Journal of Stem Cell Research & Therapy

Growth of Mesenchymal Stem Cells in Hypoxia Accelerates Wound Healing in vitro

Sushma Bartaula-Brevik^* Department of Clinical Dentistry, University of Bergen, Norway
^*Correspondence: Sushma Bartaula-Brevik, Department of Clinical Dentistry, University of Bergen, Norway, Email:

Published: 26-Dec-2021

Introduction

The ability of stem cells to self-renew and differentiate into mature cells of different lineages is regulated by both intrinsic programming and extrinsic input from the stem cell niche or microenvironment. The poor post-implantation survival of transplanted cells limit therapeutic efficacy. Several strategies have been postulated to overcome this challenge, which includes preconditioning of the cells by heat shock, oxidative stress and hypoxia. The oxygen concentration in different tissues and organs varies from 2%-9%, whereas bone marrow niches have a lower oxygen concentration at about 1%. This suggests that bone marrow stem cells could favor a hypoxic microenvironment. Several studies have shown that hypoxia induces release of chemokines, cytokines and growth factors involved in cell proliferation, differentiation, migration, apoptosis and angiogenesis. However, the effect of short- and long-term hypoxic environments on survival, proliferation and differentiation of mesenchymal stem cells (MSC) is still controversial. It has been shown that by changing the culture conditions, MSC can be directed towards the endothelial cell lineage. Also, the paracrine effect of implanted MSC promotes vascularization by in growth of host microvasculature into tissue-engineered constructs.

Materials

Different strategies have been suggested to improve vascularization in tissue engineering, which include both pre-vascularized and pre-conditioned constructs. Endothelial cells (EC) have been co-cultured with different cell types, including MSC, adipose stem cells (ASC) and osteoblasts, all with the aim of improving vascularization after being implanted in vivo. It has been shown that the microvasculature in pre-vascularized constructs can interconnect with the host microvasculature, in order to ensure implant survival. Pre-conditioned tissue-engineered constructs can also be generated by incorporating different growth factors, or by changing the physical and chemical properties of the scaffold material. EC were cultured in the conditioned medium obtained from MSC under hypoxic condition, which demonstrated higher angiogenic potential of EC in vitro.

Pre-vascularization of tissue-engineered construct by directly co-culturing MSC and EC in vitro resulted in microvascular network formation in vivo. Despite of extensive work on co-culture systems, limited effort has been made to address the effect of different culture condition on direct co-culture. The aim of this study was to evaluate how hypoxia influenced MSC grown in mono- and co-culture, and the effect of MSC's secretome on wound healing and vessel formation. Human umbilical vein endothelial cells were cultured in Culture-Insert 24 (80241, ibidi, Martinsried, Germany) at a concentration of 30,000 cells/well in duplicate. The culture inserts were carefully removed after the cells reached confluency. A wound of approximately 500 μm width was created by the insert, and the wounded monolayer of cells was washed three times with phosphate buffered saline (PBS) to remove dead cells and debris.