Hydrogen/deuterium exchange mass spectrometry in the world of small molecules.

The combined use of hydrogen/deuterium exchange (HDX) and mass spectrometry (MS), referred to as HDX-MS, is a powerful tool for exploring molecular edifices and has been used for over 60 years. Initially for structural and mechanistic investigation of low-molecular weight organic compounds, then to study protein structure and dynamics, then, the craze to study small molecules by HDX-MS accelerated and has not stopped yet. The purpose of this review is to present its different facets with particular emphasis on recent developments and applications. Reversible H/D exchanges of mobilizable protons as well as stable exchanges of non-labile hydrogen are considered whether they are taking place in solution or in the gas phase, or enzymatically in a biological media. Some fundamental principles are restated, especially for gas-phase processes, and an overview of recent applications, ranging from identification to quantification through the study of metabolic pathways, is given.

Morel-Lavallée lesion associated with atypical skin damage: a case report.

A Morel-Lavallée lesion is a post-traumatic, soft tissue lesion that is little known and for which there is no standard treatment. This report describes the case of a 51-year-old man who presented with a large Morel-Lavallée lesion on the left calf that was not diagnosed on two visits to the emergency department. Given the deteriorating condition of the skin, we performed surgical drainage of the effusion because the skin was showing signs of major damage. Complications occurred following surgery, with cellulitis in the lower limb caused by Citrobacter Koseri, a gram-negative bacillus that is rarely implicated in soft tissue infections, and wound dehiscence. The purpose of our article is to present the difficulty involved in choosing the right treatment from among the many proposed in the literature, and to inform any practitioner working in an emergency setting about the existence of this often overlooked condition.

Tendon Tissue Engineering: Mechanism and Effects of Human Tenocyte Coculture With Adipose-Derived Stem Cells.

PURPOSE: Adipose-derived stem cells (ASCs) are a potential candidate for cell-based therapy targeting tendon injury; however, their therapeutic benefit relies on their ability to interact with native tenocytes. This study examines the mechanism and effects of coculturing human tenocytes and ASCs. METHODS: Tenocytes (T) were directly cocultured with either ASCs (A) or fibroblasts (F) (negative control) in the following ratios: 50% T/50% A or F; 25% T/75% A or F; and 75% T/25% A or F. Cells were indirectly cocultured using a transwell insert that allowed for exchange of soluble factors only. Proliferation and collagen I production were measured and compared with monoculture controls. Synergy was quantified using the interaction index (II), which normalizes measured values by the expected values assuming no interaction (no synergy when II = 1). The ability of ASCs to elicit tenocyte migration was examined in vitro using a transwell migration assay and ex vivo using decellularized human flexor tendon explants. RESULTS: Compared with monoculture controls, II of proliferation was greater than 1 for all tenocyte and ASC direct coculture ratios, but not for tenocyte and fibroblast direct coculture ratios or for tenocyte and ASC indirect coculture. The ASCs elicited greater tenocyte migration in vitro and ex vivo. The II of collagen I production was greater than 1 for direct coculture groups with 25% T/75% A and 75% T/25% A. CONCLUSIONS: Direct coculture of ASCs and tenocytes demonstrated synergistic proliferation and collagen I production, and ASCs elicited tenocyte migration in vitro and ex vivo. These interactions play a key role in tendon healing and were absent when ASCs were replaced with fibroblasts, supporting the use of ASCs for cell-based therapy targeting tendon injuries. CLINICAL RELEVANCE: When ASCs are delivered for cell-based therapy, they directly interact with native tenocytes to increase cell proliferation, collagen I production, and tenocyte migration, which may enhance tendon healing.

Molecular Biology of Flexor Tendon Healing in Relation to Reduction of Tendon Adhesions.

Tendon injuries are encountered after major and minor hand trauma. Despite meticulous repair technique, adhesion formation can occur, limiting recovery. Although a great deal of progress has been made toward understanding the mechanism of tendon healing and adhesions, clinically applicable solutions to prevent adhesions remain elusive. The goal of this paper is to review the most recent literature relating to the tendon healing and adhesion prevention.

Reverse Radial Forearm Flap.

Supplemental Digital Content is available in the text.

Intratendinous Injection of Hydrogel for Reseeding Decellularized Human Flexor Tendons.

