Matthew B. Klein

Genomic responses in mouse models poorly mimic human inflammatory diseases

A cornerstone of modern biomedical research is the use of mouse models to explore basic pathophysiological mechanisms, evaluate new therapeutic approaches, and make go or no-go decisions to carry new drug candidates forward into clinical trials. Systematic studies evaluating how well murine models mimic human inflammatory diseases are nonexistent. Here, we show that, although acute inflammatory stresses from different etiologies result in highly similar genomic responses in humans, the responses in corresponding mouse models correlate poorly with the human conditions and also, one another. Among genes changed significantly in humans, the murine orthologs are close to random in matching their human counterparts (e.g., R2 between 0.0 and 0.1). In addition to improvements in the current animal model systems, our study supports higher priority for translational medical research to focus on the more complex human conditions rather than relying on mouse models to study human inflammatory diseases.

A genomic storm in critically injured humans

Critical injury in humans induces a genomic storm with simultaneous changes in expression of innate and adaptive immunity genes.

The Association Between Fluid Administration and Outcome Following Major Burn: A Multicenter Study

Objective:To determine patient and injury variables that influence fluid requirements following burn injury and examine the association between fluid volume received and outcome. Background:Fluid resuscitation remains the cornerstone of acute burn management. Recent studies suggest that patients today are receiving more fluid per percent total body surface area (TBSA) than in the past. Therefore, there is a need to better define the factors that impact fluid requirements and to determine the effects of fluid volumes on outcome. Methods:This study was part of a federally funded multicenter study. Multilinear regression analyses were performed to determine the patient and injury characteristics that most influenced fluid resuscitation volumes received. To assess the association of fluid volumes on outcome, propensity scores were developed to provide a predicted volume of fluid for each patient. Logistic models were then used to assess the impact of excess fluid beyond predicted volumes on outcome. Results:Seventy-two patients were included in this analysis. Average patient age was 40.6 years and average TBSA was 44.5%. Average fluid volume received during the first 24 hours after injury was 5.2/mL/kg/TBSA. Significant predictors of fluid received included % TBSA, age, intubation status, and weight. Increased fluid volume received increased risk of development of pneumonia (odds ratio [OR] = 1.92), bloodstream infections (OR =2.33), adult respiratory distress syndrome (OR = 1.55), multiorgan failure (OR= 1.49), and death (OR = 1.74). Conclusion:TBSA, age, weight, and intubation status on admission were significant predictors of fluid received. Patients who received larger volumes of resuscitation fluid were at higher risk for injury complications and death.

High Dynamic Range Characterization of the Trauma Patient Plasma Proteome

Although human plasma represents an attractive sample for disease biomarker discovery, the extreme complexity and large dynamic range in protein concentrations present significant challenges for characterization, candidate biomarker discovery, and validation. Herein we describe a strategy that combines immunoaffinity subtraction and subsequent chemical fractionation based on cysteinyl peptide and N-glycopeptide captures with two-dimensional LC-MS/MS to increase the dynamic range of analysis for plasma. Application of this “divide-and-conquer” strategy to trauma patient plasma significantly improved the overall dynamic range of detection and resulted in confident identification of 22,267 unique peptides from four different peptide populations (cysteinyl peptides, non-cysteinyl peptides, N-glycopeptides, and non-glycopeptides) that covered 3654 different proteins with 1494 proteins identified by multiple peptides. Numerous low abundance proteins were identified, exemplified by 78 “classic” cytokines and cytokine receptors and by 136 human cell differentiation molecules. Additionally a total of 2910 different N-glycopeptides that correspond to 662 N-glycoproteins and 1553 N-glycosylation sites were identified. A panel of the proteins identified in this study is known to be involved in inflammation and immune responses. This study established an extensive reference protein database for trauma patients that provides a foundation for future high throughput quantitative plasma proteomic studies designed to elucidate the mechanisms that underlie systemic inflammatory responses.

