A new method for the detection of viable cells in tissue sections using 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT): an application in the assessment of tissue damage by surgical instruments

Thermosensitive and antioxidant wound dressings capable of adaptively regulating TGFβ pathways promote diabetic wound healing

Various therapies have been utilized for treating diabetic wounds, yet current regiments do not simultaneously address the key intrinsic causes of slow wound healing, i.e., abnormal skin cell functions (particularly migration), delayed angiogenesis, and chronic inflammation. To address this clinical gap, we develop a wound dressing that contains a peptide-based TGFβ receptor II inhibitor (PTβR2I), and a thermosensitive and reactive oxygen species (ROS)-scavenging hydrogel. The wound dressing can quickly solidify on the diabetic wounds following administration. The released PTβR2I inhibits the TGFβ1/p38 pathway, leading to improved cell migration and angiogenesis, and decreased inflammation. Meanwhile, the PTβR2I does not interfere with the TGFβ1/Smad2/3 pathway that is required to regulate myofibroblasts, a critical cell type for wound healing. The hydrogel's ability to scavenge ROS in diabetic wounds further decreases inflammation. Single-dose application of the wound dressing significantly accelerates wound healing with complete wound closure after 14 days. Overall, using wound dressings capable of adaptively modulating TGFβ pathways provides a new strategy for diabetic wound treatment.

Impact of Three Different Processing Techniques on the Strength and Structure of Juvenile Ovine Pulmonary Homografts

Homografts are routinely stored by cryopreservation; however, donor cells and remnants contribute to immunogenicity. Although decellularization strategies can address immunogenicity, additional fixation might be required to maintain strength. This study investigated the effect of cryopreservation, decellularization, and decellularization with additional glutaraldhyde fixation on the strength and structure of ovine pulmonary homografts harvested 48 h post-mortem. Cells and cellular remnants were present for the cryopreserved group, while the decellularized groups were acellular. The decellularized group had large interfibrillar spaces in the extracellular matrix with uniform collagen distribution, while the additional fixation led to the collagen network becoming dense and compacted. The collagen of the cryopreserved group was collapsed and appeared disrupted and fractured. There were no significant differences in strength and elasticity between the groups. Compared to cryopreservation, decellularization without fixation can be considered an alternative processing technique to maintain a well-organized collagen matrix and tissue strength of homografts.

Coming to Consensus: What Defines Deep Partial Thickness Burn Injuries in Porcine Models?

Deep partial thickness burns are clinically prevalent and difficult to diagnose. In order to develop methods to assess burn depth and therapies to treat deep partial thickness burns, reliable, accurate animal models are needed. The variety of animal models in the literature and the lack of precise details reported for the experimental procedures make comparison of research between investigators challenging and ultimately affect translation to patients. They sought to compare deep partial thickness porcine burn models from five well-established laboratories. In doing so, they uncovered a lack of consistency in approaches to the evaluation of burn injury depth that was present within and among various models. They then used an iterative process to develop a scoring rubric with an educational component to facilitate burn injury depth evaluation that improved reliability of the scoring. Using the developed rubric to re-score the five burn models, they found that all models created a deep partial thickness injury and that agreement about specific characteristics identified on histological staining was improved. Finally, they present consensus statements on the evaluation and interpretation of the microanatomy of deep partial thickness burns in pigs.

Effects of scaffold material used in cardiovascular surgery on mesenchymal stem cells and cardiac progenitor cells

BACKGROUND

Polytetrafluoroethylene (PTFE) and porcine small intestinal submucosa (pSIS) are patch materials used in congenital heart surgery. Porcine SIS is an extracellular-matrix scaffold that may interact with stem or progenitor cells. To evaluate this, we determined the in vitro effects of pSIS and PTFE on human bone marrow mesenchymal stromal cells (MSCs) and cardiac progenitor cells (CPCs) in 3 areas; cell proliferation, angiogenic growth-factor production, and differentiation.

