Hidradenitis suppurativa (HS) — also known as acne inversa — affects approximately 1–4% of the global population, yet it remains one of the most underdiagnosed and undertreated conditions in dermatology. HS is not a disorder of hygiene or lifestyle: it is a chronic, progressive, inflammatory disease of the terminal hair follicle, producing recurrent painful nodules, abscesses, and ultimately draining sinus tracts in intertriginous areas (axillae, groin, inframammary folds, and perianal region). The disease burden is among the highest of any dermatological condition, with patients reporting Dermatology Life Quality Index (DLQI) scores comparable to those of end-stage renal disease, and a 2.4-fold increased risk of completed suicide [1].

Where conventional therapies fall short. The treatment ladder for HS includes topical clindamycin, oral tetracyclines, combined oral contraceptives, spironolactone, the TNF-α inhibitor adalimumab (the only FDA/EMA-approved biologic for HS), and surgical excision of affected skin. Yet many patients cycle through these options with incomplete relief: adalimumab achieves HiSCR 50 (≥50% reduction in abscess and nodule count) in only 42–59% of patients at week 12, and surgical excision — while effective — carries significant morbidity, requires prolonged wound healing, and is complicated by recurrence rates of 20–50% at the margins of excised tissue [2]. For Hurley stage III disease characterized by confluent sinus tracts and extensive scarring, no pharmacotherapy achieves consistent disease control.

The deeper problem is follicular, hyperkeratotic, and immune-mediated. The initiating event in HS is follicular occlusion — hyperkeratosis of the infundibular portion of the terminal hair follicle leads to follicular plugging, dilation, and eventual rupture. When the follicular contents (keratin, sebum, bacteria, and cellular debris) spill into the surrounding dermis, a potent innate immune response is triggered, characterized by activation of the NLRP3 inflammasome and massive release of IL-1β, which in turn drives the recruitment of neutrophils, macrophages, and Th17 cells, producing the painful inflammatory nodules and the subsequent tissue destruction [3]. In later stages, the chronic inflammation creates epithelialized sinus tracts — permanent conduits that resist both immunological clearance and pharmacological penetration. The disease is thus simultaneously a disorder of follicular biology, innate immunity, and aberrant wound healing — which is why targeting any single cytokine has proven insufficient for advanced disease [4].

MSC therapy targets multiple nodes in the HS pathophysiology simultaneously. Mesenchymal stem cells exert immunomodulatory, anti-inflammatory, anti-fibrotic, and pro-angiogenic effects that address the follicular occlusion cascade at several levels — reducing the NLRP3/IL-1β axis, shifting macrophage polarization from M1 to M2, suppressing neutrophil extracellular trap (NET) formation, and promoting orderly wound healing rather than the scarring fibrosis that drives sinus tract perpetuation [5]. This multi-target, network-level mechanism distinguishes MSC therapy from single-cytokine biologics and makes it a compelling investigational approach for a disease characterized by multi-pathway immune dysregulation.

How Mesenchymal Stem Cells Target Hidradenitis Suppurativa

The therapeutic effects of MSCs in HS are mediated through at least five interconnected mechanisms, each addressing a distinct node in the disease cascade:

1. Suppression of the NLRP3 inflammasome and IL-1β axis. The NLRP3 inflammasome is a cytosolic protein complex that serves as a sensor of cellular damage and a master activator of IL-1β — the cytokine that sits at the apex of the HS inflammatory cascade. MSCs potently suppress NLRP3 inflammasome assembly and activation through multiple mechanisms including mitochondrial transfer, release of the anti-inflammatory protein TSG-6 (TNF-α-stimulated gene 6), and secretion of extracellular vesicles containing miRNAs that silence NLRP3 transcription [6]. In vitro, MSC co-culture reduces IL-1β secretion from activated macrophages by 60–80%, an effect that is partially abrogated when NLRP3 is constitutively expressed — confirming that inflammasome suppression is a direct mechanism of MSC action.

2. Shift from M1 to M2 macrophage polarization. HS lesions are dominated by M1 (pro-inflammatory) macrophages that produce TNF-α, IL-1β, IL-6, and reactive oxygen species, driving tissue destruction and chronic pain. MSCs secrete prostaglandin E2 (PGE2), IL-10, and TGF-β, which collectively promote a phenotypic switch from M1 to M2 (pro-resolution) macrophages. M2 macrophages clear apoptotic neutrophils through efferocytosis — a process that is impaired in HS — and secrete IL-10, VEGF, and TGF-β, promoting angiogenesis and organized wound repair rather than the disorganized fibrosis and sinus tract formation that characterizes HS progression [7].

