Experimental In-Vivo Models Used in Fat Grafting Research for Volume Augmentation in Soft Tissue Reconstruction

As the popularity of fat grafting research increases, animal models are being used as the source of pre-clinical experimental information for discovery and to enhance techniques. To date, animal models used in this research have not been compared to provide a standardized model. We analyzed publications from 1968-2015 to compare published accounts of animal models in fat grafting research. Data collected included: species used, graft characteristics (donor tissue, recipient area, amount injected, injection technique), time of sacrifice and quantification methods. Mice were most commonly used (56% of studies), with the athymic nude strain utilized most frequently (44%). Autologous fat was the most common source of grafted tissue (52%). Subcutaneous dorsum was the most common recipient site (51%). On average, 0.80+/-0.60 mL of fat was grafted. A single bolus technique was used in 57% of studies. Fat volume assessment was typically completed at the end of the study, occurring at less than 1 week to one year. Graft volume was quantified by weight (63%), usually in conjunction with another analysis. The results demonstrate the current heterogeneity of animal models in this research. We propose that the research community reach a consensus to allow better comparison of techniques and results. One example is the model used in our laboratory and others; this model is described in detail. Eventually, larger animal models may better translate to the human condition but, given increased financial costs and animal facility capability, should be explored when data obtained from small animal studies is exhausted or inconclusive

Transversus abdominis-plane block versus local anesthetic wound infiltration in lower abdominal surgery: a systematic review and meta-analysis of randomized controlled trials

Background: Postoperative pain management is of great importance in perioperative anesthetic care. Transversus abdominis plane (TAP) block has been described as an effective technique to reduce postoperative pain and morphine consumption after open lower abdominal operations. Meanwhile, local anesthetic infiltration (LAI) is also commonly used as a traditional method. However, the effectiveness of these two methods has not been compared before. Methods: A meta-analysis of all relevant randomized controlled trials (RCTs) was conducted to compare the efficacy of single shot TAP block with that of single shot LAI for postoperative analgesia in adults. Major medical databases and trial registries were searched for published and unpublished RCTs. The endpoints include postoperative visual analog scale (VAS) pain score, morphine requirement, and rate of postoperative nausea and vomiting (PONV). For continuous data, weighted mean differences (WMDs) were formulated; for dichotomous data, risk ratios (RR) were calculated. Results were derived using a random-/fixed-effects model with 95% confidence interval (CI). Results: Four RCTs, encompassing 96 TAP-block and 100 LAI patients, were included in the final analysis. Patients in the TAP-block group had lower VAS pain scores 24 hours postoperatively compared with the LAI group, both at rest (WMD [95% CI] = -0.67 [p < 0.01] and with movement (WMD = -0.89, p < 0.01). There were no significant between-group differences in 24-hour postoperative morphine requirements, the rates if PONV or VAS pain scores at 2 and 4 h postoperatively. Conclusion: TAP block and LAI provide comparable short-term postoperative analgesia, but TAP block has better long-lasting effect. Electronic supplementary material The online version of this article (doi:10.1186/1471-2253-14-121) contains supplementary material, which is available to authorized users

Breast Reconstruction: Closing the Loop after Breast Cancer

Conclusion: As physicians involved at multiple levels in the treatment of breast cancer patients, it is our duty to understand the basics of diagnostic and treatment options for our patients, but also to promote specific counseling about the potential benefits of reconstruction within the medical and general communities. Raising awareness about breast reconstruction enables more women to consider it as an option that for many will translate into an improved quality of life as a breast cancer survivor

