Stem cell Niche refers to a micro-environment where stem cells are found, which interacts with stem cell to regulate cell fate .stem cells are considered as the building blocks of body because of their ability to self renew and differentiate into specific tissue types. These stem cells; reside in a specific niche in vivo where various micro-environment cues form and interwined signaling regulatory network that maintains stem cells fate and functions. Within the human body,stem cell niches maintain adult stem cells in a quiescent state, but after tissue injury, the components of the niche pass signals to these stem cells to activate them to multiply, differentiate and proliferate.
In this niche there are different regulators such as ECM molecules (Extra cellular Matrix) molecules,bio-chemical cues such as soluble growth factors and cytokines and mechanical cues such as intrinsic matrix stiffness and extrinsic forces which play a major role in deciding the fate of the stem cell.Along with that cell-cell interaction,interaction between stem cells and adhesion molecules,physio chemical nature of environment including pH,ionic strength and oxygen tension are also important.Clustering of cell surface receptors often serves to polarize cells and in some cases it activates downstream signaling pathways may be different for different types of stem cells.For example when hematopoietic stem cell are injected inside the body of the patient,homing of these stem cells depends on different signaling pathways.Several pathways have been studied in relation to hematopoesis which are SDF-1(CXCL 12)/CXCR4 signaling,BMP signaling,Mpl/Thrombopoietin (TPO) signaling,Tie2/Ang-1 signaling,hedgehog and notch signaling, as well as Wingless (Wnt) signaling.
The microenvironment or niche can be specific to the type of the cells and accordingly niches are further classified as ‘blood cell niche’,’bone cell niche’,’intestinal cell niche,’hair follicle cell niche’ ‘brain cell niche’ etc. Adult stem cells remain in undifferentiated state throughout adult life; however when they are cultured in vitro,they often undergo an aging process in which their morphology is changed and their proliferative capacity is decreased so it is believed that proper culturing conditions of adult stem cells needs to be improved so that adult stem cell needs to be improved so that adult stem cell can maintain their stemness over time. In future there is a need to engineer or optimize niches cues for differentiation towards the different lineages in vitro and anaylizing these homing pathways will definitely provide an understanding insight of the development of some new therapies for the treatment of even chronic diseases where stem cells may prove the only remedy. how these niches can be engineered in vito.It is very important to understand how these niches can be engineered in vitro This will help in deciding the fate of the stem cells administrated in vitro. The niche must have both anatomic and functional dimensions. The niche may differ as per the type of the cell in which it has to be differentiated.
In therapeutic applications, when stem cells; are administrated inside the body of the receptive patient. the defined niche factors (growth factors) play an important role in giving the direction to stem cells to differentiate required lineage.The formed lineages are then well supported by the cytokines releasent by immune cells inside the body of the patient which increases the proliferation and differentiation capacity of the cells and function of the damaged system is recovered.However though the process looks simple it involves lots of signaling pathways which regulates the entire process. Many a times scaffolding also play an important role in therapeutic applications
You can watch Dr. Mahajan’s presentation on stem cells niche