Preparation of hair beads and hair follicle germs for regenerative medicine

Tissue engineering strategies for human hair follicle regeneration: How far from a hairy goal?

“…Additionally, two recent studies have achieved growth of mouse hair in vivo after transplantation of in vitro formed structures, either consisting of mouse adult DP and epidermal cells, or of mouse iPSCs, encapsulated in hydrogel matrices. Different artificial 3D microenvironments composed of silk‐gelatin, hyaluronic acid, and collagen were shown to improve hair germs for hair regenerative medicine. In a similar approach, human HF resembling vellus hair were recreated in vitro from a mixture of DP cells, keratinocytes and melanocytes in a collagen matrix, and named “microfollicles.” Presently, researchers are joining efforts to develop more complex structures that can mimic the DP tridimensional morphology while providing a spatiotemporal delivery of molecular cues needed for human hair morphogenesis.…”

“…Effective 3D‐printing of skin substitutes with human HFs has been recently reported . Additionally, custom‐designed array plates were produced to allow scalable fabrication of inductive DP microtissues …”

“…To date, fully functional HF reconstruction in vitro was only achieved using mouse embryonic skin cells. 37,64 Several studies have reported improved HF neogenic potential either by using cells with higher differentiation potential, namely adult HFCS, neonatal keratinocytes and embryonic cells, 37,65 or by coupling human and mouse cells to form chimeric HFs (eg, human mesenchymal inductive cells and rodent epithelial keratinocytes). 66,67 As expected, such cellular constructs evidence greater HF inductive potential when implanted into a mouse skin.…”

“…37,70 Additionally, two recent studies have achieved growth of mouse hair in vivo after transplantation of in vitro formed structures, either consisting of mouse adult DP and epidermal cells, 72 Considering the negative effects of in vitro follicular cell culture expansion, signaling modulation, 3D culture, biomaterial-based culture, or a combination of these approaches may be used to restore cell's trichogenicity. By combining epithelial and mesenchymal components, engineered instructive mini-bulbs can be obtained in vitro for a successful tissue engineering solution able to generate mature and functional HFs in the bald scalps; FUE, follicular unit excision and collagen 65 were shown to improve hair germs for hair regenerative medicine. In a similar approach, human HF resembling vellus hair were recreated in vitro from a mixture of DP cells, keratinocytes and melanocytes in a collagen matrix, and named "microfollicles."…”

“…36 Additionally, custom-designed array plates were produced to allow scalable fabrication of inductive DP microtissues. 50,65 Finally, an emerging trend in HF research is the in vitro reconstruction of artificial hair-bearing skin. Relevantly, Zhang et al were able to generate HFs from cultured mouse DP cells in de novo engineered skin model.…”