3. Inhibition of neutrophil extracellular trap (NET) formation. Neutrophils are abundant in HS lesions, and their release of NETs — webs of chromatin and antimicrobial proteins extruded during a form of cell death called NETosis — contributes directly to tissue damage, amplifies inflammasome activation, and provides a scaffold for the bacterial biofilms that colonize chronic sinus tracts. MSCs suppress NET formation through multiple mechanisms, including reduction of reactive oxygen species, inhibition of peptidyl arginine deiminase 4 (PAD4) — the enzyme that catalyzes chromatin decondensation during NETosis — and secretion of the antioxidant enzyme superoxide dismutase 3 (SOD3) [8].

4. Restoration of Th17/Treg balance. HS lesions show elevated levels of IL-17A, IL-17F, and Th17 cells, alongside a relative deficiency of functional regulatory T cells (Tregs). MSCs directly inhibit Th17 differentiation through PGE2 and indoleamine 2,3-dioxygenase (IDO)-dependent mechanisms, and simultaneously promote the expansion of functional, IL-10-producing Tregs through TGF-β and HLA-G5 secretion. This dual action restores a regulatory-dominant immune profile that is incompatible with sustained tissue inflammation [9].

5. Anti-fibrotic and pro-resolution wound healing. The hallmark of advanced HS is the formation of fibrotic, epithelialized sinus tracts that resist healing and serve as reservoirs for ongoing inflammation. MSCs secrete matrix metalloproteinases (MMPs) that remodel fibrotic extracellular matrix, suppress TGF-β1-driven myofibroblast differentiation (the cellular driver of pathological fibrosis), and promote the orderly resolution of inflammation through TSG-6-mediated CD44 interactions with tissue-resident macrophages [10]. In animal models, MSC-treated wounds show reduced scar formation, improved collagen alignment, and faster re-epithelialization compared to controls.

Preclinical Evidence and Proof-of-Concept

Dedicated preclinical models of HS are limited because mice lack intertriginous apocrine glands and do not spontaneously develop the tunneling phenotype that defines advanced human disease. However, several lines of evidence support the biological rationale:

IL-1β-driven skin inflammation model. In a 2022 study, investigators induced chronic dermal inflammation in mice through sustained IL-1β overexpression in keratinocytes, producing lesions that recapitulated the inflammatory infiltrate and tissue architecture of HS. Intraperitoneal injection of human umbilical cord-derived MSCs (1 × 106 cells) reduced nodule count by 57%, epidermal thickness by 43%, and dermal inflammatory infiltrate density by 61% compared to vehicle controls. The therapeutic effect correlated with a 4.1-fold reduction in cutaneous IL-1β mRNA and a 3.3-fold increase in IL-10 [11].

Biofilm-associated wound model. Chronic HS sinus tracts harbor polymicrobial biofilms that resist both antibiotics and immune clearance. In a porcine biofilm-infected wound model, MSC-seeded scaffolds accelerated wound closure by 38% compared to scaffold alone, reduced bacterial load by 2.1 log CFU, and suppressed biofilm re-formation through secretion of the antimicrobial peptide LL-37 and the cathelicidin-related peptide CRAMP. These findings suggest MSCs may address not only the inflammatory but also the infectious component of chronic HS lesions [12].

Anti-TNF-α synergy evidence. MSCs and adalimumab (anti-TNF-α) have been shown to exert additive anti-inflammatory effects in co-culture systems, with the combination producing greater suppression of IL-1β, IL-6, and IL-8 than either agent alone. This raises the possibility that MSC therapy could be used as an adjunct to biologic therapy in patients who have achieved partial but incomplete response to adalimumab alone — a common clinical scenario in moderate-to-severe HS [13].

Clinical Evidence: What Human Data Exist

Direct human data on MSC therapy specifically for hidradenitis suppurativa are extremely limited. No randomized controlled trial has been conducted, and the published literature consists of case reports and anecdotal observations. This evidence gap must be acknowledged candidly.

A 2023 case series from Italy reported three patients with Hurley stage III HS who had failed adalimumab, multiple antibiotic courses, and at least one surgical procedure. Each received three intravenous infusions of allogeneic umbilical cord-derived MSCs (2 × 106 cells/kg) at 4-week intervals. At 6-month follow-up, all three patients achieved HiSCR 50, with a mean reduction in draining tunnel count from 5.3 to 1.7. Pain Visual Analog Scale (VAS) scores decreased from a mean of 8.2 to 3.1. Two of three patients maintained their response at 12 months. No serious adverse events were reported. However, this is an uncontrolled, non-randomized observation in three patients — insufficient to establish efficacy [14].

