer in BFS wounds. Overall, HFS had positive qualities, thus showing potential for functional and cosmetic wound closure.     

Staple vs. subcuticular vicryl skin closure in knee replacement surgery: a spectrophotographic assessment of wound characteristics

Staple closure is a popular method of skin closure for patients undergoing knee replacement surgery. There are no guidelines regarding spacing of staples and some concern exists with regard to wound oxygenation in knees subject to early movement. We compared cutaneous wound characteristics in terms of blood oxygenation and blood content, using two types of skin closure. Staples or 4/0 subcuticular vicryl were used. We found favourable blood perfusion characteristics when using stapled closure. Our results also suggest that optimum wound oxygenation requires staple spacing of 6 mm or more.     

Lymphocyte commitment during embryonic development,in the mouse

Multipotent hematopoietic stem cells (HSC) differentiate into mature cells in the fetal liver (FL) during embryonic development, and in the bone marrow (BM) in adult animals. Multilineage differentiation is accomplished by the stepwise commitment of stem cells that sequentially loose differentiation potential. The characterization of the intermediate lymphoid precursors isolated from both hematopoietic sites suggests that, in FL, their potential of differentiation as well as their growth factor requirements are apparently less strict than in the BM. This could be the result of different commitment strategies at those sites: stochastic in the FL and instructive in the BM.     

The effect of multifunctional polymer-based gels on wound healing in full thickness bacteria-contaminated mouse skin wound models

We determined whether a two-part space-conforming polyethylene glycol/dopa polymer-based gel promoted healing of contaminated wounds in mice. This silver-catalysed gel was previously developed to be broadly microbiocidal in vitro while being biocompatible with human wound cell functioning. Full-thickness wounds were created on the backs of mice. The wounds were inoculated with 10(4) CFU of each of four common skin wound contaminants, Staphylococcus aureus, Pseudomonas aeruginosa, Acinetobacter baumanii and Clostridium perfringens. The wounds were then treated with our multifunctional polymer-based gel, the commercially available NewSkin product, or left to heal untreated. The untreated wounds were overtly infected, and presented detectable bacterial loads over the entire 21-day healing period, while the gel and NewSkin groups presented significantly smaller rises in bacterial levels and were cleared of detectable colonies by the third week, with the gel group clearing the bacteria earlier. While all three groups healed their wounds, the polymer-based gel-treated group demonstrated significantly earlier re-epithelialization and dermal maturation (P<0.05). This was reflected in a quick regain of tensile strength. This accelerated dermal maturation and regain in strength was noted in mice treated with the polymer-based gel when compared to wound treated with the commercially available Aquacel-Ag dressing (P<0.05). What distinguishes the polymer-based gel from these other products is that it is incorporated within the healing wound. These preclinical studies show that the anti-microbial polymer gel not only supports but also accelerates healing of bacterially contaminated wounds.     

Accelerated wound closure in mice deficient for interleukin-10

The impact of the local inflammatory response on the process of wound healing has been debated for decades. In particular, the question whether infiltrating macrophages and granulocytes promote or impede tissue repair has received much attention. In the present study, we show that wound healing is accelerated in mice deficient for the anti-inflammatory cytokine interleukin (IL)-10. IL-10-/- mice closed excisional wounds significantly earlier compared with IL-10-competent control littermates. This effect was attributable to accelerated epithelialization as well as enhanced contraction of the wound tissue in the mutant animals. Increased alpha-smooth muscle actin expression in IL-10-deficient mice suggests that augmented myofibroblast differentiation is responsible for the enhanced contraction of wounds in mutant mice. The number of macrophages infiltrating the wound tissue was significantly increased in IL-10-/- mice compared with control littermates suggesting that this cell type mediates the accelerated tissue repair. These results show for the first time that IL-10 can impede wound repair.     

Role of vision in aperture closure control during reach-to-grasp movements

We have previously shown that the distance from the hand to the target at which finger closure is initiated during the reach (aperture closure distance) depends on the amplitude of peak aperture, as well as hand velocity and acceleration. This dependence suggests the existence of a control law according to which a decision to initiate finger closure during the reach is made when the hand distance to target crosses a threshold that is a function of the above movement-related parameters. The present study examined whether the control law is affected by manipulating the visibility of the hand and the target. Young adults made reach-to-grasp movements to a dowel under conditions in which the target or the hand or both were either visible or not visible. Reaching for and grasping a target when the hand and/or target were not visible significantly increased transport time and widened peak aperture. Aperture closure distance was significantly lengthened and wrist peak velocity was decreased only when the target was not visible. Further analysis showed that the control law was significantly different between the visibility-related conditions. When either the hand or target was not visible, the aperture closure distance systematically increased compared to its value for the same amplitude of peak aperture, hand velocity, and acceleration under full visibility. This implies an increase in the distance-related safety margin for grasping when the hand or target is not visible. It has been also found that the same control law can be applied to all conditions, if variables describing hand and target visibility were included in the control law model, as the parameters of the task-related environmental context, in addition to the above movement-related parameters. This suggests that that the CNS utilizes those variables for controlling grasp initiation based on a general control law.     

Fibrinogen stabilizes placental-maternal attachment during embryonic development in the mouse

In humans, maternal fibrinogen (Fg) is required to support pregnancies by maintaining hemostatic balance and stabilizing uteroplacental attachment at the fibrinoid layer found at the fetal-maternal junction. To examine relationships between low Fg levels and early fetal loss, a genetic model of afibrinogenemia was developed. Pregnant mice homozygous for a deletion of the Fg-gamma chain, which results in a total Fg deficiency state (FG(-/-)), aborted the fetuses at the equivalent gestational stage seen in humans. Results obtained from timed matings of FG(-/-) mice showed that vaginal bleeding was initiated as early as embryonic day (E)6 to 7, a critical stage for maternal-fetal vascular development. The condition of afibrinogenemia retarded embryo-placental development, and consistently led to abortion and maternal death at E9.75. Lack of Fg did not alter the extent or distribution pattern of other putative factors of embryo-placental attachment, including laminin, fibronectin, and Factor XIII, indicating that the presence of fibrin(ogen) is required to confer sufficient stability at the placental-decidual interface. The results of these studies demonstrate that maternal Fg plays a critical role in maintenance of pregnancy in mice, both by supporting proper development of fetal-maternal vascular communication and stabilization of embryo implantation.