Fetal diaphragmatic wounds heal with scar formation

Fetal wound healing is fundamentally different from wound healing in the adult. Although experimental work in mice, rats, rabbits, monkeys, and sheep has demonstrated that fetal healing occurs without inflammation and scarring, all of these studies have been limited to fetal skin wounds. Whether all fetal tissues heal in a regenerative-like fashion is unknown. Amniotic fluid exposure may play an important role in scarless fetal skin wound healing, but the effect of amniotic fluid on fetal mesothelial wound healing has not been characterized. To investigate these questions we created bilateral linear diaphragmatic wounds in 100-day gestation fetal lambs (term = 145 days). The right thoracotomy was closed to exclude amniotic fluid. In contrast, the left thoracotomy was fashioned into an Eloesser flap which permitted the left diaphragmatic wound to be continually bathed in amniotic fluid. Wounds were harvested after 1, 2, 7, or 14 days and analyzed by light microscopy and immunohistochemistry with antibodies to collagen types I, III, IV, and VI. Whether bathed in or excluded from amniotic fluid, the mesothelial-lined diaphragm healed with scar formation and without evidence of muscle regeneration. Interestingly, diaphragmatic wounds exposed to amniotic fluid were covered by a thick fibrous collagen peel similar to that seen in gastroschisis bowel. These findings indicate that not all fetal tissues share the unique scarless healing properties of fetal skin.     

Adult skin wounds in the fetal environment heal with scar formation.

OBJECTIVE: This study investigated the influence of the fetal environment on the healing characteristics of adult skin. SUMMARY BACKGROUND DATA: The remarkable ability of the fetus to heal without scarring is poorly understood. The unique qualities of fetal wound healing may be caused by the fetal environment, the fetal tissues, or a combination of both. There are numerous differences between the prenatal and postnatal environments that may play a role in the unique fetal response to injury. METHODS: Full-thickness adult sheep skin was transplanted onto the backs of 60-day-gestation fetal lambs (term, 145 days of gestation). The adult skin grafts were thus perfused by fetal blood and bathed in amniotic fluid. Previous work has demonstrated that, before midgestation, fetal lambs do not reject allogenic skin grafts. Forty days later (100 days of gestation), incisional wounds were made on both the adult skin graft and the adjacent fetal skin. The wounds were harvested 14 days postwounding and analyzed by both light microscopy and immunohistochemical testing using antibodies to collagen types I, III, and VI. RESULTS: The wounds in the adult skin grafts healed with scar formation. This observation contrasts strongly with the scarless healing of the incisional fetal skin wounds. CONCLUSIONS: This study suggests that scarless fetal skin healing properties are intrinsic to fetal skin and are not primarily the result of the fetal environment.     

Differential cutaneous wound healing in thermally injured MRL/MPJ mice

Adult wound repair occurs with an initial inflammatory response, reepithelialization, and the formation of a permanent scar. MRL/MpJ mice following ear‐hole punch biopsies display accelerated healing and tissue regeneration. In this study, we characterized the healing responses in both MRL/MpJ and BALB/c mice following a 15% total body surface area full‐thickness cutaneous burn injury. Macroscopic and histological observations show that delayed wound closure in MRL/MpJ mice is accompanied by an increase in edema, reduced neutrophil infiltration, and more prominent eschar. In vivo bromodeoxyuridine labeling showed no defect in keratinocyte proliferation and migration (reepithelialization). In comparison with BALB/c mice, MRL/MpJ wounds had greater collagen deposition, less granulation tissue formation, and contained fewer α‐smooth muscle actin‐positive myofibroblasts. An observed reduction in dermal neutrophil infiltration and myofibroblast development correlated with enhanced angiogenesis. Overall, BALB/c wounds contracted sooner and to a larger degree, resulting in a significant decrease in scar formation. Interestingly, MRL/MpJ mice showed overt abnormalities in hair follicle proliferation, morphogenesis, and subsequent hair regrowth postburn injury. No substantial evidence of tissue regeneration was observed in either BALB/c or MRL/MpJ wounds. Our results convincingly demonstrate that MRL/MpJ skin burn wounds heal with scar formation with delays in two critical wound healing events: wound closure, and myofibroblast development.     

