Developmental features of neural stem cells in frontal cortex of embryonic human brain at various ages

Xiaojuan YIN; Zhichun FENG

ABSTRACT

BACKGROUND:

Neural stem cells(NSCs) have been used to treat brain injury or some degenerating diseases of nervous system. Since in vitro culture conditions for NSCs differ from normal physiological conditions, whether the properties of the cultured cells are consistent with those of cells under physiological conditions? Therefore, inducing endogenous NSCs to proliferate and differentiate may be more promising for practise of NSCs.

OBJECTIVE:

This study was designed to investigate the developmental properties of NSCs in frontal cortex of embryonic human brain at various ages.

DESIGN:

It was a randomized experimental study.

SETTING:

This study was conducted at Department of Pediatrics, Zhujiang Hospital, Southern Medical University.

PARTICIPANTS:

Totally 90 16-to-36-week-old fetuses underwent inducing abortion by water bag were selected at the Obstetrics & Gynecology Department of Zhujiang Hospital Affiliated to Southern Medical University from October 2003 to March 2004. Brain tissue was taken from the frontal cortex of the aborted fetuses. All the mothers had normal physical examination findings. The informed consents on inducing abortion by water bag had been obtained from relatives and the mothers. The study was conducted with a prior permission from the competent department of the First Military Medical University. According to their ages, the fetuses were divided into 6 groups,16-week group, 20-week group, 24-week group, 28-week group and 36-week group, each group containing 15 cases.

METHODS:

After inducing abortion by water bag, under axenic conditions, the aborted fetus was dissected, with the scalp excisd, the skull opened and the membrane covering brain pull apart. Then the frontal cerebral cortex was taken out, fixed and sliced. Employing immunohistochemical staining and light microscope, distribution, morphological features, phenotypes, growth patterns and quantity of NSCs in the frontal cortex were observed. Morphological features of the cells and expressions of markers in the cells were examined under light microscope. Negative control was set according to the substitution method. Under a × 400 field of microscope, some nestin-positive cells with speckled brown cytoplasmic staining were defined as NSCs. Two slides of each sample were detected and 10 fields of each slide were observed. Based on these observations, in each group, the total number of cells and the number of positive-stained cells in 300 fields were counted. The rates of nestin-positive cells were calculated.MAIN OUTCOME

MEASURES:

Morphological features, quantitative assessment and developmental features of the nestin-positive NSCs in frontal cortex of embryonic human brain at various ages were main outcome measurements in this study.

RESULTS:

NSCs were found in frontal cortex of embryonic human brain. They mainly were distributed in the pyramidal layer and the internal granular layer. They were small round-or oval-shaped, most were small round-shaped. These cells had a relatively large vacuolar nucleus with 1 - 3 nucleoli, loose chromatin and marked cytoplasmic staining. Some of the round-shaped cells were mitral cells with short neurites. The oval-shaped cells had 2 neurites. A distinct territorial distribution of NSCs could be observed. Some colonies, consisting of a few NSCs and looked like the neurospheres in in vitro culture, could be seen. Occasionally, symmetrical division of NSCs could be observed. In all the groups, 16-week, 20-week, 24-week,28-week, 32-week and 36-week group, the rates of nestin-positive NSCs in frontal cortex of embryonic human brain decreased with the increase of age (15.59%, 13.48%, 11.62%, 10.52% ,9.87% ,6.68% ,X2 = 1 265. 152, P＜ 0.01).

CONCLUSION:

The distribution, morphological features, phenotypes, growth pattern and quantity of the NSCs in frontal cortex of embryonic human brain at various ages are different and auto-developmental features exist. The number of these cells decreases with the increase of age.