The World-Wide Adaptations of Diabetic Management in the Face of COVID-19 and Socioeconomic Disparities: A Scoping Review.

Diabetes is an increasingly prevalent chronic disease throughout the world. It is imperative for patients to have access to reliable treatment and resources in order to avoid long-term complications. Economic and social factors contribute to the accessibility of these resources and have a direct impact on diabetes management. Socioeconomic status (SES) presents challenges to diabetic management due to financial and geographical access to care, medications, educational resources, healthy food options, and physical activity. The coronavirus (COVID-19) pandemic exacerbated these challenges, especially during the height of lockdowns. Therefore, it is important to gain insight into how the pandemic challenged diabetes management, taking into consideration socioeconomic disparities. The objective is to assess how the COVID-19 pandemic has impacted the care of chronic diabetic patients internationally and determine how these outcomes vary between patients of different socioeconomic classes. The following study was designed as a scoping review and utilized PubMed, EMBASE, CINAHL, and Web of Science. A Boolean search strategy combined search terms as follows: (((COVID-19) AND (diabetes)) AND ((socioeconomic factors) OR (social inequality OR standard of living))) AND (treatment OR management). Inclusion criteria included studies addressing diabetic patients, socioeconomic variables (income, occupation, level of education, and ethnicity), glycemic control, and degree of access to quality healthcare. Studies exploring the pathophysiology of COVID-19 or diabetes mellitus were excluded. In addition, studies were chosen between the years 2020 and 2022. The search resulted in 214 articles. The full-text assessment was then conducted on the remaining 67 articles. After screening for eligibility and relevance, 19 articles were retained for this review. The results of this study indicate that 8 out of the 18 studies revealed worse outcomes for those with diabetes mellitus and concomitant COVID-19 infection. Patients with diabetes were more likely to be hospitalized and represent a larger percentage of COVID-19 fatalities. In addition, patients with diabetes and co-morbid COVID-19 infection were more likely to have a higher hemoglobin A1c (HbA1c), belong to a lower SES, and have worse glycemic control due to pandemic-associated lockdown. In order to combat the effects of the pandemic, many countries created novel and innovative management strategies. Overall, there are positive and negative effects from the pandemic on diabetic management strategies. This scoping review identified successes in diabetic treatment under pandemic conditions and areas that need optimization. The successful adaptations of many nations convey the capacity for new policy implementation to care for diabetic patients regardless of SES.

Pannexin 1 regulates adipose stromal cell differentiation and fat accumulation.

Pannexin 1 (Panx1) is a channel-forming glycoprotein important in paracrine signaling and cellular development. In this study, we discovered that mice globally lacking Panx1 (KO) have significantly greater total fat mass and reduced lean mass compared to wild type (WT) mice under a normal diet. Despite having higher fat content, Panx1 KO mice on a high fat diet exhibited no differences in weight gain and blood markers of obesity as compared to WT controls, except for an increase in glucose and insulin levels. However, metabolic cage data revealed that these Panx1 KO mice display significantly increased activity levels, higher ambulatory activity, and reduced sleep duration relative to their WT littermates on a high-fat diet. To uncover the cellular mechanism responsible for the increased fat content in the KO, we isolated primary cultures of adipose-derived stromal cells (ASCs) from WT and KO fat pads. In WT ASCs we observed that Panx1 protein levels increase upon induction into an adipogenic lineage. ASCs isolated from Panx1 KO mice proliferate less but demonstrate enhanced adipogenic differentiation with increased intracellular lipid accumulation, glycerol-3-phosphate dehydrogenase (GPDH) enzyme activity, and adipokine secretion, as compared to WT ASCs. This was consistent with the increased adipocyte size and decreased adipocyte numbers observed in subcutaneous fat of the Panx1 KO mice compared to WT. We concluded that Panx1 plays a key role in adipose stromal cells during the early stages of adipogenic proliferation and differentiation, regulating fat accumulation in vivo.

Decellularized Adipose Tissue Scaffolds for Soft Tissue Regeneration and Adipose-Derived Stem/Stromal Cell Delivery.

Surgically discarded adipose tissue is not only an abundant source of multipotent adipose-derived stem/stromal cells (ASCs) but can also be decellularized to obtain a biomimetic microenvironment for tissue engineering applications. The decellularization methods involve processing excised fat through a series of chemical, mechanical, and enzymatic treatment stages designed to extract cells, cellular components, and lipid from the tissues. This process yields a complex 3D bioscaffold enriched in collagens that mimics the biochemical and biomechanical properties of the native extracellular matrix (ECM). For ASC culture and delivery, decellularized adipose tissue (DAT) provides a cell-supportive platform that is conducive to adipogenesis. While DAT can be applied in its intact form as an off-the-shelf adipogenic matrix, it can also be used as an ECM source for the fabrication of an array of other scaffold formats including adipose ECM-derived microcarriers and porous foams. In this chapter, we describe the methods developed in our lab to decellularize human adipose tissue and to further process it into a variety of scaffolding materials for a range of applications in soft tissue regeneration, wound healing, and cell culture.

