I am trying to induce psoriasis in a mice model. In the publication attached, imiquimod application for 6 days would induce formation of the lesion. However, i have discovered that this is not so in my case. There is only a slight redness of the skin with none of the other features of psoriasis (scaling, increase skin thickness etc) after 6 days of treatment. I would really appreciate some advice. Thank you.
Article Imiquimod-Induced Psoriasis-Like Skin Inflammation in Mice I...
I am working extensively on the imiquimod model with different protocols to induce psoriasis. I must mention that to check efficacy of a antipsoriatic drug, systemically or topically, 62.3mg per mice is enough. But this is highly schedule (pretretreatment followed with imiquimod or imiquimod followed with drug therapy) and dose dependant. For topical study, 62.3 mg is fine, since imiquimod is such a potent inducer of immune system, this much dose is enough to get to know the difference in treated group (testing compund) and imiquimod control group
While for severe psoriatic phenotype, 81.5 mg is also used, but this is good only if you need to study long term effects.
However, in both cases, you cant get to trace the cytokine levels. As this is an acute model and activation of cytokine is transient. Thus if your study emphasis on cytokine levels, day 3 or maximum day 4 is good timepoint to detect cytokines. At later timepoint you cant get detectable levels.
Hope this will be helpful.
That should work. Do you shave the skin? Apply exactly the same amount of ALdara? Or are you using a different brand or concentration??
Sorry for late reply. Yes, I am using Aldara. Each pack is 250 mg, 5%w/w. The cream is applied to the shaved back (shaving a mouse is hard work!) and also the back of the ear.
I should also say that the mice are placed in self contained cages, with filtered air. One mouse per cage. I have increased the aldara/imiquimod dose to 125 mg/ mouse. Is that a right thing to do?
The 62,5 mg should work, but you can try 125.
are the mice betwen 8 and 12 week old?
Yes, we are measuring the skin and ear thickness. The basal values are the values before administration of IMQ. Yes, we noticed that the skin thickness increases. We are also scoring for the redness and also the increase in scaliness. The three parameters.
can someone please provide details of the method.
1. What is the area of application ( how many cm2) to understand the dose per unit area.
2. are you housing them singly so that other mice dont lick the cream off.
3. Are you covering the cream prior to returning the mice to their cages
If you apply a patch over the treatment you should see a quick response as it will insure deep penetration of the drug and obtain the response you desire.
thank you Richard! I know occlusion will facilitate permeation, I was wondering for how long do you leave the drug on and what measures do you take to prevent ingestion when mice groom themselves.
If you shave the site first you will greatly enhance the absorption of Aldara/imiquimod-5%. The only answer I can give you on time-frames to psoriasis is that you will first have to reach the stage of delayed- hypersensitivity of the application site. Now, that will occur at non-specific time periods relative to the mice species and its immune status or characteristics but it can occur in short order under the right circumstances and within 48-hours or so when left in place. Be ware that this occlusion method will most likely induce a number of other side effects that you may not want to have going on at the same time in your research.
As for the prevention of ingestion of drug, I have used heavy aluminum foil circle with body glue that women use to glue on garments, etc., to their skin to keep them in place. Just one of many types of skin friendly adhesives. Apply very sparingly to the underneath side and outer perimeter of the circle just enough to keep it pinned down and in place. Removal is done per instructions that come with the respective glue or adhesive agent but is quit friendly to the animal. But remember to use as little as possible and make sure the circle is big enough to extend well outside of the treatment site so as not to interfere with the skin erosion area induced by the drug. Hope this helps. Also, if you are concerned that the aluminum might contaminate your study results use a thin sheet of plastic food wrap such as SuranWrap (sp) just under the aluminum circle. Place the circle of wrap on the treatment site first then install the aluminum circle. That should keep the site consistent with study protocols.
The first possible side-effect you may notice will most likely include herpes-simplex like blisters, pemphigus lesions, just to name a few. These may occur rapidly or not at all. I would suggest that after 48-hrs of contact with IQ that you remove the patch and try and continue with open-air treatment of the site in order to have the site experience some time of dryness which will allow you to plainly see the initiation of psoriasis if and when it manifests.
What is the optimal dose for imiquimod in mice and best time to apply?
Generally scaling should appear fourth day onwards at 62.5 mg dose/day. Have you tried to increase days of imiquimod application? For instance upto 10 days. Prolong application of imiquimod will enhance the hyperproliferation of keratinocytes and scaling too.
Dear Effat, There is clear cut redness in the ear if you keep applying IMQ daily for seven days. It is clearly visible by observation and measurable by digital micrometer. Same goes for back skin. Scaling sometimes is not that prominent but redness is after 7 days of application. Also back hair should be removed completely by Veet cream/other depilatory cream to see a good effect of IMQ. Histopathology by HnE confirms these findings both in ear and back skin. It is difficult to lengthen the model beyond 7-8 days as hair start reappearing. Increase in ear weight and spleen weight are also suggestive of proper IMQ applications at the end of the study. Last but not the least, Original Aldara cream induces better psoriasis than generic IMQ creams. I hope these tips help you.
