Self-organization process in newborn skin organoid formation inspires strategy to restore hair regeneration of adult cells

Abstract

Organoids made from dissociated progenitor cells undergo tissue-like organization. This in vitro self-organization process is not identical to embryonic organ formation, but it achieves a similar phenotype in vivo. This implies genetic codes do not specify morphology directly; instead, complex tissue architectures may be achieved through several intermediate layers of cross talk between genetic information and biophysical processes. Here we use newborn and adult skin organoids for analyses. Dissociated cells from newborn mouse skin form hair primordia-bearing organoids that grow hairs robustly in vivo after transplantation to nude mice. Detailed time-lapse imaging of 3D cultures revealed unexpected morphological transitions between six distinct phases: dissociated cells, cell aggregates, polarized cysts, cyst coalescence, planar skin, and hair-bearing skin. Transcriptome profiling reveals the sequential expression of adhesion molecules, growth factors, Wnts, and matrix metalloproteinases (MMPs). Functional perturbations at different times discern their roles in regulating the switch from one phase to another. In contrast, adult cells form small aggregates, but then development stalls in vitro. Comparative transcriptome analyses suggest suppressing epidermal differentiation in adult cells is critical. These results inspire a strategy that can restore morphological transitions and rescue the hair-forming ability of adult organoids: (i) continuous PKC inhibition and (ii) timely supply of growth factors (IGF, VEGF), Wnts, and MMPs. This comprehensive study demonstrates that alternating molecular events and physical processes are in action during organoid morphogenesis and that the self-organizing processes can be restored via environmental reprogramming. This tissue-level phase transition could drive self-organization behavior in organoid morphogenies beyond the skin.

Self‐organizing hair peg‐like structures from dissociated skin progenitor cells: New insights for human hair follicle organoid engineering and Turing patterning in an asymmetric morphogenetic field

“…Over the years, our group's research has focused on the morphogenesis of skin appendages. Recently, we examined the self‐organizing behaviour of dissociated epidermal and dermal newborn mouse cells and their ability to reconstitute functional follicles . Similar studies of human follicular morphogenesis have been difficult to achieve, due to the low efficiency of follicle formation from readily available adult cells and the long time to follicle formation.…”

“…Protein kinase C (PKC) and retinoic acid pathways play a role in epidermal differentiation and stratification during skin development. Excessive retinoic acid causes cessation of hair follicle development at the germ stage in mice, while inhibition of PKC promotes folliculogenesis from adult mouse cells . The addition of PKC inhibitors and an RAR antagonist exhibited positive effects on the length and diameter of the epidermal stalk but was insufficient to drive further folliculogenesis, suggesting that other factors are required for progressive development.…”

“…When grafted onto a full thickness dermal wound on a nude mouse, the cultured organoids formed mature, cycling hair follicles within a planar skin configuration. Transcriptomic analysis of the murine skin organoids has identified factors that can rescue the hair forming ability of adult mouse cells . However, similar success with human cells has been more difficult.…”

“…But, to effectively adopt the synthetic biology approach, we must learn more about organoid cultures made of cells from different ages, locations or species, so we can apply key molecules to restore hair forming ability . To this end, we sought to develop a three‐dimensional, culture system in which different types of skin progenitors, such as epidermal‐ or dermal‐like somatic cells, embryonic stem cells or iPS cells, can be guided to form ectodermal organs in a planar configuration (Figure ) .…”

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

“…Bioengineered follicle germs were shown to develop a correct structure when transplanted into the back skin of nude mice . 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.…”