Muscle Phenotyping and Imaging

Director


Melissa J. Spencer, Ph.D.
mspencer@mednet.ucla.edu
310-794-5225

Description


The Muscle Phenotyping and Imagine Core is designed to enable muscle and non-muscle researchers alike to access a variety of assessment tools for the study of muscle phenotypes. This Core provides a means for investigators to test lead therapeutic compounds in mice to evaluate their effect on muscle pathology. Drugs that delay the onset of disease or reduce muscle pathology will be identified through the small molecule high-throughput screen (Core B) or can be investigator initiated.  For these assessments, both traditional (histology, muscle function tests) and non-traditional (optical imaging, MRI) methods are available for UCLA researchers to utilize on a fee for service basis.  Also, because most muscular dystrophies involve changes in the dystrophin-glycoprotein complex, biochemical assessments of muscular dystrophy-related proteins are an additional service offered by this core. Finally, Core C enables non-muscle researchers to explore muscle phenotypes in their novel knock out and transgenic animals.  This Core provides access to resources, expertise and training necessary to allow them to explore muscle morphology and function. 

Services


Please see price list for fees associated with these services. 

Service A. Muscle Dissection and Frozen Sectioning
Core C will provide assistance in mouse muscle dissection and freezing for histology or biochemistry. Too many mice to transfer? In this case, our "Mobile Dissection Unit" (MDU) can send a team to your lab to help with dissection and freezing of mouse muscles.

Service B. Immunohistochemistry of CD11b, NCAM, type I collagen or DGC components 
The core houses a panel of antibodies to components of the dystrophin- and utrophin-glycoprotein complexes (including ab-dystroglycan, as well as the sarcoglycan-sarcospan subcomplex) will be available for use.  Antibodies to CD11b, NCAM and Type I collagen will also be available as markers of inflammation, regeneration and fibrosis, respectively. Assistance will be available for analysis of muscle cryosections.  

Service C. Optical Imaging
Mice expressing the Cox 2 luciferase transgene (crossed to mdx mouse) can be optically imaged using a Xenogen Optical Imager (IVIS, Xenogen).  The transgene produces light when the Cox2 gene is activated.  In the mdx mouse, this activation occurs primarily in immune cells and to a lesser extent in regenerating muscle fibers.  Animals can be treated with drug (done by the investigator) starting from 6 days of age.  Animals will be optically imaged (front and back) starting from 3 weeks of age until 8 weeks of age, once per week.  Mice will be exercised on a treadmill 3 times per week to exacerbate disease.  This will be the standard protocol; however, individual Center Investigators may choose to design their experiments differently depending on the model being used or the drug treatment.  Reimbursement to the Core is on a per-mouse/per session basis.  Prior to imaging, mice will be anesthetized using gas anesthesia and the hair on the limbs shaved.  Following anesthesia, the mice will be weighed and injected with 126µg D-luciferin per gram and placed in a special holder to keep constant the position of each mouse. Imaging will be carried out using a cooled CCD camera after establishing a standardized region of interest (ROI). The ROI will be placed over both upper legs (quadriceps and hamstrings) and mice imaged for one hour. At the end of the imaging, a grey scale image will be taken of the mice as a reference. In the event that the signal to noise level is not adequate, the muscles of the mouse can be dissected and imaged.  The large muscles (gastrocnemius, quadriceps and hamstrings) are dissected and placed in a Petri dish and imaged. After imaging one side of the muscles, they will be turned over and the other side imaged. The sum of all light for all three muscles from each mouse will be the data point.  At the end of the imaging, a grey scale image will be taken of the muscles as a reference. 

FUNCTIONAL ASSESSMENTS 

Service D. Grip Strength Test
Grip strength will be assessed using a grip strength meter consisting of a horizontal bar connected to a force transducer (Columbus Instruments).  The animals are acclimatized to the apparatus for several trials (over a minutes time) and then data are collected using 5 separate trials.  For each trial, the animal is brought to the bar and when it is close to the bar, it instinctively grabs for it.  The mouse is handled by the neck and tail, and is slowly pulled away from the apparatus until it lets go and the peak force is recorded by the force transducer.  Data are normalized by the mouse weight. 

Service E. Wire Test
These tests are carried out using a wire apparatus suspended 2 feet from the base. The wire test is made up of 5 trials, with each trial consisting of a hanging period for 1-5 min followed by a rest period of 1 min.  The hanging time is recorded for each trial and times are averaged for each mouse. 

