Comparison of mouse brown and white adipose‑derived stem cell differentiation into pacemaker‑like cells induced by TBX18 transduction

The Impact of Centrifugal Force on Isolation of Bone Marrow Mononuclear Cells Using Density Gradient Centrifugation

BACKGROUND

Bone marrow mononuclear cells (BMMNCs) have great potential in bone regenerative therapy. The main method used today to obtain BMMNCs is Ficoll density gradient centrifugation. However, the centrifugal force for this isolation method is still suboptimal.

OBJECTIVES

To determine the optimal centrifugal force in Ficoll density gradient centrifugation of bone marrow (BM) to achieve high stem/progenitor cell content BMMNCs for regenerative therapy.

METHODS

BM was aspirated from nine minipigs and divided into three groups according to different centrifugal forces (200 g, 300 g and 400 g). Immediately after BMMNCs were obtained from each group by Ficoll density gradient centrifugation, residual red blood cell (RBC) level, nucleated cell counting, viability and flow cytometric analyses of apoptosis and reactive oxygen species (ROS) generation were measured. The phenotypic CD90 and colony formation analyses of BMMNCs of each group were performed as well. Bone marrow-derived mesenchymal stem cells (BMSCs) were harvested at passage 2, then morphology, cell phenotype, proliferation, adipogenic, chondrogenic and osteogenic lineage differentiation potential of BMSCs from each group were compared.

RESULTS

The 300 g centrifugal force was able to isolate BMMNCs from BM with the same efficiency as 400 g and provided significantly higher yields of CD90+ BMSCs and fibroblastic colony-forming units of BMSC (CFU-f(BMSC)), which is more crucial for the regenerative efficacy of BMMNCs. Meanwhile, 200 g hosted the most RBC contamination and minimum CFU-f (BMSC) yield, which will be disadvantageous for BMMNC-based cell therapy. As for in vitro cultured BMSCs which were isolated from BMMNCs by different centrifugal forces, no significant differences were found on morphology, cell proliferation rate, phenotypic marker, adipogenic, chondrogenic and osteogenic differentiation potential.

CONCLUSIONS

300 g may be the optimal centrifugal force when using Ficoll density gradient centrifugation to isolate BMMNCs for bone regenerative therapy.

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Application of adipose-derived stem cells in ischemic heart disease: theory, potency, and advantage

Adipose-derived mesenchymal stem cells (ASCs) represent an innovative candidate to treat ischemic heart disease (IHD) due to their abundance, renewable sources, minor invasiveness to obtain, and no ethical limitations. Compared with other mesenchymal stem cells, ASCs have demonstrated great advantages, especially in the commercialization of stem cell-based therapy. Mechanistically, ASCs exert a cardioprotective effect not only through differentiation into functional cells but also via robust paracrine of various bioactive factors that promote angiogenesis and immunomodulation. Exosomes from ASCs also play an indispensable role in this process. However, due to the distinct biological functions of ASCs from different origins or donors with varing health statuses (such as aging, diabetes, or atherosclerosis), the heterogeneity of ASCs deserves more attention. This prompts scientists to select optimal donors for clinical applications. In addition, to overcome the primary obstacle of poor retention and low survival after transplantation, a variety of studies have been dedicated to the engineering of ASCs with biomaterials. Besides, clinical trials have confirmed the safety and efficacy of ASCs therapy in the context of heart failure or myocardial infarction. This article reviews the theory, efficacy, and advantages of ASCs-based therapy, the factors affecting ASCs function, heterogeneity, engineering strategies and clinical application of ASCs.

Harnessing adipose stem cell diversity in regenerative medicine

Since the first isolation of mesenchymal stem cells from lipoaspirate in the early 2000s, adipose tissue has been a darling of regenerative medicine. It is abundant, easy to access, and contains high concentrations of stem cells (ADSCs) exhibiting multipotency, proregenerative paracrine signaling, and immunomodulation-a winning combination for stem cell-based therapeutics. While basic science, preclinical and clinical findings back up the translational potential of ADSCs, the vast majority of these used cells from a single location-subcutaneous abdominal fat. New data highlight incredible diversity in the adipose morphology and function in different anatomical locations or depots. Even in isolation, ADSCs retain a memory of this diversity, suggesting that the optimal adipose source material for ADSC isolation may be application specific. This review discusses our current understanding of the heterogeneity in the adipose organ, how that heterogeneity translates into depot-specific ADSC characteristics, and how atypical ADSC populations might be harnessed for regenerative medicine applications. While our understanding of the breadth of ADSC heterogeneity is still in its infancy, clear trends are emerging for application-specific sourcing to improve regenerative outcomes.

The cell yields and biological characteristics of stromal/stem cells from lipoaspirate with different digestion loading ratio

Effective harvesting procedure for adipose tissue is demanded by the affordable Good Manufacturing Practice-Compliant Production of clinical-grade adipose tissue-derived stem cells (hADSCs). Enzymatic digestion using collagenase is the most reliable method of adipose tissue-derived stem cells (hADSCs) isolation, while the optimized loading volume ratios of digestion to container during the shaking process of adipose tissue and collagenase mixture are still lacking. This study was conducted to determine the optimized loading volume ratio (mixture to container) for enzymatic digestion of Stromal/Stem Cells from lipoaspirate. Lipoaspirates were obtained from twelve women immediately after liposuction. Then tissue from each patient was divided into four groups according to different loading volume ratios in 50 ml centrifugal tube: 0.2 group, 0.4 group, 0.6 group, 0.8 group. Stromal vascular fractions (SVF) were obtained from each group, then total cell counts, viability and viable cell count were performed. hADSCs were harvested at passage (P) 2, whose morphologies, immunophenotypes, proliferation, and tri-differentiation abilities were compared. 0.4 loading volume ratio provided the highest cell yield, favorable viability and viable cell yield. The proliferation and triple differentiation ability of hADSCs obtained by 0.4 group was not inferior to that of other groups. Therefore, 0.4 may be the optimal loading volume ratio for hADSCs isolation from lipoaspirate by enzymatic digestion in current setting.

