Single-Cell Transcriptomics Reveals the Molecular Anatomy of Sheep Hair Follicle Heterogeneity and Wool Curvature

SP1 and KROX20 Regulate the Proliferation of Dermal Papilla Cells and Target the CUX1 Gene

Previous studies have demonstrated that CUX1 could contribute to the proliferation of DPCs in vitro, but the upstream transcriptional regulatory mechanisms of CUX1 remain largely unknown. This study aimed to investigate the upstream transcriptional regulators of CUX1 to enhance our comprehension of the mechanism of action of the CUX1 gene in ovine DPCs. Initially, the JASPAR (2024) software was used to predict the upstream target transcription factors for the CUX1 gene. Subsequently, through RT-qPCR and a double luciferase reporter assay, the interaction between SP1, KROX20, and CUX1 was established, respectively. The results indicated that SP1 and KROX20 were two highly reliable upstream transcription regulators for the CUX1 gene. Additionally, we found that SP1 promoted the proliferation of DPCs by overexpressing SP1 in DPCs, and KROX20 inhibited the proliferation of DPCs by overexpressing KROX20 in DPCs. These findings are also consistent with the transcriptional regulation of CUX1 by SP1 and KROX20, respectively. This study suggests that the effect of DPC proliferation in vitro by CUX1 may regulated by the transcription factors SP1 and KROX20.

Single-Cell Transcriptome Sequence Profiling on the Morphogenesis of Secondary Hair Follicles in Ordos Fine-Wool Sheep

The Ordos fine-wool sheep is a high-quality breed in China that produces superior natural textiles and raw materials such as wool and lamb meat. However, compared to the Australian Merino sheep, there is still a gap in terms of the wool fiber fineness and wool yield. The hair follicle is the main organ that controls the type of wool fiber, and the morphological changes in the secondary hair follicle are crucial in determining wool quality. However, the process and molecular mechanisms of hair follicle morphogenesis in Ordos fine-wool sheep are not yet clear. Therefore, analyzing the molecular mechanisms underlying the process of follicle formation is of great significance for improving the fiber diameter and wool production of Ordos fine-wool sheep. The differential expressed genes, APOD, POSTN, KRT5, and KRT15, which related to primary hair follicles and secondary hair follicles, were extracted from the dermal papillae. Based on pseudo-time analysis, the differentiation trajectories of dermal lineage cells and epidermal lineage cells in the Ordos fine-wool sheep were successfully constructed, providing a theoretical basis for breeding research in Ordos fine-wool sheep.

Preliminary study of melatonin in the proliferation and apoptosis of Hu sheep dermal papilla cells in vitro

Previous studies have shown that melatonin has a certain regulatory effect on the growth of sheep wool. However, the mechanism of melatonin action remains unknown. In the present study, we aimed to understand the role of exogenous melatonin in the dermal papilla cells of Hu sheep. To confirm the optimal melatonin treatment regimen for Hu sheep dermal papilla cells, we detected the cell viability by exposing them to different concentrations of melatonin and different treatment times. The results showed that cell viability was best when dermal papilla cells were treated with 1000 pg/ml of melatonin for 48 h. According to the results of qPCR, CCK-8, EDU, Western blot, and Flow cytometry analysis, we found that 1000 pg/ml melatonin promoted the proliferation and inhibited the apoptosis of dermal papilla cells compared with the exogenous melatonin blank group (control group). Furthermore, we also found that 1000 pg/ml of melatonin promoted the cell cycle progress of dermal papilla cells according to the results of qPCR and Flow cytometry analysis. Overall, our findings showed that melatonin plays an important role in the dermal papilla cells of Hu sheep.

SOX18 Promotes the Proliferation of Dermal Papilla Cells via the Wnt/β-Catenin Signaling Pathway

SRY-box transcription factor 18 (SOX18) is known to play a crucial role in the growth and development of hair follicles (HF) in both humans and mice. However, the specific effect of SOX18 on sheep hair follicles remains largely unknown. In our previous study, we observed that SOX18 was specifically expressed within dermal papilla cells (DPCs) in ovine hair follicles, leading us to investigate its potential role in the growth of hair follicles in sheep. In the present study, we aimed to examine the effect of SOX18 in DPCs and preliminarily study its regulatory mechanism through RNA-seq. We initially found that the overexpression of SOX18 promoted the proliferation of DPCs compared to the negative control group, while the interference of SOX18 had the opposite effect. To gain further insight into the regulatory mechanism of SOX18, we conducted RNA-seq analysis after knocking down SOX18 in Hu sheep DPCs. The result showed that the Wnt/β-Catenin signaling pathway was involved in the growth process of DPC after SOX18 knockdown. Subsequently, we investigated the effect of SOX18 on the Wnt/β-Catenin signaling pathway in DPCs using TOP/FOP-flash, qRT-PCR, and Western blot (WB) analysis. Our data demonstrated that SOX18 could activate the Wnt/β-Catenin signaling pathway in DPCs. Additionally, we observed that SOX18 could rescue the proliferation of DPCs after inhibiting the Wnt/β-Catenin signaling pathway. These findings underscore the essential role of SOX18 as a functional molecule governing the proliferation of DPCs. Additionally, these findings also greatly enhance our understanding of the role of SOX18 in the proliferation of DPCs and the growth of wool in Hu sheep.