Dear Faisal,
There is no need to anesthetize as applying Aldara is very easy. Just hold the tail and apply using plastic spatula/cotton bud etc on the shaved back. Anesthesia everyday may complicate your findings.
Dear Ahmed
That's true on true on the recurrent application. Shaving and naring the back for the first time will need anesthesia. Thank you
One sachet of Aldara contains 250 mg cream which can be divided in 4 equal parts on a non-sticky paper using a sensitive balance. Use one sachet for 4 mice.
Yes, it is possible if IMQ treatment is longer than 5 days, around 1-2 out of 10 mice may die on prolonged exposure.
Thanks Ahmed, I read that IMQ induced psoriasis is on peak on day 7 so most of the models are 9 days. Is it possible that within 5 days we understand the efficacy of the compounds.
Ideally should be 7 days to test efficacy of a compound but 5-6 days may work; try it out.
If you are using C57BL6 some mice may die due to dehydration, this can be solved by injection PBS IP.
I am using Balb c mice will PBS IP work for them too?? Also i want to know if IMQ induced model is Best for testing topically applied drugs.
Can anyone please suggest me....
How much amount of IMQ ( in mg) and on how much area of back skin (cm2) and ear (cm2) of Balb/c female mice do we need to apply [out of total 62.5mg of 5% Aldara] to induce Psoriasis in five days.
Many Thanks in advance.
I am working extensively on the imiquimod model with different protocols to induce psoriasis. I must mention that to check efficacy of a antipsoriatic drug, systemically or topically, 62.3mg per mice is enough. But this is highly schedule (pretretreatment followed with imiquimod or imiquimod followed with drug therapy) and dose dependant. For topical study, 62.3 mg is fine, since imiquimod is such a potent inducer of immune system, this much dose is enough to get to know the difference in treated group (testing compund) and imiquimod control group
While for severe psoriatic phenotype, 81.5 mg is also used, but this is good only if you need to study long term effects.
However, in both cases, you cant get to trace the cytokine levels. As this is an acute model and activation of cytokine is transient. Thus if your study emphasis on cytokine levels, day 3 or maximum day 4 is good timepoint to detect cytokines. At later timepoint you cant get detectable levels.
Hope this will be helpful.
Dear Nitesh Shirsath, I'm really interested in the cytokine levels of this model. So i'm wondering about despite of using the affected skin at day 3 or 4 to detect the levels of cytokines' mRNA, is it useful to use the blood to detect the cytokine levels and when should i extract blood from the mice in order to achieve this goal? Thx
Please suggest me that in Psoriasis cytokine determination in skin homogenate, How much dilutions should i need to prepare for cytokine detection in ELISA.
Please
this my first time I study the effect of imiquimod induction in psoriasis
I am now want to select a mouse model
so I d like to know what are the models can be used, and what is the best one?
thank you
Dear Haimeng Wang, depending on your duration of the experiment and goal you can collect blood to check the cytokine chemokine network from time to time like from day 3 till day 6 and then can isolate the skin at the end of your study. This can be achieved by withdrawing 200 µl of blood from the retro-orbital route with heparinized microhematocrit capillary tubes.
regards,
Both can be used as a measure of psoriasis- like inflammation. Ear thickness can be measured everyday after IMQ application to see the development of the disease or effect of a treatment. Moreover histopathology and flow is easy to do on ear skin. IMQ can also be applied for longer duration on ear skin as compared to back skin if required. However several inflammation related parameters can be carried out on back skin because of more amount of tissue. One drwaback is hair regrowth on back skin after 8-9 days. That's why one or both are used by scientists depending upon the study design.
Ahmed Nadeem , thanks for sharing the experience with us! May I ask 2 questions, 1. Mice and rats are both used for this model, which one is better for this imiquimod psoriasisi model, I prefer mice as it is more freqently mentioned, howerver, some CRO claimed mice have not so significant response window than rats? 2. the positive control is usually hydrocortisone, which will reduce body weight loss significantly, therefore generates lower value of skin thickness than background, so how do you make control of this to make hydrocortisone play substantial function as a real control without the interference from body weight change? Thank you. Other friends' opinions are also appreciated!
Mice for sure show psoriasis-like inflammation within 6-7 days which can be extended upto 10-15 days; Balbc mice show more psoriatic inflammation than C57 black, two most commonly used strains used for this model. This is a well validated model in mice and many therapies have been tested using this model. I'm not sure about people who have not got significant response using this model in mice. Regarding your 2nd Q, people have used betamethasone/clobetasol cream topically as a reference. If you you wanna avoid side effects, you can either reduce the dose or use it on alternate days.
