I have been researching as of late the mechanisms behind the production of collagen, and I've stumbled on some facts that may of interest to you all. I believe Retin A may increase scarring, and potentially reduce the efficacy of Microneedling, since it inhibits MMP, which is necessary for the skin proliferation and degradation of excessive fibrous tissue:
"Matrix-Metallo-Proteinases (MMPs) are thought to play a vital role in cell proliferation, but it is not known if these enzymes are expressed, when normal, non-fibrotic skin is needled. However, we speculate that they play a vital role following scar needling. The formation of scar tissue is controlled by TGF-²1 and ²2. However, Aust et al5 have indicated that after microneedling only TGF-²3 seems to control collagen fiber integration into the skin's matrix (Figure 6). MMPs are controlled by inhibitors (TIMPS). They continue to be active to degrade excessive fibrotic tissue until degradation of surplus tissue is complete." https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3921236/
" Fibroblasts and keratinocytes produce enzymes including those that determine the architecture of the extracellular matrix metalloproteinases (MMPs) and tissue inhibitors of MMPs. MMPs are extracellular matrix (ECM) degrading enzymes that interact and form a lytic cascade for ECM remodeling [18]. As a consequence, an imbalance in the ratio of MMPs to tissue inhibitors of MMPs results in the development of atrophic or hypertrophic scars. Inadequate response results in diminished deposition of collagen factors and formation of an atrophic scar while, if the healing response is too exuberant, a raised nodule of fibrotic tissue forms hypertrophic scars." https://www.hindawi.com/journals/drp/2010/893080/
Accordingly, I think Retin A could cause excess scarring, which can otherwise be avoided, as it inhibits MMPs and their function, which is to degrade excessive fibrotic tissue. This is a catch 22 since Retin A decreases acne, and is a successful treatment for many acne sufferers. However, one may be trading acne for possibly more scarring by using Retin A. In addition to this, Retin A may decrease the efficacy of microneedling, which works by activating the process of fibrotic tissue degradation by using MMPs.
Anyone well-informed of the mechanics behind Retin A and microneedling is welcomed to discuss this with me! I would actually be ecstatic if my thoughts regarding Retin A and its risks are successfully argued against. 
@beautifulambition
I would like to know your thoughts on this since you are well informed!
I agree with Bollundus, this sounds like it's talking about Accutane. Anything you take while on Accutane can be quite harmful, the skin cannot heal itself and it thin, dry, and in bad order. This is why doctors tell you to wait 6 months after Accutane to treat. Accutane as you know is also vitamin A but in a different form, it changes the body, not just topically effects skin having higher cell turn over fromRetin A was altered to just produce these results. Differin was further altered to work only on Acnes P in the folicle.
Regarding Microneedling, we all heal differently, some of us it does not work for,some of us it does, some of us just needling enough is not enough to improve. Anything can cause someone not to heal with the right conditions. Even water. What I have seen is people using topicals and getting them in the fresh wound, their face reacts and it does not heal right. When I advise people I strongly suggest one uses pure ha to needle with and cleans their skin.What the Godfather of Microneedle, he wrote a book for practitioners on Amazon said it many use topicals and it basically causes infection, allergy, or edema. These were not made to be injected into the skin. When I say retin A I often say when the channels are closed several hours later and to be safe one should not use retin a when doing any treatment or healing from one. I can speak from personal experience and all the Drs who often post about this on RealSelf.com ... they say Retin A and Vitamin C serum are great topicals to use after needling because of their antioxidant and stimulating effects of healing. One can use retin a or a retinoid at night and not use it (just like BP for acne spots). I have seen the benefits of Retin A on many's skin who did not need to use even acid peels because it improved their scars.
PM me if you need help
On 6/22/2017 at 8:31 PM, beautifulambition said:I agree with Bollundus, this sounds like it's talking about Accutane. Anything you take while on Accutane can be quite harmful, the skin cannot heal itself and it thin, dry, and in bad order. This is why doctors tell you to wait 6 months after Accutane to treat. Accutane as you know is also vitamin A but in a different form, it changes the body, not just topically effects skin having higher cell turn over fromRetin A was altered to just produce these results. Differin was further altered to work only on Acnes P in the folicle.