BACKGROUND: Decellularized cadaveric tendons are a potential source for reconstruction. Reseeding to enhance healing is ideal; however, cells placed on the tendon surface result in inadequate delivery. The authors used an injection technique to evaluate intratendinous cell delivery. METHODS: Decellularized tendons were reseeded with adipose-derived stem cells in culture, and injected with fetal bovine serum or hydrogel. PKH26-stained cells in cross-section were quantified. To evaluate cell viability, the authors delivered luciferase-labeled cells and performed bioluminescent imaging. To evaluate synthetic ability, the authors performed immunohistochemistry of procollagen. Adipose-derived stem cells' ability to attract tenocytes was assessed using transwell inserts. Cell-to-cell interaction was assessed by co-culturing, measuring proliferation and collagen production, and quantifying synergy. Finally, tensile strength was tested. RESULTS: Both fetal bovine serum (p < 0.001) and hydrogel (p < 0.001) injection led to more cells inside the tendon compared with culturing. Hydrogel injection initially demonstrated greater bioluminescence than culturing (p < 0.005) and fetal bovine serum injection (p < 0.05). Injection groups demonstrated intratendinous procollagen staining correlating with the cells' location. Co-culture led to greater tenocyte migration (p < 0.05). Interaction index of proliferation and collagen production assays were greater than 1 for all co-culture ratios, demonstrating synergistic proliferation and collagen production compared with controls (p < 0.05). There were no differences in tensile strength. CONCLUSIONS: Hydrogel injection demonstrated the greatest intratendinous seeding efficiency and consistency, without compromising tensile strength. Intratendinous cells demonstrated synthetic capabilities and can potentially attract tenocytes inside the tendon, where synergy would promote intrinsic tendon healing. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, V.

An Inexpensive Bismuth-Petrolatum Dressing for Treatment of Burns.

BACKGROUND: Xeroform remains the current standard for treating superficial partial-thickness burns but can be prohibitively expensive in developing countries with prevalent burn injuries. This study (1) describes the production of an alternative low-cost dressing and (2) compares the alternative dressing and Xeroform using the metrics of cost-effectiveness, antimicrobial activity, and biocompatibility in vitro, and wound healing in vivo. METHODS: To produce the alternative dressing, 3% bismuth tribromophenate powder was combined with petroleum jelly by hand and applied to Kerlix gauze. To assess cost-effectiveness, the unit costs of Xeroform and components of the alternative dressing were compared. To assess antimicrobial properties, the dressings were placed on agar plated with Escherichia coli and the Kirby-Bauer assay performed. To assess biocompatibility, the dressings were incubated with human dermal fibroblasts and cells stained with methylene blue. To assess in vivo wound healing, dressings were applied to excisional wounds on rats and the rate of re-epithelialization calculated. RESULTS: The alternative dressing costs 34% of the least expensive brand of Xeroform. Antimicrobial assays showed that both dressings had similar bacteriostatic effects. Biocompatibility assays showed that there was no statistical difference (P < 0.05) in the cytotoxicity of Xeroform, alternative dressing, and Kerlix gauze. Finally, the in vivo healing model showed no statistical difference (P < 0.05) in mean re-epithelialization time between Xeroform (13.0 ± 1.6 days) and alternative dressing (13.5 ± 1.0 days). CONCLUSIONS: Xeroform is biocompatible, reduces infection, and enhances healing of burn wounds by preventing desiccation and mechanical trauma. Handmade petrolatum gauze may be a low-cost replacement for Xeroform. Future studies will focus on clinical trials in burn units.

Tendon Regeneration with Tendon Hydrogel-Based Cell Delivery: A Comparison of Fibroblasts and Adipose-Derived Stem Cells.

BACKGROUND: Tendon hydrogel is a promising biomaterial for improving repair strength after tendon injury. This study compares the capacity of fibroblasts and adipose-derived stem cells to proliferate, survive, and acquire tenogenic properties when seeded into tendon hydrogel in vitro and in vivo. METHODS: The effect of cell density on hydrogel contraction was measured macroscopically. To assess tenogenic properties, RNA was isolated from cells seeded in vitro in hydrogel, and tenocyte markers were quantified. To assess in vitro proliferation and survival, MTS and live-dead assays were performed. Finally, to assess the in vivo survival of cells in hydrogel, subcutaneous injections were performed on rats and in vivo imaging was performed. RESULTS: At 0.5 million cells/ml, both the fibroblasts and adipose-derived stem cells induced minimal hydrogel contraction compared with higher cellular concentrations. Fibroblasts and adipose-derived stem cells seeded at 0.5 million cells/ml in tendon hydrogel up-regulated several tenocyte markers after 1 week. On MTS assay, fibroblasts and adipose-derived stem cells proliferated in hydrogel at similar rates. On live-dead assay, fibroblasts survived longer than adipose-derived stem cells. With use of the in vivo imaging system and histologic evaluation, fibroblasts survived longer than adipose-derived stem cells in hydrogel in vivo. CONCLUSIONS: Tendon healing is mediated by the proliferation, survival, and tenogenic differentiation of cells at the site of injury. Tendon hydrogel delivering dermal fibroblasts may improve and stimulate this process compared with adipose-derived stem cells. Future studies will be needed to evaluate the effects of this hydrogel-based cell delivery on chronic tendon injuries.