Fig. 7.

Bmp-2 and bmp-4 transcripts are expressed within EB lesions while noggin mRNA is only weakly expressed. Retroviral transduction of adult OPCs with the BMP antagonist noggin is sufficient to block their differentiation into Schwann-like cells following engraftment into EB lesions. White arrows (E, F) denote P0⁺ ventral nerve roots. (A) RT-PCR analysis of micro-dissected EB lesioned tissue and contralateral uninjured VLF 6 days after EB injection reveals expression of both bmp-2 and bmp-4 mRNA in both demyelinated and uninjured tissue. Noggin mRNA is clearly present in the uninjured VLF tissue but barely detectable in the demyelinated VLF. (B) Adult OPCs are potentially responsive to BMPs as evidenced by their expression of transcripts for bmpr-Ia and bmpr-II. Adult OPCs only weakly express bmpr-Ib. (C) RT-PCR analysis of astrocytes, naïve adult OPCs, and noggin-transduced adult OPCs reveals expression of noggin mRNA in transduced adult OPCs and astrocytes while naïve adult OPCs only weakly express noggin. (D–F) Adult OPCs transduced with a retrovirus to express green fluorescent protein (GFP) and noggin fail to differentiate into P0⁺ Schwann-like cells 4 weeks after engraftment. Upper left inset in (D) shows GFP expression by engrafted cells, confirming the presence of noggin-transduced cells within these EB lesions. (G–I) Noggin⁺ adult OPCs do not differentiate into remyelinating oligodendrocytes as evidenced by a lack of MBP expression within Noggin-adult OPC engrafted EB-X lesions. Scale bar = 250 μm (D–F); 100 μm (G–I).