Research on mesenchymal stem cells (MSCs) continues to progress rapidly. Nevertheless, the field faces several challenges, such as inherent cell heterogeneity and the absence of unique MSCs markers. Due to MSCs’ ability to differentiate into multiple tissues, these cells represent a promising tool for new cell‐based therapies. However, for tissue engineering applications, it is critical to start with a well‐defined cell population. Additionally, evidence that MSCs subpopulations may also feature distinct characteristics and regeneration potential has arisen. In this report, we present an overview of the identification of MSCs based on the expression of several surface markers and their current tissue sources. We review the use of MSCs subpopulations in recent years and the main methodologies that have addressed their isolation, and we emphasize the most‐used surface markers for selection, isolation, and characterization. Next, we discuss the osteogenic and chondrogenic differentiation from MSCs subpopulations. We conclude that MSCs subpopulation selection is not a minor concern because each subpopulation has particular potential for promoting the differentiation into osteoblasts and chondrocytes. The accurate selection of the subpopulation advances possibilities suitable for preclinical and clinical studies and determines the safest and most efficacious regeneration process.

Human amniotic membrane-derived mesenchymal stem cells (hAM-MSCs) are a potential source of cells for therapeutic applications in bone regeneration. Recent evidence reveals a role for microRNAs (miRNAs) in the fine-tuning regulation of osteogenesis (osteomiRs) suggesting that they can be potential targets for skeleton diseases treatment. However, the functions of osteomiRs during differentiation of hAM-MSCs to osteogenic lineage are poorly understood. In this investigation, we discovered a novel miRNAs expression signature corresponding to the matrix maturation (preosteoblast) and mineralization (mature osteoblast) stages of dexamethasone-induced osteoblastic differentiation of hAM-MSCs. Comprehensive miRNAs profiling using TaqMan Low Density Arrays showed that 18 miRNAs were significantly downregulated, whereas 3 were upregulated in the matrix maturation stage (7 days after osteogenic induction) in comparison to undifferentiated cells used as control. Likewise, 47 miRNAs were suppressed and 25 were overexpressed at mineralization stage (14 days after osteogenic induction) in comparison to osteoprogenitors cells. Five out 93 miRNAs (miR-19b-3p, miR-335-3p, miR-197-3p, miR-34b-39, and miR-576-3p) were regulated at both 7 and 14 days suggesting a role in coordinated guidance of osteoblastic differentiation. Exhaustive bioinformatic predictions showed that the set of modulated miRNAs may target multiple genes involved in regulatory networks driving osteogenesis including key members of BMP, TGF-β, and WNT/β-catenin signaling pathways. Of these miRNAs, we selected miR-204, a noncoding small RNA that was expressed at matrix maturation phase and downregulated at maturation stage, for further functional studies. Interestingly, gain-of-function analysis showed that restoration of miR-204 using RNA mimics at the onset of mineralization stage dramatically inhibited deposition of calcium and osteogenic maturation of hAM-MSCs. Moreover in silico analysis detected a conserved miR-204 binding site at the 3′UTR of TGF-βR2 receptor gene. Using luciferase assays we confirmed that TGF-βR2 is a downstream effector of miR-204. In conclusion, we have identified a miRNAs signature for osteoblast differentiation of hAM-MSCs. The results from this study suggested that these miRNAs may act as potential inhibitors or activators of osteogenesis. Our findings also points towards the idea that miR-204/TGF-βR2 axis has a regulatory role in differentiation of hAM-MSCs committed to osteoblastic lineage.