Mechanically resilient injectable scaffolds for intramuscular stem cell delivery and cytokine release.

A promising strategy for treating peripheral ischemia involves the delivery of stem cells to promote angiogenesis through paracrine signaling. Treatment success depends on cell localization, retention, and survival within the mechanically dynamic intramuscular (IM) environment. Herein we describe an injectable, in situ-gelling hydrogel for the IM delivery of adipose-derived stem/stromal cells (ASCs), specifically designed to withstand the dynamic loading conditions of the lower limb and facilitate cytokine release from encapsulated cells. Copolymers of poly(trimethylene carbonate)-b-poly(ethylene glycol)-b-poly(trimethylene carbonate) diacrylate were used to modulate the properties of methacrylated glycol chitosan hydrogels crosslinked by thermally-initiated polymerization using ammonium persulfate and N,N,N',N'-tetramethylethylenediamine. The scaffolds had an ultimate compressive strain over 75% and maintained mechanical properties during compressive fatigue testing at physiological levels. Rapid crosslinking (<3 min) was achieved at low initiator concentration (5 mM). Following injection and crosslinking within the scaffolds, human ASCs demonstrated high viability (>90%) over two weeks in culture under both normoxia and hypoxia. Release of angiogenic and chemotactic cytokines was enhanced from encapsulated cells under sustained hypoxia, in comparison to normoxic and tissue culture polystyrene controls. When delivered by IM injection in a mouse model of hindlimb ischemia, human ASCs were well retained in the scaffold over 28 days and significantly increased the IM vascular density compared to untreated controls.

Collagenase treatment enhances proteomic coverage of low-abundance proteins in decellularized matrix bioscaffolds.

There is great interest in the application of advanced proteomic techniques to characterize decellularized tissues in order to develop a deeper understanding of the effects of the complex extracellular matrix (ECM) composition on the cellular response to these pro-regenerative bioscaffolds. However, the identification of proteins in ECM-derived bioscaffolds is hindered by the high abundance of collagen in the samples, which can interfere with the detection of lower-abundance constituents that may be important regulators of cell function. To address this limitation, we developed a novel multi-enzyme digestion approach using treatment with a highly-purified collagenase derived from Clostridium Histolyticum to selectively deplete collagen from ECM-derived protein extracts, reducing its relative abundance from up to 90% to below 10%. Moreover, we applied this new method to characterize the proteome of human decellularized adipose tissue (DAT), human decellularized cancellous bone (DCB), and commercially-available bovine tendon collagen (BTC). We successfully demonstrated with all three sources that collagenase treatment increased the depth of detection and enabled the identification of a variety of signaling proteins that were masked by collagen in standard digestion protocols with trypsin/LysC, increasing the number of proteins identified in the DAT by ∼2.2 fold, the DCB by ∼1.3 fold, and the BTC by ∼1.6 fold. In addition, quantitative proteomics using label-free quantification demonstrated that the DAT and DCB extracts were compositionally distinct, and identified a number of adipogenic and osteogenic proteins that were consistently more highly expressed in the DAT and DCB respectively. Overall, we have developed a new processing method that may be applied in advanced mass spectrometry studies to improve the high-throughput proteomic characterization of bioscaffolds derived from mammalian tissues. Further, our study provides new insight into the complex ECM composition of two human decellularized tissues of interest as cell-instructive platforms for regenerative medicine.

Fabrication of Extracellular Matrix-derived Foams and Microcarriers as Tissue-specific Cell Culture and Delivery Platforms.

Cell function is mediated by interactions with the extracellular matrix (ECM), which has complex tissue-specific composition and architecture. The focus of this article is on the methods for fabricating ECM-derived porous foams and microcarriers for use as biologically-relevant substrates in advanced 3D in vitro cell culture models or as pro-regenerative scaffolds and cell delivery systems for tissue engineering and regenerative medicine. Using decellularized tissues or purified insoluble collagen as a starting material, the techniques can be applied to synthesize a broad array of tissue-specific bioscaffolds with customizable geometries. The approach involves mechanical processing and mild enzymatic digestion to yield an ECM suspension that is used to fabricate the three-dimensional foams or microcarriers through controlled freezing and lyophilization procedures. These pure ECM-derived scaffolds are highly porous, yet stable without the need for chemical crosslinking agents or other additives that may negatively impact cell function. The scaffold properties can be tuned to some extent by varying factors such as the ECM suspension concentration, mechanical processing methods, or synthesis conditions. In general, the scaffolds are robust and easy to handle, and can be processed as tissues for most standard biological assays, providing a versatile and user-friendly 3D cell culture platform that mimics the native ECM composition. Overall, these straightforward methods for fabricating customized ECM-derived foams and microcarriers may be of interest to both biologists and biomedical engineers as tissue-specific cell-instructive platforms for in vitro and in vivo applications.

