Double knockdown of DKK1 and SFRP1, two key players in androgenetic alopecia, does not accelerate the hair-growth promoting effect of individual SFRP1 knockdown in healthy human hair follicles ex vivo

Summary: Abstract Body: Androgen receptor (AR) signaling plays a key role in male pattern baldness. Here, we investigates the potential of targeting multiple AR-regulated genes as a therapeutic approach for hair loss management. AR mRNA and protein were identified in the dermal papilla (DP), dermal cup (DC), and proximal outer root sheath (ORS) of human hair follicles (HFs) ex vivo. AR knockdown (KD) reduced AR mRNA (qPCR) and protein (IF) levels; however, it did not sustain the anagen phase. Notably, AR KD decreased the mRNA levels of Wnt modulators SFRP1 and DKK1. SFRP1 mRNA was detected in the DP and ORS, with its protein expressed in the DP and hair matrix (HM). Meanwhile, DKK1 mRNA was found in the distal ORS and connective tissue sheath, with protein present in the DC. This distinct localization suggests that simultaneous targeting of these AR-regulated genes may yield additive or synergistic effects on HF function. Supporting this, siRNA-mediated DKK1 KD resulted in a compensatory upregulation of SFRP1 mRNA in HEK239 cells, and SFRP1 KD triggered an increase in DKK1 mRNA in DP cells in vitro. To further explore this interaction, combined and single siRNA KD of DKK1 and SFRP1 was performed in human HFs ex vivo. While KD was confirmed at both mRNA (qPCR) and protein (ELISA) levels, only SFRP1 KD prolonged the anagen phase, significantly increased HM keratinocyte proliferation, and reduced apoptosis. The combination of SFRP1 and DKK1 KD did not enhance the effetcs observed with SFRP1 KD alone. Interestingly, SFRP1 KD induced a compensatory upregulation of DKK1 expression at both mRNA and protein levels, an effect not observed with DKK1 KD. These findings reveal a culture system-dependent regulatory interaction between DKK1 and SFRP1, emphasize the complexity of modulating Wnt signaling for anagen phase maintenance, and underline the therapeutic potential of SFRP1 as a target for addressing hair loss. David Broadley¹, Alizée Le Riche¹, Ying Yu², Mikhail Geyfman², Neil Polonso², Janin Edelkamp¹, Marta Bertolini¹ 1. QIMA Life Sciences, QIMA Monasterium, Münster, Germany. 2. Abbvie Inc, Irvine, CA, United States. Translational Studies: Cell and Molecular Biology