Pseudofracture, a reproducible murine model of sterile musculoskeletal trauma, allows for evaluation of late term post-traumatic immune responses. This article describes the procedural execution of the model step by step, including the potential for experimental model combinations to permit study of multiple trauma.
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Method Article
Pseudofracture: An Acute Peripheral Tissue Trauma Model
In This Article
Summary
Abstract
Following trauma there is an early hyper-reactive inflammatory response that can lead to multiple organ dysfunction and high mortality in trauma patients; this response is often accompanied by a delayed immunosuppression that adds the clinical complications of infection and can also increase mortality.1-9 Many studies have begun to assess these changes in the reactivity of the immune system following trauma.10-15
Immunologic studies are greatly supported through the wide variety of transgenic and knockout mice available for in vivo modeling; these strains aid in detailed investigations to assess the molecular pathways involved in the immunologic responses.16-21
The challenge in experimental murine trauma modeling is long term investigation, as fracture fixation techniques in mice, can be complex and not easily reproducible.22-30
This pseudofracture model, an easily reproduced trauma model, overcomes these difficulties by immunologically mimicking an extremity fracture environment, while allowing freedom of movement in the animals and long term survival without the continual, prolonged use of anaesthesia. The intent is to recreate the features of long bone fracture; injured muscle and soft tissue are exposed to damaged bone and bone marrow without breaking the native bone.
The pseudofracture model consists of two parts: a bilateral muscle crush injury to the hindlimbs, followed by injection of a bone solution into these injured muscles. The bone solution is prepared by harvesting the long bones from both hindlimbs of an age- and weight-matched syngeneic donor. These bones are then crushed and resuspended in phosphate buffered saline to create the bone solution.
Bilateral femur fracture is a commonly used and well-established model of extremity trauma, and was the comparative model during the development of the pseudofracture model. Among the variety of available fracture models, we chose to use a closed method of fracture with soft tissue injury as our comparison to the pseudofracture, as we wanted a sterile yet proportionally severe peripheral tissue trauma model. 31
Hemorrhagic shock is a common finding in the setting of severe trauma, and the global hypoperfusion adds a very relevant element to a trauma model. 32-36 The pseudofracture model can be easily combined with a hemorrhagic shock model for a multiple trauma model of high severity. 37
Protocol
1. Instrument and Surgical Field Preparation:
All experimental procedures are performed using aseptic techniques. Before beginning, the experimental area must be thoroughly cleaned and sterilized. The benchtop should be disinfected, allowed to air dry and then wiped down with 70% alcohol. Place a surgical blue pad and sterile field dressing in the experimental work area.
All materials and instruments are autoclave sterilized before use. Syringes and needles are received sterile. The researcher should be appropriately garbed in lab coat, surgical mask, and sterile surgical gloves.
Our su....
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Discussion
Pseudofracture, a reproducible murine model of sterile musculoskeletal trauma, allows for evaluation of post-traumatic immune responses. The pseudofracture model immunologically mimics an extremity fracture environment through recreation of the features of a long bone fracture: injured muscle and soft tissue are exposed to damaged bone and bone marrow without breaking the native bone.38,39 A biphasic immune response can be seen following pseudofracture trauma which consists of an early hyperinflammatory respon.......
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Disclosures
Experiments on animals were performed in accordance with the guidelines and regulations set forth by the Institutional Animal Care and Use Committee and the Research Conduct and Compliance Office of the University of Pittsburgh, an AALAS/AAALAC accredited institution. Animal sources include Jackson Laboratories and Charles Rivers Laboratories. All animals undergo extensive health assurance through each vendor as well as the University of Pittsburgh's internal animal health monitoring programs. This research is conducted in accordance with the US government principals for Use of vertebrate animals. The program is registered with the USDA, and has a letter of assurance with the Public Health Service Office of Laboratory Animal Welfare.
Acknowledgements
Funding Source /Number Molecular Biology of Hemorrhagic Shock GM053789
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Materials
| Name | Company | Catalog Number | Comments |
|---|---|---|---|
| Surgical blue pad | Fisher Scientific | 50-7105 | |
| Sterile Field dressings | Fisher Scientific | NC9517505 | |
| Circulating heating pad 18"x26" | Harvard Apparatus | py872-5272 | |
| Hot bead instrument sterilizer | VWR international | 11156-002 | |
| Stainless steel tray 8" x 11" | VWR international | 62687-049 | |
| Plexiglass boards (10x15x0.5cm) | University of Pittsburgh Machine shop | ||
| Tape rolls 1" | Corporate Express | MMM26001 | |
| 50cc conical tube | Any Supplier | ||
| Straight side wide mouth jars (used as cap for nose cone) | VWR international | 159000-058 | |
| Oster A5 clippers w. size 40 blade | VWR international | 10749-020 | |
| Surgical scissors (straight – 12cm) | Fine Science Tools | 14068-12 | |
| Hemostats curved -18cm | Harvard Apparatus | 81331718 | |
| Forceps (0.8mm-tip, curved-10cm) | Fine Science Tools | 11050-10 | |
| Gauze 4"x4" | Any Supplier | ||
| 1.5cc microfuge tube | Any Supplier | ||
| Ice bucket | Any Supplier | ||
| Mortar and Pestle | Fisher Scientific | 12-961AA | |
| 1cc syringe w/ 25G needle | Fisher Scientific | 14-826-88 | |
| 20G needle | Any Supplier | ||
| 1mL pipetteman | Any Supplier | ||
| 1mL pipette tips | Any Supplier | ||
| Falcon polystyrene 8ml tubes | VWR international | 60819-331 | |
| Sterilization pouch 3"x8" | VWR international | 24008 | |
| Sterilization pouch 5"x10" | VWR international | 24010 | |
| MacConkey II Agar plate | BD Biosciences | 221172 | |
| Ethyl Alcohol - 200 proof | Pharmco-AAPER | [70%] | |
| Pentobarbital Sodium (Nembutol Sodium Solution) | OVATION Pharmaceuticals | 70mg/kg | |
| Aerrane (Isoflurane) | Baxter Internationl Inc. | 99.9% | |
| Triadine Povidone Iodine (Betadine) | Triad disposables | ||
| Phosphate Buffered Saline (PBS) | |||
| Buprenorphine HCl | Bedford Laboratories | 0.1mg/kg |
References
- DeCamp, M. M., Demling, R. H. Posttraumatic multisystem organ failure. JAMA. 260, 530-534 (1988).
- Deitch, E. A. Multiple organ failure. Pathophysiology and potential future therapy. Ann Surg. 216, 117-134 (1992).
- Carrico, C. J., Meakins, J. L., Marshall, J. C.
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