Kurtis E. Moyer

Complications in tissue expander breast reconstruction: a comparison of AlloDerm, DermaMatrix, and FlexHD acellular inferior pole dermal slings.

AbstractAcellular dermal matrix (ADM) is frequently used in tissue expander breast reconstruction (TEBR) for coverage of the inferior pole. Several published studies have suggested increased rates of complications with the use of ADM. It is unknown, however, if the type of ADM used for TEBR impacts complication rates. The aim of this study is to compare 3 different types of ADM for TEBR in regard to clinically significant complications, specifically infection. We performed a retrospective analysis of primary breast cancer-related TEBR with or without ADM. Exclusion criteria consisted of prior major breast surgery, inadequate data, or loss to follow-up. Reconstructions were grouped by dermal sling type, AlloDerm, DermaMatrix (DM), FlexHD (FHD), or no ADM. Complications included cellulitis, abscess, seroma, expander leak or puncture, skin necrosis, wound dehiscence, or hematoma. Those requiring admission to hospital or reoperation were considered significant. Of 284 breasts reconstructed, 49 used AlloDerm, 110 used DM, 62 used FHD, and 64 used no ADM. The total complication rate with AlloDerm was 22% [95% confidence interval (CI), 11–34], with DM was 15% (95% CI, 8–21), and with FHD was 18% (95% CI, 8–28) (P = 0.47). Infectious complication rates for AlloDerm, DM, and FHD were equal at 10% (P = 0.97). The total complication rate of all ADM reconstructions as a grouped cohort was 17% compared to 11% without ADM (P = 0.48). The overall incidence of infectious complications with ADM was 10% compared to 2% without ADM (P = 0.09). There is no difference in the clinically significant overall complication rate or incidence of infection between AlloDerm, DM, and FHD. Isolating infectious complications, there is a trend toward increased incidence with ADM compared to reconstructions without.

Mast cells promote fibroblast populated collagen lattice contraction through gap junction intercellular communication

The release of mast cell granules is commonly associated with inflammation and fibrosis. However, does direct communication between mast cells and fibroblasts through gap junction intercellular communication (GJIC) occur? Fibroblast populated collagen lattice (FPCL) cast with mast cells show enhanced lattice contraction. Do released granules or GJIC between mast cells and fibroblasts promote enhanced lattice contraction? Mast cells preloaded with a fluorescent dye that readily passes through gap junctions were cast in FPCL. Dye passed from mast cells into fibroblasts within these cocultured mast cell‐FPCLs. Fatty acid amide hydrolase inhibitor blocks the breakdown of oleamide, which is a potent endogenous inhibitor of GJIC. GJIC was blocked for 3 days when mast cells were pulsed for 3 hours with fatty acid amide hydrolase inhibitor. Mast cells pretreated with fatty acid amide hydrolase inhibitor cast in cocultured mast cell‐FPCLs failed to enhance cocultured lattice contraction. Mast cell‐FPCLs made with mouse fibroblasts unable to generate GJIC failed to show enhanced lattice contraction. Degranulated mast cells were equal to intact mast cells at enhancing cocultured mast cell‐FPCL contraction. The supernatant from degranulated mast cells had no effect upon FPCL contraction. Therefore, enhanced mast cell‐FPCL contraction appears to be independent of mast cell granules, but dependent upon GJIC between fibroblasts and mast cells. We speculate that mast cell–fibroblast GJIC may play a role in fibrosis.

Effects of interleukin‐8 on granulation tissue maturation

The inflammatory α‐chemokine, interleukin‐8 (IL‐8), affects the function and recruitment of various inflammatory cells, fibroblasts, and keratinocytes. Gap junctions are anatomical channels that facilitate the direct passage of small molecules between cells. The hypothesis is that IL‐8 enhances gap junctional intercellular communication (GJIC) between fibroblasts in granulation tissue, which increases the rate of granulation tissue maturation. In vitro, human dermal fibroblasts were incubated with IL‐8 prior to scrape loading, a technique that quantifies GJIC. Polyvinyl alcohol (PVA) sponges were implanted within subcutaneous pockets in rats and received local injections of either IL‐8 or saline and were harvested on day 11. In vitro, IL‐8 treated fibroblasts demonstrated an increase in GJIC by scrape loading compared to saline treated controls. In vivo, IL‐8 treated PVA sponges demonstrated a decrease in cell density and an increase in vascularization compared to saline controls by H&E staining. Polarized light viewed Sirius red‐stained specimens demonstrated greater collagen birefringence intensity, indicating thicker, more‐mature collagen fibers. IL‐8 increases GJIC in cultured fibroblasts and induces a more rapid maturation of granulation tissue.

