The Relative Functionality of Freshly Isolated and Cryopreserved Human Adipose-Derived Stromal/Stem Cells

Polycaprolactone-co-polylactic acid nanofiber scaffold in combination with 5-azacytidine and transforming growth factor-β to induce cardiomyocyte differentiation of adipose-derived mesenchymal stem cells

Adipose-derived mesenchymal stem cells (Ad-MSCs) are promising candidates for cardiac repair/regeneration. The application of copolymer nanoscaffolds has received great attention in tissue engineering to support differentiation and functional tissue organization toward effective tissue regeneration. The objective of the current study was to develop functional and bioactive scaffolds by combining polycaprolactone (PCL) and polylactic acid (PLA) for cardiomyocyte differentiation of human Ad-MSC (hAd-MSCs) in the absence or presence of 5-azacytidine and transforming growth factor-β (TGF-β). To that end, the human MSCs were extracted from human adipose tissue (AD). The cardiomyocyte differentiation potency of hAd-MSCs was evaluated on the novel synthetic PCL/PLA nanofiber scaffolds prepared in the absence and presence of 5-azacytidine and TGF-β supplements. A PCL/PLA nanofibrous scaffold was fabricated using the electrospinning method and its nanotopography and porous structure were characterized using scanning electron microscopy. In addition, the attachment of hAd-MSCs on the PCL/PLA scaffolds was semiquantitatively investigated. Compared with other treatments, the PCL/PLA nanofibrous scaffold supplemented with both 5-azacytidine and TGF-β was observed to differentiate hAd-MSCs into cardiomyocytes at Day 21 as evidenced by real-time PCR for cardiac-specific genes including cardiac troponin I (cTnI), GATA4, MYH7, and NKX2.5. In addition, flow cytometric analysis of cTnI-positive cells demonstrated that the cardiomyocyte differentiation of hAd-MSCs was more efficient on the PCL/PLA nanofibrous scaffold supplemented with both 5-azacytidine and TGF-β than it was in the other treatment groups. Generally speaking, the results show that PCL/PLA nanofibrous scaffolds may be applied as a platform for efficient differentiation of hAd-MSCs into functional cardiomyocytes.

Adipose tissue-derived stem cells: a comparative review on isolation, culture, and differentiation methods

Adipose tissue-derived stem cells (ADSCs) are an available source of mesenchymal stem cells with the appropriate capacity to in vitro survive, propagate, and differentiate into cells from three lineages of ectoderm, mesoderm, and endoderm. The biological features of ADSCs depend on the donor physiology and health status, isolation procedure, culture conditions, and differentiation protocols used. Adipose tissue samples are provided by surgery and lipoaspiration-based methods and subjected to various mechanical and chemical digestion techniques to finally generate a heterogeneous mixture named stromal vascular fraction (SVF). ADSCs are purified through varied cell populations that exist within SVF and cultured under standard conditions to give rise to a highly rich resource of stem cells directly applied in the clinic or differentiated into a wide range of cells. The development and optimization of conventional isolation, expansion, and differentiation methods seem noteworthy to preserve the desirable biological functions of ADSCs in pre-clinical and clinical investigations.

Tissue Harvesting Site Effect on the Canine Adipose Stromal Vascular Fraction Quantity and Quality

Simple Summary

Adipose stromal vascular fraction (SVF) cells are freshly isolated non-cultured mesenchymal stem cells, which have been recently applied in the treatment of several musculoskeletal inflammatory conditions in dogs. However, the best adipose tissue (AT) sampling site is still challenging. This study first addressed the ideal AT harvesting site in canines ranging between middle and old age, the most susceptible age to chronic musculoskeletal problems. Our results showed that the peri-ovarian region is the best AT harvesting site, which yields high amounts of SVF cells with enough adipose-derived stem cells. These data may help the further set-up of cell-based regenerative therapies at the preclinical and experimental level in canines.