METHODS

Human MSCs and CPCs were seeded onto pSIS and PTFE patches. Cell-seeded patches were cultured and then assessed for cell viability and proliferation and supernatant vascular endothelial growth factor A (VEGFA) levels. Cell proliferation was quantified by MTT assay (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide). Quantitative real-time polymerase chain reaction was performed on cell-seeded scaffolds to determine relative changes in gene expression related to angiogenesis and cardiogenesis.

RESULTS

The MSCs and CPCs were able to attach and proliferate on pSIS and PTFE. The proliferation rate of each cell type was similar on pSIS. Total RNA isolation was only possible from the cell-seeded pSIS patches. The MSC VEGFA production was increased by pSIS. Porcine SIS promoted an angiogenic gene profile in MSCs and an early cardiogenic profile in CPCs.

CONCLUSIONS

Both PTFE and pSIS allow for varying degrees of cell proliferation. Porcine SIS elicits different phenotypical responses in MSCs as compared with CPCs, which indicates that pSIS may be a bioactive scaffold that modulates stem cell activation and proliferation. These findings highlight the differences in scaffold material strategies and suggest potential advantages of bioactive approaches.

Application of immunohistochemical staining to detect antigen destruction as a measure of tissue damage

Electrocautery and directed energy devices (DEDs) such as lasers, which are used in surgery, result in tissue damage that cannot be readily detected by traditional histological methods, such as hematoxylin and eosin staining. Alternative staining methods, including 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) to stain live tissue, have been reported. Despite providing superior detection of damaged tissue relative to the hematoxylin and eosin (H&E) method, the MTT method possesses a number of drawbacks, most notably that it must be carried out on live tissue samples. Herein, we report the development of a novel staining method, "antigen destruction immunohistochemistry" (ADI), which can be carried out on paraffin-embedded tissue. The ADI method takes advantage of epitope loss to define the area of tissue damage and provides many of the benefits of live tissue MTT staining without the drawbacks inherent to that method. In addition, the authors provide data to support the use of antibodies directed at a number of gene products for use in animal tissue for which there are no species-specific antibodies commercially available, as well as an example of a species-specific direct antibody. Data are provided that support the use of this method in many tissue models, as well as evidence that ADI is comparable to the live tissue MTT method.

Injectable, rapid gelling and highly flexible hydrogel composites as growth factor and cell carriers

A family of injectable, rapid gelling and highly flexible hydrogel composites capable of releasing insulin-like growth factor (IGF-1) and delivering mesenchymal stromal cell (MSC) were developed. Hydrogel composites were fabricated from Type I collagen, chondroitin sulfate (CS) and a thermosensitive and degradable hydrogel copolymer based on N-isopropylacrylamide, acrylic acid, N-acryloxysuccinimide and a macromer poly(trimethylene carbonate)-hydroxyethyl methacrylate. The hydrogel copolymer was gellable at body temperature before degradation and soluble at body temperature after degradation. Hydrogel composites exhibited LCSTs around room temperature. They could easily be injected through a 26-gauge needle at 4 degrees C, and were capable of gelling within 6s at 37 degrees C to form highly flexible gels with moduli matching those of the rat and human myocardium. The hydrogel composites showed good oxygen permeability; the oxygen pressure within the hydrogel composites was similar to that in the air. The effects of collagen and CS contents on LCST, gelation time, injectability, mechanical properties and degradation properties were investigated. IGF-1 was loaded into the hydrogel composites for enhanced cell survival/growth. The released IGF-1 remained bioactive during a 2-week release period. Small fraction of CS in the hydrogel composites significantly decreased IGF-1 release rate. The release kinetics appeared to be controlled mainly by hydrogel composite water content, degradation and interaction with IGF-1. Human MSC adhesion on the hydrogel composites was comparable to that on the tissue culture plate. MSCs were encapsulated in the hydrogel composites and were found to grow inside during a 7-day culture period. IGF-1 loading significantly accelerated MSC growth. RT-PCR analysis demonstrated that MSCs maintained their multipotent differentiation potential in hydrogel composites with and without IGF-1. These injectable and rapid gelling hydrogel composites demonstrated attractive properties for serving as growth factor and cell carriers for cardiovascular tissue engineering applications.