Patterns and Outcomes of Pediatric Facial Fractures in the United States: A Survey of the National Trauma Data Bank

BACKGROUND Pediatric trauma involving the bones of the face is associated with severe injury and disability. Although much is known about the epidemiology of facial fractures in adults, little is known about national injury patterns and outcomes in children in the US. STUDY DESIGN The epidemiology of facial injuries in children and adolescents (ages 0 to 18 years) was described using the National Trauma Data Bank (2001 to 2005) to examine facial fracture pattern, mechanism, and concomitant injury by age. RESULTS A total of 12,739 (4.6%) facial fractures were identified among 277,008 pediatric trauma patient admissions. The proportion of patients with facial fractures increased substantially with age. The most common facial fractures were mandible (32.7%), nasal (30.2%), and maxillary/zygoma (28.6%). The most common mechanisms of injury were motor vehicle collision (55.1%), violence (11.8%), and falls (8.6%). These fracture patterns and mechanisms of injury varied with age. Compared with patients without facial fractures, patients with fractures exhibited substantial injury severity, hospital lengths of stay, ICU lengths of stay, ventilator days, and hospital charges. In addition, patients with facial fractures had more severe associated injury to the head and chest and considerably higher overall mortality. CONCLUSIONS Causes and patterns of facial fractures vary with age. Cranial and central facial injuries are more common among toddlers and infants, and mandible injuries are more common among adolescents. Although bony craniofacial trauma is relatively uncommon among the pediatric population, it remains a substantial source of mortality, morbidity, and hospital resource use. Continued efforts toward injury prevention are warranted.

Epidemiology and impact of scarring after burn injury: a systematic review of the literature.

The purpose of this study was to perform a systematic review of the existing literature on the incidence of hypertrophic scarring and the psychosocial impact of burn scars. In a comprehensive literature review, the authors identified 48 articles published since 1965 and written in English which reported the incidence and risk factors for hypertrophic scarring or assessed outcomes related to scarring. Most studies had important methodological limitations limiting the generalizability of the findings. In particular, the absence of standardized valid measures of scarring and other outcome variables was a major barrier to drawing strong conclusions. Among studies on hypertrophic scarring, the prevalence rate varied between 32 and 72%. Identified risk factors included dark skin, female gender, young age, burn site on neck and upper limb, multiple surgical procedures, meshed skin graph, time to healing, and burn severity. With regard to psychosocial outcomes, two studies compared pediatric burn survivors with a nonburn comparison group on a body image measure; neither study found differences between groups. Across studies, burn severity and location had a modest relationship with psychosocial outcome variables. Psychosocial variables such as social comfort and perceived stigmatization were more highly associated with body image than burn characteristics. To advance our knowledge of the epidemiology of scars and the burden of scars, future studies need to implement more rigorous methodologies. In particular, standardized valid measures of scarring and other outcomes should be developed. This process could be facilitated by an international collaboration among burn centers.

Temporal Cytokine Profiles in Severely Burned Patients : A Comparison of Adults and Children

A severe burn leads to hypermetabolism and catabolism resulting in compromised function and structural changes of essential organs. The release of cytokines has been implicated in this hypermetabolic response. The severity of the hypermetabolic response following burn injury increases with age, as does the mortality rate. Due to the relationship between the hypermetabolic and inflammatory responses, we sought to compare the plasma cytokine profiles following a severe burn in adults and in children. We enrolled 25 adults and 24 children who survived a flame burn covering more than 20% of total body surface area (TBSA). The concentrations of 22 cytokines were measured using the Linco multiplex array system (St. Charles, MO, USA). Large perturbations in the expression of pro- and anti-inflammatory cytokines were seen following thermal injury. During the first week following burn injury, IFN-γ, IL-10, IL-17, IL-4, IL-6, and IL-8 were detected at significantly higher levels in adults compared with children, P < 0.05. Significant differences were measured during the second week post-burn for IL-1β (higher in children) and IL-5 (higher in adults), P < 0.05. IL-18 was more abundant in children compared with adults during the third week post-burn, P < 0.05. Between post-burn d 21 and d 66, IL-1α was detected at higher concentrations in pediatric compared with adult patients, P < 0.05. Only GM-CSF expression was significantly different at all time points; it was detected at lower levels in pediatric patients, P < 0.05. Eotaxin, G-CSF, IL-13, IL-15, IP-10, MCP-1, and MIP-1α were detected at significantly different concentrations in adult compared with pediatric patients at multiple time points, P < 0.05. There were no differences in IL-12, IL-2, IL-7, or TNF levels in adult compared with pediatric burn patients at any of these time points. Following severe flame burns, the cytokine profiles in pediatric patients differ compared with those in adult patients, which may provide insight with respect to the higher morbidity rate in adults. Furthermore, the dramatic discrepancies observed in plasma cytokine detection between children and adults suggest that these two patient populations may benefit from different therapeutic interventions to achieve attenuation of the post-burn inflammatory response.

