High-Resolution Dissection of Chemical Reprogramming from Mouse Embryonic Fibroblasts into Fibrocartilaginous Cells

Organelle-tuning condition robustly fabricates energetic mitochondria for cartilage regeneration

Mitochondria are vital organelles whose impairment leads to numerous metabolic disorders. Mitochondrial transplantation serves as a promising clinical therapy. However, its widespread application is hindered by the limited availability of healthy mitochondria, with the dose required reaching up to 109 mitochondria per injection/patient. This necessitates sustainable and tractable approaches for producing high-quality human mitochondria. In this study, we demonstrated a highly efficient mitochondria-producing strategy by manipulating mitobiogenesis and tuning organelle balance in human mesenchymal stem cells (MSCs). Utilizing an optimized culture medium (mito-condition) developed from our established formula, we achieved an 854-fold increase in mitochondria production compared to normal MSC culture within 15 days. These mitochondria were not only significantly expanded but also exhibited superior function both before and after isolation, with ATP production levels reaching 5.71 times that of normal mitochondria. Mechanistically, we revealed activation of the AMPK pathway and the establishment of a novel cellular state ideal for mitochondrial fabrication, characterized by enhanced proliferation and mitobiogenesis while suppressing other energy-consuming activities. Furthermore, the in vivo function of these mitochondria was validated in the mitotherapy in a mouse osteoarthritis model, resulting in significant cartilage regeneration over a 12-week period. Overall, this study presented a new strategy for the off-the-shelf fabrication of human mitochondria and provided insights into the molecular mechanisms governing organelle synthesis.

Direct reprogramming of human fibroblasts into hair-inducing dermal papilla cell-like cells by a single small molecule

Dermal papilla cells (DPCs) are a crucial subset of mesenchymal cells in the skin responsible for regulating hair follicle development and growth, making them invaluable for cell-based therapies targeting hair loss. However, obtaining sufficient DPCs with potent hair-inducing abilities remains a persistent challenge. In this study, the Food and Drug Administration (FDA)-approved drug library was utilized to screen small molecules capable of reprogramming readily accessible human skin fibroblasts into functional DPCs. In the initial screening, five candidate small molecules were identified from a pool of 1,817 compounds, and the small molecule peficitinib was further identified by the further hair follicle regeneration experiments. Following peficitinib treatment, fibroblasts derived from primary human foreskin and scalp exhibited the capability to induce hair growth and possessed a molecular profile highly similar to that of primary DPCs. We refer to these cells as dermal papilla cell-like cells (DPC-LCs). Furthermore, transcriptome analysis showed that the wingless/integrated (Wnt) signaling pathway and the transforming growth factor β (TGF-β) signaling pathway, both of which play crucial roles in hair follicle morphogenesis, are upregulated and enriched in these DPC-LCs. These functional DPC-LCs offer a promising avenue for obtaining a plentiful supply of hair-inducing cells, thereby advancing the development of therapeutic strategies for hair loss treatment.

Limitations and challenges of direct cell reprogramming in vitro and in vivo

Direct reprogramming, whether in vitro or in vivo, has attracted great attention because of its advantages of convenience, short-term conversion, direct targets, no immune rejection, and potential clinical applications. In addition, due to its independence from the pluripotent state, direct programming minimizes some safety concerns associated with the use of human pluripotent stem cells. However, the significant limitations of reprogrammed cells, such as poor proliferative ability, low efficiency, and immature function, need to be addressed before the clinical application potential can be expanded. Here, we review the recent achievements of direct reprogramming in 2D and 3D systems in vitro and in vivo, covering cells derived from the three germ layers from stem/progenitor cells to terminal cells, such as hepatocytes, pancreatic β cells, cardiomyocytes, endothelial cells, osteoblasts, chondrocytes, neurons, and melanocytes. Combining our lab experiences with current work, we summarize the practical and potential issues that need to be solved and the prospects of strategies for addressing the current dilemmas. Through comprehensive analyses, it is concluded that the directions for dealing with efficiency and functionality issues could be the optimization of transcription factors, the upgradation for delivery systems, the regulation of epigenetic factors and pathways, and the improvement of cellular maintenance conditions. Besides, converting cells into the progenitor state firstly and then differentiating them into the desired cell types with chemical compounds may provide an approach to obtaining functional and safe converted cells in batches with a better proliferative ability. With the emergence of more and more direct reprogramming techniques and approaches with both safety and effectiveness, it is bound to bring a new dawn for mechanism research and therapeutic applications for relevant diseases in the future.