Skin substitutes with noncultured autologous skin cell suspension heal porcine full-thickness wounds in a one-stage procedure

Clinical application of skin substitute is typically a two-stage procedure with application of skin substitute matrix to the wound followed by engraftment of a split-thickness skin graft (STSG). This two-stage procedure requires multiple interventions, increasing the time until the wound is epithelialised. In this study, the feasibility of a one-stage procedure by combining bioengineered collagen-chondroitin-6-sulfate (DS1) or decellularised fetal bovine skin substitute (DS2) with autologous skin cell suspension (ASCS) in a porcine full-thickness wound healing model was evaluated. Twelve full-thickness excisional wounds on the backs of pigs received one of six different treatments: empty; ASCS; DS1 with or without ASCS; DS2 with or without ASCS. The ASCS was prepared using a point-of-care device and was seeded onto the bottom side of DS1, DS2, and empty wounds at 80 000 cells/cm². Wound measurements and photographs were taken on days 0, 9, 14, 21, 28, 35, and 42 post-wounding. Histological analysis was performed on samples obtained on days 9, 14, 28, and 42. Wounds in the empty group or with ASCS alone showed increased wound contraction, fibrosis, and myofibroblast density compared with other treatment groups. The addition of ASCS to DS1 or DS2 resulted in a marked increase in re-epithelialisation of wounds at 14 days, from 15 ± 11% to 71 ± 20% (DS1 vs DS1 + ASCS) or 28 ± 14% to 77 ± 26 (DS2 vs DS2 + ASCS) despite different mechanisms of tissue regeneration employed by the DS used. These results suggest that this approach may be a viable one-stage treatment in clinical practice.     

Opioids heal ischemic wounds in the rat

Opioids are sometimes used to treat pain in ulcerative wounds, and it is speculated that pain interferes with the healing process. Because the direct effect of opioids on this process remains unknown, we examined the effect of topically applied opioids on the healing of open ischemic wounds in rats. Topically applied opioids hastened wound closure, particularly in the first 4 days when no healing was initiated in phosphate buffered saline solution-treated wounds. After 1 week of application, fentanyl, hydromorphone, and morphine resulted in 66%, 55%, and 42% wound closure, respectively, as compared to only 15% in control wounds. Opioid-induced healing was accompanied by a 1.5- to 2.5-fold increase in nuclear density in the granulation tissue and 45-87% increase in angiogenesis as compared to phosphate buffered saline solution-treated wounds. Fentanyl showed significantly improved healing compared to morphine and hydromorphone (p < 0.05, fentanyl vs. others). Fentanyl-induced healing was inhibited by the opioid receptor antagonist naloxone, suggesting that peripheral opioid receptor(s) mediate the healing process. Opioids accelerate healing by up-regulating both endothelial and inducible nitric oxide synthase and the vascular endothelial-derived growth factor receptor Flk1 in the wounds. We envision that opioids can be used topically to accelerate wound healing in diverse clinical conditions ranging from surgical incisions to nonhealing ischemic ulcers in pathophysiological conditions and in hospice patients.     

MRL mice fail to heal the heart in response to ischemia-reperfusion injury

The MRL/MpJ mouse strain has been reported to recover after right ventricular cryoinjury without scar formation or evidence of ventricular dysfunction, suggesting that this mouse strain harbors genetic traits that confer the capacity for adult myocardium to regenerate. We therefore sought to assess the capacity of adult MRL myocardium to regenerate in a left ventricular ischemia-reperfusion model of myocardial infarction, which more closely recapitulates injury that occurs in human disease. MRL (n = 13) and control C57/Bl6 (n = 12) mice underwent transient occlusion of the left anterior descending coronary artery. After 10 weeks, MRL and C57Bl/6 mice were euthanized and the extent of infarcted myocardium quantified with (2,3,5)-triphenyltetrazolium chloride and trichrome staining. There was no evidence of resistance to cardiac injury or of reduced scar formation in the MRL mice compared to C57/Bl6 controls. Myocardial infarct size (percentage of total heart weight +/- SEM) did not significantly differ between MRL and C57/Bl6 controls (18.9 +/- 1.8% for MRL vs. 15.7 + 1.3% for C57/Bl6, p = 0.20). Thickness of the infarcted anterior LV wall at the mid-papillary level normalized to body weight was not significantly different between the two groups (0.017 + 0.003 mm/mg for MRL and 0.017 + 0.002 mm/mg for C57/BL6, p = 0.91). Trichrome staining showed intense scar formation in both C57/BL6 and MRL hearts. We conclude that there appears to be no effect of the MRL genetic background on resistance to myocardial infarction in mice.     