Service F. Rotor Rod Test
All mice are run through two practice trials to acclimate them to the Rotor Rod apparatus prior to the commencement of the test trials.  Each trial consists of a maximum run of 300s or 5 min.  During this time the rotating dowel speed increases every 30s from time 0s until the speed reaches 10 rpm (i.e., 2.5 rpm/2s, 5 rpm/30s, 7.5 rpm/60s, 10 rpm/90s- 300s).  The end of a trial is marked when all of the mice fall off the dowel.  The time spent on the dowel will be recorded as the latency to fall (L.T.F.).  Between each trial there is a rest period of 1 min.  Each mouse is put through 2 practice trials and 3 test trials. 

Service G. Pulmonary Function Testing
The Core utilizes plethysmography to non-invasively assess pulmonary function in mice. Previous studies have shown that older mdx mice have a reduced tidal volume and increased respiratory rate at rest.  Following a hypercapnic stimulus, mdx mice do not increase their respiratory rate to the same extent as wild type mice. To assess respiratory patterns in conscious mice, we use unrestricted whole body barometric plethysmography (Buxco Electronic, Inc.). The data will be monitored and analyzed using Biosystem XA Software, which is supplied with the system (Buxco Electronics, Inc.). Up to 8 mice can be tested simultaneously. Previous studies have shown that older (greater than 7 mo) mdx mice have a blunted hypercapnic respiratory rate.  Using this method, respiratory dysfunction can be correlated to diaphragm degeneration. Respiratory patterns are recorded based on pressure changes inside the testing chamber.  Initially, mice are weighed and placed into a single chamber with a volume of 0.8L where they are allowed to move freely and acclimate for at least 15 minutes. To provide a base line reading, a room air-reading will be taken as follows: compressed air will be supplied to the chamber at a flow rate of 1L/min for 45 minutes. At this point, the chamber will be completely sealed, with airflow momentarily stopped. The changes in pressure caused by breathing will be recorded and amplified by the software. Subsequently, the mice will be allowed to rest for at least 5 minutes or until the breathing returns to baseline before conducting the hypercapnia phase.  In the hypercapnia phase, a gas mixture containing 7% CO2, 21% O2 and balanced N2 will be supplied to the chamber at a flow of 1 L/min. After 5 minutes, the chamber will be sealed and ventilatory patterns recorded. During the breathing room-air and hypercapnia phase, the average tidal volume (TV) and respiratory rate (RR) will be measured for a period of at least 10 consecutive breaths. 

Service H. MRI
Investigators may choose to evaluate the efficacy of therapeutic compounds using the animal MRI that we will have available.  Investigators who choose to use the MRI services will consult with the Core director (Melissa Spencer) and/or consultants (Jeffrey Alger or Neil Harris) about their individual projects to determine the data points and assessments that can best be used to answer the questions in their study.  The charge per mouse is the same for any or all of the above measurements. For the MRI procedure, mice will be anesthetized using gas anesthesia. 

MRI Methods
Data will be acquired using a 7T Oxford/Bruker magnet and console with a purpose-built animal cradle and a bird-cage volume coil for radiofrequency transmission. A proton-decoupled surface coil positioned over the leg was used to receive data. Mice will be maintained under light isoflurane anesthesia vaporized in oxygen flowing at 0.4l/min and maintained at 37c using homeostatically controlled warm-air flowing into the magnet bore (SA Inst., USA).  

T2 Imaging
T2-weighted, multi-spin echo data will be acquired (echo times 14, 28, 42ms) with a repetition time of 1.5s, 16 1mm slices and a 256x256 matrix, acquired in a 2.56cm2 FOV resulting in a 100µm in-plane resolution. Regions of pathology indicated by hypo-intense regions on the T2-weighted data will be defined and superimposed on T2 maps calculated from the raw data using Image J software (NIH, USA).  We will determine whether changes in T2 can be used as an indicator of muscle fiber breakdown, reductions in number of fibers/unit volume and an increase in water content that replaces lost fibers.  

Downloadable forms 

Core C Services and Prices

Cores

The Core Center is dedicated to understanding processes in degenerative muscle disorders and to identifying therapeutic interventions. In order to most rapidly effect gains, the Center provides a host of interactive intellectual, administrative and research cores. The Center is comprised of four core facilities, all designed to facilitate discovery of therapeutics and test hypotheses related to muscle research. These cores include:

Highthroughput Screening and Cell Repository Muscle Phenotyping and Imaging Bioinformatics and Genomics Back

A primary goal for the Center in creating these Cores is to make available generically useful resources that can be distributed to other researchers in muscular dystrophy or to basic scientists interested in muscle research. The Center is structured to enrich existing muscle research programs on campus by providing its members with access to unique core facilities, pilot funding mechanisms, seminars and an annual retreat focused on muscle research.

Furthermore, the Core Center brings together investigators with a variety of specific interests, some of which are not directly muscle related, to benefit research in muscle disorders.