Intratunical injection of rat-derived bone marrow mesenchymal stem cells prevents fibrosis and is associated with increased Smad7 expression in a rat model of Peyronie's disease

Objective

Peyronie’s disease (PD) is a fibrotic disorder of the penis, but effective treatments are lacking. Here, we observed the effects of rat-derived bone marrow mesenchymal stem cells (BMSCs) injection in the active phase and chronic phase in a rat model of PD, and the possible mechanism was analysed with fibroblasts derived from rat penile tunica albuginea (TA).

Methods

Thirty-two male Sprague-Dawley rats were divided into four groups. In sham group, the rats were injected with 50 µL of vehicle. In the PD group, the rats were injected with 50 µg TGF-β1. In the PD + BMSCs early treatment group, the rats were injected with 50 µg TGF-β1 and injected with 1 × 10⁶ BMSCs after 1 day. In the PD + BMSCs late treatment group, the rats were injected with 50 µg TGF-β1 and injected with 1 × 10⁶ BMSCs after 28 days. Twenty-seven days after the last injection, the erectile function of the rats was measured, and then, penile fibrosis was analysed by histology and western blot. In vitro, fibroblasts derived from rat penile TA were used to identify a possible antifibrotic mechanism of BMSCs, and a Smad7 expression vector was used as a positive control. Fibroblasts were pretreated with the Smad7 expression vector or BMSCs for 48 h and then activated with 10 ng/mL TGF-β1 for 24 h. Cells viability was assessed, and Smad7, collagen 3, elastase-2B and osteopontin expression levels were analysed by immunofluorescence and western blot. Furthermore, fibroblasts were transfected with Smad7 siRNA or scramble control to observe whether the effects of BMSCs could be offset.

Results

Erectile function obviously improved, and fibrosis of penile TA was prevented after BMSCs treatment compared with that in the rats with PD. Furthermore, the effects of BMSCs treatment in the active phase were better than those in the chronic phase. After cocultured with BMSCs, cell viability was not affected, Smad7 expression was upregulated, and collagen 3, elastase-2B and osteopontin levels were decreased in the TGF-β1-treated fibroblasts. After transfection with Smad7 siRNA, the antifibrotic effects of BMSCs were offset.

Conclusions

The antifibrotic effects of BMSCs treatment in the active phase of the PD rat model were better than those in the chronic phase. A possible mechanism of BMSCs treatment was related to increased Smad7 expression, suggesting a possible effective and safe procedure for the treatment of PD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-03090-w.

A high-resolution route map reveals distinct stages of chondrocyte dedifferentiation for cartilage regeneration