Conversion of human cardiac progenitor cells into cardiac pacemaker-like cells

We used a screening strategy to test for reprogramming factors for the conversion of human cardiac progenitor cells (CPCs) into Pacemaker-like cells. Human transcription factors SHOX2, TBX3, TBX5, TBX18, and the channel protein HCN2, were transiently induced as single factors and in trio combinations into CPCs, first transduced with the connexin 30.2 (CX30.2) mCherry reporter. Following screens for reporter CX30.2 mCherry gene activation and FACS enrichment, we observed the definitive expression of many pacemaker specific genes; including, CX30.2, KCNN4, HCN4, HCN3, HCN1, and SCN3b. These findings suggest that the SHOX2, HCN2, and TBX5 (SHT5) combination of transcription factors is a much better candidate in driving the CPCs into Pacemaker-like cells than other combinations and single transcription factors. Additionally, single-cell RNA sequencing of SHT5 mCherry+ cells revealed cellular enrichment of pacemaker specific genes including TBX3, KCNN4, CX30.2, and BMP2, as well as pacemaker specific potassium and calcium channels (KCND2, KCNK2, and CACNB1). In addition, similar to human and mouse sinoatrial node (SAN) studies, we also observed the down-regulation of NKX2.5. Patch-clamp recordings of the converted Pacemaker-like cells exhibited HCN currents demonstrated the functional characteristic of pacemaker cells. These studies will facilitate the development of an optimal Pacemaker-like cell-based therapy within failing hearts through the recovery of SAN dysfunction.

Transcription Factor prrx1 Promotes Brown Adipose-Derived Stem Cells Differentiation to Sinus Node-Like Cells

This study investigated whether overexpression of paired-related homeobox 1 (prrx1) can successfully induce differentiation of brown adipose-derived stem cells (BADSCs) into sinus node-like cells. The experiments were performed in two groups: adenovirus-green fluorescent protein (Ad-GFP) group and Ad-prrx1 group. After 5-7 days of adenoviral transfection, the expression levels of sinus node cell-associated pacing protein (hyperpolarization-activated cyclic nucleotide-gated potassium channel 4 [HCN4]) and ion channel (calcium channel, voltage-dependent, T type, alpha 1G subunit [Cacna1g]), as well as transcription factors (T-box 18 [TBX18], insulin gene enhancer binding protein 1 [ISL-1], paired-like homeodomain transcription factor 2 [pitx2], short stature homeobox 2 [shox2]), were detected by western blot and reverse transcription-quantitative polymerase chain reaction. Immunofluorescence assay was carried out to detect whether prrx1 was coexpressed with HCN4, TBX18, and ISL-1. Finally, whole-cell patch-clamp technique was used to record pacing current hyperpolarization-activated inward current (I_f). The isolated cells were CD90⁺, CD29⁺, and CD45^-, indicating that pure BADSCs were successfully isolated. After 5-7 days of Ad transfection into cells, the mRNA levels and protein levels of pacing-related factors (TBX18, ISL-1, HCN4, shox2, and Cacna1g) in Ad-prrx1 group were significantly higher than those in Ad-GFP group. However, the expression level of pitx2 was decreased. Immunofluorescence analysis showed that prrx1 was coexpressed with TBX18, ISL-1, and HCN4 in the Ad-prrx1 group, which did not appear in the Ad-GFP group. Whole-cell patch clamps were able to record the I_f current in the experimental group rather than in the Ad-GFP group. Overexpression of prrx1 can successfully induce sinus node-like cells.

Plasticity of Adipose Tissue-Derived Stem Cells and Regulation of Angiogenesis

Adipose tissue is recognized as an important organ with metabolic, regulatory, and plastic roles. Adipose tissue-derived stem cells (ASCs) with self-renewal properties localize in the stromal vascular fraction (SVF) being present in a vascular niche, thereby, contributing to local regulation of angiogenesis and vessel remodeling. In the past decades, ASCs have attracted much attention from biologists and bioengineers, particularly, because of their multilineage differentiation potential, strong proliferation, and migration abilities in vitro and high resistance to oxidative stress and senescence. Current data suggest that the SVF serves as an important source of endothelial progenitors, endothelial cells, and pericytes, thereby, contributing to vessel remodeling and growth. In addition, ASCs demonstrate intriguing metabolic and interlineage plasticity, which makes them good candidates for creating regenerative therapeutic protocols, in vitro tissue models and microphysiological systems, and tissue-on-chip devices for diagnostic and regeneration-supporting purposes. This review covers recent achievements in understanding the metabolic activity within the SVF niches (lactate and NAD+ metabolism), which is critical for maintaining the pool of ASCs, and discloses their pro-angiogenic potential, particularly, in the complex therapy of cardiovascular and cerebrovascular diseases.