A PEGylated Fibrin Patch for Mesenchymal Stem Cell Delivery

A potential therapy for myocardial infarction is to deliver isolated mesenchymal stem cells (MSCs) to the infarcted site. A key issue with this technology is the development of a suitable system for MSC delivery. Our delivery system of interest is a fibrin-based patch used to entrap cells during polymerization. This delivery vehicle has many advantages; however the mechanical properties and the limited capacity for tailoring cell response may restrict its application. We have developed a PEGylated fibrin patch for MSC transplantation by modifying fibrinogen (Fgn) with the benzotriazole carbonate derivative of PEG to create secondary crosslinking. In this study, the chemical PEGylation of fibrinogen was verified by both amine group quantification and SDS-PAGE. The clotting characteristics and physical properties were compared between the fibrin patch and PEGylated fibrin patch. After seeding with porcine MSCs, the cell viability, morphology, and motility in the novel patch were observed. Phenotypic changes in the embedded MSCs were examined using immunohistochemistry and RT-PCR. The optimal molar ratio (PEG:Fgn = 10:1) was determined for loading MSCs in vitro into the PEGylated fibrin patch. The results suggest that our PEGylated fibrin patch increases MSC viability. Furthermore, the PEGylated fibrin causes phenotypic changes in MSCs consistent with endothelial cells.

Immediate histological changes in soft palate after uvulopalatopharyngoplasty with CO2, contact Nd:YAG or combined CO2 and Nd:YAG laser beams

CO2, contact Nd:YAG and Combolaser (combined, simultaneous and coaxial CO2 + Nd:YAG laser beam) were used for uvulopalatopharyngoplasty (UPPP). It has been proposed that the combined beam geometry diminishes thermal damage to surrounding tissues when compared with single laser radiation. To study the extent of thermal tissue damage produced by the lasers, tissue samples for light (LM) and transmission electron microscopy (TEM) were taken from the surface of the resected area and 2 and 4 mm below the resection plane. The depth of tissue damage and coagulation was measured. The results showed no consistent differences in the inflammatory reactions or the amount and depth of tissue coagulation observed in samples taken immediately after the operation. The CO2 laser typically produced a carbonized and coagulated wound edge. Combolaser and contact Nd:YAG lasers generated slightly less charring but otherwise resembled each other with coagulated and vacuolized resecate margins. These results indicate that the beam geometry in Combolaser does not diminish thermal damage to surrounding tissues.

Reduced in vivo local recurrence with contact neodymium: Yttrium-Aluminium-Garnet (Nd:YAG) laser scalpels

BACKGROUND AND OBJECTIVE

Local recurrence after surgical resection for breast cancer is a significant problem and is often not controlled by radiation or chemotherapy treatments. Local recurrence is thought to be, at least in part, due to residual disease, and/or due to the contamination of the surgical field during resection. STUDY DESIGN MATERIALS AND METHODS: To address this later concern, we defined a model system using the mouse mammary cell line, EMT6. Using this model system, we have directly compared the rate of local recurrence of two different surgical approaches. One approach employed the use of traditional surgical instruments, and the other used a comparatively new contact Nd:YAG laser system. Tumor-bearing animals (242) were randomized into three groups. One group consisted of 50 animals that were not treated; 103 animals were randomized into a treatment group that received surgical resection using traditional instruments; 89 animals were resected using the contact laser system. In both surgical procedures, an intentional incision was made through the tumor and then through an uninvolved portion of the surgical field in an attempt to "seed" the incision using the contaminated surgical instrument.

RESULTS

Twenty-one of the 103 scalpel-treated animals had local recurrence; only seven of the 89 laser-treated animal had local recurrence. The untreated group died of disease within 8 weeks. In the treatment groups, recurrences were palpable within 1 week. At the time of death for all groups, no metastatic lesions were noted.

CONCLUSION

These findings support the conclusions that the EMT6 cell line is a useful model to study local recurrence and that contact laser surgery provides about a 50% improvement in the control of local disease in vivo (P < 0.05).