Hyperspectral Imaging for Burn Depth Assessment in an Animal Model

Differentiating between superficial and deep-dermal (DD) burns remains challenging. Superficial-dermal burns heal with conservative treatment; DD burns often require excision and skin grafting. Decision of surgical treatment is often delayed until burn depth is definitively identified. This study\u27s aim is to assess the ability of hyperspectral imaging (HSI) to differentiate burn depth. METHODS: Thermal injury of graded severity was generated on the dorsum of hairless mice with a heated brass rod. Perfusion and oxygenation parameters of injured skin were measured with HSI, a noninvasive method of diffuse reflectance spectroscopy, at 2 minutes, 1, 24, 48 and 72 hours after wounding. Burn depth was measured histologically in 12 mice from each burn group (n = 72) at 72 hours. RESULTS: Three levels of burn depth were verified histologically: intermediate-dermal (ID), DD, and full-thickness. At 24 hours post injury, total hemoglobin (tHb) increased by 67% and 16% in ID and DD burns, respectively. In contrast, tHb decreased to 36% of its original levels in full-thickness burns. Differences in deoxygenated and tHb among all groups were significant (P \u3c 0.001) at 24 hours post injury. CONCLUSIONS: HSI was able to differentiate among 3 discrete levels of burn injury. This is likely because of its correlation with skin perfusion: superficial burn injury causes an inflammatory response and increased perfusion to the burn site, whereas deeper burns destroy the dermal microvasculature and a decrease in perfusion follows. This study supports further investigation of HSI in early burn depth assessment

Marjolin’s ulcer: a preventable malignancy arising from scars

Background: Marjolin’s ulcer (MU) is a rare malignancy arising from various forms of scars. This potentially fatal complication typically occurs after a certain latency period. This article attempts to reveal the importance of the latency period in the prevention and early treatment of the malignancy. Methods: A retrospective review of 17 MU patients who underwent surgical procedures between June of 2005 and December 2011 was conducted. Etiology of injuries, latency period, repeated ulceration, and outcomes were recorded. This observational report reveals characteristics of patients who develop MU. Results: An incidence of 0.7% of MU was found amongst patients complaining of existing scars in our study; burns and trauma were the most common etiology of MU. The mean latency period was 29 years (SD = 19) and the mean post-ulceration period was 7 years (SD = 9). Statistical analysis revealed a negative correlation between the age of patients at injury and the length of latency period (r = −0.8, P <0.01), as well as the lengths of pre-ulceration and post-ulceration periods (r = −0.7, P <0.01). Conclusions: Patients experience different lengths of pre- and post-ulceration periods during the latency period. Younger patients tend to have a longer latency period. Skin breakdown on chronic scars and chronic unhealed ulcers are two main sources of MU. MU may be preventable with a close surveillance of the ulcer during the latency period

Perfusion Changes by Hyperspectral Imaging in a Burn Model

BACKGROUND: Early excision and skin grafting of full-thickness and deep-dermal burns is therapeutically advantageous. However, while full-thickness burns are clinically evident, differentiating between superficial versus deep partial-thickness burns presents a diagnostic challenge, with only 50-75% accuracy. Superficial-dermal burns heal, while deep-dermal burns often require excision and skin grafting. Decision of surgical treatment is often delayed until burn depth is definitively identified. This study’s aim is to establish a thermal burn model in mice in order to assess the ability of Hyperspectral Imaging (HSI) in differentiating burn depth. METHODS: Burns of graded severity were generated on the dorsum of seventy-six hairless mice with a brass rod heated to 50, 60, 70, 80, or 90°C. Perfusion and oxygenation parameters of the injured skin were measured with HSI, a non-invasive method of wide-field, diffuse reflectance spectroscopy at 2 minutes, 1 hour, 24 hours, 48 hours, and 72 hours after wounding. Burn depth was measured histologically (n=44) at 72 hours post injury using Masson’s trichrome staining. RESULTS: Three discrete levels of burn depth were verified histologically, as follows in order of increasing depth: intermediate-dermal, deep-dermal, and full-thickness injury. At 24 hours post injury, total hemoglobin increased by 67% and 18% in intermediate and deep dermal burns, respectively. In contrast, total hemoglobin decreased by 64% in full-thickness burns. Differences in deoxygenated hemoglobin, total hemoglobin, and oxygen saturation for all group comparisons were statistically significant (p CONCLUSION: HSI was able to differentiate among three discrete levels of burn injury. This is likely due to its correlation with skin perfusion: superficial burn injury causes an inflammatory response and increased perfusion to the burn site, while deeper burns destroy the dermal microvasculature and a decrease in perfusion follows. This study supports further investigation in the use of HSI in early burn depth assessment

