Downregulation of heat shock protein B8 decreases osteogenic differentiation potential of dental pulp stem cells during in vitro proliferation

Current concepts of microRNA-mediated regulatory mechanisms in human pulp tissue-derived stem cells: a snapshot in the regenerative dentistry

One of the most studied class of non-coding RNAs is microRNAs (miRNAs) which regulate more than 60% of human genes. A network of miRNA gene interactions participates in stem cell self-renewal, proliferation, migration, apoptosis, immunomodulation, and differentiation. Human pulp tissue-derived stem cells (PSCs) are an attractive source of dental mesenchymal stem cells (MSCs) which comprise human dental pulp stem cells (hDPSCs) obtained from the dental pulp of permanent teeth and stem cells isolated from exfoliated deciduous teeth (SHEDs) that would be a therapeutic opportunity in stomatognathic system reconstruction and repair of other damaged tissues. The regenerative capacity of hDPSCs and SHEDs is mediated by osteogenic, odontogenic, myogenic, neurogenic, angiogenic differentiation, and immunomodulatory function. Multi-lineage differentiation of PSCs can be induced or inhibited by the interaction of miRNAs with their target genes. Manipulating the expression of functional miRNAs in PSCs by mimicking miRNAs or inhibiting miRNAs emerged as a therapeutic tool in the clinical translation. However, the effectiveness and safety of miRNA-based therapeutics, besides higher stability, biocompatibility, less off-target effects, and immunologic reactions, have received particular attention. This review aimed to comprehensively overview the molecular mechanisms underlying miRNA-modified PSCs as a futuristic therapeutic option in regenerative dentistry.

HSPB7 oppositely regulates human mesenchymal stromal cell-derived osteogenesis and adipogenesis

BACKGROUND

Recent evidence suggests that accumulation of marrow adipose tissue induced by aberrant lineage allocation of bone marrow-derived mesenchymal stromal cells (BMSCs) contributes to the pathophysiologic processes of osteoporosis. Although master regulators of lineage commitment have been well documented, molecular switches between osteogenesis and adipogenesis are largely unknown.

METHODS

HSPB7 gene expression during osteogenic and adipogenic differentiation of BMSCs was evaluated by qPCR and Western blot analyses. Lentiviral-mediated knockdown or overexpression of HSPB7 and its deletion constructs were used to assess its function. The organization of cytoskeleton was examined by immunofluorescent staining. ALP activity, calcium assay, Alizarin Red S staining and Oil Red O staining were performed in vitro during osteoblast or adipocyte differentiation. SB431542 and Activin A antibody were used to identify the mechanism of Activin A in the regulation of osteogenic differentiation in BMSCs.

RESULTS

In this study, we identified HSPB7 capable of oppositely regulating osteogenic and adipogenic differentiation of BMSCs. HSPB7 silencing promoted adipogenesis while reducing osteogenic differentiation and mineralization. Conversely, overexpression of HSPB7 strongly enhanced osteogenesis, but no effect was observed on adipogenic differentiation. Deletion of the N-terminal or C-terminal domain of HSPB7 led to decreased osteoblastic potency and mineralization. Mechanistically, our data showed that Activin A is a downstream target participating in HSPB7 knockdown-mediated osteogenic inhibition.

CONCLUSIONS

Our findings suggest that HSPB7 plays a positive role in driving osteoblastic differentiation, and with the capability in maintaining the osteo-adipogenesis balance. It holds great promise as a potential therapeutic target in the treatment of bone metabolic diseases.

Animal-derived products in science and current alternatives

More than fifty years after the 3Rs definition and despite the continuous implementation of regulatory measures, animals continue to be widely used in basic research. Their use comprises not only in vivo experiments with animal models, but also the production of a variety of supplements and products of animal origin for cell and tissue culture, cell-based assays, and therapeutics. The animal-derived products most used in basic research are fetal bovine serum (FBS), extracellular matrix proteins such as Matrigel™, and antibodies. However, their production raises several ethical issues regarding animal welfare. Additionally, their biological origin is associated with a high risk of contamination, resulting, frequently, in poor scientific data for clinical translation. These issues support the search for new animal-free products able to replace FBS, Matrigel™, and antibodies in basic research. In addition, in silico methodologies play an important role in the reduction of animal use in research by refining the data previously to in vitro and in vivo experiments. In this review, we depicted the current available animal-free alternatives in in vitro research.

