Trends in flap reconstruction of pelvic oncologic defects: Analysis of the national inpatient sample

BACKGROUND

Flap reconstruction of radiated pelvic oncologic defects decreases perineal wound-healing complications. How widely and how often reconstructions are performed, and how technical mastery and improved perioperative care has affected outcomes, is unknown. Our objective is to 1) provide a comprehensive evaluation of national trends in flap reconstruction of pelvic oncologic defects and 2) compare complications and length of stay (LOS) in patients with/without reconstruction.

METHODS

The National Inpatient Sample (NIS) database was queried (1998-2014) for patients diagnosed with cancer, primarily of the rectum and anus, who underwent abdominoperineal resection (APR) or pelvic exenteration (PE). Differences in complications and LOS were compared between patients with flap reconstruction versus primary closure. Regional and hospital outcomes were also analyzed.

RESULTS

The cohort included 117,923 adult patients; 3,673 (3.1%) underwent flap reconstruction. Flap reconstruction rates increased from 0.8% in 1998 to 9.8% in 2014. Extirpative procedures decreased 37.4% from 1998 to 2014. Flap reconstruction decreased risk of wound breakdown (OR 0.87; p = 0.0029) and need for secondary closure of dehiscence (OR 0.82; p = 0.0023) between periods 1998-2009 and 2010-2014. Median LOS was higher for flap patients (median [IQR] of 9.8 [7.2,14.8] vs. 7.9 [6.1-11.0; p < 0.0001) and decreased over time.

CONCLUSIONS

The use of flap reconstruction for pelvic oncologic defects increased from 1998 to 2014, with a reduction in LOS. Following flap reconstruction, overall complications are higher, but wound breakdown and dehiscence requiring reclosure are decreasing, suggesting technique maturation. We anticipate flap reconstruction rates will increase with further improvement in patient outcomes.

Comparison of wound strength, histologic, and aesthetic outcomes after microsurgical versus conventional skin closure in a rat model

The purpose of this study was to compare the healing, strength, and cosmetic outcome of linear incisions after repair with the naked eye, surgical loupes, or a surgical microscope. Two parallel incisions were made on the dorsal skin of Sprague-Dawley rats (n = 36) and the rats randomized into four groups. A single surgeon repaired the incisions using 5-0 poliglecaprone in a running subcuticular pattern using the naked eye (Group I), surgical loupes with 2.5× magnification (Group II), surgical microscope with 5-10× magnification (Group III), and 6-0 poliglecaprone with a surgical microscope (Group IV). Rats were sacrificed at 1, 3, and 6 weeks. At each time point, the tensile strength of each closure was assessed. Macroscopic outcomes were evaluated using the Vancouver Scar Scale (VSS) and histology assessed by a blinded observer. Microscope closure took significantly longer than closure with the naked eye (p < 0.05). There was no significant difference in tensile strength or VSS ratings between the closure methods at any of the time points. On histopathologic analysis, there were a greater number of inflammatory cells and fibroblasts in the 6-0 microscope closure group versus the naked eye closure group at week 3 (p ≤ 0.05). In conclusion, wound repair under magnification did not yield a significant difference in cosmesis or wound tensile strength, but did increase operative time. Moreover, there was a trend toward increased inflammation with microscope-assisted closures, perhaps due to the increased suture burden.

Defining hydrogel properties to instruct lineage- and cell-specific mesenchymal differentiation

The maintenance and direction of stem cell lineage after implantation remains challenging for clinical translation. Aggregation and encapsulation into instructive biomaterials after preconditioning can bolster retention of differentiated phenotypes. Since these procedures do not depend on cell type or lineage, we hypothesized we could use a common, tunable platform to engineer formulations that retain and enhance multiple lineages from different cell populations. To test this, we varied alginate stiffness and adhesive ligand content, then encapsulated spheroids of varying cellularity. We used Design-of-Experiments to determine the effect of these parameters and their interactions on phenotype retention. The combination of parameters leading to maximal differentiation varied with lineage and cell type, inducing a 2-4-fold increase over non-optimized levels. Phenotype was also retained for 4 weeks in a murine subcutaneous model. This widely applicable approach can facilitate translation of cell-based therapies by instructing phenotype in situ without prolonged induction or costly growth factors.