Tissue profiling MALDI mass spectrometry reveals prominent calcium-binding proteins in the proteome of regenerative MRL mouse wounds

MRL/MpJ‐Fas^lpr mice exhibit the ability to regenerate ear tissue excised by dermal punches. This is an exceptional model to identify candidate proteins that may regulate regeneration in typically nonregenerative tissues. Identification of key molecules involved in regeneration can broaden our understanding of the wound‐healing process and generate novel therapeutic approaches. Tissue profiling by matrix‐assisted laser desorption ionization mass spectrometry is a rapid, powerful proteomic tool that allows hundreds of proteins to be detected from specific regions of intact tissue specimens. To identify these candidate molecules, protein expression in ear punches was examined after 4 and 7 days using tissue profiling of MRL/MpJ‐Fas^lpr mice and the nonregenerative mouse strain C57BL/6J. Spectral analysis revealed distinct proteomic differences between the regenerative and nonregenerative phenotypes, including the calcium‐binding proteins calgranulin A and B, calgizzarin, and calmodulin. Spatial distributions for these differentially expressed proteins within the injured regions were confirmed by immunohistochemistry.     

Steroid-responsive cochlear dysfunction in the MRL/lpr autoimmune mouse.

Corticosteroids historically have been used to treat autoimmune sensorineural hearing loss, although little is known of how steroids restore normal inner ear function. Therefore, to identify a potential model for this field of research, this study examined the effects of prednisolone on auditory brain stem response thresholds in the MRL/lpr mouse model of autoimmune sensorineural hearing loss. Mice treated with prednisolone after auditory threshold elevations demonstrated significant improvement and stabilization of thresholds compared with untreated controls. MRL/lpr mice treated with steroids before the onset of autoimmune disease and cochlear dysfunction demonstrated decreased serum immune complexes, higher survival rates, and lower auditory thresholds compared with untreated controls. These positive results suggest the autoimmune mouse may be useful for studies of steroid-responsive mechanisms of the cochlea in autoimmune sensorineural hearing loss, as well as any hearing disorder in which steroid therapy is currently used.     

不增加辅助切口的带瘢痕皮肤扩张切疤术

目的：探讨如何消除常规皮肤扩张后行切疤术时必然增加的辅助切口瘢痕,以达到更佳美容效果。方法：以待切除的瘢痕为中心,扩张器置于瘢痕正下方,连带瘢痕周围的皮肤同时扩张。通过采用“Z”形折线切口、皮下紧密缝合切口、注意引流、延迟注水开始时间、严格控制每次注水量等方法,有效避免扩张过程中手术切口因张力过大而开裂。结果：面、颌颈、前臂等部位以带瘢痕皮肤扩张术切除瘢痕7例,不增加任何辅助切口,效果满意。结论：带瘢痕皮肤扩张术对适当面积的瘢痕切除具有更好的治疗效果。     

Skin substitutes in chronic wounds

Skin substitutes in chronic wounds. There is a large demand for skin substitutes for the coverage of chronic wounds. Due to a intensive and local wound treatment the impaired dermal and epidermal repair still remains a major problem. Known treatmentes as split-skin-, reverdin- and pinch grafts make a sufficient and solid wound closure possible. However in such procedures the take rate of grafting often failes. The graft healing is increased with combined mesh-graft and vacuum-sealing technique. Temporary and permanent skin substitutes extend the spectrum in closure of chronic defects. Sheets and single cell suspensions of keratinocytes are available for clincial treatments. First clinical results with autologous keratinocyte transplantation are described. In the future approaches in gen therapy becomes more and more important for skin substitutes.     