Increased Expression of miR-7a-5p and miR-592 during Expansion of Rat Dental Pulp Stem Cells and Their Implication in Osteogenic Differentiation

Dental pulp stem cells (DPSCs) possess strong osteogenic differentiation potential and are promising cell sources in regenerative medicine. However, such differentiation capacity progressively declines during their in vitro expansion. MicroRNAs (miRNAs) play important roles in modulating stem cell differentiation. This study aimed (1) to determine if miR-7a-5p and miR-592 are involved in maintaining and regulating osteogenic differentiation of DPSCs, and (2) to explore their potential regulatory pathways. We found that the expression of miR-7a-5p and miR-592 was significantly upregulated during the expansion of rat DPSCs (rDPSCs). Overexpression of these miRNAs inhibited the osteogenic/odontogenic differentiation of rDPSCs, as evidenced by calcium deposition and osteogenic/odontogenic gene expression. RT-qPCR determined that miR-592 could downregulate heat shock protein B8, whose expression is reduced during the expansion of rDPSCs. Furthermore, RNA-seq and bioinformatics analysis identified significant signaling pathways of miR-7a-5p and miR-592 in regulating osteogenic differentiation, including TNF, MAPK, and PI3K-Akt pathways. We conclude that upregulating miR-7a-5p and miR-592 suppresses the osteogenic differentiation of rDPSCs during their in vitro expansion, likely via TNF, MAPK, and PI3K-Akt pathways. The results may shed light on application of miR-7a-5p and miR-592 for maintaining osteo-differentiation potential in stem cells for bone regeneration and bone-related disease treatment.

Single-cell characterization of monolayer cultured human dental pulp stem cells with enhanced differentiation capacity

Human dental pulp stem cells (hDPSCs) are easily obtained multipotent cells, however, their potential value in regenerative medicine is hindered by the phenotypic and functional changes after conventional monolayer expansion. Here, we employed single-cell RNA sequencing (scRNA-seq) to comprehensively study the transcriptional difference between the freshly isolated and monolayer cultured DPSCs. The cell cluster analysis based on our scRNA-seq data showed that monolayer culture resulted in a significant cellular composition switch compared to the freshly isolated DPSCs. However, one subpopulation, characterized as MCAM(+)JAG(+)PDGFRA(-), maintained the most transcriptional characteristics compared to their freshly isolated counterparts. Notably, immunofluorescent staining revealed that the MCAM(+)JAG(+)PDGFRA(-) hDPSCs uniquely located in the perivascular region of human dental pulp tissue. Flow-cytometry analysis confirmed that their proportion remained relatively stable (~2%) regardless of physiological senescence or dental caries. Consistent with the annotation of scRNA-seq data, MCAM(+)JAG(+)PDGFRA(-) hDPSCs showed higher proliferation capacity and enhanced in vitro multilineage differentiation potentials (osteogenic, chondrogenic and adipogenic) compared with their counterparts PDGFRA(+) subpopulation. Furthermore, the MCAM(+)JAG(+)PDGFRA(-) hDPSCs showed enhanced bone tissue formation and adipose tissue formation after 4-week subcutaneous implantation in nude mice. Taken together, our study for the first time revealed the cellular composition switch of monolayer cultured hDPSCs compared to the freshly isolated hDPSCs. After in vitro expansion, the MCAM(+)JAG(+)PDGFRA(-) subpopulation resembled the most transcriptional characteristics of fresh hDPSCs which may be beneficial for further tissue regeneration applications.

Epigenetic regulation of dental pulp stem cells and its potential in regenerative endodontics

Regenerative endodontics (RE) therapy means physiologically replacing damaged pulp tissue and regaining functional dentin–pulp complex. Current clinical RE procedures recruit endogenous stem cells from the apical papilla, periodontal tissue, bone marrow and peripheral blood, with or without application of scaffolds and growth factors in the root canal space, resulting in cementum-like and bone-like tissue formation. Without the involvement of dental pulp stem cells (DPSCs), it is unlikely that functional pulp regeneration can be achieved, even though acceptable repair can be acquired. DPSCs, due to their specific odontogenic potential, high proliferation, neurovascular property, and easy accessibility, are considered as the most eligible cell source for dentin–pulp regeneration. The regenerative potential of DPSCs has been demonstrated by recent clinical progress. DPSC transplantation following pulpectomy has successfully reconstructed neurovascularized pulp that simulates the physiological structure of natural pulp. The self-renewal, proliferation, and odontogenic differentiation of DPSCs are under the control of a cascade of transcription factors. Over recent decades, epigenetic modulations implicating histone modifications, DNA methylation, and noncoding (nc)RNAs have manifested as a new layer of gene regulation. These modulations exhibit a profound effect on the cellular activities of DPSCs. In this review, we offer an overview about epigenetic regulation of the fate of DPSCs; in particular, on the proliferation, odontogenic differentiation, angiogenesis, and neurogenesis. We emphasize recent discoveries of epigenetic molecules that can alter DPSC status and promote pulp regeneration through manipulation over epigenetic profiles.