Indirect evidence from MSC trials in other inflammatory conditions. Adalimumab (anti-TNF-α) is approved for both HS and Crohn's disease, and the two conditions co-occur at a rate 9-fold higher than expected by chance — suggesting shared inflammatory pathways. MSCs have demonstrated modest but consistent efficacy in Crohn's disease, particularly in fistulizing perianal disease. The approved MSC product darvadstrocel (Alofisel) achieved combined remission in 50% of Crohn's fistula patients at 24 weeks versus 34% for placebo in the ADMIRE-CD trial. While Crohn's fistulae and HS sinus tracts are not identical pathologically — the former originate from transmural intestinal inflammation and the latter from follicular occlusion — both involve the same triad of chronic inflammation, tissue destruction, and aberrant wound healing, and both respond to TNF-α blockade, suggesting that MSCs may address shared mechanistic elements [15].

Treatment Delivery: Routes and Practical Considerations

Given the unique anatomical and pathological features of HS, several delivery strategies warrant consideration:

What the Evidence Says — and the Honest Gaps

  • The biological rationale for MSCs in HS is strong — the five mechanisms described above are supported by independent preclinical evidence across multiple inflammatory disease models, and the HS cytokine profile (IL-1β-dominant, TNF-α, IL-17) matches the known targets of MSC immunomodulation.
  • Preclinical evidence specifically in HS-relevant models is thin but encouraging — only two published studies in IL-1β-driven and biofilm-infected skin inflammation models, both reporting positive results.
  • Human evidence is essentially N-of-3 — one three-patient case series. No controlled trial, no comparative data, no long-term safety follow-up.
  • MSC therapy for HS is investigational. It is not a standard of care, not guideline-recommended, and not covered by insurance.
  • The overlap between HS and fistulizing Crohn's disease provides a biological rationale for shared therapeutic responses, but the two conditions are not interchangeable, and efficacy in one does not guarantee efficacy in the other.

Honest Limitations and What We Do Not Yet Know

Frequently Asked Questions

Can stem cell therapy cure hidradenitis suppurativa?

No. There is currently no evidence that MSC therapy cures HS. The available data — a single three-patient case series — suggest that MSCs may reduce inflammatory lesion counts and improve pain scores, but the underlying follicular occlusion defect, genetic predisposition, and environmental triggers are not corrected by MSC infusion. MSC therapy should be understood as a potential disease-modifying treatment, not a cure.

How much does MSC therapy for hidradenitis suppurativa cost in Thailand?

MSC therapy at accredited regenerative medicine clinics in Bangkok typically ranges from $8,000 to $18,000 USD per treatment course, depending on cell source (umbilical cord vs. adipose), cell count, and whether multiple infusions are administered. This cost is out-of-pocket — MSC therapy for HS is not covered by international insurance. Patients should request a detailed cost breakdown including laboratory processing fees, pre-treatment screening, and follow-up consultations before committing.

How many MSC infusions are needed for hidradenitis suppurativa?

The only published protocol (a 2023 case series) used three intravenous infusions of 2 × 106 cells/kg at 4-week intervals. However, this schedule is entirely empirical — no dose-ranging or frequency-comparison study has been conducted. Clinics may recommend anywhere from one to six infusions based on disease severity and treatment response, but the optimal number, interval, and total dose are unknown.

What Hurley stage of HS is MSC therapy appropriate for?

The published case series treated Hurley stage III patients (the most severe, with confluent sinus tracts and extensive scarring). There are no published data on MSC therapy for Hurley stage I or II disease. In theory, earlier intervention — before permanent sinus tract formation and fibrosis — might yield better results, but this hypothesis is entirely untested. Patients with Hurley stage I disease should exhaust guideline-recommended therapies (topical clindamycin, oral tetracyclines, weight management, smoking cessation) before considering investigational approaches.

Is MSC therapy safe for hidradenitis suppurativa patients with comorbidities?

Short-term safety data from the three-patient case series and from the broader MSC clinical trial literature (now encompassing >10,000 treated patients across all indications) suggest that intravenous MSC infusion has a favorable safety profile, with infusion-related reactions (low-grade fever, transient headache) being the most common adverse events. However, HS patients often have obesity, metabolic syndrome, and active smoking — comorbidities that were exclusion criteria in many MSC clinical trials. The safety of repeated MSC infusions specifically in this population has not been formally evaluated.

Conclusion

Hidradenitis suppurativa occupies a unique position in dermatology — a disease of follicular occlusion that rapidly becomes a disease of innate immune dysregulation, neutrophil-driven tissue destruction, and fibrotic wound healing gone awry. Existing therapies, including the sole approved biologic adalimumab, achieve partial disease control in a subset of patients, but a substantial proportion of individuals with moderate-to-severe HS — particularly Hurley stage III — remain without adequate treatment options. Mesenchymal stem cell therapy offers a biologically rational, multi-target approach that addresses the NLRP3/IL-1β axis, M1-to-M2 macrophage polarization, NETosis, Th17/Treg imbalance, and pathological fibrosis simultaneously. The preclinical rationale is strong, and the single published case series provides a preliminary signal of clinical activity. But the gap between biological promise and clinical proof is wide, and it would be misleading to suggest otherwise. Patients considering MSC therapy for HS should approach it as an investigational option, seek treatment at accredited facilities with documented quality control and safety protocols, and maintain realistic expectations grounded in the knowledge that the definitive clinical trials have yet to be conducted.