Whole-Genome Resequencing Reveals Selection Signal Related to Sheep Wool Fineness

Wool fineness affects the quality of wool, and some studies have identified about forty candidate genes that affect sheep wool fineness, but these genes often reveal only a certain proportion of the variation in wool thickness. We further explore additional genes associated with the fineness of sheep wool. Whole-genome resequencing of eight sheep breeds was performed to reveal selection signals associated with wool fineness, including four coarse wool and four fine/semi-fine wool sheep breeds. Multiple methods to reveal selection signals (Fst and θπ Ratio and XP-EHH) were applied for sheep wool fineness traits. In total, 269 and 319 genes were annotated in the fine wool (F vs. C) group and the coarse wool (C vs. F) group, such as LGR4, PIK3CA, and SEMA3C and NFIB, OPHN1, and THADA. In F vs. C, 269 genes were enriched in 15 significant GO Terms (p < 0.05) and 38 significant KEGG Pathways (p < 0.05), such as protein localization to plasma membrane (GO: 0072659) and Inositol phosphate metabolism (oas 00562). In C vs. F, 319 genes were enriched in 21 GO Terms (p < 0.05) and 16 KEGG Pathways (p < 0.05), such as negative regulation of focal adhesion assembly (GO: 0051895) and Axon guidance (oas 04360). Our study has uncovered genomic information pertaining to significant traits in sheep and has identified valuable candidate genes. This will pave the way for subsequent investigations into related traits.

CRABP2 Promotes the Proliferation of Dermal Papilla Cells via the Wnt/β-Catenin Pathway

In our previous study of Hu sheep hair follicles, we found that CRABP2 was highly expressed in DPCs, which suggested that CRABP2 may influence the number of DPCs. In the present study, we aimed to understand the effect of CRABP2 in Hu sheep dermal papilla cells (DPCs). First, we explored the influence of CRABP2 on the ability of Hu sheep DPCs' proliferation. Based on the results obtained from some experiments, such as CCK-8, EDU, qPCR, and Western blot experiment, we found that the overexpression of CRABP2 facilitated the proliferation of DPCs compared to the negative control group. Then, we also detected the effect of CRABP2 on the Wnt/β-catenin pathway based on the important function of the Wnt/β-catenin pathway in hair follicles. The results showed that CRABP2 could activate the Wnt/β-catenin pathway in DPCs, and it rescues the proliferation of DPCs when the Wnt/β-catenin pathway was inhibited. In summary, our findings indicate that CRABP2 is a vital functional gene in the proliferation of Hu sheep DPCs. Our study will be of great use for revealing the roles of CRABP2 in the hair follicles of Hu sheep.

Defining ovine dermal papilla cell markers and identifying key signaling pathways regulating its intrinsic properties

Dermal papilla cell (DPC), one of the key cell types during hair follicle development and regeneration, specifies hair size, shape and cycling. It is also an important in vitro screening model for hair growth. Although some characteristics of DPCs, such as agglutinative growth and marker genes, have been studied in mice and humans, the intrinsic properties of ovine DPCs and the regulatory mechanism of the intrinsic properties during continued culture in vitro remained unknown. In this study, based on our previous single-cell transcriptome sequencing on sheep lambskin, we verified SOX18 and PDGFRA as the novel marker genes of ovine DPCs through immunofluorescence staining on skin sections and cultured DPCs. Using continued cell culture and alkaline phosphatase staining, we found that different from mice and humans, ovine DPCs exhibit particularly robust and stable aggregation with unbated alkaline phosphatase activity till 30 passages during continued culture in vitro. Also, we found that the expression of some marker genes and the activity of Wnt/β-catenin signaling differ between early passaged DPCs and multiple passaged DPCs. Further, using Wnt/β-catenin agonist and antagonist, we demonstrated that Wnt/β-catenin signaling could regulate cell aggregation and alkaline phosphatase activity of ovine DPCs through regulating FGF and IGF signaling. This study provides the basis for isolating ovine DPCs and defines their intrinsic properties, which contribute to improving wool performance and medicine of hair regeneration.