Decellularized adipose tissue microcarriers as a dynamic culture platform for human adipose-derived stem/stromal cell expansion.

With the goal of designing a clinically-relevant expansion strategy for human adipose-derived stem/stromal cells (ASCs), methods were developed to synthesize porous microcarriers derived purely from human decellularized adipose tissue (DAT). An electrospraying approach was applied to generate spherical DAT microcarriers with an average diameter of 428 ± 41 µm, which were soft, compliant, and stable in long-term culture without chemical crosslinking. Human ASCs demonstrated enhanced proliferation on the DAT microcarriers relative to commercially-sourced Cultispher-S microcarriers within a spinner culture system over 1 month. ASC immunophenotype was maintained post expansion, with a trend for reduced expression of the cell adhesion receptors CD73, CD105, and CD29 under dynamic conditions. Upregulation of the early lineage-specific genes PPARγ, LPL, and COMP was observed in the ASCs expanded on the DAT microcarriers, but the cells retained their multilineage differentiation capacity. Comparison of adipogenic and osteogenic differentiation in 2-D cultures prepared with ASCs pre-expanded on the DAT microcarriers or Cultispher-S microcarriers revealed similar adipogenic and enhanced osteogenic marker expression in the DAT microcarrier group, which had undergone a higher population fold change. Further, histological staining results suggested a more homogeneous differentiation response in the ASCs expanded on the DAT microcarriers as compared to either Cultispher-S microcarriers or tissue culture polystyrene. A pilot chondrogenesis study revealed higher levels of chondrogenic gene and protein expression in the ASCs expanded on the DAT microcarriers relative to all other groups, including the baseline controls. Overall, this study demonstrates the promise of applying dynamic culture with tissue-specific DAT microcarriers as a means of deriving regenerative cell populations.

Effect of decellularized adipose tissue particle size and cell density on adipose-derived stem cell proliferation and adipogenic differentiation in composite methacrylated chondroitin sulphate hydrogels.

An injectable composite scaffold incorporating decellularized adipose tissue (DAT) as a bioactive matrix within a hydrogel phase capable of in situ polymerization would be advantageous for adipose-derived stem cell (ASC) delivery in the filling of small or irregular soft tissue defects. Building on previous work, the current study investigates DAT milling methods and the effects of DAT particle size and cell seeding density on the response of human ASCs encapsulated in photo-cross-linkable methacrylated chondroitin sulphate (MCS)-DAT composite hydrogels. DAT particles were generated by milling lyophilized DAT and the particle size was controlled through the processing conditions with the goal of developing composite scaffolds with a tissue-specific 3D microenvironment tuned to enhance adipogenesis. ASC proliferation and adipogenic differentiation were assessed in vitro in scaffolds incorporating small (average diameter of 38 ± 6 µm) or large (average diameter of 278 ± 3 µm) DAT particles in comparison to MCS controls over a period of up to 21 d. Adipogenic differentiation was enhanced in the composites incorporating the smaller DAT particles and seeded at the higher density of 5 × 10(5) ASCs/scaffold, as measured by glycerol-3-phosphate dehydrogenase (GPDH) enzyme activity, semi-quantitative analysis of perilipin expression and oil red O staining of intracellular lipid accumulation. Overall, this study demonstrates that decellularized tissue particle size can impact stem cell differentiation through cell-cell and cell-matrix interactions, providing relevant insight towards the rational design of composite biomaterial scaffolds for adipose tissue engineering.

Porous decellularized adipose tissue foams for soft tissue regeneration.

To design tissue-specific bioscaffolds with well-defined properties and 3-D architecture, methods were developed for preparing porous foams from enzyme-solubilized human decellularized adipose tissue (DAT). Additionally, a technique was established for fabricating "bead foams" comprised of interconnected networks of porous DAT beads fused through a controlled freeze-thawing and lyophilization procedure. In characterization studies, the foams were stable without the need for chemical crosslinking, with properties that could be tuned by controlling the protein concentration and freezing rate during synthesis. Adipogenic differentiation studies with human adipose-derived stem cells (ASCs) suggested that stiffness influenced ASC adipogenesis on the foams. In support of our previous work with DAT scaffolds and microcarriers, the DAT foams and bead foams strongly supported adipogenesis and were also adipo-inductive, as demonstrated by glycerol-3-phosphate dehydrogenase (GPDH) enzyme activity, endpoint RT-PCR analysis of adipogenic gene expression, and intracellular lipid accumulation. Adipogenic differentiation was enhanced on the microporous DAT foams, potentially due to increased cell-cell interactions in this group. In vivo assessment in a subcutaneous Wistar rat model demonstrated that the DAT bioscaffolds were well tolerated and integrated into the host tissues, supporting angiogenesis and adipogenesis. The DAT-based foams induced a strong angiogenic response, promoted inflammatory cell migration and gradually resorbed over the course of 12 weeks, demonstrating potential as scaffolds for wound healing and soft tissue regeneration.