On 6/22/2017 at 4:52 PM, Bollundus said:Hello trompel'oeil,
thank you for the research. But this accounts only for accutane-pills and not for a topic like Paula's Choice Retinol Products.
What are your thoughts about that?
What are you both talking about? Have I missed something here? One link references delayed reepithelialisation following isotretinoin (Roaccutane), however that's not what the OP is talking about.
Topical tretinoin inhibit MMPs, that's established. (It's why it's such a great product for preventing photoaging - they degrade collagen by production of collagenase, stromelysin and gelatinase.) OP is speculating that this could impair wound healing, resulting in scars (and/or reduced efficacy) because of their role in the process.
While I'm not about to agree, I've found one study showing that "Treatment with topical tretinoin before wounding accelerated epithelial wound healing in partial thickness wounds. Continued tretinoin treatment on the wounds themselves retarded reepithelialization." [Edited link out] that could give credence to the idea, at least in part.
Was there any need for the two paragraphs of rambling?
On 6/22/2017 at 10:15 PM, machiavelli said:What are you both talking about? Have I missed something here? One link references delayed reepithelialisation following isotretinoin (Roaccutane), however that's not what the OP is talking about.
Topical tretinoin inhibit MMPs, that's established. (It's why it's such a great product for preventing photoaging - they degrade collagen by production of collagenase, stromelysin and gelatinase.) OP is speculating that this could impair wound healing, resulting in scars (and/or reduced efficacy) because of their role in the process.
While I'm not about to agree, I've found one study showing that "Treatment with topical tretinoin before wounding accelerated epithelial wound healing in partial thickness wounds. Continued tretinoin treatment on the wounds themselves retarded reepithelialization." [Edited link out] that could give credence to the idea, at least in part.
Was there any need for the two paragraphs of rambling?
@machiavelli @beautifulambition
Read the article and it's quite disheartening! I am beginning to wonder if wound healing truly becomes impaired from tretinoin use. I have been investigating the role of MMPs and they play a significant role in wound healing. I think retin a and how it affects wound healing should be further investigated. I am not sure as to why scientists have not focused on this issue, knowing that MMPs are vital in the wound healing process. Also, I don't think Retin A heps with scarring. It most likely only helps with pigmentation issues. The collagen it builds may reduce mild scarring, but other forms of scarring need collagen induction therapy, which retin a cannot do.
Here is something that might be of interest to you:
"Even though the importance of MMPs in wound healing cannot be underestimated, they can negatively affect healing if not present in the correct amount [14, 15]. Under normal conditions, the interaction of MMPs with growth factors and receptors is capable of maintaining the balance of the ECM. In such circumstances, the amount of MMP is decreased. However, predictors of healing will depend on the ratio between MMPs and TIMPs." https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4893587/
So, if Retin A inhibits MMP then the ratio between MMPs and TIMPs have been altered. This possibly negatively affects wound healing, since the ratio between MMP and TIMP is a delicate one, and if it alters, wound healing becomes impaired. Retin A alters the ratio, since it has an inhibitory effect on MMPs. I find this concerning.
I will be posting this on reddit and realself! Let's see what they say
Something else I found:
"The rate of reepithelialization was significantly enhanced by treatment with capsaicin, bacitracin, silver sulfadiazine, and scarlet red, and was markedly retarded by treatment with tretinoin."
https://www.researchgate.net/publication/20692986_Topical_tretinoin_and_epithelial_wound_healing
I have stopped using retin - a and my skin is healing much faster. When I was using it, even a whitehead would leave a small indentation. Retin A helped with hyperpigmentation but I sense that it caused by skin to be more susceptible to pitted scars, which I am not surprised about since it functions in the same manner as Accutane, and Accutane may cause your skin to scar. Now I use a glycolic serum instead to exfoliate my skin.