Metabolic and Functional Characterization of Human Adipose-Derived Stem Cells in Tissue Engineering

Background: The use of adipose-derived stem cells for tissue engineering involves exposing them to metabolically adverse conditions. This study examines the metabolism, proliferation, and differentiation of adipose-derived stem cells under various conditions. Methods: Adipose-derived stem cells were cultured in 16 media conditions containing 0.6, 2.4, 4.3, or 6.1 mM glucose; 0.1, 2.5, 4.1, or 6.1 mM glutamine; and then grown in either 0.1% or 20% oxygen. Conditioned media were collected and assayed for glucose, lactate, and pyruvate. Cell proliferation and cell death were measured at several time points. Osteogenic differentiation was analyzed by alizarin red staining/quantification and alkaline phosphatase activity, measured weekly over 4 weeks. Results: Adipose-derived stem cells remained metabolically active in all nutrient and oxygen conditions tested. Glucose consumption and lactate production increased under hypoxic conditions, but pyruvate consumption was jointly dependent on oxygen and glucose concentration. The 20% oxygen environment produced greater proliferation and cell death compared with the hypoxic environment. Osteogenic differentiation of adipose-derived stem cells was observed only when glucose and/or oxygen concentrations were physiologically normal to high. Conclusions: Adipose-derived stem cells are an excellent source of multipotent cells and are capable of advancing current tissue engineering methodologies. These data show that adipose-derived stem cells remain viable under adverse conditions of low glucose, glutamine, and oxygen concentrations. However, there are variable levels of differentiation in the various culture conditions, which could lead to challenges in de novo osteogenesis and other forms of tissue engineering. Therefore, these results should be used in developing specific strategies to ensure successful application of adipose-derived stem cells in bone engineering and similar applications.

Dupuytren's disease: physiologic changes in nodule and cord fibroblasts through aging in vitro.

The pathogenesis of the fibrotic disease Dupuytrens contracture remains unclear. The disease process includes two structurally distinct fibrotic elements, the nodule and the cord. It has been proposed that as the disease progresses, nodules develop into cords. To corroborate that hypothesis, the authors took advantage of cultured fibroblast differences found between gap junction intercellular communication and fibroblast-populated collagen lattice contraction. Paired fibroblast cell lines of nodules and cords derived from four patients with Dupuytrens disease were maintained in culture for at least eight passages. The presence of gap junction intercellular communication in nodule- and cord-derived fibroblasts was documented and reported as a coupling index. The contraction of free-floating nodule- or cord-derived collagen lattices was also documented and reported. Early passage (passage 4) cord-derived fibroblasts showed a significant increase in coupling index compared with passage 4 nodule-derived fibroblasts (4.0 +/- 0.4 versus 2.5 +/- 0.3, respectively), where p < or = 0.01. However, late passage (passage 8) nodule- and cord-derived fibroblasts were equivalent in their coupling index (4.1 +/- 0.4 versus 4.4 +/- 0.4, respectively). Early passage nodule-derived fibroblast-populated collagen lattices contracted by 64 percent, whereas late passage nodule-derived lattices showed less contraction, at only 40 percent. Early and late passage cord-derived lattices contracted 46 and 37 percent, respectively. All nodule- and cord-derived cell lines were statistically equivalent at lattice contraction by passage 8. These in vitro studies support the hypothesis that fibroblasts derived from Dupuytrens contracture nodules change their phenotype after undergoing repeated cell passage, acquiring a cord-like fibroblast phenotype. Dupuytrens nodules represent the early, active form of fibrosis in which cells are more proliferative, better at fibroblast-populated collagen lattice contraction, and display less gap junction intercellular communication. The speculation is that alterations in gap junction intercellular communication may be involved in the progression of Dupuytrens nodules to cords as the disease progresses.

Calmodulin‐myosin light chain kinase inhibition changes fibroblast‐populated collagen lattice contraction, cell migration, focal adhesion formation, and wound contraction

Wound healing requires fibroblast migration, synthesis of new extracellular matrix, and organization of that matrix, all of which depend upon myosin ATPase activation and subsequent cytoplasmic actin‐myosin contraction. Myosin ATPase activity is optimized by phosphorylation of myosin light chain at serine 19. Several different signaling pathways can perform that phosphorylation, the focus here is calcium saturated calmodulin dependent ‐myosin light chain kinase (CaM‐MLCK). It is proposed that CaM‐MLCK phosphorylation of myosin light chain and subsequent myosin ATPase activation affects granulation tissue fibroblast behavior and contributes to wound contraction. Myosin ATPase activity generates actin‐myosin contraction within fibroblasts. Myosin ATPase activity is involved in ATP‐induced cell contraction, the generation of focal adhesions, fibroblast migration, fibroblast populated collagen lattice (FPCL) contraction, and wound contraction. The MLCK inhibitors ML‐9 and ML‐7 inhibited ATP‐induced cell contraction, fibroblast migration, FA formation, and FPCL contraction. The calmodulin inhibitors W7 and fluphenazine blocked rat open wound contraction. In addition, fluphenazine delayed re‐epithelialization. These findings support the idea that fibroblast CaM‐MLCK activity is essential for tissue repair. We speculate that inhibition of CaM‐MLCK may reduce or prevent detrimental fibrotic contracture.