Cell-secreted extracellular matrix, independent of cell source, promotes the osteogenic differentiation of human stromal vascular fraction

Lipoaspirates contain a readily accessible heterogeneous cell source for use in bone regeneration collectively referred to as the stromal vascular fraction (SVF). However, the osteogenic potential of SVF is inferior to other progenitor cell populations, thereby requiring alternative strategies to potentiate its effective use in cell-based therapies of bone repair. Cell-secreted extracellular matrix (ECM) is a promising substrate to guide cell phenotype or for use in biomaterial design, yet the instructional capacity of ECMs produced by various cell types is unknown. To determine whether the bioactivity of cell-secreted ECM was dependent on cell source, we assessed the osteogenic response of human SVF on ECMs secreted by bone marrow-derived mesenchymal stem cells (MSCs), adipose stromal cells (ASCs), and human dermal fibroblasts (HDFs). Tissue culture plastic (TCP), type I collagen, and ECM induced expression of integrin subunits α₂, α₅, and β₁ in SVF, yet seeding efficiency was only improved on MSC-derived ECM. Regardless of ECM source, SVF deposited over 8- and 1.3-fold more calcium compared to TCP and collagen-coated controls, respectively. Flow cytometry confirmed that SVF cultured on ECM retained CD31 and CD34 positive cell populations better than TCP. After depleting accessory cells, ASCs deposited significantly less calcium compared to donor-matched SVF. This function was partially restored in the presence of MSC-derived ECM when donor-matched endothelial cells (ECs) were added in an ASC/EC co-culture, confirming a role for ECs in osteogenic differentiation. These findings support the use of cell-derived ECM as a means to promote cell retention and osteogenic differentiation of SVF.

Comparison of AlloDerm and AlloMax tissue incorporation in rats

BACKGROUND

Human acellular dermal matrices (HADMs) are used in a variety of settings. AlloMax is a new HADM currently being used for breast reconstruction and hernia repair. We compared the in vivo tissue integration of AlloMax to AlloDerm, a well-studied HADM, in rats.

METHODS

We implanted AlloDerm and AlloMax patches into subcutaneous pockets on the backs of 32 male Sprague-Dawley rats. The animals were killed after either 4 or 8 weeks, and the patches were recovered and stained for histopathologic analyses. Microscopic end points included patch thickness, vascularization, tissue in-growth, fibroblast proliferation, and inflammation.

RESULTS

All animals completed the study without complications or infection. There were no significant differences in graft thicknesses at 4 and 8 weeks. Microscopically, at 4 weeks, AlloDerm sections had significantly more microvessels than AlloMax (P = 0.02). This disparity increased by 8 weeks (P < 0.01). Similarly, we found greater tissue in-growth and fibroblast proliferation in AlloDerm than AlloMax sections at 4 (P < 0.01) and at 8 (P < 0.01) weeks. Inflammatory infiltrates consisted of lymphocytes, histiocytes, eosinophils, and plasma cells. Deep graft infiltration by predominately lymphocytic inflammatory cells was significantly higher in AlloDerm than AlloMax grafts at 4 (P = 0.01) and 8 (P = 0.02) weeks. Graft necrosis was uncommon, but marginal fibrosis was similar in both.

CONCLUSIONS

AlloDerm grafts had greater neovascularization, tissue infiltration, fibroblast proliferation, and inflammatory reaction than AlloMax grafts when placed subcutaneously in rats. AlloDerm may be better incorporated than AlloMax when placed in vivo.

Total posterior leg open wound management with free anterolateral thigh flap: case and literature review

Soft tissue coverage of the exposed Achilles tendon is a unique reconstructive challenge. In this report, we describe the management of a large posterior leg wound with exposed Achilles tendon using a free anterolateral thigh (ALT) flap. A careful review of alternative reconstructive options is included, along with their respective advantages and disadvantages. A 32-year-old white man suffered a fulminant right lower extremity soft tissue infection requiring extensive debridement of the entire posterior surface of the right leg. The resulting large soft tissue defect included exposure of the Achilles tendon. Reconstruction of the defect was achieved with an ALT flap and split-thickness skin graft for coverage of the Achilles tendon and gastrocnemius muscle, respectively. The patient was able to ambulate independently within 2 months of the procedure.