Abstract

Mesenchymal stem cells (MSCs) constitute a great promise for regenerative therapy, but these cells are difficultly recovered in large amounts. A potent alternative is the stromal vascular fraction (SVF), non-cultured MSCs, separated from adipose tissue (AT). We aim to evaluate AT harvesting site effect on the SVF cells’ quantity and quality in dogs. Subcutaneous abdominal fat, falciform ligament and peri-ovarian fat were sampled. After SVF isolation, the trypan blue exclusion test and a hemocytometer were used to assess the cell viability and cellular yield. SVF cells were labeled for four surface antigenic markers, clusters of differentiation CD90, CD44, CD29, and CD45, and then examined by flow cytometry. Semi-quantitative RT-PCR was used to evaluate the gene expression of the former markers in addition to OCT-4 and CD34. SVF cells in the peri-ovarian AT recorded the highest viability% (99.63 ± 0.2%), as well as a significantly higher cellular yield (36.87 ± 19.6 × 10⁶ viable cells/gm fat, p < 0.001) and a higher expression of adipose-derived mesenchymal stem cells AD-MSCs surface markers than that of other sites. SVF cells from the peri-ovarian site revealed a higher expression of MSC markers (CD90, CD44, and CD29) and OCT-4 compared to the other sites, with weak CD45 and CD34 expressions. The positive OCT-4 expression demonstrated the pluripotency of SVF cells isolated from different sites. To conclude, the harvesting site is a strong determinant of SVF cells’ quantity and quality, and the peri-ovarian site could be the best AT sampling site in dogs.

Non-toxic freezing media to retain the stem cell reserves in adipose tissues

Subcutaneous adipose tissue is a rich source of stromal vascular fraction (SVF) and adipose-derived stromal/stem cells (ASCs) that are inherently multipotent and exhibit regenerative properties. In current practice, lipoaspirate specimens harvested from liposuction surgeries are routinely discarded as a biohazard waste due to a lack of simple, cost effective, and validated cryopreservation protocols. The aim of this study is to develop a xenoprotein-free cryoprotective agent cocktail that will allow for short-term (up to 6 months) preservation of lipoaspirate tissues suitable for fat grafting and/or stromal/stem cell isolation when stored at achievable temperatures (-20 °C or -80 °C). Lipoaspirates donated by three consenting healthy donors undergoing elective cosmetic liposuction surgeries were suspended in five freezing media (FM1: 10% DMSO and 35% BSA; FM2: 2% DMSO and 43% BSA; FM3: 10% DMSO and 35% lipoaspirate saline; FM4: 2% DMSO and 6% HSA; and FM5: 40% lipoaspirate saline and 10% PVP) all suspended in 1X DMEM/F12 and frozen using commercially available freezers (-20 °C or -80 °C) and stored at least for a 1 month. After 1 month of freezing storage, SVF cells and ASCs were isolated from the frozen-thawed lipoaspirates by digestion with collagenase type I. Cell viability was evaluated by fluorescence microscopy after staining with acridine orange and ethidium bromide. The SVF isolated from lipoaspirates frozen at -80 °C retained comparable cell viability with the tested freezing media (FM2, FM3, FM4) comparable with the conventional DMSO and animal serum media (FM1), whereas the FM5 media resulted in lower viability. In contrast, tissues frozen and stored at -20 °C did not yield live SVF cells after thawing and collagenase digestion. The surface marker expression (CD90, CD29, CD34, CD146, CD31, and CD45) of ASCs from frozen lipoaspirates at -80 °C in different cryoprotectant media were also evaluated and no significant differences were found between the groups. The adipogenic and osteogenic differentiation potential were studied by histochemical staining and gene expression by qRT-PCR. Oil Red O staining for adipogenesis revealed that the CPA media FM1, FM4 and FM5 displayed robust differentiation. Alizarin Red S staining for osteogenesis revealed that FM1 and FM4 media displayed superior differentiation in comparison to other tested media. Measurement of adipogenic and osteogenic gene expression by qRT-PCR provided similar outcomes and indicated that FM4 CPA media comparable with FM1 for adipogenesis and osteogenesis.