Reduction of scar formation in full-thickness wounds with topical celecoxib treatment

Adult wound repair occurs with an initial inflammatory response, reepithelialization, and the formation of a permanent scar. Although the inflammatory phase is often considered a necessity for successful adult wound healing, fetal healing studies have shown the ability to regenerate skin and to heal wounds in a scarless manner in the absence of inflammation. The cyclooxygenase-2 (COX-2) enzyme, a known mediator of inflammation, has been shown to contribute to a variety of inflammatory conditions and to the development of cancer in many organs. To examine the role of COX-2 in the wound healing process, incisional wounds were treated topically with the anti-inflammatory COX-2 inhibitor celecoxib. Acutely, celecoxib inhibited several parameters of inflammation in the wound site. This decrease in the early inflammatory phase of wound healing had a significant effect on later events in the wound healing process, namely a reduction in scar tissue formation, without disrupting reepithelialization or decreasing tensile strength. Our data suggest that in the absence of infection, adult wound healing is able to commence with decreased inflammation and that anti-inflammatory drugs may be used to improve the outcome of the repair process in the skin by limiting scar formation.     

Skin stapling of wounds in the accident department

In a randomized prospective study of 100 consecutive patients presenting to the accident and emergency department with superficial lacerations, staples and sutures wert compared for skin closure. Acceptability of the methods by staff and patients, and end results were similar. Staples were more expensive than sutures, but were significantly quicker, simpler to use and safer. They are, therefore, particularly suitable for use in a busy accident and emergency department.     

Wound edge biopsy sites in chronic wounds heal rapidly and do not result in delayed overall healing of the wounds

Wound biopsies are an essential diagnostic component in the management of chronic wounds. First, the possibility of malignancy or infection in the wound often requires sampling of the wound edge and its bed. Secondly, several practice guidelines recommend biopsying wounds that have not responded to treatment after 2–6 weeks. However, there has always been a concern that the biopsy may worsen the wound and delay overall healing. In this report, we investigated the safety and effects of wound biopsies on overall chronic wound healing rates (advance of the wound edge per week toward the center) before and after the biopsy was performed. In a cohort of 14 consecutive patients with chronic wounds of the lower extremity, we found that postbiopsy chronic wound healing rates (0.99±1.18 mm/week; mean±SD) were not decreased and were actually higher than prebiopsy chronic wound healing rates (0.49±0.85 mm/week; mean±SD, p <0.05). In addition, we documented that healing of the biopsy sites up to the original wound edge occurred within 6 weeks in 11 of the 14 subjects. Therefore, we conclude that chronic wounds do not worsen after being biopsied and that wound biopsies are a safe procedure that does not delay overall healing of the chronic wound.     

腓肠肌内侧头穿支皮瓣修复胭窝瘢痕创面

目的 了解腓肠肌内侧头穿支皮瓣修复腘窝瘢痕创面的效果. 方法 对2005年1月-2010年1月笔者单位收治的10例胭窝瘢痕患者创面,行腓肠肌内侧头穿支皮瓣修复.10例患者中烧伤后瘢痕8例,手术后瘢痕2例,病程3个月～11年.创面范围6 cm×3 cm～10 cm×6 cm.患者手术前采用超声多普勒血流探测仪在距胭窝皱褶10～17 cm、距后正中线2～5 cm处探测腓肠内侧动脉的肌皮穿支,然后行皮瓣手术.供区创面宽度小于或等于5 cm直接缝合,大于5 cm植皮修复. 结果 10例患者术后皮瓣均成活.皮瓣面积为7 cm×5 cm～12 cm×7 cm.随访3～30个月,皮瓣外形良好,患肢可负重行走,无踱行,膝关节功能与对侧一致.供区无明显凹陷畸形. 结论 腓肠肌内侧头穿支皮瓣可较好地修复腘窝部瘢痕创面.