Comparative study on the efficacy and safety of insulin versus autologous platelet-rich plasma (PRP) with microneedling in the treatment of atrophic post-acne scars

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Atrophic acne scars are a common cosmetic concern with a psychological impact. Microneedling promotes collagen remodelling via controlled dermal injury.¹ Platelet-rich plasma (PRP), rich in autologous growth factors, enhances wound healing and tissue regeneration.² Recent evidence suggests insulin may independently stimulate fibroblast activity, collagen synthesis, and neovascularisation.^3,4 This study compares the efficacy and safety of microneedling with insulin versus microneedling with PRP in the treatment of atrophic acne scars.

This prospective, comparative study was conducted in the Dermatology outpatient department of a tertiary care hospital in 2024, following ethical approval (IRB Number: KMC/IEC/PG_Research/002/2024). Fifty patients aged 18-35 years with clinically diagnosed atrophic acne scars were enrolled after obtaining informed consent. This age group was chosen in view of possibly better healing, higher scar prevalence, and minimal systemic confounders.

Exclusion criteria included active acne, pregnancy, lactation, diabetes mellitus, bleeding disorders, hepatitis, HIV Infections, keloidal tendency, anticoagulant therapy, and active skin infections. Patients who had received oral isotretinoin within the past 6 months were excluded due to its known effects on collagen synthesis and wound healing.

Patients were randomly divided into two groups (25 patients each) using a computer-generated randomisation chart. Group 1 received microneedling with regular human insulin (10 units of Actrapid, 40 IU/mL, Novo Nordisk), while Group 2 received microneedling with autologous PRP. PRP was prepared using a double-spin method and activated with calcium chloride before application.

The sample size was calculated using G*Power software (version 3.1.9.7) Assuming a large effect size (Cohen’s d = 0.8) with an alpha value of 0.05 and power of 80%, the minimum required sample size was determined to be 46 (23 per group). To account for potential dropouts, the final sample size was set at 50, with 25 patients in each group.

Microneedling was performed using a 36-needle pen microneedling device (Dr. Pen Ultima A6, Guangzhou, China) at 2 mm depth with perpendicular stamping until uniform pinpoint bleeding was achieved.⁵ Patients underwent four treatment sessions at 3-week intervals. Post-procedure care included sunscreen application three times daily and strict photo-protection. For the insulin group, blood glucose was monitored before and after each session to ensure glycaemic stability.

The primary outcome was the percentage reduction in Acne Scar Assessment Scale (ASAS) score from baseline to the end of treatment, calculated using the formula: [(baseline ASAS − post-treatment ASAS)/Baseline ASAS] × 100. The ASAS is a validated physician-assessed tool that grades acne scars from 0 (“Clear”) to 4 (“Severe”), providing a standardised method to quantify acne scar severity. Secondary outcomes included the proportion of patients achieving >75% clinical improvement, assessed through the Scar Quartile Grading Scale (SQGS), a photographic evaluation method that classifies scar improvement into four categories: <25%, 25-50%, 50-75%, and >75%. Additional secondary outcomes included patient satisfaction on a 4-point Likert scale (poor, fair, good, excellent) and documenting any adverse effects such as erythema, oedema, post-inflammatory hyperpigmentation, and secondary infections.

Statistical analysis was performed using IBM SPSS software version 26.0. Paired t-tests were used for within-group comparisons of pre- and post-treatment ASAS scores, while unpaired t-tests were applied for between-group comparisons. Categorical data were analysed using the chi-square test.

Both groups demonstrated statistically significant improvement from baseline. The mean percentage reduction in ASAS score was 41.10% ± 11.86 in the insulin group vs 25.32% ± 9.72 in the PRP group (p = 0.0003). In the insulin group, the mean ASAS score decreased from 2.92 ± 0.93 to 1.72 ± 0.78 (p = 0.0001), while in the PRP group, it decreased from 3.16 ± 0.73 to 2.36 ± 0.84 (p = 0.001). Intergroup comparison based on percentage reduction in ASAS score revealed a significantly greater reduction in the insulin group (p = 0.015), as shown in Table 1. On SQGS, 36% of insulin group patients achieved >75% improvement, compared to 8% in the PRP group (p = 0.023), as shown in Table 2. 48% of patients in the insulin group reported “excellent” satisfaction compared to 8% in the PRP group (p = 0.0008). Adverse effects were mild and self-limiting in both groups. Erythema was observed in 12% of the PRP group and 8% of the insulin group; oedema in 12% of PRP-treated patients and 8% in the insulin group; and post-inflammatory hyperpigmentation (PIH) in 8% of PRP patients versus 4% in the insulin group. No serious complications were observed in either group.

On subgroup analysis based on scar morphology, a better therapeutic response was observed in rolling and boxcar scars with insulin treatment. In contrast, deep ice-pick scars demonstrated minimal improvement across both groups, suggesting limited efficacy of both insulin and PRP- based microneedling therapies in treating deep ice-pick scars.

Representive clinical improvement in a patient treated with insulin-based microneedling is shown in Figure 1a and 1b. Similarly, improvement in a patient treated with PRP-based microneedling is depicted in Figure 2a and 2b.

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Figure 1a:

A 35-year-old man with atrophic acne scars, including boxcar, rolling, and icepick scars, showing the pre-treatment condition on the right side of the face.

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Figure 1b:

Post-treatment results at week 12 following microneedling with insulin, demonstrating a significant reduction in scar depth and improved skin texture on the right side.

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Figure 2a:

A 28-year-old man with atrophic acne scars, including boxcar, rolling, and icepick scars, showing the pre-treatment condition on the right side of the face.

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Figure 2b:

Post-treatment results at week 12 following microneedling with autologous PRP, demonstrating visible improvement in scar depth and texture on the right side.

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The superior efficacy of insulin compared to PRP may be attributed to enhanced fibroblast stimulation, collagen remodelling, and vascular endothelial growth factor (VEGF)-mediated neovascularisation. PRP outcomes can vary based on platelet concentration and preparation techniques.⁶ Insulin can prove to be more cost-effective and accessible, particularly in resource-limited settings where PRP preparation is challenging.

However, insulin-based microneedling showed limited efficacy in improving deep ice-pick scars, which often require additional targeted interventions such as trichloroacetic acid chemical reconstruction of skin scars (TCA CROSS) or punch excision for optimal results. These findings align with Abbas et al. (2023), who reported greater improvement in acne scars with microneedling and insulin vs microneedling with vitamin C.⁷

Limitations include the small sample size and short follow-up duration. Future research involving larger cohorts, longer follow-up periods, and histopathological evaluation is recommended to validate these findings and optimise treatment protocols.