The transcription factor GATA-binding protein 3 (GATA-3) and the transcriptional program it regulates have emerged as oncogenic drivers across diverse T-cell lymphomas (TCLs), many of which are resistant to conventional chemotherapeutic agents and characterized by recurrent losses of key tumor suppressor genes, including TP53 and PTEN, both of which are clients of the nuclear export protein XPO1. Here, we demonstrated that XPO1 is highly expressed by malignant T cells expressing GATA-3 and by lymphoma-associated macrophages (LAMs) within their tumor microenvironment (TME). Using complementary genetically engineered mouse models, we demonstrated that TP53- and/or phosphate and tensin homolog (PTEN)-deficient TCLs, and LAMs within their TME, are sensitive to the selective exportin-1 (XPO1) antagonist selinexor. In an effort to identify TP53- and PTEN-independent mechanisms, we used complementary and orthogonal approaches to investigate the role of eIF4E and XPO1-dependent messenger RNA nuclear export in these TCLs. We identified a novel role for eIF4E/XPO1 in exporting GATA-3 and GATA-3–dependent transcripts from the nucleus in TCLs, and in the export of therapeutically relevant transcripts, including colony-stimulating factor-1 receptor, from LAMs. Therefore, XPO1 antagonism, by impairing oncogenic transcriptional programs in TCLs and depleting LAMs from their TME, is a novel approach to target 2 independent dependencies in a group of therapeutically challenging TCLs.

Articular cartilage injuries remain as a therapeutic challenge due to the limited regeneration potential of this tissue. Cartilage engineering grafts combining chondrogenic cells, scaffold materials, and microenvironmental factors are emerging as promissory alternatives. The design of an adequate scaffold resembling the physicochemical features of natural cartilage and able to support chondrogenesis in the implants is a crucial topic to solve. This study reports the development of an implant constructed with IGF1-transduced adipose-derived mesenchymal stem cells (immunophenotypes: CD105⁺, CD90⁺, CD73⁺, CD14^-, and CD34^-) embedded in a scaffold composed of a mix of alginate/milled bovine decellularized knee material which was cultivated in vitro for 28 days (3CI). Histological analyses demonstrated the distribution into isogenous groups of chondrocytes surrounded by a de novo dense extracellular matrix with balanced proportions of collagens II and I and high amounts of sulfated proteoglycans which also evidenced adequate cell proliferation and differentiation. This graft also shoved mechanical properties resembling the natural knee cartilage. A modified Bern/O’Driscoll scale showed that the 3CI implants had a significantly higher score than the 2CI implants lacking cells transduced with IGF1 (16/18 vs. 14/18), representing high-quality engineering cartilage suitable for in vivo tests. This study suggests that this graft resembles several features of typical hyaline cartilage and will be promissory for preclinical studies for cartilage regeneration.

Exposures to complex environmental chemical mixtures during pregnancy reach and target the feto-placental unit. This study investigates the influence of environmental chemical mixtures on placental bioenergetics. Recognizing the essential role of the epidermal growth factor receptor (EGFR) in placental development and its role in stimulating glycolysis and mitochondrial respiration in trophoblast cells, we explored the effects of chemicals known to disrupt EGFR signaling on cellular energy production. Human primary cytotrophoblasts (hCTBs) and a first-trimester extravillous trophoblast cell line (HTR-8/SVneo) were exposed to a mixture of EGFR-interfering chemicals, including atrazine, bisphenol S, niclosamide, PCB-126, PCB-153, and trans-nonachlor. An RNA sequencing approach revealed that the mixture altered the transcriptional signature of genes involved in cellular energetics. Next, the impact of the mixture on cellular bioenergetics was evaluated using a combination of mitochondrial and glycolytic stress tests, ATP production, glucose consumption, lactate synthesis, and super-resolution imaging. The chemical mixture did not alter basal oxygen consumption but diminished the maximum respiratory capacity in a dose-dependent manner, indicating a disruption of mitochondrial function. The respiratory capacity and ATP production were increased by EGF, while the Chem-Mix reduced both EGF- and non-EGF-mediated oxygen consumption rate in hCTBs. A similar pattern was observed in the glycolytic medium acidification, with EGF increasing the acidification, and the Chem-Mix blocking EGF-induced glycolytic acidification. Furthermore, direct stochastic optical reconstruction microscopy (dSTORM) imaging demonstrated that the Chem-Mix led to a reduction of the mitochondrial network architecture, with findings supported by a decrease in the abundance of OPA1, a mitochondrial membrane GTPase involved in mitochondrial fusion. In conclusion, we demonstrated that a mixture of EGFR-disrupting chemicals alters mitochondrial remodeling, resulting in disturbed cellular bioenergetics, reducing the capacity of human cytotrophoblast cells to generate energy. Future studies should investigate the mechanism by which mitochondrial dynamics are disrupted and the pathological significance of these findings.