A Systematic Review of Stem Cell Differentiation into Keratinocytes for Regenerative Applications

Small molecules direct the generation of ameloblast-like cells from human embryonic stem cells

BACKGROUND

Ameloblasts present a promising avenue for the investigation of enamel and tooth regeneration. Previous protocols for directing the differentiation of human embryonic stem cells (hESCs) into dental epithelial (DE) cells involving the need for additional cells, conditional medium, and the use of costly cytokines. Importantly, ameloblasts have not been generated from hESCs in previous studies. Hence, we aimed to identify defined differentiation conditions that would solely utilize small molecules to achieve the production of ameloblasts.

METHODS

We developed a three-step strategy entailing the progression of hESCs through non-neural ectoderm (NNE) and DE to generate functional ameloblasts in vitro. Initially, the NNE fate was induced from hESCs using a 6-day differentiation protocol with 1 µmol/L Retinoic acid (RA). Subsequently, the NNE lineage was differentiated into DE by employing a combination of 1 µmol/L LDN193189 (a BMP signaling inhibitor) and 1 µmol/L XAV939 (a WNT signaling inhibitor). In the final phase, 3 µmol/L CHIR99021 (a WNT signaling activator) and 2 µmol/L DAPT (a NOTCH signaling inhibitor) were utilized to achieve the fate of ameloblasts from DE cells. Three-dimensional cultures were investigated to enhance the ameloblast differentiation ability of the induced DE cells. Quantitative reverse transcription polymerase chain reaction (qRT-PCR) and immunofluorescence were conducted to assess the expression of lineage-specific markers. Alizarin Red S (ARS) staining was performed to evaluate the formation of mineralization nodules.

RESULTS

The application of RA facilitated the efficient generation of NNE within a six-day period. Subsequently, upon stimulation with LDN193189 and XAV939, a notable emergence of DE cells was observed on the eighth days. By the tenth day, ameloblast-like cells derived from hESCs were generated. Upon cultivation in spheroids, these cells exhibited elevated levels of ameloblast markers AMBN and AMELX expression, suggesting that spheroid culture augments the differentiation of ameloblasts.

CONCLUSION

We established an efficient small molecule-based method to differentiate hESCs into ameloblast-like cells through the concerted modulation of RA, BMP, WNT, and NOTCH signaling pathways, potentially advancing research in enamel and tooth regeneration.

Controlled therapeutic cholesterol delivery to cells for the proliferation and differentiation of keratinocytes

The challenge of enhancing wound healing and skin regeneration, particularly in conditions like burns and diabetic wounds, necessitates innovative solutions. Cholesterol, often associated with cardiovascular diseases, plays vital roles in cellular functions, maintaining skin integrity and preserving the skin barrier. Here, we explore cholesterol's significance, its influence on keratinocytes, and its potential application in skin regeneration. The study utilizes electrospun polyimide (PI) fibers as a cholesterol carrier model and investigates its impact on HaCaT keratinocytes, marking the first time tracked cholesterol delivery from the scaffold into cells. We demonstrate that an optimal concentration of 0.7 mM cholesterol in the medium enhances cell proliferation, while higher concentrations have negative effects. Cholesterol-enriched scaffolds significantly increase cell proliferation and replicative activity, especially in a 3D culture environment. Moreover, cholesterol influences keratinocyte differentiation, promoting early differentiation while inhibiting late differentiation. These findings suggest that cholesterol-loaded scaffolds can have applications in wound healing by promoting cell growth, regulating differentiation, and potentially accelerating wound closure. Further research in this area will lead to innovative wound management and tissue regeneration strategies.

Development of a Composite Hydrogel Containing Statistically Optimized PDGF-Loaded Polymeric Nanospheres for Skin Regeneration: In Vitro Evaluation and Stem Cell Differentiation Studies

Platelet-derived growth factor-BB (PDGF-BB) is a polypeptide growth factor generated by platelet granules faced to cytokines. It plays a role in forming and remodeling various tissue types, including epithelial tissue, through interaction with cell-surface receptors on most mesenchymal origin cells. However, it breaks down quickly in biological fluids, emphasizing the importance of preserving them from biodegradation. To address this challenge, we formulated and evaluated PDGF-encapsulated nanospheres (PD@PCEC) using polycaprolactone-polyethylene glycol-polycaprolactone. PD@PCECs were fabricated through the triple emulsion methodology and optimized by using the Box-Behnken design. The encapsulation efficiency (EE) of nanoencapsulated PDGF-BB was investigated concerning four variables: stirring rate (X1), stirring duration (X2), poly(vinyl alcohol) concentration (X3), and PDGF-BB concentration (X4). The selected optimized nanospheres were integrated into a gelatin-collagen scaffold (PD@PCEC@GC) and assessed for morphology, biocompatibility, in vitro release, and differentiation-inducing activity in human adipose-derived stem cells (hADSCs). The optimized PD@PCEC nanospheres exhibited a particle size of 177.9 ± 91 nm, a zeta potential of 5.2 mV, and an EE of 87.7 ± 0.44%. The release profile demonstrated approximately 85% of loaded PDGF-BB released during the first 360 h, with a sustained release over the entire 504 h period, maintaining bioactivity of 87.3%. The study also included an evaluation of the physicochemical properties of the scaffolds and an assessment of hADSC adhesion to the scaffold's surface. Additionally, hADSCs cultivated within the scaffold effectively differentiated into keratinocyte-like cells (KLCs) over 21 days, evidenced by morphological changes and upregulation of keratinocyte-specific genes, including cytokeratin 18, cytokeratin 19, and involucrin, at both transcriptional and protein levels.