Many conditions and technical features specific to the rat or mice species or for that matter any species including human must be considered when replicating psoriasis and other autoimmune like induced conditions in subjects. It is very difficult to list the most influential elements having the most impact on driving the host IQ immune response into this desired rogue hyper area of altered immune activity due to the enormous variables that inherently exists across the entire spectrum associated with a specifically chosen host population. However, a few things can be noted from past experiments. 1. Consider first the innate cytokine make up of your host immune system as a whole. By this I mean when each of the family of 14 or so cytokines that are directly impacted or stimulated by IQ first enter the immune response in your experiment. The individual levels of each are also very very important to understanding how to best drive your host's into the desired autoimmune response necessary for establishing conditions such as psoriasis. Example: does IL-2 or IL-12 or IL-8, etc, respond first in the induced hypersensitive reaction to IQ and once these all have been identified and recorded list them, the best you can, in the order in which each entered the immune response to the IQ target area. Did I mention this is extremely difficult to discuss given the hundreds if not thousands of variables and numerical possibilities we are dealing with in analyzing and predicting an IQ induced altered immune response in any given host? 2. The timing of each cytokine response is so important to this discussion as the cascading effect begins with which of the IQ family of cytokines enter the response first and which of the remaining cytokines will be influenced by the second, and so forth. This is a totally unpredictable area because the levels for each cytokine must also be known and understood as that too can impact the timing for bringing in the next cytokine to the IQ induced response. What we have seen historically is that the higher the host level of innate immune activity at rest the more responsive the host will be to an IQ challenge. And, the closer that innate immune system level is operating to the high end level of that spectrum the easier and quicker the host will be driven into the desired autoimmunity condition. I hope some of this helps but as I have mentioned a very thick book can be compiled on this subject and still volumes more would be needed to properly address the issue.
Sorry for the late "Thank you", Ahmed and Richard. By the way, how to measure the back skin thickness without sacrificing them? to pull the skin up, and measure the thickness as double fold? Sorry for such a naive question...
Dear Gong, I would not recommend doing that as it will give erroneous results and not a method I have come across. Best is to measure it after the sacrifice like like a sheet of paper at 3-4 different places and take an average of that.
I'm developing a similar model in the lab. I would like to know if there is any standard validation protocol to confirm the psoriatic skin? Are both qPCR and immunohistochemistry needed? If qPCR is recommended, which target(s) should I look for? Thanks!
I would say, you should first do the skin swelling thickness reading ( everyday till last day of treatment) which is a initial read-out of skin inflammation and can give you immediate validation wheather the skin inflammation is happening with substantial difference in IMQ treated skin and untreated. Later, at the end of 6-7 day treatment when visible psoriatic skin like phenotype develops you can conifrm either by IHC or qPCR for markers for Th17 cytokines.
Nitesh Shirsath Thanks for the replied. May I know how would you measure the swelling thickness of the skin?
Please read my article, " 8-Methoxypsoralen Plus Ultraviolet A Reduces the Susceptibility of Murine Skin to Mount a Psoriatic Response to Imiquimod Linked with Senescence and Downregulation of Interleukin-9, 17 and Interferon-gamma". the full text is also available on research gate. This should answer your query.
Hi everyone,
I also working on the IMQ model and I am looking for articles describing if skin alteration remains after 6-day treatment and for how long?
Is anyone has already experience with that, it would be very helpful.
Many thanks in advance
Kindly check the age of the mice. Use 8-10 week old mice for the experiment. If you had used overage mice then you may not get proper results
Errol P Prens Many thanks for your response. Do you know how long it takes after stopping the treatment ?
Would it be ok to treat with formulations & induce the psoriatic skin at the same time? Or I should do it until the psoriatic condition is well developed? I came across some papers which started on the 1st or 3rd day.
IMQ model is a short term model and psoriatic inflammation doesn't develop until 3 after days, that's why most interventions are done preventively in this model, i.e. starting 1st day.
Thanks Ahmed Nadeem for the comment. I would worry if I were to start on the first day, will it be a false positive result? But if it is a preventive intervention in this model, perhaps to start on the 1st day seems reasonable. May I know if the IMQ cream shall be removed for application of topical formulation?
It's not required as IMQ is absorbed quite well by the skin. Apply your formulation with some time gap, 1-2 hr is ok.
Hello, I have some questions about IMQ psoriasis model:
-I see different doses of IMQ (62.5 mg but they don't specify the area and in some paper they mentioned 20mg/cm2 so equivalent of 80 mg/4cm2 that some papers considered a high dose )
- What is the time needed for the absorption of IMQ if I want to rinse my skin before applying my treatment? and if I apply my formulation after 2 hours, should I rinse the skin before? and we rinse the skin with PBS or something else ?
-Which day we should collect blood to check the cytokine levels?
Thank you
I have a question regarding IMQ psoriasis model. is there any drug except aldara cream from which we can induce psoriasis in an animal model? Effat Omar Ahmed Nadeem
IMQ is the only one in my experience as it resembles features of psoriasis in humans. It activates TLR7 and inflammasome pathways which closely resemble inflammatory pathways induced in human skin by different agents.
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