PubMed · 4313682
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K Tomita. 1969. [Thyroid hormone and catecholamines].. https://pubmed.ncbi.nlm.nih.gov/4313682/
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Decellularized tissues provide biological cues owing to the wealth of structural and regulatory factors that promote angiogenesis, adipogenesis, and myogenesis and facilitate neurite outgrowth. Here, we demonstrated the advantages of decellularized adipose tissue (adipoECM) over defined collagen-based biomaterials for host tissue integration. Three batches of human adipose tissue were decellularized using a rapid decellularization protocol and analyzed using mass spectrometry. To assess the biological activity of the decellularized materials, adipoECM and a reference standard of care biomaterial (Integra®DRT, also containing collagen I and glycosaminoglycans) were implanted subcutaneously, but far from the wound bed (in anatomical potential spaces) of immunocompetent BALB/c mice. The mice were euthanized in the acute (1 day) and chronic (day 60) inflammatory reaction phases, followed by biomaterial excision and Masson’s trichrome immunohistofluorescence imaging of the paraffin-embedded specimens. Each batch of processed tissue passed a quality control check, showing a low level of donor genomic DNA, lack of nuclei, lipids, endotoxins, and bacterial contamination. Mass spectrometry revealed that all batches of decellularized tissue mainly contained collagen I and, to a lesser degree, collagen III, collagen IV, collagen V, laminin, fibrillin, fibronectin, tenascin, and elastin. No acute inflammatory reaction was observed in either material one day post-transplantation. At 60 days post-implantation, different cell types were detected in adipoECM specimens, whereas Integra®DRT remained acellular. Additional immunohistochemical staining of adipoECM revealed CD31-positive cells in the blood vessels. Mesenchymal (CD90 positive) and myeloid (CD14 positive) cells were also detected. Primary cell types involved in soft tissue healing and remodeling were found in the adipoECM-treated group. The ingrowth of blood vessels and mesenchymal cells confirmed the effective integration of adipoECM with host tissues. Our results demonstrate that decellularized adipose tissue implanted away from the wound bed possesses contextual biological activities that promote efficient integration with host tissues.
End product application is an important consideration when evaluating a material in an in vivo setting (Didisheim, Cardiovasc Pathol 1993;2:1S-2S). Small animal models allow high through-put evaluation of biocompatability. Previous preclinical evaluations have often used a rat subcutaneous model for the characterization of material-tissue interaction. Recent advances in genetic manipulation have provided mouse models with selective expression of a wide range of critical proteins. The rat model does not have many of the resources (i.e., knockouts, SCID, nude) that are present in mouse strains. The availability of these mice provides a resource to delineate the mechanisms regulating the healing associated with implants. However, before the mouse models can be used, they must be validated with respect to their ability to accurately assess tissue responses to materials. In this study the tissue responses after the implantation of expanded polytetrafluoroethylene (ePTFE) were compared between rat and mouse. Discs of ePTFE (30-microm internodal distance) were implanted in subcutaneous and epididymal fat tissue of rats (Sprague-Dawley) and mice (129-SVJ). After 5 weeks the samples were removed and evaluated for vascular density, inflammation, and fibrous encapsulation. No difference in the vessel density was observed within the peri-implant subcutaneous and adipose tissue or within the porous material. However, a significant difference was found in the number of activated macrophages and giant cells between these two species. Implants in the rat exhibited greater numbers of activated inflammatory cells in the peri-implant tissue. The data indicate that the mouse and rat provide a comparable model for evaluating angiogenesis and neovascularization associated with synthetic porous implants.
In the obese state, enlarged adipose cells display an altered gene-expression profile and metabolic capacity. The aim of this study was to gain insight into their secretory function, by assessing two secreted proteins, leptin and angiotensinogen, in adipose cells of obese (fa/fa) Zucker rats. A marked and co-ordinate increase in leptin mRNA, gene transcription and promoter activity was observed in obese compared with lean (Fa/fa) rat adipose cells, and this resulted in increased leptin release in culture. Two sets of observations suggest that this effect is due to the fa mutation. First, adipose-cell leptin release was higher in heterozygous (Fa/fa) than in homozygous (Fa/Fa) lean rats. Second, leptin release was not enhanced in enlarged adipose cells of FalFa rats fed a high-fat diet for 15 days. At variance with leptin, angiotensinogen production was not significantly increased in the obese cells. Dexamethasone stimulated both leptin and angiotensinogen release in lean and obese rat adipose cells. The magnitude of leptin stimulation was higher in fa/fa than in Fa/fa rats, whereas angiotensinogen release was increased to the same extent in both genotypes. These observations suggest that leptin production is specifically enhanced in enlarged adipose cells of obese Zucker rats and that cell hypertrophy is not the sole determinant of this feature. Increased leptin production might be related to disruption of leptin signalling by the fa mutation.