Influence of hypoxia prevailing in post-infarction heart on proangiogenic gene expression and biological features of human myoblast cells applied as a pro-regenerative therapeutic tool

Cardiovascular diseases along with MI (myocardial infarction) lead to regional ischaemia and hypoxic conditions, which prevail after infarction. Diminished O₂ saturation which is related to elevated level of hypoxia inducible factor 1 (HIF-1) transcription factor, may switch the expression of many genes. To maximize effect of therapies proposed by regenerative medicine, it is essential to verify (within different time points after MI) the expression of proangiogenic genes and their receptors that are regulated, along with the expression of HIF-1α. We demonstrated a connection between the expression of Hif-1α (in murine post infarcted heart model) and the proangiogenic genes Vegf-a; and Plgf and their receptors during myocardial hypoxia. The innovative part of the study required establishment of the most accurate in vitro O₂ level corresponding to the hypoxia level prevailing in myocardium after MI. We determined the influence of hypoxia on the biology of human myoblasts in in vitro oxygen conditions (3%), corresponding to those prevailing in the heart after an infarction using a murine model. We also tested myoblasts that were genetically modified with VEGF-A/FGF-4 and PlGF under hypoxic conditions and compared their characteristics with cells cultured under normoxia and hyperoxia (standard in vitro conditions) with respect to myogenic gene expression, cell proliferation, fusion potential and proangiogenic function. The examination of genetically modified myoblasts under optimized in vitro hypoxia conditions led to the conclusion that hypoxia did not negatively influence the biological functions of the myoblasts, such as cell proliferation and/or proangiogenic characteristics. These results support the expected increased proregenerative effects of such genetically modified human myoblasts.

Biological and Pro-Angiogenic Properties of Genetically Modified Human Primary Myoblasts Overexpressing Placental Growth Factor in In Vitro and In Vivo Studies

Cardiovascular diseases are a growing problem in developing countries; therefore, there is an ongoing intensive search for new approaches to treat these disorders. Currently, cellular therapies are focused on healing the damaged heart by implanting stem cells modified with pro-angiogenic factors. This approach ensures that the introduced cells are capable of fulfilling the complex requirements of the environment, including the replacement of the post-infarction scar with cells that are able to contract and promote the formation of new blood vessels that can supply the ischaemic region with nutrients and oxygen. This study focused on the genetic modification of human skeletal muscle cells (SkMCs). We chose myoblast cells due to their close biological resemblance to cardiomyocytes and the placental growth factor (PlGF) gene due to its pro-angiogenic potential. In our in vitro studies, we transfected SkMCs with the PlGF gene using electroporation, which has previously been proven to be efficient and generate robust overexpression of the PlGF gene and elevate PlGF protein secretion. Moreover, the functionality of the secreted pro-angiogenic proteins was confirmed using an in vitro capillary development assay. We have also examined the influence of PlGF overexpression on VEGF-A and VEGF-B, which are well-known factors described in the literature as the most potent activators of blood vessel formation. We were able to confirm the overexpression of VEGF-A in myoblasts transfected with the PlGF gene. The results obtained in this study were further verified in an animal model. These data were able to confirm the potential therapeutic effects of the applied treatments.

Comparison of trace element concentration in bone and intervertebral disc tissue by atomic absorption spectrometry techniques

BACKGROUND

Trace element (TE) analysis in human tissue has the dual purpose of assessing environmental pollution and metabolism. In literature, bone TE analysis is common, but studies in intervertebral disc (IVD) tissue are lacking. The aim of the study was evaluation of the difference of TE concentration in intervertebral disc and bone in patients with degenerative changes. The comparison of the tissues differing in metabolism, blood perfusion, or separateness from adjoining tissues but playing similar biomechanical role and presenting some common morphological traits may shed new light on metabolism nuances, degenerative process, as well as accumulation potential of IVD in respect to bone.

METHODS

In the study, we analyzed two types of samples: intervertebral disc (n =30, from 22 patients operated due to degenerative disc disease) and femoral bone (n =26, separately femoral head and neck, from 26 patients, acquired in total hip arthroplasty procedure in course of idiopathic osteoarthritis of the hip joint). In the samples we analyzed, with atomic absorption spectrometry, the concentrations of Pb, Ni, Mo, Cu, Mg, and Zn.

RESULTS

The element concentrations identified in bone are comparable to those presented in the literature. In the case of Pb, Ni, Mo, Mg, and Zn, the concentration in the bone was 2 to 25.8 times higher than that observed in the disc. Only the Cu concentration was higher in disc tissue than in bone. In disc tissue, fewer samples had TE concentrations below the detection threshold. We found significant differences in TE profiles in the compared tissues.

CONCLUSIONS

The results show that the disc could serve as a more stable compartment for evaluating TE concentration, especially for TEs that are environmentally related.