Articular cartilage damage is a universal health problem. Despite recent progress, chondrocyte dedifferentiation has severely compromised the clinical outcomes of cell-based cartilage regeneration. Loss-of-function changes are frequently observed in chondrocyte expansion and other pathological conditions, but the characteristics and intermediate molecular mechanisms remain unclear. In this study, we demonstrate a time-lapse atlas of chondrocyte dedifferentiation to provide molecular details and informative biomarkers associated with clinical chondrocyte evaluation. We performed various assays, such as single-cell RNA sequencing (scRNA-seq), live-cell metabolic assays, and assays for transposase-accessible chromatin with high-throughput sequencing (ATAC-seq), to develop a biphasic dedifferentiation model consisting of early and late dedifferentiation stages. Early-stage chondrocytes exhibited a glycolytic phenotype with increased expression of genes involved in metabolism and antioxidation, whereas late-stage chondrocytes exhibited ultrastructural changes involving mitochondrial damage and stress-associated chromatin remodeling. Using the chemical inhibitor BTB06584, we revealed that early and late dedifferentiated chondrocytes possessed distinct recovery potentials from functional phenotype loss. Notably, this two-stage transition was also validated in human chondrocytes. An image-based approach was established for clinical use to efficiently predict chondrocyte plasticity using stage-specific biomarkers. Overall, this study lays a foundation to improve the quality of chondrocytes in clinical use and provides deep insights into chondrocyte dedifferentiation.

Pharmaceutical therapeutics for articular regeneration and restoration: state-of-the-art technology for screening small molecular drugs

Articular cartilage damage caused by sports injury or osteoarthritis (OA) has gained increased attention as a worldwide health burden. Pharmaceutical treatments are considered cost-effective means of promoting cartilage regeneration, but are limited by their inability to generate sufficient functional chondrocytes and modify disease progression. Small molecular chemical compounds are an abundant source of new pharmaceutical therapeutics for cartilage regeneration, as they have advantages in design, fabrication, and application, and, when used in combination, act as powerful tools for manipulating cellular fate. In this review, we present current achievements in the development of small molecular drugs for cartilage regeneration, particularly in the fields of chondrocyte generation and reversion of chondrocyte degenerative phenotypes. Several clinically or preclinically available small molecules, which have been shown to facilitate chondrogenesis, chondrocyte dedifferentiation, and cellular reprogramming, and subsequently ameliorate cartilage degeneration by targeting inflammation, matrix degradation, metabolism, and epigenetics, are summarized. Notably, this review introduces essential parameters for high-throughput screening strategies, including models of different chondrogenic cell sources, phenotype readout methodologies, and transferable advanced systems from other fields. Overall, this review provides new insights into future pharmaceutical therapies for cartilage regeneration.

Phenotypic technologies in stem cell biology

The high-throughput phenotypic screen (HTPS) has become an emerging technology to discover synthetic small molecules that regulate stem cell fates. Here, we review the application of HTPS to identify small molecules controlling stem cell renewal, reprogramming, differentiation, and lineage conversion. Moreover, we discuss the use of HTPS to discover small molecules/polymers mimicking the stem cell extracellular niche. Furthermore, HTPSs have been applied on whole-animal models to identify small molecules regulating stem cell renewal or differentiation in vivo. Finally, we discuss the examples of the utilization of HTPS in stem cell-based disease modeling, as well as in the discovery of novel drug candidates for cancer, diabetes, and infectious diseases. Overall, HTPSs have provided many powerful tools for the stem cell field, which not only facilitate the generation of functional cells/tissues for replacement therapy, disease modeling, and drug screening, but also help dissect molecular mechanisms regulating physiological and pathological processes.

Small Molecule Epigenetic Modulators in Pure Chemical Cell Fate Conversion

Although innovative technologies for somatic cell reprogramming and transdifferentiation provide new strategies for the research of translational medicine, including disease modeling, drug screening, artificial organ development, and cell therapy, recipient safety remains a concern due to the use of exogenous transcription factors during induction. To resolve this problem, new induction approaches containing clinically applicable small molecules have been explored. Small molecule epigenetic modulators such as DNA methylation writer inhibitors, histone methylation writer inhibitors, histone acylation reader inhibitors, and histone acetylation eraser inhibitors could overcome epigenetic barriers during cell fate conversion. In the past few years, significant progress has been made in reprogramming and transdifferentiation of somatic cells with small molecule approaches. In the present review, we systematically discuss recent achievements of pure chemical reprogramming and transdifferentiation.