Effect of adipose tissue-derived osteogenic and endothelial cells on bone allograft osteogenesis and vascularization in critical-sized calvarial defects

The use of processed bone allograft to repair large osseous defects of the skull has been limited, given that it lacks the osteogenic cellularity and intrinsic vascular supply which are essential elements for successful graft healing and, at the same time, the areas to be targeted through tissue-engineering applications. In this study, we investigated the effect of predifferentiated rat adipose tissue-derived osteoblastic cells (OBs) and endothelial cells (ECs) on calvarial bone allograft healing and vascularization using an orthotopic critical-sized calvarial defect model. For this purpose, thirty-seven 8 mm critical calvarial defects in Lewis rats were treated with bone allografts seeded with no cells, undifferentiated adipose tissue-derived stem cells (ASC), OBs, ECs, and OBs and ECs simultaneously. After 8 weeks, the bone volume and mineral density were calculated using microcomputed tomography and the microvessel formation using immunohistochemical staining and imaging software. The amount of bone within the 8 mm defect was significantly higher for the allografts treated with ECs compared with the allografts treated with OBs (p=0.05) and simultaneously with the two cell lineages (p=0.02). There were no significant differences in bone formation between the latter two groups and the control groups (allografts treated with no cells and undifferentiated ASC). There were no significant differences in bone mineral density among the groups. The amount of microvessels was significantly higher in the group treated with ECs relative to all groups (p=< 0.05). Our results show that the implantation of ASC-derived ECs improves the vascularization of calvarial bone allografts at 8 weeks after treatment. This cell-based vascularization strategy can be used to improve the paucity of perfusion in allogenic bone implants. However, in this study, the treatment of allografts with OBs alone or in combination with ECs did not support bone formation or vascularization.

Unique modulation of cadherin expression pattern during posterior frontal cranial suture development and closure

Cranial suture development involves coordinated expression of multiple genes and tissue contribution from neural crest cells and paraxial mesoderm for timely sutural morphogenesis. Transcription factors, growth factors, and neural crest determinant genes play critical roles in calvarial growth ensuring normal development of the underlying brain. In vitro studies have implicated cell-cell adhesion molecules as a driving force behind suture closure. We performed cDNA microarray to study differential expression of adhesion molecules during the timing of suture closure in a mouse model where only the posterior frontal (PF) suture closes. Our results indicate increased expression of E-cadherin during the period of PF suture closure. Quantitative RT-PCR analysis of E- and N-cadherin in PF closing suture revealed a biphasic expression of N-cadherin, the first phase coinciding with cellular condensation preceding chondrogenesis followed by a second phase coinciding with E-cadherin co-expression and suture closure. Furthermore, expression analysis of the N-cadherin and E-cadherin transcriptional repressors Wnt7a and Snail indicate a specific temporal regulation of these genes, suggesting their potential role as regulators of both E- and N-cadherin during the PF suture development and closure. Finally, given the in vitro evidence of fibroblast growth factor (FGF)-2 as a potential regulator of E- and N-cadherin we investigated the expression of E-cadherin during PF suture closure in Fgf-2 deficient mice. In contrast to in vitrodata previously reported, E-cadherin expression is normal in these animals, and PF suture closure occurs properly, probably due to potential redundancy of FGF ligands ensuring normal temporal expression of E-cadherin and PF suture closure.

Sox9 neural crest determinant gene controls patterning and closure of the posterior frontal cranial suture

Cranial suture development involves a complex interaction of genes and tissues derived from neural crest cells (NCC) and paraxial mesoderm. In mice, the posterior frontal (PF) suture closes during the first month of life while other sutures remain patent throughout the life of the animal. Given the unique NCC origin of PF suture complex (analogous to metopic suture in humans), we performed quantitative real-time PCR and immunohistochemistry to study the expression pattern of the NCC determinant gene Sox9 and select markers of extracellular matrix. Our results indicated a unique up-regulated expression of Sox9, a regulator of chondrogenesis, during initiation of PF suture closure, along with the expression of specific cartilage markers (Type II Collagen and Type X Collagen), as well as cartilage tissue formation in the PF suture. This process was followed by expression of bone markers (Type I Collagen and Osteocalcin), suggesting endochondral ossification. Moreover, we studied the effect of haploinsufficiency of the NCC determinant gene Sox9 in the NCC derived PF suture complex. A decrease in dosage of Sox9 by haploinsufficiency in NCC-derived tissues resulted in delayed PF suture closure. These results demonstrate a unique development of the PF suture complex and the role of Sox9 as an important contributor to timely and proper closure of the PF suture through endochondral ossification.

