Unconjugated
Bone morphogenetic proteins (BMPs) are members of the transforming growth factor β (TGF-β) superfamily. BMPs, such as BMP2 and BMP4, exert its biological functions by interacting with membrane bound receptors belonging to the serine/threonine kinase family including bone morphogenetic protein receptor I (BMPRIA, BMPRIB) and type II (BMPRII). Functions of BMPs are also regulated in the extracellular space by secreted antagonistic regulators such as noggin. Although BMP2, BMP4, noggin, BMPRIA, BMPRIB, and BMPRII expressions have been well described in the central nervous system, little information is available for their expressions in the spinal cord. We, thus, investigated these protein expressions in the adult rat spinal cord using immunohistochemistry. Here, we show that BMP2, BMP4, noggin, BMPRIA, BMPRIB, and BMPRII are widely and differentially expressed in the spinal cord. Besides abundant BMP2, BMP4, noggin, BMPRIA, BMPRIB, and BMPRII protein expressions in neurons, we detected them also in astrocytes, oligodendrocytes, and ependymal cells. In addition, we found BMPRIA, BMPRIB, and BMPRII protein expressions in microglia. Interestingly, we also observed that these proteins are strongly expressed in many kinds of axons in both ascending and descending tracts. These data indicate that BMP2, BMP4, noggin, BMPRIA, BMPRIB, and BMPRII proteins are more widely expressed in the adult spinal cord than previously reported, and their continued abundant expressions in the adult spinal cord strongly support the idea that BMP signaling plays pivotal roles in the adult spinal cord.
STUDY DESIGN:
We used a complete spinal cord transection model and locomotor function, histological, and immunohistochemical examinations to evaluate the effects of local injection of lentivirus/LINGO-1-short hairpin RNA (VL) on rats with spinal cord injury (SCI).
OBJECTIVE:
To demonstrate the neuroregenerative and neuroprotective effects of LINGO-1 RNAi on complete transection SCI rats.
SUMMARY OF BACKGROUND DATA:
LINGO-1 has been reported as a negative regulator of axonal sprouting and its antagonist was determined to improve functional outcomes in SCI rats. However, it has not been assessed whether blockade of LINGO-1 mediated by lentivirus vectors could stimulate neural recovery after SCI.
METHODS:
Complete spinal cord transection was made at T10 level. Suspension of lentivirus vectors encoding LINGO-1-short hairpin RNA was injected into the lesion gap. Controls received control vectors in the same manner and the sham group was subjected to laminectomy only. The Basso-Beattie-Bresnahan scale and surface righting reflex test were used to evaluate functional outcomes. Finally, the spinal cords were harvested for histological and immunohistochemical analysis.
RESULTS:
The treatment with VL improved Basso-Beattie-Bresnahan scores and surface righting reflex after SCI. Tissue repair was facilitated and the cavity area was significantly decreased in VL-treated animals. More sprouting and myelinated nerve fibers were detected within the injured site in the VL group as compared with the control. In addition, the number of survival neurons and oligodendrocytes around the epicenter was notably higher under the VL condition.
CONCLUSION:
Local injection of lentivirus/LINGO-1-short hairpin RNA after complete transection of spinal cord resulted in meaningful histological and functional outcomes in rats. The mechanism of VL protection may be related to its promotion of axonal sprouting, remyelination, and cell survival.