Diffusion and Perfusion: The Keys to Fat Grafting

Background: Fat grafting is now widely used in plastic surgery. Long-term graft retention can be unpredictable. Fat grafts must obtain oxygen via diffusion until neovascularization occurs, so oxygen delivery may be the overarching variable in graft retention. Methods: We studied the peer-reviewed literature to determine which aspects of a fat graft and the microenvironment surrounding a fat graft affect oxygen delivery and created 3 models relating distinct variables to oxygen delivery and graft retention. Results: Our models confirm that thin microribbons of fat maximize oxygen transport when injected into a large, compliant, well-vascularized recipient site. The “Microribbon Model” predicts that, in a typical human, fat injections larger than 0.16 cm in radius will have a region of central necrosis. Our “Fluid Accommodation Model” predicts that once grafted tissues approach a critical interstitial fluid pressure of 9 mm Hg, any additional fluid will drastically increase interstitial fluid pressure and reduce capillary perfusion and oxygen delivery. Our “External Volume Expansion Effect Model” predicts the effect of vascular changes induced by preoperative external volume expansion that allow for greater volumes of fat to be successfully grafted. Conclusions: These models confirm that initial fat grafting survival is limited by oxygen diffusion. Preoperative expansion increases oxygen diffusion capacity allowing for additional graft retention. These models provide a scientific framework for testing the current fat grafting theories

Adipose Tissue Therapeutics for Scar Rehabilitation after Thermal Injury

Background: Burn injuries are common and in the long term can lead to hypertrophic or keloid scars, pain and pruritus, limited mobility across joints, and disfigurement. Numerous reports suggest adipose derived tissues, including adipose derived stem cells (ADSCs) and processed lipoaspirate, can improve acutely healing wounds from a variety of etiologies including excisional, thermal, and radiation injuries by both secretion of growth factors and direct differentiation. There are many options for scar treatment, including laser therapy, silicone sheets, steroid injection, and even skin grafting however these techniques either lack optimal efficacy or involve significant cost and morbidity. Clinical case series suggest a beneficial effect of adipose tissues in improving scarred tissues, however this phenomenon has not been extensively studied in animal models especially in a thermal scar model. Objectives: (1) Determine if adipose tissue can accelerate and improve scar remodeling subacutely after acute wound healing has occurred. (2) Determine if the effect is related to adipose derived stem cells or other components of lipoaspirate. Methods: 50 CD1 nu/nu athymic mice received a standardized 70°C 10 second burn with a brass rod to the dorsal skin. Digital photographs and hyperspectral images were taken immediately following injury and serially over the study’s entirety. Burned skin reliably progressed through normal stages of wound healing to a scarred and granulating state. At six weeks post-burn animals received subcutaneous injection immediately beneath the scar with fresh human lipoaspirate (n=10), high dose hADSCs in matrigel (n=10), low dose hADSCs in matrigel (n=10), matrigel control (n=10), or were not injected (n=10). At 4 weeks post-injection (10 weeks post-burn) animals were sacrificed and tissue samples were harvested for histological molecular analysis. Results: Oxygenation and perfusion profiles from hyperspectral imaging and scar wound area correlated between groups suggesting methodological consistency of burns prior to any intervention. Oxygenated hemoglobin at 10 weeks in scars treated with lipoaspirate increased significantly more compared to 6-week pre-treatment baseline than all other groups (1.57x vs. 0.85x, p Conclusion: A consistent model of burn injury and scar maturation is described. Preliminary HSI and scar area data suggest scar improvement in lipoaspirate treated scars compared to ADSCs and controls