Applications of a mouse model of calvarial healing: differences in regenerative abilities of juveniles and adults

Young children are capable of healing large calvarial defects, whereas adults lack this endogenous osseous tissue-engineering capacity. Despite the important clinical implications, little is known about the molecular and cell biology underlying this differential ability. Traditionally, guinea pig, rabbit, and rat models have been used to study the orchestration of calvarial healing. To harness the research potential of knockout and transgenic mice, the authors developed a mouse model for calvarial healing. Nonsuture-associated parietal defects 3, 4, and 5 mm in diameter were made in both juvenile (6-day-old, n = 15) and adult (60-day-old, n = 15) mice. Calvariae were harvested after 8 weeks and analyzed radiographically and histologically. Percentage of healing was quantified using Scion Image software analysis of calvarial radiographs. A significant difference in the ability to heal calvarial defects was seen between 6-day-old and 60-day-old mice when 3-, 4-, or 5-mm defects were created. The authors' analysis revealed that juvenile mice healed a significantly greater percentage of their calvarial defects than adult mice (juvenile mean percentage of healing: 3-mm defects, 59 percent; 4-mm defects, 65 percent; 5-mm defects, 44 percent; adult mean percentage of healing: <5 percent in all groups; p < 0.05). All three defect sizes were found to be critical in the adult, whereas significant healing was seen regardless of the size of the defect in juvenile mice. The establishment of this model will facilitate further, detailed evaluation of the molecular biology underlying the different regenerative abilities of juvenile versus adult mice and enhance research into membranous bone induction by making available powerful tools such as knockout and transgenic animals.

In Vitro Murine Posterior Frontal Suture Fate Is Age-Dependent:

In CD-1 mice, the posterior frontal suture (analogous to the human metopic suture) fuses while all other cranial sutures remain patent. In an in vitro organ culture model, the authors previously demonstrated that posterior frontal sutures explanted immediately before the onset of suture fusion (at 25 days old) mimic in vivo physiologic fusion. In the first portion of this study, the authors defined how early in development the posterior frontal suture fuses in their tension-free, serum-free organ culture system by serially analyzing posterior frontal suture fusion from calvariae explanted at different stages of postnatal development. Their results revealed a divergence of suture fate leading to abnormal patency or physiologic fusion between the first and second weeks of life, respectively, despite viability and continued growth of the calvarial explants in vitro. From these data, the authors postulated that the gene expression patterns present in the suture complex at the time of explant may determine whether the posterior frontal suture fuses or remains patent in organ culture. Therefore, to elucidate potentially important differences in gene expression within this "window of opportunity," they performed a cDNA microarray analysis on 5-day-old and 15-day-old posterior frontal and sagittal whole suture complexes corresponding to the age ranges for unsuccessful (1 to 7 days old) and successful (14 to 21 days old) in vitro posterior frontal suture fusion. Overall, their microarray results reveal interesting differential expression patterns of candidate genes in different categories, including angiogenic cytokines and mechanosensitive genes potentially important in cranial suture biology.

The Candida albicans INT1 gene facilitates cecal colonization in endotoxin-treated mice

Increased intestinal colonization with Candida albicans is believed to be a major predisposing factor to systemic candidiasis. Previous evidence has implicated the C. albicans INT1 gene in hyphal development, epithelial adherence, and mouse virulence. The effect of INT1 on mouse cecal colonization was measured using a parent strain (CAF2, INT1/INT1), an int1 deletion homozygote (CAG3, int1/int1), and a heterozygous reintegrant (CAG5, int1/int1 + INT1). Forty-eight hours after oral inoculation of 10(7) C. albicans into normal mice, only low numbers of each strain were recovered from the cecal flora. In mice pretreated with oral bacitracin/streptomycin, cecal colonization of each C. albicans strain was increased compared to the corresponding strain inoculated into untreated mice, with the CAF2 parent strain greater (P < 0.01) than the two mutant strains, and with the heterozygous and homozygous mutants not different from each other. In mice pretreated with parenteral lipopolysaccharide (LPS), in addition to oral antibiotics, numbers of cecal CAF2, CAG5, and CAG3 were increased (P < 0.01) compared to the corresponding strain inoculated into mice treated with antibiotics alone. In LPS-treated mice, numbers of cecal C. albicans CAF2 (INT1/INT1) were greater (P < 0.05) than C. albicans CAG3 (int1/int1). Thus, parenteral LPS had an additive effect on C. albicans cecal colonization in antibiotic-treated mice, and the presence of two functional copies of the INT1 gene appeared to facilitate colonization in both antibiotic-treated mice and in mice treated with antibiotics plus parenteral endotoxin.