Diabetic microenvironment deteriorates the regenerative capacities of adipose mesenchymal stromal cells

BACKGROUND

Type 2 diabetes is an endocrine disorder characterized by compromised insulin sensitivity that eventually leads to overt disease. Adipose stem cells (ASCs) showed promising potency in improving type 2 diabetes and its complications through their immunomodulatory and differentiation capabilities. However, the hyperglycaemia of the diabetic microenvironment may exert a detrimental effect on the functionality of ASCs. Herein, we investigate ASC homeostasis and regenerative potential in the diabetic milieu.

METHODS

We conducted data collection and functional enrichment analysis to investigate the differential gene expression profile of MSCs in the diabetic microenvironment. Next, ASCs were cultured in a medium containing diabetic serum (DS) or normal non-diabetic serum (NS) for six days and one-month periods. Proteomic analysis was carried out, and ASCs were then evaluated for apoptosis, changes in the expression of surface markers and DNA repair genes, intracellular oxidative stress, and differentiation capacity. The crosstalk between the ASCs and the diabetic microenvironment was determined by the expression of pro and anti-inflammatory cytokines and cytokine receptors.

RESULTS

The enrichment of MSCs differentially expressed genes in diabetes points to an alteration in oxidative stress regulating pathways in MSCs. Next, proteomic analysis of ASCs in DS revealed differentially expressed proteins that are related to enhanced cellular apoptosis, DNA damage and oxidative stress, altered immunomodulatory and differentiation potential. Our experiments confirmed these data and showed that ASCs cultured in DS suffered apoptosis, intracellular oxidative stress, and defective DNA repair. Under diabetic conditions, ASCs also showed compromised osteogenic, adipogenic, and angiogenic differentiation capacities. Both pro- and anti-inflammatory cytokine expression were significantly altered by culture of ASCs in DS denoting defective immunomodulatory potential. Interestingly, ASCs showed induction of antioxidative stress genes and proteins such as SIRT1, TERF1, Clusterin and PKM2.

CONCLUSION

We propose that this deterioration in the regenerative function of ASCs is partially mediated by the induced oxidative stress and the diabetic inflammatory milieu. The induction of antioxidative stress factors in ASCs may indicate an adaptation mechanism to the increased oxidative stress in the diabetic microenvironment.

Cellular senescence, rejuvenation and potential immortality

Ageing, death, and potential immortality lie at the heart of biology, but two seemingly incompatible paradigms coexist in different research communities and have done since the nineteenth century. The universal senescence paradigm sees senescence as inevitable in all cells. Damage accumulates. The potential immortality paradigm sees some cells as potentially immortal, especially unicellular organisms, germ cells and cancerous cells. Recent research with animal cells, yeasts and bacteria show that damaged cell constituents do in fact build up, but can be diluted by growth and cell division, especially by asymmetric cell division. By contrast, mammalian embryonic stem cells and many cancerous and 'immortalized' cell lines divide symmetrically, and yet replicate indefinitely. How do they acquire their potential immortality? I suggest they are rejuvenated by excreting damaged cell constituents in extracellular vesicles. If so, our understanding of cellular senescence, rejuvenation and potential immortality could be brought together in a new synthesis, which I call the cellular rejuvenation hypothesis: damaged cell constituents build up in all cells, but cells can be rejuvenated either by growth and cell division or, in 'immortal' cell lines, by excreting damaged cell constituents. In electronic supplementary material, appendix, I outline nine ways in which this hypothesis could be tested.

BCG vaccination and the risk of COVID 19: A possible correlation

Bacillus Calmette-Guérin (BCG) vaccine is currently used to prevent tuberculosis infection. The vaccine was found to enhance resistance to certain types of infection including positive sense RNA viruses. The current COVID-19 pandemic is caused by positive sense RNA, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). A higher mortality rate of COVID-19 patients was reported in countries where BCG vaccination is not routinely administered, when compared to the vaccinated ones. We hypothesized that BCG vaccine may control SARS-CoV2 infection via modulating the monocyte immune response. We analyzed GSE104149 dataset to investigate whether human monocytes of BCG-vaccinated individuals acquire resistance to SARS-CoV-2 infection. Differentially expressed genes obtained from the dataset were used to determine enriched pathways, biological processes, and molecular functions for monocytes post BCG vaccination. Our data show that BCG vaccine promotes a more effective immune response of monocytes against SARS-CoV2, but probably not sufficient to prevent the infection.

Characterization of the absence of an unique DNA-binding protein in senescent but not in their young growing and nongrowing counterparts provides the means to mark the final stage of the cellular aging process

In senescent fibroblasts, the incapability of cell replication is permanent, and may involve the irreversible loss of gene expressions potentiating the engagement in DNA replication. The initial attempt is to identify gene products that are permanently lost in irreversibly growth-arrested cells. In this article, we report the success in identifying a DNA-associated S6 antigen found in the nuclei of growing and growth-arrested young cells, but not in the nuclei of their senescent counterparts. The presence of the S6 antigen is uniform throughout the nucleoplasm, except in the regions of the nucleoli, and found to be associated with condensed chromosomes in mitotic cells. Treatment with RNase does not abolish the antibody staining activity in the nuclei, while treatment with DNase does remove the activity. Equal intensity of S6 antibody staining is observed in transformed, growing, and contact-inhibited young fibroblasts. Significant reduced level of S6 antibody staining activity is found in the nuclei of senescent fibroblasts, indicating the loss of the expression of this protein during cellular aging process. Immunoblotting assay shows that the S6 antigen is of 50 kDa and with a possibility of a 100 kDa as a dimeric precursor. Our results suggests that a permanent turning off of unique gene expression is associated with the onset of senescence or terminal differentiation, and this hypothesis is supported by the characterization of S6 antigen's absence in in vitro-aged fibroblasts.