Fournier’s Gangrene: Population Based Epidemiology and Outcomes

PURPOSE Case series have shown a Fourniers gangrene mortality rate of 20% to 40% with an incidence of as high as 88% in some studies. Because to our knowledge there are no population based data, we used a national database to investigate the epidemiology of Fourniers gangrene. MATERIALS AND METHODS We used the State Inpatient Databases, the largest hospital based database available in the United States, which includes 100% of hospital discharges from participating states. Inpatients diagnosed with Fourniers gangrene (ICD-9 CM 608.83) who underwent genital/perineal débridement or died in the hospital were identified from 13 participating states in 2001 and from 21 in 2004. Population based incidence, regional trends and case fatality rates were estimated. RESULTS We identified 1,641 males and 39 females with Fourniers gangrene. Cases represented less than 0.02% of hospital admissions. The overall incidence was 1.6/100,000 males, which peaked in males who were 50 to 79 years old (3.3/100,000) with the highest rate in the South (1.9/100,000). The overall case fatality rate was 7.5%. Patients with Fourniers gangrene were rarely treated at hospitals (mean +/- SD 0.6 +/- 1.2 per year, median 0, range 0 to 23). Overall 0 to 4 and 5 or greater cases were treated at 66%, 17%, 10%, 4%, 1% and 1% of hospitals, respectively. CONCLUSIONS Patients with Fourniers gangrene are rarely treated at most hospitals. The population based mortality rate of 7.5% was substantially lower than that reported in case series from tertiary care centers.

Cell-specific expression and pathway analyses reveal alterations in trauma-related human T cell and monocyte pathways.

Monitoring genome-wide, cell-specific responses to human disease, although challenging, holds great promise for the future of medicine. Patients with injuries severe enough to develop multiple organ dysfunction syndrome have multiple immune derangements, including T cell apoptosis and anergy combined with depressed monocyte antigen presentation. Genome-wide expression analysis of highly enriched circulating leukocyte subpopulations, combined with cell-specific pathway analyses, offers an opportunity to discover leukocyte regulatory networks in critically injured patients. Severe injury induced significant changes in T cell (5,693 genes), monocyte (2,801 genes), and total leukocyte (3,437 genes) transcriptomes, with only 911 of these genes common to all three cell populations (12%). T cell-specific pathway analyses identified increased gene expression of several inhibitory receptors (PD-1, CD152, NRP-1, and Lag3) and concomitant decreases in stimulatory receptors (CD28, CD4, and IL-2Rα). Functional analysis of T cells and monocytes confirmed reduced T cell proliferation and increased cell surface expression of negative signaling receptors paired with decreased monocyte costimulation ligands. Thus, genome-wide expression from highly enriched cell populations combined with knowledge-based pathway analyses leads to the identification of regulatory networks differentially expressed in injured patients. Importantly, application of cell separation, genome-wide expression, and cell-specific pathway analyses can be used to discover pathway alterations in human disease.

Epidemiology and Outcomes of Older Adults With Burn Injury: An Analysis of the National Burn Repository

Improvements in outcomes for older adults sustaining burn injuries have lagged far behind those of younger patients. As this segment of the population grows, there has been an increasing interest in better understanding the epidemiology and outcomes of injury in older adults. The National Burn Repository (NBR) provides a unique opportunity to examine burn injuries on a national level. We aimed to characterize specific injury and outcome trends in older adult with burns through analysis of the NBR. We examined the records of all patients in the NBR aged 55 and older. To characterize age effects on injury and outcomes, patients were stratified into three age categories: 55 to 64 years, 65 to 74 years, and 75 years and older. Baseline characteristics, details of hospital treatment, mortality, and disposition were compared among these three age groups using &khgr;2 or analysis of variance. Logistic regression analysis was performed to assess the impact of age on burn mortality. A total of 180,401 patient records were available from 1991 to 2005, of which 23,180 (14%) met age inclusion criteria. Mean burn size (9.6% TBSA) and percent with inhalation injury (11.3%) did not markedly differ by age. Men predominated overall (ratio 1.4:1), although women (4290) outnumbered men (3439) in the oldest age category. Length of stay per TBSA and median hospital charges increased with increasing age category, suggesting higher resource consumption with aging. Mean number of operations per patient, however, decreased with age. Mortality rates and discharge to nonindependent status increased with age. By logistic regression, the adjusted odds ratio for mortality was 2.3 (95% CI 2.1–2.7) in the 65 to 74 age group, and 5.4 (95% CI 4.8–6.1) in the oldest group when compared with the 55 to 64 age group. Mortality rates decreased significantly after 2001 across all age groups. This analysis demonstrates age-dependent differences in resource utilization and mortality risk within the older burn population and highlights the need for a national research agenda focused on management practices and outcomes in older adult with burns.