Autophagy and Biomaterials: A Brief Overview of the Impact of Autophagy in Biomaterial Applications

Macroautophagy (hereafter autophagy), a tightly regulated physiological process that obliterates dysfunctional and damaged organelles and proteins, has a crucial role when biomaterials are applied for various purposes, including diagnosis, treatment, tissue engineering, and targeted drug delivery. The unparalleled physiochemical properties of nanomaterials make them a key component of medical strategies in different areas, such as osteogenesis, angiogenesis, neurodegenerative disease treatment, and cancer therapy. The application of implants and their modulatory effects on autophagy have been known in recent years. However, more studies are necessary to clarify the interactions and all the involved mechanisms. The advantages and disadvantages of nanomaterial-mediated autophagy need serious attention in both the biological and bioengineering fields. In this mini-review, the role of autophagy after biomaterial exploitation and the possible related mechanisms are explored.

Targeting cholesterol metabolism in glioblastoma: a new therapeutic approach in cancer therapy

Glioblastoma multiforme (GBM) is the most aggressive malignant brain tumor known with a poor survival rate despite current advances in the field of cancer. Additional research into the pathophysiology of GBM is urgently needed given the devastating nature of this disease. Recent studies have revealed the unique cellular physiology of GBM cells as compared with healthy astrocytes. Intriguingly, GBM cells are incapable of de novo cholesterol synthesis via the mevalonate pathway. Thus, the survival of GBM cells depends on cholesterol uptake via low-density lipoprotein receptors (LDLRs) in the form of apolipoprotein-E-containing lipoproteins and ATP-binding cassette transporter A1 (ABCA1) that efflux surplus cholesterol out of cells. Liver X receptors regulate intracellular cholesterol levels in neurons and healthy astrocytes through changes in the expression of LDLR and ABCA1 in response to cholesterol and its derivatives. In GBM cells, due to the dysregulation of this surveillance pathway, there is an accumulation of intracellular cholesterol. Furthermore, intracellular cholesterol regulates temozolomide-induced cell death in glioblastoma cells via accumulation and activation of death receptor 5 in plasma membrane lipid rafts. The mevalonate pathway and autophagy flux are also fundamentally related with implications for cell health and death. Thus, via cholesterol metabolism, the mevalonate pathway may be a crucial player in the pathogenesis and treatment of GBM where our current understanding is still lacking. Targeting cholesterol metabolism in GBM may hold promise as a novel adjunctive clinical therapy for this devastating cancer.

Quantitative Assessment of Proliferative Effects of Oral Vanadium on Pancreatic Islet Volumes and Beta Cell Numbers of Diabetic Rats

Background:

Oral vanadyl sulfate (vanadium) induces normoglycemia, proliferates beta cells and prevents pancreatic islet atrophy in streptozotocin-induced diabetic rats. Soteriological method is used to quantitate the proliferative effects of vanadium on beta-cell numbers and islet volumes of normal and diabetic rats.

Methods:

Adult male Sprague-Dawley rats were made diabetic with intravenous streptozotocin injection (40 mg/kg). Normal and diabetic rats were divided into four groups. While control normal and diabetic (CD) groups used water, vanadium-treated normal (VTN) and diabetic (VTD) groups used solutions containing vanadyl sulfate (0.5-1 mg/mL, VOSO₄+5H₂O). Tail blood samples were used to measure blood glucose (BG) and plasma insulin. Two months after treatment, rats were sacrificed, pancreata prepared, and stereology method was used to quantitatively evaluate total beta cell numbers (TBCN) and total islet volumes (TISVOL).

Results:

Normoglycemia persisted in VTN with significantly decreased plasma insulin (0.190.08 vs. 0.970.27 ng/dL, P<0.002). The respective high BG (53249 vs. 14446 mg/dL, P<0.0001) and reduced plasma insulin (0.260.15 vs. 0.540.19 ng/dL, P<0.002) seen in CD were reversed in VTD during vanadium treatment or withdrawal. While the induction of diabetes, compared to their control, significantly decreased TISVOL (1.90.2 vs. 3.030.6 mm³, P<0.003) and TBCN (0.990.1 vs. 3.20.2 x 10⁶, P<0.003), vanadium treatment significantly increased TISVOL (2.90.8 and 4.071.0 mm³, P<0.003) and TBCN (1.50.3 and 3.80.6 x 10⁶, P<0.03).

Conclusion:

Two-month oral vanadium therapy in STZ-diabetic rats ameliorated hyperglycemia by partially restoring plasma insulin. This action was through proliferative actions of vanadium in preventing islet atrophy by increasing beta-cell numbers.

Does the relief of glucose toxicity act as a mediator in proliferative actions of vanadium on pancreatic islet beta cells in streptozocin diabetic rats?

