Alterations of MEK1/2-ERK1/2, IFNγ and Smad2/3 associated Signalling pathways during cryopreservation of ASCs affect their differentiation towards VSMC-like cells

SVF-GEL Cryopreserved for Different Times Exhibits Varied Preservation and Regeneration Potential After Transplantation in a Mouse Model

BACKGROUND

Matrix vascular component (SVF) gels derived from fat preserve tissue integrity and cell viability under cryopreserved conditions, making them easy to inject again for later use. Here, we compared the preservation power and regeneration potential of SVF-gel under different cryopreservation times.

METHODS

The SVF-gel stored under - 20 °C, without cryoprotectant cryopreservation for 5, 15, and 45 days, with fresh SVF-gel as control. We evaluated the rate of volume retention after thawing the SVF-gel and the apoptosis rate of adipose-derived stem cells. Next, we analyzed retention rated, adipogenesis, angiogenesis, and connective tissue hyperplasia of the grafts, one month after subcutaneously transplanting the specimen into immunodeficient mice.

RESULTS

SVF-gel cryopreserved for 5 and 15 days exhibited no significant different in apoptosis rates relative to the control group. Extending the cryopreservation time to 45 days resulted in significantly increased and decreased apoptosis and volume retention rates of SVF-gel, respectively. SVF-gel grafts cryopreserved for 5 and 15 days exhibited no significant differences from those in the control group, although their weights and volumes still fluctuated. Extending the cryopreservation time to 45 days resulted in significantly decreased retention rates of the grafts. Histologically, extending freezing time resulted in a gradual decline in the graft's health adipose tissue, as well as decreased angiogenesis, and connective tissue hyperplasia.

CONCLUSION

Simple freezing of SVF-gel at - 20 °C conferred them with sufficient cell viability. Notably, short-term cryopreservation did not significantly increase the apoptosis rate, and it still had a certain regeneration after transplantation. However, prolonging freezing time to 45 days resulted in increased apoptosis rate and worsened transplantation effect.

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Paracrine signalling from monocytes enables desirable extracellular matrix accumulation and temporally appropriate phenotype of vascular smooth muscle cell-like cells derived from adipose stromal cells

In vascular tissue engineering, the ability to obtain a robust and safe vascular tissue cell source (e.g. vascular smooth muscle cells (VSMCs)) and to promote vascular tissue-specific extracellular matrix (ECM) protein production is critically important. Mature blood vessel-derived VSMCs are not practical for in vitro vascular tissue regeneration. The authors have conceived a strategy to differentiate adipose derived stromal cells (ASCs) into VSMC-like cells (ASC-VSMCs) that were similar to mature umbilical artery VSMCs at the transcriptional, protein and contraction function levels. Monocytes/macrophages are known as important regulators of the inflammation and regeneration processes within different tissue types of the body. However, our understanding of the potential interactions between specific tissue-like cells differentiated from stem/stromal cells (e.g. ASC-VSMCs) and monocytes/macrophages (cued by specific biomaterial scaffolds) is still limited. In this study, indirect and direct ASC-VSMC-monocyte co-cultures were constructed within a porous polyurethane scaffold (D-PHI) previously shown to have an immunomodulatory character. The effects of monocytes/macrophages on the cellularity (cell number detected with DNA quantification assay), ECM (glycosaminoglycan (GAG), collagen, and elastin) accumulation as well as the maintenance of contractile VSMC markers (calponin and smoothelin) of the ASC-VSMCs after a month of co-culture were investigated. It was found that monocyte paracrine signalling in D-PHI positively affected the cellularity and ECM accumulation of ASC-VSMCs in co-culture. Cause-effect relationships were also identified between the release of pro-inflammatory/anti-inflammatory factors (i.e. IL6, TGF-β1) in co-culture and the expression of contractile proteins (calponin and smoothelin) by ASC-VSMCs. This study demonstrated the importance of combining an immune cell strategy with stromal cell derived VSMCs (i.e. ASC-VSMCs) to achieve a practical vascular tissue engineering outcome. STATEMENT OF SIGNIFICANCE: Adipose stromal cell derived-vascular smooth muscle cells (ASC-VSMCs) are a promising cell source for vascular tissue engineering. Monocytes/monocyte derived macrophages can be harnessed as an immune-assisted strategy to promote vascular tissue regeneration. This study demonstrated that the co-culture of human ASC-VSMCs with monocytes significantly enhanced the cellularity and extracellular matrix (ECM) accumulation within anionic polyurethane (D-PHI) scaffolds, partially mediated by monocyte paracrine signalling mechanisms. In addition, specific VSMC contractile markers (calponin and smoothelin) were still present in ASC-VSMCs when the cells were exposed to monocytes for a month in vitro. This study corroborated the potential selection of ASC-VSMCs for in vitro engineering of vascular tissue in an immunomodulatory biomaterial scaffold (e.g. D-PHI) based co-culture system containing monocytes.

Adipose-derived stem cells contribute to cardiovascular remodeling

Obesity is an independent risk factor for cardiovascular disease. Adipose tissue was initially thought to be involved in metabolism through paracrine. Recent researches discovered mesenchymal stem cells inside adipose tissue which could differentiate into vascular lineages in vitro and in vivo, participating vascular remodeling. However, there were few researches focusing on distinct characteristics and functions of adipose-derived stem cells (ADSCs) from different regions. This is the first comprehensive review demonstrating the variances of ADSCs from the perspective of their origins.

Hair-follicle-associated pluripotent stem cells derived from cryopreserved intact human hair follicles sustain multilineage differentiation potential

The bulge area of the hair follicle contains hair-follicle-associated pluripotent (HAP) stem cells. Here, we present effective cryopreservation procedures of the human hair follicle that preserve the differentiation potential of HAP stem cells. Whole hair follicles isolated from human scalp were cryopreserved by a slow-rate cooling medium and stored in liquid nitrogen. A careful thawing method was used to collect the upper parts of the human hair follicles which were cultured for four weeks in a Dulbecco’s Modified Eagle’s Medium with fetal bovine serum (FBS). Proliferating hair follicle cells were then shifted to DMEM/Ham’s Nutrient Mixture F-12 medium without FBS and allowed to grow for one week. These proliferating cells were able to produce HAP stem cell colonies with multilineage differentiation capacity. They produced keratinocytes, smooth muscle cells, cardiac muscle cells, neurons and glial cells. Interestingly, these cryopreserved hair follicles produced pluripotent HAP stem cell colonies similar to fresh follicles. These findings suggest that the cryopreserved whole human hair follicle preserves the ability to produce HAP stem cells, which will enable any individual to preserve a bank of these stem cells for personalized regenerative medicine.