A computational approach on studying the regulation of TGF-β1-stimulated Runx2 expression by MicroRNAs in human breast cancer cells

BACKGROUND

Transforming growth factor-beta1 (TGF-β1) acts as a most effective growth inhibitor for normal epithelial cells. Loss of this anti-proliferative factor in breast tissues favors invasion and development of osteolytic metastases, aided by a master transcription factor, runt-related transcription factor 2 (Runx2). Several reports identified Runx2 regulation with the help of non-coding RNAs such as microRNAs (miRNAs) under physiological and pathological conditions.

METHODS

Using bioinformatics tools such as miRDB, STarMir, Venny, TarBase, a unique list of miRNAs that putatively target the 3' UTR Runx2 was identified. Further, the expression patterns of those miRNAs at the precursor and mature levels were studied by RT-qPCR analyses. Following this, computational analyses using software like TransmiR and bc-GenExMiner v4.6 were done to speculate the miRNA's other target genes that indirectly regulate Runx2 activity in breast cancer.

RESULTS

There were 13 miRNAs that putatively target Runx2 identified using bioinformatics tools. Among these miRNAs, miR-5703 expression was significantly downregulated at both precursor and mature levels upon TGF-β1-treatment in human breast cancer cells. Computational analyses speculated an indirect targeting of Runx2 by miR-5703 by influencing multiple Runx2 regulatory signaling pathways including Jak/Stat, MAPK, Wnt/β-Catenin, Notch, BMP, and PKA pathways. Furthermore, a correlation of the expression profiles of the speculated genes and Runx2 with miR-5703 was depicted in triple-negative breast cancer patients.

CONCLUSION

Identification of miR-5703 and its network for Runx2 regulation directly or indirectly in breast cancer cells could significantly advance our understanding of breast cancer-mediated bone metastasis. In addition, it would potentially pave the way for miRNAs to be used as biomarkers and therapeutic agents in cancer research.

Umbilical mesenchymal stem cell-derived extracellular vesicles as enzyme delivery vehicle to treat Morquio A fibroblasts

BACKGROUND

Mucopolysaccharidosis IVA (Morquio A syndrome) is a lysosomal storage disease caused by the deficiency of enzyme N-acetylgalactosamine-6-sulfate sulfatase (GALNS), which results in the accumulation of the glycosaminoglycans (GAGs), keratan sulfate, and chondroitin-6-sulfate in the lysosomes of all tissues causing systemic dysfunction. Current treatments include enzyme replacement therapy (ERT) which can treat only certain aspects of the disease such as endurance-related biological endpoints. A key challenge in ERT is ineffective enzyme uptake in avascular tissues, which makes the treatment of the corneal, cartilage, and heart valvular tissue difficult. The aim of this study was to culture human umbilical mesenchymal stem cells (UMSC), demonstrate presence of GALNS enzyme activity within the extracellular vesicles (EVs) derived from these UMSC, and study how these secreted EVs are taken up by GALNS-deficient cells and used by the deficient cell's lysosomes.

METHODS

We obtained and cultured UMSC from the umbilical cord tissue from anonymous donors from the Saint Louis Cord Blood Bank. We characterized UMSC cell surface markers to confirm phenotype by cell sorting analyses. In addition, we confirmed that UMSC secrete GALNS enzyme creating conditioned media for co-culture experiments with GALNS deficient cells. Lastly, we isolated EVs derived from UMSC by ultracentrifugation to confirm source of GALNS enzyme.

RESULTS

Co-culture and confocal microscopy experiments indicated that the lysosomal content from UMSC migrated to deficient cells as evidenced by the peak signal intensity occurring at 15 min. EVs released by UMSC were characterized indicating that the EVs contained the active GALNS enzyme. Uptake of GALNS within EVs by deficient fibroblasts was not affected by mannose-6-phosphate (M6P) inhibition, suggesting that EV uptake by these fibroblasts is gradual and might be mediated by a different means than the M6P receptor.

CONCLUSIONS

UMSC can deliver EVs containing functional GALNS enzyme to deficient cells. This enzyme delivery method, which was unaffected by M6P inhibition, can function as a novel technique for reducing GAG accumulation in cells in avascular tissues, thereby providing a potential treatment option for Morquio A syndrome.