Human Adipose Derived Cells in Two- and Three-Dimensional Cultures: Functional Validation of an In Vitro Fat Construct

Obesity, defined as a body mass index of 30 kg/m² or above, has increased considerably in incidence and frequency within the United States and globally. Associated comorbidities including cardiovascular disease, type 2 diabetes mellitus, metabolic syndrome, and nonalcoholic fatty liver disease have led to a focus on the mechanisms promoting the prevention and treatment of obesity. Commonly utilized in vitro models employ human or mouse preadipocyte cell lines in a 2-dimensional (2D) format. Due to the structural, biochemical, and biological limitations of these models, increased attention has been placed on "organ on a chip" technologies for a 3-dimensional (3D) culture. Herein, we describe a method employing cryopreserved primary human stromal vascular fraction (SVF) cells and a human blood product-derived biological scaffold to create a 3D adipose depot in vitro. The "fat-on-chip" 3D cultures have been validated relative to 2D cultures based on proliferation, flow cytometry, adipogenic differentiation, confocal microscopy/immunofluorescence, and functional assays (adipokine secretion, glucose uptake, and lipolysis). Thus, the in vitro culture system demonstrates the critical characteristics required for a humanized 3D white adipose tissue (WAT) model.

Fidelity of long-term cryopreserved adipose-derived stem cells for differentiation into cells of ocular and other lineages

Adipose-Derived Stem Cells (ADSCs) have an important contribution in regenerative medicine ranging from testing stem cell therapy for disease treatment in pre-clinical models to clinical trials. For immediate use of stem cells for therapy, there is a requirement of the high dose of stem cells at different time points which can be met by cryopreservation. In this study, we evaluated the characteristics of long-term cryopreserved ADSCs and their regenerative potential after an average of twelve-year cryopreservation. Revived ADSCs were examined for cell viability and proliferation by trypan blue, Calcein/Hoechst and MTT assay. Expression of stem cell markers was examined by flow cytometry, immunostaining and qPCR. Colony forming efficiency and spheroid formation ability were also assessed. Multilineage differentiation potential was evaluated by induction into osteocytes, adipocytes, neural cells, corneal keratocytes and trabecular meshwork (TM) cells. Post-thaw, ADSCs maintained expression of stem cell markers CD90, CD73, CD105, CD166, NOTCH1, STRO-1, ABCG2, OCT4, KLF4. ADSCs retained colony and spheroid forming potential. These cells were able to differentiate into osteocytes, confirmed by Alizarin Red S staining and elevated expression of osteocalcin and osteopontin; into adipocytes by Oil Red O staining and elevated expression of PPARγ2. ADSCs could differentiate into neural cells, stained positive to β-III tubulin, neurofilament, GFAP as well as elevated expression of nestin and neurofilament mRNAs. ADSCs could also give rise to corneal keratocytes expressing keratocan, keratan sulfate, ALDH and collagen V, and to TM cells expressing CHI3L1 and AQP1. Differentiated TM cells responded to dexamethasone treatment with increased Myocilin expression, which could be used as in vitro glaucoma model for further studies. Conditioned medium from ADSCs was found to impart a regenerative effect on primary TM cells. In conclusion, ADSCs maintained their stemness and multipotency after long-term cryopreservation with variability between different donors. This study can have great repercussions in regenerative medicine and pave the way for future clinical trials using cryopreserved ADSCs.

Current Strategies to Enhance Adipose Stem Cell Function: An Update

Mesenchymal stem cells (MSCs) emerged as a promising therapeutic tool targeting a variety of inflammatory disorders due to their multiple remarkable properties, such as superior immunomodulatory function and tissue-regenerative capacity. Although bone marrow (BM) is a dominant source for adult MSCs, increasing evidence suggests that adipose tissue-derived stem cells (ASCs), which can be easily obtained at a relatively high yield, have potent therapeutic advantages comparable with BM-MSCs. Despite its outstanding benefits in pre-clinical settings, the practical efficacy of ASCs remains controversial since clinical trials with ASC application often resulted in unsatisfactory outcomes. To overcome this challenge, scientists established several strategies to generate highly functional ASCs beyond the naïve cells, including (1) pre-conditioning of ASCs with various stimulants such as inflammatory agents, (2) genetic manipulation of ASCs and (3) modification of culture conditions with three-dimensional (3D) aggregate formation and hypoxic culture. Also, exosomes and other extracellular vesicles secreted from ASCs can be applied directly to recapitulate the beneficial performance of ASCs. This review summarizes the current strategies to improve the therapeutic features of ASCs for successful clinical implementation.