Modulation of human fibroblast gap junction intercellular communication by hyaluronan

The composition of the extracellular matrix changes during dermal repair. Initially, hyaluronan (HA) concentration is high, however, by day 3, HA is eliminated. HA optimizes collagen organization within granulation tissue. One possible mechanism of HA modulation of collagen packing is through the promotion of gap junction intercellular communication (GJIC). Gap junctions are gated channels that allow rapid intercellular communication and synchronization of coupled cell activities. The gap junction channel is composed of connexin (Cx) proteins that form a gated channel between coupled cells. HA is reported to enhance Cx43 expression in transformed fibroblasts. GJIC was quantified by the scrape loading technique and reported as a coupling index. The coupling index for human dermal fibroblasts was 4.6 ± 0.2, while the coupling index for fibroblasts treated with HA more than doubled to 10.6 ± 0.7. By Western blot analysis no differences were appreciated in the protein levels of Cx43 or β‐catenin, a protein involved in the translocation of Cx to the cell surface. By immuno‐histology Cx43 and β‐catenin were evenly distributed throughout the cell in controls, but in cells treated with HA these proteins were co‐localized to the cell surface. Coupled fibroblasts are reported to enhance the organization of collagen fibrils. It is proposed that HA increases the accumulation of Cx43 and β‐catenin on the cell surface, leading to greater GJIC and enhanced collagen organization.

Soft-tissue defects and exposed hardware: a review of indications for soft-tissue reconstruction and hardware preservation.

Background: Traditionally, management of exposed hardware has included irrigation and débridement, intravenous antibiotics, and likely removal of the hardware. Increasingly, the goal of wound closure without hardware removal using plastic surgical techniques of soft-tissue reconstruction has been emphasized. Identification of parameters for retaining exposed hardware may assist surgeons with management decisions and outcomes. Methods: A current literature review was performed to identify parameters with prognostic relevance for management of exposed hardware before soft-tissue reconstruction. Results: The following parameters were identified as important for the potential salvage of exposed hardware with soft-tissue coverage: hardware location, infection, duration of exposure, and presence of hardware loosening. Conclusions: Management of exposed hardware has included the removal of the hardware. However, if certain criteria are met—specifically, stable hardware, time of exposure less than 2 weeks, lack of infection, and location of hardware—salvage of the hardware with plastic surgical soft-tissue coverage may be a therapeutic option.

Analysis of clinically significant seroma formation in breast reconstruction using acellular dermal grafts.

AbstractWith a rise in tissue expander-based breast reconstructions (TEBRs) using acellular dermal matrix (ADM), we have seen an increase in ADM-specific complications. In this study, we aimed to evaluate clinically significant seroma (CSS) formation—defined by the need for a drainage procedure—to determine if there was a difference in incidence between product types: AlloDerm (AL), DermaMatrix (DM), and FlexHD (FHD). This was a retrospective review of consecutive patients who underwent TEBR at a single institution. The total number of reconstructed breasts was separated into the following 4 groups according to the product type: AL, DM, FHD, or no ADM. We identified the total number of CSSs and compared these data between product types. A logistic regression was performed in an attempt to identify independent risk factors associated with seroma formation. In total, we identified 284 consecutive TEBRs. Overall, there were 17 (7.7%) seromas in 220 breast reconstructions in which ADM was used. When comparing the number of CSS between groups—AL (n = 2, 4.0%), DM (n = 6, 5.4%), FHD (n = 9, 14.75%), and no ADM (n = 1, 1.5%)—we found a significant difference in seroma incidence between product types (P = 0.016). Multivariate analysis identified a strong trend toward FHD as an independent predictor of seroma formation (P = 0.061). Our review suggests that there is strong trend in CSS formation with the use of FHD as compared to other product types and reconstructions in which no ADM was used.

Systemic vanadate ingestion modulates rat tendon repair

The chronic ingestion of vanadate prevents the appearance of myofibroblasts within granulation tissue of full excision wounds in rats, yet these wounds close at an optimal rate. Myofibroblasts are reported in the repair of transected tendons. Here we investigate tendon repair in the absence of myofibroblasts. Vanadate in saline drinking water was given to rats in the experimental group, while rats in the control group received saline alone. The Achilles tendon of the left leg of each rat was transected and suture repaired. On day 10, both repaired tendons and uninjured tendons from the right leg were harvested and processed for histology. By immunohistology the repaired tendons of control rats had myofibroblasts (fibroblasts with alpha smooth muscle actin positive stress fibers), while myofibroblasts were absent in healing tendons from vanadate-treated rats. By transmission electron microscopy and polarized light optics, repaired tendons of control rats demonstrated thin, loosely packed, immature collagen fiber bundles. Collagen fiber bundles from healing tendons of the vanadate-treated group were thicker, uniformly packed, and more mature. The chronic ingestion of vanadate promotes the more rapid organization of collagen fiber bundles of healing transected tendons in the absence of myofibroblasts.