Physiological processes of inflammation and edema initiated by sustained mechanical loading in subcutaneous tissues : a scoping review

Deep tissue injuries are pressure ulcers which initiate in the subcutaneous tissues and extend through a bottom-up pathway. Once deep tissue injuries are visual at skin level, serious irreversible tissue damage has already occurred. In pressure ulcer development, inflammation and edema are coupled physiological processes associated with tissue damage arising due to sustained mechanical loading. This study aimed to provide an in-depth overview of the physiological processes of inflammation and edema initiated by sustained mechanical loading in subcutaneous tissues, in the context of pressure ulceration. A scoping review was performed according to the framework by Arksey and O'Malley. The databases MEDLINE, EMBASE, Web of Science, and Scopus, and the reference lists of included studies were searched for in vivo (animal, human), and in vitro studies matching the study objectives (from inception to 28 May 2018). No restrictions for inclusion were applied for study design, setting, participants, and year of publication. A total of 12 studies were included, varying in study design, sample characteristics, amount and duration of mechanical loads that were applied, follow-up time, and assessment methods. Neutrophil infiltration and edema occur in the subcutaneous tissues nearly immediately after the application of load on soft tissues. The amount of neutrophils and edema increase in the first days after the mechanical insult and decrease once healing has been initiated and no supplementary mechanical load was applied. One study indicated that edema may extend up to the level of the dermo-epidermal junction. Further research should focus on how deep tissue inflammation and edema are reflected into unique tissue changes at skin level, and how abnormal inflammatory responses manifest (e.g. when the nervous system is not functioning normally)

Analysis of the Collagen I and Fibronectin of Temporomandibular Joint Synovial Fluid and Discs

Purpose: The objective of this study was to investigate the content of synovial fluid aspirates and temporomandibular joint (TMJ) disc tissue for collagen I and total fibronectin in patients with closed lock. Fibronectin contains dual properties of assisting with wound healing and inducing cartilage degradation. Native fibronectin has been shown to assist with wound repair, whereas particular fibronectin fragments may degrade cartilage. In addition, collagen I is the major supporting protein of the TMJ disc and will degrade as osteoarthritis progresses. Fibronectin or collagen I expression in human TMJ synovial aspirates and disc tissue may indicate the proteins\u27 involvement in closed lock. The hypothesis of this study is that TMJ discs and serum of patients with closed lock will contain an increased amount of fibronectin and decreased amount of collagen I. Materials and Methods: We analyzed a total of 8 diseased TMJ discs and 4 diseased synovial fluid aspirates. For our control samples, we assessed 5 synovial samples from healthy patients and control skin samples. Using an enzyme-linked immunosorbent assay allowed us to measure the total amount of fibronectin and collagen I in synovial aspirates. Furthermore, we used light microscopy to assess TMJ disc histology and collagen architecture in control skin samples. Lastly, using fluorescent staining, we examined fibronectin and collagen I expression in TMJ discs. We compared the fluorescent staining and light microscopy results of both proteins within each disc to confirm fibronectin and collagen I expression. Results: Disc specimens with advanced morphologic pathology showed significant labeling for fibronectin in 3 of 3 cases and for collagen I in 4 of 4 cases. There was no considerable difference in detection of either fibronectin or collagen I in TMJ synovial aspirates from patients with advanced disc pathology compared with controls. Conclusions: The levels of fibronectin and collagen I in the TMJ disc and synovial fluid may be influenced by the stage of disease. The results did not provide a clear understanding of fibronectin and collagen I involvement with tissue repair in closed-lock cases. Detection of fibronectin fragments may provide more meaningful results. © 2009 American Association of Oral and Maxillofacial Surgeons