Interaction of NG2(+) glial progenitors and microglia/macrophages from the injured spinal cord.
Spinal cord contusion produces a central lesion surrounded by a peripheral rim of residual white matter. Despite stimulation of NG2(+) progenitor cell proliferation, the lesion remains devoid of normal glia chronically after spinal cord injury (SCI). To investigate potential cell-cell interactions of the predominant cells in the lesion at 3 days after injury, we used magnetic activated cell sorting to purify NG2(+) progenitors and OX42(+) microglia/macrophages from contused rat spinal cord. Purified NG2(+) cells from the injured cord grew into spherical masses when cultured in defined medium with FGF2 plus GGF2. The purified OX42(+) cells did not form spheroids and significantly reduced sphere growth by NG2(+) cells in co-cultures. Conditioned medium from these OX42(+) cells, unlike that from normal peritoneal macrophages or astrocytes also inhibited growth of NG2(+) cells, suggesting inhibition by secreted factors. Expression analysis of freshly purified OX42(+) cells for a panel of six genes for secreted factors showed expression of several that could contribute to inhibition of NG2(+) cells. Further, the pattern of expression of four of these, TNFalpha, TSP1, TIMP1, MMP9, in sequential coronal tissue segments from a 2 cm length of cord centered on the injury epicenter correlated with the expression of Iba1, a marker gene for OX42(+) cells, strongly suggesting a potential regional influence by activated microglia/macrophages on NG2(+) cells in vivo after SCI. Thus, the nonreplacement of lost glial cells in the central lesion zone may involve, at least in part, inhibitory factors produced by microglia/macrophages that are concentrated within the lesion.
Department of Neuroscience, Georgetown University Medical Center, Washington, District of Columbia, USA.
Junfang
J
Wu
Soonmoon
S
Yoo
Donna
D
Wilcock
Judith M
JM
Lytle
Philberta Y
PY
Leung
Carol A
CA
Colton
Jean R
JR
Wrathall
D000818:Animals; D000941:Antigens / Q000378:metabolism*; D001253:Astrocytes / Q000502:physiology; D002135:Calcium-Binding Proteins / Q000378:metabolism; D002478:Cells, Cultured; D018920:Coculture Techniques; D017077:Culture Media, Conditioned; D005260:Female; D008264:Macrophages / Q000502:physiology*; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism; D008840:Microfilament Proteins; D017628:Microglia / Q000502:physiology*; D009457:Neuroglia / Q000502:physiology*; D011509:Proteoglycans / Q000378:metabolism*; D051381:Rats; D013119:Spinal Cord Injuries / Q000503:physiopathology*; D013234:Stem Cells / Q000502:physiology*; D019700:Thrombospondin 1 / Q000378:metabolism; D019715:Tissue Inhibitor of Metalloproteinase-1 / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D000099216:Chondroitin Sulfate Proteoglycan 4
D000941:Antigens; D002135:Calcium-Binding Proteins; D017077:Culture Media, Conditioned; D020780:Matrix Metalloproteinase 9; D008840:Microfilament Proteins; D011509:Proteoglycans; D019700:Thrombospondin 1; D019715:Tissue Inhibitor of Metalloproteinase-1; D014409:Tumor Necrosis Factor-alpha; D000099216:Chondroitin Sulfate Proteoglycan 4; C100745:Aif1 protein, rat