Nerve growth factor (NGF) and NGF receptors in mesenchymal stem/stromal cells: Impact on potential therapies

Mesenchymal stem/stromal cells (MSCs) are promising for the treatment of degenerative diseases and traumatic injuries. However, MSC engraftment is not always successful and requires a strong comprehension of the cytokines and their receptors that mediate the biological behaviors of MSCs. The effects of nerve growth factor (NGF) and its two receptors, TrkA and p75NTR, on neural cells are well studied. Increasing evidence shows that NGF, TrkA, and p75NTR are also involved in various aspects of MSC function, including their survival, growth, differentiation, and angiogenesis. The regulatory effect of NGF on MSCs is thought to be achieved mainly through its binding to TrkA. p75NTR, another receptor of NGF, is regarded as a novel surface marker of MSCs. This review provides an overview of advances in understanding the roles of NGF and its receptors in MSCs as well as the effects of MSC‐derived NGF on other cell types, which will provide new insight for the optimization of MSC‐based therapy.

HSPB7 regulates osteogenic differentiation of human adipose derived stem cells via ERK signaling pathway

Background

Heat shock protein B7 (HSPB7), which belongs to small heat shock protein family, has been reported to be involved in diverse biological processes and diseases. However, whether HSPB7 regulates osteogenic differentiation of human adipose derived stem cells (hASCs) remains unexplored.

Methods

The expression level of HSPB7 during the osteogenesis of hASCs was examined by quantitative reverse transcription polymerase chain reaction (qRT-PCR) and Western blot analysis. Lentivirus transfection was used to knock down or overexpress HSPB7, which enabled us to investigate the effect of HSPB7 on osteogenic differentiation of hASCs. U0126 and extracellular signal-regulated protein kinase 1/2 (ERK1/2) siRNA were used to identify the mechanism of the HSPB7/ERK1/2 axis in regulating osteogenic differentiation of hASCs. Moreover, ectopic bone formation in nude mice and osteoporosis mice model was used to investigate the effect of HSPB7 on osteogenesis in vivo.

Results

In this study, we found the expression of HSPB7 was significantly downregulated during the osteogenic differentiation of hASCs. HSPB7 knockdown remarkably promoted osteogenic differentiation of hASCs, while HSPB7 overexpression suppressed osteogenic differentiation of hASCs both in vitro and in vivo. Moreover, we discovered that the enhancing effect of HSPB7 knockdown on osteogenic differentiation was related to the activation of extracellular signal-regulated protein kinase (ERK) signaling pathway. Inhibition of ERK signaling pathway with U0126 or silencing ERK1/2 effectively blocked the stimulation of osteogenic differentiation induced by HSPB7 knockdown. Additionally, we found that HSPB7 expression was markedly increased in mouse bone marrow mesenchymal stem cells (mBMSCs) from the osteoporotic mice which suggested that HSPB7 might be utilized as a potential target in the development of effective therapeutic strategies to treat osteoporosis and other bone diseases.

Conclusion

Taken together, these findings uncover a previously unrecognized function of HSPB7 in regulating osteogenic differentiation of hASCs, partly via the ERK signaling pathway.

Expression of microRNAs targeting heat shock protein B8 during in vitro expansion of dental pulp stem cells in regulating osteogenic differentiation

OBJECTIVE

The objectives of this study were (a) to determine the differentially expressed microRNAs that can target heat shock protein B8 (HspB8) during in vitro expansion of dental pulp stem cells (DPSCs); (b) to identify microRNAs involved in posttranscriptional regulation of HspB8 expression; and (c) to determine if HspB8-targeting microRNAs play roles on osteogenic differentiation of DPSCs.

DESIGN

DPSCs were established from rat first molars and expanded in vitro until the passage that cells lost osteogenic potential. TargetScan was used to predict the microRNAs that target HspB8 mRNA. Stem-loop quantitative RT-PCR was conducted to identify the HspB8-targeting microRNAs that were upregulated in late passages. The microRNAs mimics were transfected into DPSCs to assess their effects on HspB8 expression and on osteogenic differentiation.

RESULTS

let-7b-5p, miR-98-5p, miR-215, miR-219a-1-3p and miR-295-5p were found to consistently increase expression in DPSCs after expansion. HspB8 mRNA and/or protein were significantly decreased in the DPSCs after transfection of miR-215 and miR-219a-1-3p mimics; whereas no significant reduction was seen after transfecting let-7b-5p, miR-98-5p and miR-295-5p mimics. When subjecting the transfected DPSCs to osteogenic induction, reduction of calcium deposition or osteogenic marker expression were observed with miR-215, miR-219a-1-3p and miR-295-5p transfection.