Clonal aging in Paramecium tetraurelia. II. Evidence of functional changes in the macronucleus with age

The contribution of the macronucleus of Paramecium tetraurelia to the long term proliferation potential of a cell line was tested using a nuclear transplantation protocol. Macronuclei from young or old wild-type cells were injected into genetically marked host cells of a standard clonal age. The subsequent proliferation to clonal death of successfully and stably transformed hybrids was compared to the proliferation of injected but untransformed lines (injection controls). Young macronuclear donor material significantly prolonged the proliferation of the hybrid cell lines over that of the injection controls, but old donor material caused only a slight increase in post-injection proliferation of the hybrids. Total cell proliferation was also considered. Comparison of the total life spans of injected, non-transformed lines with uninjected host controls demonstrates that the injection itself has no significant effect upon proliferation potential. The mean life spans of uninjected donor controls and the mean total life spans of the transplanted macronuclear material (donor age at injection plus subsequent hybrid proliferation) are similar, regardless of the age of the donor at the time of transplantation. These results suggest that there is an age-related decrease in the ability of a macronucleus to support subsequent cell growth and division. The results also show that the proliferation potential of the donor macronucleus does not appear to be changed to any great degree by transplantation into a host cell of different clonal age. The macronucleus thus "remembers its age" after transplantation. Coupled with an absence of any detectable cytoplasmic effects upon aging during vegetative growth, these results argue in favor of a macronuclear determination of the proliferation potential of a cell line. The identification of a macronuclear basis for clonal aging in P. tetraurelia should permit a better directed approach for further research in this area.

Clonal aging in Paramecium tetraurelia. Absence of evidence for a cytoplasmic factor

Cells of Paramecium tetraurelia show clonal aging with characteristics comparable to the aging seen in tissue culture cell lines. An investigation is underway to determine the relative contributions, if any, of the cytoplasm and the macronucleus to the onset of senescence. Using a microinjection protocol, the importance of the cytoplasm to aging was tested. Cytoplasm was transferred from young cells into old cells to see if the mean age of death of the injected cell lines could be increased, compared with uninjected controls and sham injected controls. Cytoplasm from old cells was transferred into young cells to see if the mean age of death of the injected cell lines could be decreased, compared with sham injected and uninjected controls. In neither case was there any statistically significant change in mean ages of death. Furthermore, no changes can be demonstrated even with a protocol which transplanted 3 times the normal cytoplasmic volume. Thus, a cytoplasmic effect upon vegetative aging in P. tetraurelia cannot be demonstrated. Tests of a macronuclear influence are now underway.

Modeling cellular systems and aging processes: I. Mathematics of cell system models-a review

A review of the literature on mathematical models of populations of cellular systems is presented. Continuous, discrete, and stochastic models are presented in a semihistorical manner as a prelude to answering the question of how to model an asynchronously dividing cellular system. This analysis is then broadened, in an attempt to broach the more general question of modeling the distribution of a set or collection of cell properties through an asynchronously dividing cellular system. Such properties might be cell motility, cell cycle length, time to mitosis, or number of epigenetic particles. It is shown that one fruitful approach to this modeling question is a coupled continuous-probabilistic model. The ramifications of this type of formalism are discussed.

Replicative potentials of various fusion products between WI-38 and SV40 transformed WI-38 cells and their components

Hybrid cells derived from whole-cell fusions of replicating phase-II normal fibroblast cells (WI-38s) with SV40 transformed WI-38 fibroblast cells (CL-1s) demonstrated that the majority of the hybrid experimental cells still maintained a finite life-span. Approximately 2% demonstrated sustained and possibly indefinite replication. Experimental binucleate cells and subsequent hybrid synkaryons were also formed by fusing CL-1 karyoplasts into phase-II WI-38 replicating normal fibroblasts. In addition, viable cells were constructed from WI-38 fibroblast cytoplasts with CL-1 karyoplasts. Sustained replication was not observed in these crosses.

DNA repair and longevity assurance in Paramecium tetraurelia

At given doses and clonal ages, ultraviolet irradiation-induced DNA damage reduced clonal life-span, but when followed by photoreactivation, extension of clonal life-span was observed. If photoreactivation preceded the ultraviolet treatment, no significant beneficial effect was detected. Because studies of others have shown that photoreactivation repair monomerizes the ultraviolet-induced cyclobutane dimers in DNA, but does not affect the other photoproducts, these results indicate that DNA damage can influence the duration of clonal life-span unless that damage is repaired. Repeated treatment with ultraviolet and photoreactivation resulted in significant mean and maximal clonal life-span extension when compared with untreated controls, and it is assumed that the rejuvenation effect was due to the correction or prevention of some age damage.

Cell size in aging monolayer cultures

Changes in the size of the area covered by individual cultured WI-38 cells as the cultures age have been studied by using a new microphotographic paper cutout technique. This method is nondestructive and noninstrusive and avoids a number of artifacts which can occur in the measurement of suspended cells. The measurements reveal that the decreased cell yield of late passage cultures reflects not only the appearance of a subpopulation of larger cells but also the failure of the cells to utilize all the growth surface available to them.