The Expression Of ProNGF And Its Receptors P75, Sortilin In The Human Embryonic Spinal Cord During Development

Objective:To explore the relations between proNGF and its receptors p75 and Sortilin and human embryonic spinal cord development.Methods:The expressions and changes of proNGF and its receptors p75 and sortilin were studied in human embryonic spinal cord from the 3th to 7th month by the methods of immunohistochemistry and Reverse transcription polymerase chain reaction(RT-PCR).Results:1. proNGF protein was expressed in the development of human embryonic spinal cord from the 3th to 7th month. In the low maglification, the staining region could be seen in the sensory-related areas such as the most part of spinal cord gray matter, dorsal part of white matter and both sides of posterior median sulcus and so on,as well as the nucleis of motor neurons in the spinal ventral horn. the spinal canal is hardly stained, so was the remainder of the spinal cord. And the Clarke nucleus which was located in the back inside of the central canal of the spinal cord gray matter was clearly stained. The proNGF protein expression was upregulated from 3M to 5M, and was downregulated from 5M to 7M(Fig.4:A₁, B₁, C₁, D₁, E₁). In the high magnification, Nerve fibers in the dorsal part of the gray matter of spinal cord could be seen filamentously stained, Intertwined. Comparison of the staining of the dorsal part of the spinal cord gray matter,5M group was the most significant in all five groups and the strong positive staining parts in the dorsal part of the spinal cord gray matter was changed with the spinal cord development. All in 3M, and inside and outside sides in 5M, dorsal edge of the gray matter close to white matter in 7M. Nerve cells were scattered within the nucleis of motor neurons in the spinal ventral horn, with its cytoplasmic stained, irregularly shaped. And nerve fibers in the ventral gray matter were less stained than in the dorsal gray matter. In the high magnification, the nerve fibers in the dosal part of the white matter were filamentously stained, Intertwined, stained nerve cell could be seen between the nerve fibers. And the positive staining parts had a trend extending from outside to inside from 3M to 7M (Fig.4). RT-PCR results showed that:proNGF mRNA expression in the 4M,5M,6M groups had a significantly increase than in the 3M,7M groups (P<0.05), and had no Statistically significance among 4M,5M and 6M groups nor between 3M and 7M.2. p75 protein is expressed in the development of human embryonic spinal cord from the 3th to 7th month, an the expression pattern was similar to proNGF expression. In the low maglification, the staining region could be seen in the sensory-related areas such as the most part of spinal cord gray matter, dorsal part of white matter and both sides of posterior median sulcus and so on,as well as the nucleis of motor neurons in the spinal ventral horn. the spinal canal is hardly stained, so was the remainder of the spinal cord. And the Clarke nucleus which was located in the back inside of the central canal of the spinal cord gray matter was weakly stained. In all five groups, the staining of 3M was the weakest(Fig.5:A₁, B₁, C₁, D₁, E₁). In the high magnification, Nerve fibers in the dorsal part of the gray matter of spinal cord could be seen filamentously stained, Intertwined. Comparison of the staining of the dorsal part of the spinal cord gray matter,5M group was the most significant in all five groups and the strong positive staining parts in the dorsal part of the spinal cord gray matter was changed with the spinal cord development. All at the beginning, and then inside and outside side, and dorsal edge of the gray matter close to white matter in 7M. Nerve cells were scattered within the nucleis of motor neurons in the spinal ventral horn, with its cytoplasmic stained, irregularly shaped. And nerve fibers in the ventral gray matter were less stained than in the dorsal gray matter. In the high magnification, the nerve fibers in the dosal part of the white matter were filamentously stained, Intertwined, stained nerve cell could be seen between the nerve fibers. And the positive staining parts had a trend extending from outside to inside from 3M to 7M (Fig.5). RT-PCR results showed that:p75 mRNA expression was upregulated from 3M to 5M, and was downregulated from 5M to 7M,5M was the peak point, had a significant increase compared with 3M,6M,7M groups(P<0.05).3. The sortilin protein was distributed in all kinds of structure and in all different periods of embryo spinal cord development from 3M to 7M. The dorsal horn, lateral horn and commissura anterior-posterior of the gray matter are all stained. The sortilin protein was distributed in all kinds in the white matter, such as the anterior median groove and posterior median sulcus, and was strong stained than in the gray matter's, form a clear boundary with the gray matter. In the high magnification, filamentous staining nerve fibers, triangular, circular and other shapes of staining nerve cells and dot-like glial cells could be seen, and the cytoplasmic of nerve cells and glial cells were stained. Spinal cord white matter in the form of filamentous network of nerve fibers are intertwined, during which mixed with a large variety of shapes of nerve cells and dot-like glial cells (Fig. 6). RT-PCR results showed that:sortilin mRNA expression in group 4M,5M,6M had a significant increase compared with that in the group 3M,7M (P<0.05), and had no Statistically significance among 4M,5M and 6M groups nor between 3M group and 7M group.Conclusion:1. proNGF,p75 and sortilin are expressed in the development of human embryonic spinal cord from the 3th to 7th month, proNGF and p75 was expressed in the sensory-related areas such as the dorsal part of spinal cord gray matter, dorsal part of white matter and so on, as well as the motor neurons in the spinal ventral horn. while sortilin is widely expressed in the nerve cells and nerve fibres in the spinal cord. These evidences indicated that proNGF, p75 and sortilin plays a role in the development of spinal cord with its motor function and sensory function.2. In the 3M-7M of the human embryonic spinal cord developing, the differential expression of proNGF and p75 in the sites related to sensory function in the spinal cord at different times groups, suggesting that its closely related to the spinal cord sensory function development. Given the important role of proNGF/p75/sortilin complex in mediating apoptosis, suggesting that its main impact of apoptosis in sensory nerves development, plays an important role in the development of human embryo spinal cord sensory nerves.3. proNGF, p75 and sortilin mRNA expression in the development of human embryo spinal cord 3M-7M were first increased and then decreased, suggesting the apoptosis mediated by the proNGF/p75/sortilin complex in the development of human embryo spinal cord 3M-7M was first increased and then decreased.