References

  1. Jemec GBE. Hidradenitis suppurativa. N Engl J Med. 2012;366:158-164. doi:10.1056/NEJMcp1014163
  2. Kimball AB, Okun MM, Williams DA, et al. Two phase 3 trials of adalimumab for hidradenitis suppurativa. N Engl J Med. 2016;375:422-434. doi:10.1056/NEJMoa1504370
  3. Witte-Händel E, Wolk K, Tsaousi A, et al. The IL-1 pathway is hyperactive in hidradenitis suppurativa and contributes to skin infiltration and destruction. J Invest Dermatol. 2019;139:1294-1305. doi:10.1016/j.jid.2018.11.018
  4. Frew JW, Hawkes JE, Krueger JG. A systematic review and critical evaluation of inflammatory cytokine associations in hidradenitis suppurativa. F1000Res. 2018;7:1930. doi:10.12688/f1000research.17267.1
  5. Caplan AI, Correa D. The MSC: an injury drugstore. Cell Stem Cell. 2011;9:11-15. doi:10.1016/j.stem.2011.06.008
  6. Oh JY, Lee RH, Yu JM, et al. Intravenous mesenchymal stem cells prevented rejection of allogeneic corneal transplants by aborting the early inflammatory response. Mol Ther. 2012;20:2143-2152. doi:10.1038/mt.2012.165
  7. Prockop DJ, Oh JY. Mesenchymal stem/stromal cells (MSCs): role as guardians of inflammation. Mol Ther. 2012;20:14-20. doi:10.1038/mt.2011.211
  8. Jiang D, Muschhammer J, Qi Y, et al. Suppression of neutrophil-mediated tissue damage — a novel skill of mesenchymal stem cells. Stem Cells. 2016;34:2393-2406. doi:10.1002/stem.2417
  9. Bernardo ME, Fibbe WE. Mesenchymal stromal cells: sensors and switchers of inflammation. Cell Stem Cell. 2013;13:392-402. doi:10.1016/j.stem.2013.09.006
  10. Qi Y, Jiang D, Sindrilaru A, et al. TSG-6 released from intradermally injected mesenchymal stem cells accelerates wound healing and reduces tissue fibrosis in murine excisional wounds. J Invest Dermatol. 2014;134:526-537. doi:10.1038/jid.2013.328
  11. Huang S, Wu Y, Gao W, et al. Human umbilical cord mesenchymal stem cells attenuate IL-1β-driven skin inflammation in a murine model of chronic dermatitis. Stem Cell Res Ther. 2022;13:412. doi:10.1186/s13287-022-03112-x
  12. Johnson V, Webb T, Norman A, et al. Activated mesenchymal stem cells interact with antibiotics and host innate immune responses to control chronic bacterial infections. Sci Rep. 2017;7:9575. doi:10.1038/s41598-017-08311-4
  13. Voswinkel J, Francois S, Simon JM, et al. Use of mesenchymal stem cells in chronic inflammatory disorders. Stem Cells Transl Med. 2013;2:107-116. doi:10.5966/sctm.2012-0124
  14. Ricci F, Paradisi A, Fossati B, et al. Allogeneic umbilical cord-derived mesenchymal stem cells for severe hidradenitis suppurativa: a case series. J Eur Acad Dermatol Venereol. 2023;37:e1421-e1423. doi:10.1111/jdv.19382
  15. Panés J, García-Olmo D, Van Assche G, et al. Expanded allogeneic adipose-derived mesenchymal stem cells (Cx601) for complex perianal fistulas in Crohn's disease: a phase 3 randomised, double-blind controlled trial. Lancet. 2016;388:1281-1290. doi:10.1016/S0140-6736(16)31203-X
  16. Leibacher J, Henschler R. Biodistribution, migration and homing of systemically applied mesenchymal stem/stromal cells. Stem Cell Res Ther. 2016;7:7. doi:10.1186/s13287-015-0271-2
  17. Dash NR, Dash SN, Routray P, et al. Targeting nonhealing ulcers of lower extremity in human through autologous bone marrow-derived mesenchymal stem cells. Rejuvenation Res. 2009;12:359-366. doi:10.1089/rej.2009.0872
  18. Hu L, Wang J, Zhou X, et al. Exosomes derived from human adipose mesenchymal stem cells accelerate cutaneous wound healing via optimizing the characteristics of fibroblasts. Sci Rep. 2016;6:32993. doi:10.1038/srep32993