PDRN CareDermal Papilla Cells
Dr. Sarah Chen
PhD, Molecular Biology
Dermal papilla (DP) cells are a compact cluster of specialized mesenchymal cells situated at the very base of the hair follicle, nestled within the bulb region where they are partially enveloped by the proliferating matrix keratinocytes that give rise to the hair shaft [1,2].
Definition and Location
Dermal papilla (DP) cells are a compact cluster of specialized mesenchymal cells situated at the very base of the hair follicle, nestled within the bulb region where they are partially enveloped by the proliferating matrix keratinocytes that give rise to the hair shaft [1][2]. Embryologically, DP cells derive from the mesoderm — distinct from the ectodermal origin of the follicular epithelium — and they retain many properties of mesenchymal stem cells throughout postnatal life, including the ability to induce new hair follicle formation when transplanted into recipient skin [1][5]. The DP functions as the hair follicle's central signaling hub: it receives systemic signals (hormones, growth factors) and translates them into local paracrine instructions that dictate whether the follicle grows, regresses, or rests [1][2]. The number of cells within the dermal papilla directly correlates with hair shaft diameter — larger papillae produce thicker hairs, and the progressive reduction in DP cell number is the cellular basis of hair miniaturization in androgenetic alopecia [2][5].
Role in Hair Follicle Cycling
The hair follicle is one of the few organs in the adult body that undergoes lifelong cycles of regeneration, and the dermal papilla orchestrates every phase of this cycle [1][2]:
Anagen (growth phase)
During anagen, DP cells secrete a cocktail of growth factors and morphogens that activate the hair germ (the cluster of epithelial progenitor cells adjacent to the papilla) and sustain rapid proliferation of matrix keratinocytes [1][2]. The matrix cells divide at one of the fastest rates in the human body — approximately every 12 to 24 hours — and differentiate into the concentric layers of the hair shaft (medulla, cortex, cuticle) and inner root sheath [1]. Anagen duration determines hair length and ranges from two to seven years on the human scalp [2]. The DP must maintain continuous pro-growth signaling throughout this extended period, and any disruption — hormonal, inflammatory, or nutritional — can trigger premature catagen entry [1][2].
Catagen (regression phase)
At the end of anagen, DP cells reduce their secretion of growth-promoting signals and the lower two-thirds of the follicle undergoes apoptosis-driven regression [1][2]. The DP condenses and migrates upward as the follicle shortens, ultimately coming to rest adjacent to the bulge region that houses follicular stem cells [1]. Catagen lasts approximately two to three weeks and is characterized by massive apoptosis of the matrix keratinocytes, while the DP itself resists apoptosis and survives the regression intact [2]. This survival is essential — without a viable DP, the follicle cannot regenerate in the next cycle [1].
Telogen (resting phase) and re-entry to anagen
During telogen, the DP remains quiescent at the base of the shortened follicle, adjacent to the bulge stem cells [1][2]. The duration of telogen is variable (approximately two to four months on the scalp) and is influenced by systemic and local factors including season, nutrition, and hormonal status [2]. Re-entry into anagen requires activating signals from the DP that reach the bulge stem cells and hair germ, stimulating them to proliferate and regenerate the lower follicle structure around the descending papilla [1][5]. This reactivation is the critical regulatory checkpoint of the hair cycle and is the step most frequently disrupted in hair loss disorders [2].
Key Signaling Molecules
DP cells communicate with surrounding follicular epithelium through a complex network of paracrine signaling pathways [1][2][5]:
Wnt/beta-catenin pathway
The Wnt pathway is perhaps the most critical signaling axis in hair biology [1][5]. DP cells secrete Wnt ligands (Wnt3a, Wnt7a, Wnt10b) that activate beta-catenin signaling in adjacent matrix keratinocytes, driving their proliferation and differentiation into hair shaft lineages [1]. Nuclear beta-catenin accumulation in DP cells is itself required for the maintenance of DP identity and hair-inductive capacity — DP cells that lose beta-catenin signaling lose their ability to induce hair growth [5]. Downregulation of Wnt signaling in DP cells is a key molecular event in hair follicle miniaturization [1][5].