Effect of Sox18 on the Induction Ability of Dermal Papilla Cells in Hu Sheep

Sox18 is a developmental gene that encodes transcription factors. It has been indicated as be a key gene affecting the growth and development of hair follicles, in which dermal papilla cells (DPCs) have been demonstrated to play an important role through their ability to induce the formation of hair follicles. Pre-laboratory studies have found that Sox18 is differentially expressed in the dermal papilla cells of different pattern types of Hu sheep. We speculated that Sox18 plays an important role in the dermal papilla cells of Hu sheep. In our study, we analyzed the effect of Sox18 on the induction ability of DPCs in order to elucidate the function and molecular mechanism of Sox18 in the DPCs of Hu sheep. We first identified the expression of Sox18 in the DPCs of Hu sheep by immunofluorescence staining. We then used alkaline phosphatase staining, cell morphology observations and RT-PCR to detect the effect of Sox18 on the induction of DPCs after overexpression of or interference with Sox18. We also used RT-PCR, WB and immunofluorescence staining to detect the effect of Sox18 on the Wnt/β-catenin signal pathway in DPCs. We found that Sox18 was specifically expressed in the DPCs of Hu sheep, and that Sox18 could enhance the alkaline phosphatase activity in the DPCs of Hu sheep and accelerate cell agglutination. The results of RT-PCR revealed that Sox18 promoted the mRNA expression of Versican, HHIP and FGFRI, and inhibited the mRNA expression of BMP4 and WIF1. Further studies showed that Sox18 promoted the expression of β-catenin and activated the Wnt/β-catenin signal pathway in DPCs. When the Wnt/β-catenin signal pathway of DPCs was activated, the induction ability of DPCs was enhanced. Overall, we believe that Sox18 could enhance the induction ability of DPCs in Hu sheep and regulate the induction ability of DPCs through the Wnt/β-catenin signal pathway.

Gene network analysis reveals candidate genes related with the hair follicle development in sheep

Background

Merino sheep are the most famous fine wool sheep in the world. They have high wool production and excellent wool quality and have attracted worldwide attention. The fleece of the Merino sheep is composed predominantly of wool fibers grown from secondary wool follicles. Therefore, it is necessary to study the development of hair follicles to understand the mechanism of wool production. The hair follicle is a complex biological system involved in a dynamic process governed by gene regulation. The hair follicle development process is very complex and poorly understood. The purpose of our research is to identify candidate genes related to hair follicle development, provide a theoretical molecular breeding basis for the cultivation of fine wool sheep, and provide a reference for the problems of hair loss and alopecia areata that affect human beings.

Results

We analyzed mRNAs data in skin tissues of 18 Merino sheep at four embryonic days (E65, E85, E105 and E135) and two postnatal days (P7 and P30). G1 to G6 represent hair follicles developmental at six stages (i.e. E65 to P30). We identified 7879 differentially expressed genes (DEGs) and 12623 novel DEGs, revealed different expression patterns of these DEGs at six stages of hair follicle development, and demonstrated their complex interactions. DEGs with stage-specific expression were significantly enriched in epidermal differentiation and development, hair follicle development and hair follicle morphogenesis and were enriched in many pathways related to hair follicle development. The key genes (LAMA5, WNT10A, KRT25, SOSTDC1, ZDHHC21, FZD1, BMP7, LRP4, TGFβ2, TMEM79, SOX10, ITGB4, KRT14, ITGA6, and GLI2) affecting hair follicle morphogenesis were identified by network analysis.

Conclusion

This study provides a new reference for the molecular basis of hair follicle development and lays a foundation for further improving sheep hair follicle breeding. Candidate genes related to hair follicular development were found, which provided a theoretical basis for molecular breeding for the culture of fine wool sheep. These results are a valuable resource for biological investigations of fleece evolution in animals.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08552-2.

3D bioprinting of complex tissues in vitro: state-of-the-art and future perspectives

The pharmacology and toxicology of a broad variety of therapies and chemicals have significantly improved with the aid of the increasing in vitro models of complex human tissues. Offering versatile and precise control over the cell population, extracellular matrix (ECM) deposition, dynamic microenvironment, and sophisticated microarchitecture, which is desired for the in vitro modeling of complex tissues, 3D bio-printing is a rapidly growing technology to be employed in the field. In this review, we will discuss the recent advancement of printing techniques and bio-ink sources, which have been spurred on by the increasing demand for modeling tactics and have facilitated the development of the refined tissue models as well as the modeling strategies, followed by a state-of-the-art update on the specialized work on cancer, heart, muscle and liver. In the end, the toxicological modeling strategies, substantial challenges, and future perspectives for 3D printed tissue models were explored.