Table 5 Summary of advantages and drawbacks of present methods

Follicle germ assembling

• Easy self-assembling procedures

• Short culturing period

• Ethical issues and immune rejection

• DPCs tend to lose trichogenicity in vitro.

• Progenitor cells may be specified from iPSCs.

• 3D culture and genetic reprogramming helps to reserve the inducibility of DPCs.

Skin organoid induction

• No ethical issues

• Abundant access to iPSCs

• iPSCs induction can not only generate HFs, but also establish HF-bearing skin.

• Long period to coax PSCs into skin organoids

• Concerning safety

• Organoids described in current studies only recapitulate facial skin, excluding the induction of scalp skin.

• Optimized environmental conditioning and genetic modifications may induce more competent organoids.

• In situ incubation may work more efficiently than chemical cocktails.

• Scalp HFs may be attained through the induction of mesodermal cells.

Bioprinting

• Automated

• High throughput

• Generating HF-bearing skin

• Realizing in situ restoration

• Primary cell sources restrain the standardized manufacture.

• Limited cell density in the printing process

• The development of universal cells holds promise for standardizing a bioprinting streamline and achieving an immediate repair.

• The spontaneous contraction may be utilized to achieve the desired density.