{'fraction_non_alphanumeric': 0.026421596783457783, 'fraction_numerical': 0.027570361860999426, 'mean_word_length': 5.006896551724138, 'pattern_counts': {'":': 0, '<': 2, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Knockout of p16INK4a promotes aggregative growth of dermal papilla cells.

OBJECTIVE
Dermal papilla cells (DPCs) are located in the hair follicles and play an important role in hair growth. These cells have the ability to induce hair follicle formation when they display aggregative behavior. DPCs derived from the androgenetic alopecia (AGA) area undergo premature senescence in vitro, associated with p16INK4a expression. The aim of the current study was to investigate the expression of p16INK4a in aggregative and non-aggregative DPCs and the effect of p16INK4a down-regulation in these cells by adenovirus-mediated RNA interference (RNAi).


METHOD
DPCs were isolated and cultured from healthy human scalp. p16INK4a gene and protein were detected in aggregative and non-aggregative cells. Expression of p16INK4a in DPCs was silenced by infection with rAd5-CDKN1A-1p2shRNA. Cell fate was monitored after infection. The growth of cells was measured by MTT assay. Cell cycle was evaluated by flow cytometry (FCM).


RESULTS
DPCs were isolated by digestion and showed aggregative behavior for six passages. The expression of p16INK4a showed a clear upward trend in non-aggregative cells when compared with aggregative group. p16INK4a expression was silenced by rAd5-CDKN1A-1p2shRNA (p<0.05). The p16INK4a-silenced cells grew more rapidly and exhibited a trend towards aggregative growth. There was an increase in the proportion of cells in G1 phase, while those in S phase were reduced after p16INK4a gene silencing (p<0.05).


CONCLUSION
Our results suggest that p16INK4a plays an important role in the premature senescence and aggregative behavior of DPCs. These observations can lead to novel therapeutic strategies for treatment of AGA.