CONCLUSIONS

Increased expression of miR-215 and miR-219a-1-3p downregulates HspB8 expression, which contributes to the reduction of osteogenic capability of DPSCs. Increased expression of miR295-5p also causes a reduction of osteogenic differentiation, but not involved in HspB8.

Adenosine triphosphate enhances osteoblast differentiation of rat dental pulp stem cells via the PLC-IP3 pathway and intracellular Ca 2+ signaling

Intracellular Ca²⁺ signals are essential for stem cell function and play a significant role in the differentiation process. Dental pulp stem cells (DPSCs) are a potential source of stem cells; however, the mechanisms controlling cell differentiation remain largely unknown. Utilizing rat DPSCs, we examined the effect of adenosine triphosphate (ATP) on osteoblast differentiation and characterized its mechanism of action using real-time Ca ²⁺ imaging analysis. Our results revealed that ATP enhanced osteogenesis as indicated by Ca ²⁺ deposition in the extracellular matrix via Alizarin Red S staining. This was consistent with upregulation of osteoblast genes BMP2, Mmp13, Col3a1, Ctsk, Flt1, and Bgn. Stimulation of DPSCs with ATP (1-300 µM) increased intracellular Ca ²⁺ signals in a concentration-dependent manner, whereas histamine, acetylcholine, arginine vasopressin, carbachol, and stromal-cell-derived factor-1α failed to do so. Depletion of intracellular Ca ²⁺ stores in the endoplasmic reticulum by thapsigargin abolished the ATP responses which, nevertheless, remained detectable under extracellular Ca ²⁺ free condition. Furthermore, the phospholipase C (PLC) inhibitor U73122 and the inositol triphosphate (IP ₃ ) receptor inhibitor 2-aminoethoxydiphenyl borate inhibited the Ca ²⁺ signals. Our findings provide a better understanding of how ATP controls osteogenesis in DPSCs, which involves a Ca ²⁺ -dependent mechanism via the PLC-IP ₃ pathway. This knowledge could help improve osteogenic differentiation protocols for tissue regeneration of bone structures.

Role of the heat shock protein family in bone metabolism

Heat shock proteins (HSPs) are a family of proteins produced by cells in response to exposure to stressful conditions. In addition to their role as chaperones, they also play an important role in the cardiovascular, immune, and other systems. Normal bone tissue is maintained by bone metabolism, particularly by the balance between osteoblasts and osteoclasts, which are physiologically regulated by multiple hormones and cytokines. In recent years, studies have reported the vital role of HSPs in bone metabolism. However, the conclusions remain largely controversial, and the exact mechanisms are still unclear, so a review and analyses of previous studies are of importance. This article reviews the current understanding of the roles and effects of HSPs on bone cells (osteoblasts, osteoclasts, and osteocytes), in relation to bone metabolism.

Downregulation of heat shock protein B8 decreases osteogenic differentiation potential of dental pulp stem cells during in vitro proliferation

OBJECTIVES

Tissue-derived stem cells, such as dental pulp stem cells (DPSCs), reduce differentiation capability during in vitro culture. We found that cultured DPSCs reduce expression of heat shock protein B8 (HspB8) and GIPC PDZ domain containing family member 2 (Gipc2). Our objectives were to evaluate the changes in DPSC composition during in vitro proliferation and to determine whether HspB8 and Gipc2 have function in differentiation potential of DPSCs.

MATERIALS AND METHODS

Different passages of rat DPSCs were evaluated for changes in CD90+ and/or CD271+ stem cells and changes in osteogenic potential. Real-time RT-PCR and immunostaining were conducted to determine expression of HspB8 and Gipc2. Expression of the genes in DPSCs was knocked down by siRNA, followed by osteogenic induction to evaluate the function of the genes.

RESULTS

About 90% of cells in the DPSC cultures were CD90+ and/or CD271+ cells without dramatic change during in vitro proliferation. The DPSCs at passages 3 to 5 (P3 to P5) possess strong osteogenic potential, but such potential was greatly reduced at later passages. Expression of HspB8 and Gipc2 was significantly reduced at P11 versus P3. Knock-down of HspB8 expression abolished osteogenic potential of the DPSCs, but knock-down of Gipc2 had no effect.

CONCLUSIONS

CD90+ and CD271+ cells are the major components of DPSCs in in vitro culture. High-level expression of HspB8 was critical for maintaining differentiation potential of DPSCs.