Background: Data shows vanadium protects pancreatic beta cells (BC) from diabetic animals. Whether this effect is direct or through the relief of glucose toxicity is not clear. This study evaluated the potential effect of oral vanadyl sulfate (vanadium) on glycemic status and pancreatic BC of normal and diabetic rats. Methods: Rats were divided into five groups of normal and diabetic. Diabetes was induced with streptozocin (40 mg/kg, i.v.). Normal rats used water (CN) or vanadium (1 mg/ml VOSO₄, VTN). Diabetic rats used water (CD), water plus daily neutral protamine Hagedorn insulin injection (80 U/kg, ITD) or vanadium (VTD). Blood samples were taken for blood glucose (BG, mg/dL) and insulin (ng/dL) measurements. After two months, the pancreata of sacrificed rats were prepared for islet staining. Results: Pre-treated normal BG was 88 ± 2, and diabetic BG was 395 ± 9. The final BG in CD, VTD, and ITD was 509 ± 22, 138 ± 14, and 141 ± 14, respectively. Insulin in VTN (0.75 ± 0.01) and VTD (0.78 ± 0.01) was similar, higher than CD (0.51 ± 0.07) but lower than CN (2.51 ± 0.02). VTN islets compared to CN had larger size and denser central core insulin immunoreactivity with plentiful BC. CD and ITD islets were atrophied and had scattered insulin immunoreactivity spots and low BC mass. VTD islets were almost similar to CN. Conclusion: Besides insulin-like activity, vanadium protected pancreatic islet BC, and the relief of glucose toxicity happening with vanadium had a little role in this action.

Trophic actions of oral vanadium and improved glycemia on the pancreatic beta-cell ultrastructure of streptozotocin-induced diabetic rats

CONTEXT

Oral vanadyl sulfate (vanadium) has potent hypoglycemic effects in diabetes animals, but data about its actions on pancreatic beta-cells (BC) ultrastructure is limited.

OBJECTIVE

Partial diabetic rats were treated with vanadium and insulin injection and their effects on BC ultrastructure are studied.

METHODS

Male rats were made diabetic with intravenous streptozotocin injection (STZ, 40 mg/kg). Animals were randomly divided to control (CD), vanadium-treated (1 mg/mL VOSO4 + 5H2O in base solution, VTD) and insulin-treated (80 U/kg/day NPH insulin injection, ITD) diabetic groups. Treatments started 10 days after STZ injection and terminated after 2 months. Intermittent tail blood samples were taken for measurements of blood glucose (BG) and plasma insulin (PI). Finally animals were sacrificed and pancreata prepared for assessments of BC ultrastructure, islets histology and insulin immunoreactivity (IIR).

RESULTS

Vanadium decreased BG (P&lt;0.0001), elevated the reduced PI (P&lt;0.001), prevented islet atrophy and restored BC ultrastructure. Low BG seen during treatment in VTD and ITD only persisted in VTD after vanadium withdrawal. Hyperglycemia worsened in CD and repaired in ITD shortly after insulin withdrawal. CD islets were atrophied, had scattered IIR spots. BC had pyknotic nuclei, vacuolated cytoplasm and few tiny insulin secretory granules. VTD islets looked normal with compact centered IIR spots. BC had well-developed endoplasmic reticulum, many insulin secretory granules and mitochondria. ITD islet structure was slightly better than CD and BC had some immature insulin secretory granules.

CONCLUSION

The trophic actions of vanadium in diabetic rats effectively renovated beta cell ultrastructure and prevented pancreatic islets atrophy, whereas the relief of glucotoxicity seen with insulin treatment could repair some beta cells and partially prevented islet atrophy.

Characterizing endothelial cells derived from the murine embryonic stem cell line CCE

Embryonic stem cells (ESC) are defined by two main properties of self-renewal and their multipotency to differentiate into virtually all cell types of the body, including endothelial cells. ESCs have been widely regarded as an unlimited source of cells in regeneration medicine and also an ideal in vitro model to investigate complex developmental processes. Here, we report a simple and efficient in vitro model to derive a nearly pure population of endothelial cells from a murine ESC line. CCE ES cells are exposed to alpha-MEM medium containing 10% FBS for 4 days and then cultured in endothelial basal-2 medium containing vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), insulin-like growth factor (IGF), epidermal growth factor (EGF), and 2% FBS for 42 days. The cells acquired a relatively uniform endothelial cell morphology and were able to propagate and expand in culture. When murine ES cell-derived endothelial cells (MESDECs) were cultured on Matrigel and incubated for 48 h, vessel-like tube structures consisting of CD31 (PECAM-1) or BS-1 immunoreactive cells were developed. Immunocytochemistry and RT-PCR analyses revealed that MESDECs express endothelial cell-specific marker proteins such as Flk-1, PECAM-1, Tie-1, and Tie-2, in which the expressions persist for long periods of time after differentiation. The cells were also capable of taking up acetylated low-density lipoprotein (LDL) in culture. Our data suggest that MESDECs could provide a suitable in vitro model to study molecular events involved in vascular development and open up a new therapeutic strategy in regeneration medicine of cardiovascular disorders.