Lipoaspirate and Adipose Stem Cells as Potential Therapeutics for Chronic Scars

Introduction: Burn injuries can lead to hypertrophic or keloid scars, causing pain and long lasting mobility issues. Current therapies are often unsatisfactory, costly, or morbid. Prior studies suggest adipose derived stem cells (ADSCs) and lipoaspirate can improve scar outcomes of acute thermal wounds. Clinical reports suggest lipoaspirate and ADSCs can improve chronic burn scar remodeling. However, this has not been extensively studied in animal models. We sought to determine if adipose tissue can improve chronic scar remodeling and to compare the effects of ADSCs and processed lipoaspirate. Methods: 50 CD1 nu/nu athymic mice received a standardized deep partial-thickness thermal burn. Scars matured for 6 weeks. Photographs and perfusion measurements by hyperspectral imaging (HSI) were taken over the entire study. Lipoaspirate and ADSCs (SVF and ex-vivo culture with flow cytometry confirmation) were obtained from a discarded human pannus specimen. After 6 weeks, animals received a 0.6cc subcutaneous graft beneath the scar of either: human lipoaspirate processed with the Coleman technique, high-dose (106) hADSCs in Matrigel, low-dose (104) hADSCs in Matrigel, Matrigel only, or not injected (n=10 per group). At 10 weeks, animals were sacrificed and scar tissue was harvested for histological and molecular analysis. Results: HSI oxygenated hemoglobin values in lipoaspirate treated scars increased significantly more compared to 6-week pre-treatment baseline than all other groups (p \u3c 0.05). Planimetry analysis showed reduction in wound area in lipoaspirate treated mice compared to control groups (p \u3c 0.01). Blood vessel density quantification on Masson’s trichrome stains suggests increased density in lipoaspirate treated scars versus controls (p \u3c 0.01). Conclusion: HSI, blood vessel density, and scar analysis suggest improvement in lipoaspirate treated scars compared to controls. Preliminary molecular data offers some insight to this trend. No effect was seen with ADSCs at either concentration at the analyzed timepoints. Molecular analyses are ongoing to investigate cellular mechanisms in regulating scar remodeling

Hyperspectral Imaging as an Early Biomarker for Radiation Exposure and Microcirculatory Damage

BACKGROUND: Radiation exposure can lead to detrimental effects in skin microcirculation. The precise relationship between radiation dose received and its effect on cutaneous perfusion still remains controversial. Previously, we have shown that hyperspectral imaging (HSI) is able to demonstrate long-term reductions in cutaneous perfusion secondary to chronic microvascular injury. This study characterizes the changes in skin microcirculation in response to varying doses of ionizing radiation and investigates these microcirculatory changes as a possible early non-invasive biomarker that may correlate with the extent of long-term microvascular damage.METHODS: Immunocompetent hairless mice (n=66) were exposed to single fractions of superficial beta-irradiation in doses of 0, 5, 10, 20, 35, or 50 Gy. A HSI device was utilized to measure deoxygenated hemoglobin levels in irradiated and control areas. HSI measurements were performed at baseline before radiation exposure and for the first three days post-irradiation. Maximum macroscopic skin reactions were graded, and histological assessment of cutaneous microvascular densities at four weeks post-irradiation was performed in harvested tissue by CD31 immunohistochemistry.RESULTS: CD31 immunohistochemistry demonstrated a significant correlation (r=0.90, p<0.0001) between dose and vessel density reduction at four weeks. Using HSI analysis, early changes in deoxygenated hemoglobin levels were observed during the first three days post-irradiation in all groups. These deoxygenated hemoglobin changes varied proportionally with dose (r=0.98, p<0.0001) and skin reactions (r=0.98, p<0.0001). There was a highly significant correlation (r= 0.91, p<0.0001) between these early changes in deoxygenated hemoglobin and late vascular injury severity assessed at the end of four weeks.CONCLUSIONS: Radiation dose is directly correlated with cutaneous microvascular injury severity at four weeks in our model. Early post-exposure measurement of cutaneous deoxygenated hemoglobin levels may be a useful biomarker for radiation dose reconstruction and predictor for chronic microvascular injury