Improvement of Tribological and Biocompatibility Properties of Orthopedic Materials Using Piezoelectric Direct Discharge Plasma Surface Modification

Various types of alloys and polymers are utilized in orthopedic implants. However, there are still several issues accompanied by the use of prosthetic materials, such as low wear performance and catastrophic failure. Surface enhancement of biomaterials is a promising method that can improve the success rate of prosthetic operations without negatively affecting their bulk properties while improving the biocompatibility of implants and reducing infections. Nonthermal plasma treatment has become a ubiquitous surface modification method in sterilization and healthcare applications. However, the clinical applications of such an approach have been limited due to the lack of detailed studies delineating the wear behavior and biocompatibility of implants after plasma treatment. In this study, we have employed a handheld piezoelectric direct discharge (PDD) plasma generator to modify the surface of two common metallic (Ti6Al4V) and nonmetallic (GUR1020 polymer) biomaterials used typically in joint and disc replacements. We have observed an approximately 60-fold reduction in tribological wear rate along with a 2- to 3-fold increase in the biocompatibility properties of plasma coated samples compared to noncoated (untreated) surfaces, respectively. Our study introduces a novel application of nonthermal PDD plasma technology that is capable of increasing the quality and success rate of joint and disc replacements.

Effects of Decade Long Freezing Storage on Adipose Derived Stem Cells Functionality

Over the last decade and half, the optimization of cryopreservation for adipose tissue derived stromal/stem cells (ASCs) especially in determining the optimal combination of cryoprotectant type, cooling rate, and thawing rate have been extensively studied. In this study, we examined the functionality of ASCs that have been frozen-stored for more than 10 years denoted as long-term freezing, frozen within the last 3 to 7 years denoted as short-term freezing and compared their response with fresh ASCs. The mean post-thaw viability for long-term frozen group was 78% whereas for short-term frozen group 79% with no significant differences between the two groups. The flow cytometry evaluation of stromal surface markers, CD29, CD90, CD105, CD44, and CD73 indicated the expression (above 95%) in passages P1-P4 in all of the frozen-thawed ASC groups and fresh ASCs whereas the hematopoietic markers CD31, CD34, CD45, and CD146 were expressed extremely low (below 2%) within both the frozen-thawed and fresh cell groups. Quantitative real time polymerase chain reaction (qPCR) analysis revealed some differences between the osteogenic gene expression of long-term frozen group in comparison to fresh ASCs. Intriguingly, one group of cells from the short-term frozen group exhibited remarkably higher expression of osteogenic genes in comparison to fresh ASCs. The adipogenic differentiation potential remained virtually unchanged between all of the frozen-thawed groups and the fresh ASCs. Long-term cryopreservation of ASCs, in general, has a somewhat negative impact on the osteogenic potential of ASCs, especially as it relates to the decrease in osteopontin gene expression but not significantly so with respect to RUNX2 and osteonectin gene expressions. However, the adipogenic potential, post thaw viability, and immunophenotype characteristics remain relatively intact between all the groups.

hASC and DFAT, Multipotent Stem Cells for Regenerative Medicine: A Comparison of Their Potential Differentiation In Vitro

Adipose tissue comprises both adipose and non-adipose cells such as mesenchymal stem cells. These cells show a surface antigenic profile similar to that of bone-marrow-derived MSC. The cells derived from the dedifferentiation of mature adipocytes (DFAT) are another cell population with characteristics of stemness. The aim of this study is to provide evidence of the stemness, proliferation, and differentiation of human adipose stem cells (hASC) and DFAT obtained from human subcutaneous AT and evaluate their potential use in regenerative medicine. Cell populations were studied by histochemical and molecular biology techniques. Both hASC and DFAT were positive for MSC markers. Their proliferative capacity was similar and both populations were able to differentiate into osteogenic, chondrogenic, and adipogenic lineages. DFAT were able to accumulate lipids and their lipoprotein lipase and adiponectin gene expression were high. Alkaline phosphatase and RUNX2 gene expression were greater in hASC than in DFAT at 14 days but became similar after three weeks. Both cell populations were able to differentiate into chondrocytes, showing positive staining with Alcian Blue and gene expression of SOX9 and ACAN. In conclusion, both hASC and DFAT populations derived from AT have a high differentiation capacity and thus may have applications in regenerative medicine.