Research On The Construction And Function Of The Vascularized Human Cerebral Organoids

The human brain is one of the most complex organs in the organism in terms of the structure and function.The complexity of the human brain acts a huge challenge to study the development and functional abnormalities of this unique organ.Researchers have been using animal models to study the development of the adult brain and the disease in tradition.However,there are big differences between the animal brain model with the human brain,so it is impossible to study the specific characteristics of the human brain,especially the special pathological function of the human brain.The culture of human pluripotent stem cells in vitro can establish a three-dimensional neural tissue development model.The cells can self-organize into complex brain structures,termed cerebral organoids.Current,there are several limitations that can't be ignored in cerebral organoids cultured in vitro,including the central cell necrosis and the nerve cell development is not mature enough for a long-time culture.So here I develop a culture platform for constructing the vascularized human cerebral organoids,in order to achieve the long-term stable culture of human cerebral organoids and obtain the more mature cerebral organoids culture model.The bioactive composite hydrogel system was prepared by crosslinking the oxidized sodium alginate?OSA?and gelatin?GTN?with calcium chloride to provide suitable extracellular environment for the proliferation and migration of nerve cells in cerebral organoids.The composition of hydrogel is 1.5% OSA,4.5% GTN and 100 mmol/L CaCl₂,which can not only guarantee the maturation of cerebral organoids,but also provide enough mechanical properties for the transplantation.The peritoneum of immunodeficient mice is rich in capillaries.It is a highly vascularized structure in peritoneum,which can support the vascularization of cerebral organoids,so as to construct cerebral organoids with microvasculature.At the same time,the use of immunodeficient mice can reduce the risk of cerebral organoids being attacked by the immune system as the foreign after the cerebral organoids transplantation due to immune response.Twelve weeks after the transplantation of cerebral organoids,the morphology of nerve cells and the distribution of blood vessels in cerebral organoids can be examined by scanning electron microscopy.The results show that there are a large number of nerve nucleus nodes like structure and blood vessels,indicating the successful construction of vascularized human cerebral organoids.By immunofluorescence analysis,there are a great many differentiated neurons and astrocytes in cerebral organoids,indicating that human cerebral organoids can further differentiate and mature with the participation of exogenous blood vessels,and the vascular networks can be detected.The microvascular network formed by the transplanted cerebral organoids in immune deficient mice can be detected in vivo by using small animal ultrasound photoacoustic imaging system.It is found that the blood vessels of immune deficient mice invade cerebral organoids,forming a combination of human cerebral organoids and mice blood vessels.The vascularized human cerebral organoids constructed in this study overcomes the drawback of central cell death caused by the lack of oxygen and nutrition in traditional cerebral organoids culture,and realizes the long-term culture of cerebral organoids to obtain more mature brain organoids.Vascularized cerebral organoids can not only be used as a model to study the development of human cortex,but also provide a new cell therapy for nervous system diseases and injuries.