BMP signaling
Bone morphogenetic proteins (BMPs) play a dual role in the hair cycle [1][2]. BMP2 and BMP4 secreted by the DP and surrounding dermal sheath maintain the quiescence of hair follicle stem cells during telogen and catagen [1]. The transition to anagen requires temporary suppression of BMP signaling — achieved through DP-derived BMP inhibitors such as noggin and the coordinated activity of the surrounding dermal macroenvironment [1][2]. The precise balance between BMP activation and inhibition is a timer that determines when the follicle re-enters the growth phase [1].
FGF family
Fibroblast growth factors, particularly FGF-7 (KGF) and FGF-10, are secreted by DP cells and act as potent mitogens for the overlying matrix keratinocytes [1][2]. FGF signaling supports matrix cell proliferation during anagen and contributes to hair shaft thickness [2]. Conversely, FGF-5 acts as a catagen-inducing signal — its expression in the outer root sheath triggers the anagen-to-catagen transition, and loss-of-function mutations in FGF-5 result in the angora phenotype (abnormally prolonged anagen and excessive hair length) in multiple mammalian species [1].
VEGF and vascularization
DP cells secrete vascular endothelial growth factor (VEGF), which maintains the perifollicular capillary network that supplies the metabolically demanding anagen follicle [1][2]. The quality of this vascular supply directly influences hair growth capacity — thicker hairs require more blood flow to sustain the rapid proliferation of matrix keratinocytes [2]. VEGF expression by DP cells is upregulated during anagen and declines during catagen, paralleling the vascular regression of the follicular plexus [1].
Dermal Papilla Dysfunction in Hair Loss
Androgenetic alopecia and DP cell miniaturization
Androgenetic alopecia (AGA) — the most common form of hair loss in both men and women — is fundamentally a disease of the dermal papilla [2][5]. In genetically susceptible follicles on the scalp, circulating androgens (particularly dihydrotestosterone, DHT) act on androgen receptors expressed by DP cells, triggering a cascade of changes that include reduced secretion of growth-promoting factors, increased production of inhibitory cytokines (TGF-beta1, DKK-1), and progressive loss of DP cell number [2]. With each successive hair cycle, the papilla shrinks, producing a progressively thinner, shorter, less pigmented hair — the process known as follicular miniaturization [2][5]. Eventually, the miniaturized follicle produces only a fine vellus hair barely visible to the naked eye [2].
Loss of DP inductive capacity
Beyond cell number reduction, DP cells in miniaturizing follicles lose their hair-inductive signaling capacity [1][5]. Cultured DP cells from balding scalp show reduced expression of Wnt ligands, alkaline phosphatase (a marker of DP identity), and versican compared to DP cells from non-balding occipital follicles [5]. Critically, this loss of identity is reversible under certain conditions: three-dimensional spheroid culture can partially restore the inductive capacity of human DP cells, suggesting that the tissue microenvironment — not irreversible genetic changes — drives the functional decline [5].
Inflammatory hair loss
In conditions such as alopecia areata, lichen planopilaris, and frontal fibrosing alopecia, inflammatory infiltrates directly target the hair follicle bulb and dermal papilla [2]. The immune-mediated destruction or dysfunction of DP cells in these conditions leads to hair loss that can be temporary (alopecia areata, if the DP survives) or permanent (cicatricial alopecias, where the DP is destroyed along with the follicular stem cells) [2].
PDRN and Dermal Papilla Cells
PDRN has emerged as a biologically rational therapeutic agent for DP cell stimulation, with direct evidence supporting its pro-growth effects on these cells [3][4]:
A2A receptor activation in DP cells
DP cells express the adenosine A2A receptor, and its activation by PDRN-derived nucleotides triggers intracellular cAMP elevation and downstream signaling through cAMP/PKA and MAPK/ERK pathways [3][4]. In cultured human DP cells, PDRN treatment has been shown to significantly increase cell proliferation in a dose-dependent manner — an effect that is abolished by the selective A2A antagonist ZM241385, confirming receptor specificity [3]. This proliferative stimulation directly addresses the core pathology of androgenetic alopecia: the progressive loss of DP cell number that drives follicular miniaturization [3].
Growth factor upregulation
PDRN treatment enhances the secretion of key growth factors by DP cells, including VEGF, FGF-7, and beta-catenin [3]. The upregulation of VEGF by PDRN-stimulated DP cells has particular therapeutic relevance: improved perifollicular vascularization supports the metabolic demands of the anagen follicle and may contribute to the reversal of miniaturization [3][4]. The enhancement of beta-catenin signaling is equally significant, as nuclear beta-catenin is required for the maintenance of DP cell identity and hair-inductive function [3][5].
Wnt pathway activation
Lee et al. demonstrated that PDRN treatment activates the Wnt/beta-catenin signaling pathway in human DP cells, increasing the expression of Wnt pathway target genes including cyclin D1 and LEF1 [3]. This finding is critical because Wnt activation in DP cells is the single most important molecular signal for anagen initiation and maintenance [1][3]. PDRN-mediated Wnt activation in DP cells recapitulates, at least in part, the signaling environment that sustains healthy hair growth — and its loss is the molecular hallmark of miniaturizing follicles in androgenetic alopecia [3][5].
Nucleotide salvage and cellular energetics
Beyond receptor-mediated signaling, PDRN provides a direct supply of deoxyribonucleotide building blocks to DP cells through the nucleotide salvage pathway [4][6]. Rapidly dividing DP cells in the anagen follicle have high nucleotide demand for DNA replication, and salvage pathway substrates supplied by PDRN support this biosynthetic need without the energetic cost of de novo nucleotide synthesis [4]. This metabolic support may be particularly relevant for DP cells in miniaturizing follicles, where cellular energetics are compromised and proliferative capacity is reduced [3][4].
Clinical Significance for PDRN Hair Treatments
The dermal papilla is the logical cellular target for any biologically-based hair regeneration therapy, and PDRN's demonstrated ability to stimulate DP cell proliferation, restore growth factor secretion, and activate Wnt signaling provides a strong mechanistic rationale for its clinical use in hair loss treatment [3][4]. PDRN-based scalp injections (mesotherapy) deliver the active polynucleotide chains directly to the perifollicular dermis where DP cells reside, achieving local concentrations sufficient for A2A receptor activation without systemic exposure [3][4].
The multi-mechanism action of PDRN — combining receptor-mediated cell signaling with metabolic nucleotide supply — distinguishes it from single-target therapies like minoxidil (primarily a vasodilator) or finasteride (a DHT synthesis inhibitor) and positions it as a complementary or adjunctive treatment that addresses the downstream cellular consequences of follicular miniaturization rather than a single upstream cause [3][4][6].
Because DP cell health determines follicle output, the therapeutic goal is to maintain or restore three key DP functions: sufficient cell number (proliferative capacity), active growth factor secretion (paracrine signaling), and intact Wnt/beta-catenin signaling (hair-inductive identity) [1][3][5]. PDRN has demonstrated positive effects on all three parameters in preclinical studies, making it one of the few available agents with a multi-target mechanism of action aligned to the biology of the dermal papilla [3]. Ongoing clinical research is evaluating PDRN both as monotherapy for early-stage androgenetic alopecia and as a combination therapy alongside established pharmacological and procedural interventions [3][4].
References
- [1]Driskell RR, Clavel C, Rendl M, Watt FM. Hair follicle dermal papilla cells at a glance. J Cell Sci. 2011;124(8):1179-1182. doi:10.1242/jcs.082446
- [2]Yang CC, Cotsarelis G. Review of hair follicle dermal cells. J Dermatol Sci. 2010;57(1):2-11. doi:10.1016/j.jdermsci.2009.11.005
- [3]Lee YR, Bae S, Kim JY, et al.. Polydeoxyribonucleotide promotes hair growth by stimulating dermal papilla cells. Int J Mol Med. 2020;46(5):1844-1854. doi:10.3892/ijmm.2020.4729
- [4]Squadrito F, Bitto A, Irrera N, et al.. Pharmacological Activity and Clinical Use of PDRN. Curr Pharm Des. 2017;23(27):3948-3957. doi:10.2174/1381612823666170516153716
- [5]Higgins CA, Chen JC, Cerise JE, Jahoda CA, Christiano AM. Microenvironmental reprogramming by three-dimensional culture enables dermal papilla cells to induce de novo human hair-follicle growth. Proc Natl Acad Sci U S A. 2013;110(49):19679-19688. doi:10.1073/pnas.1309970110
- [6]Colangelo MT, Galli C, Giannelli M. Polydeoxyribonucleotide: A Promising Biological Platform for Dermal Regeneration. Curr Pharm Des. 2020;26(17):2049-2056.