Differential proliferative responses of cultured Schwann cells to axolemma and myelin-enriched fractions. II. Morphological studies

Meador‐Woodruff, James H.; Yoshino, Jun; Bigbee, John W.; Lewis, Brenda L.; DeVries, George H.

doi:10.1007/bf01200801

Cited by 38 publications

(30 citation statements)

References 38 publications

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“…These results are in agreement with previous observations that used a fluorescein-conjugated myelin fraction (9). Despite the presence of immunoreactive material in almost every Schwann cell, only 1% of the cells treated with the myelin-enriched fraction for 24 h were labeled [3n]thymidine.…”

Section: Discussionsupporting

confidence: 93%

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Developmental changes in myelin-induced proliferation of cultured Schwann cells.

Yoshino¹,

Mason²,

DeVries³

1987

The Journal of Cell Biology

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Abstract. Schwann cell proliferation induced by a myelin-enriched fraction was examined in vitro. Although nearly all the Schwann cells contained material that was recognized by antisera to myelin basic protein after 24 h, only 1% of the cells were synthesizing DNA. 72 h after the addition of the mitogen a maximum of 10% of the cells incorporated [3H]thymidine. If the cultures were treated with the myelin-enriched fraction for 24 h and then washed, the number of proliferating Schwann cells decreased by 75 % when compared with those cells that were incubated with the mitogen continuously. When Schwann cells were labeled with [~C]thymidine followed by a pulse of [3H]thymidine 24 h later, every Schwann cell labeled with [3H]thymidine was also labeled with [~4C]thymidine. Although almost every Schwann cell can metabolize the myelin membranes within 24 h of exposure, a small population of cell initially utilizes the myelin as a mitogen, and this population continues to divide only if myelin is present in the extracellular media. The percentage of the Schwann cells that initially recognize the myelinenriched fraction as a mitogen is dependent upon the age of the animal from which the cells were prepared. CULTURED Schwann cells proliferate when treated with axolemma-or myelin-enriched fractions (15). The mitogenic activities of the membrane fractions could be differentiated by their dose-response curves and their sensitivity to the lysosomal inhibitor, ammonium chloride. Also, the rates of [3H]thymidine incorporation by Schwann cells treated with the myelin-enriched fraction were not identical when compared with those cells incubated with the axolemmal membranes. Schwann cells that were exposed to the myelin-enriched fraction for 72 h accumulated three times as much [3H]thymidine as those that were incubated with the mitogen for only 48 h. This sudden increase in proliferation coincided temporarily with similar periods of Schwann cell division during Wallerian degeneration in vitro (14) and in vivo (4).In the present study, we have examined by autoradiography the kinetics of Schwann cell proliferation induced with a myelin-enriched fraction in vitro. The large increase in proliferation that occurs 72 h after the administration of the mitogen is the result of a small population of Schwann cells that initially divides in response to the mitogen and whose daughter cells subsequently continue to proliferate if the membrane fraction is present in the extracellular media. The number of Schwann ceils that divide initially when treated with the myelin-enriched fraction is related to the age of the animal from which the cells were prepared. Materials and MethodsHF ~ is DME (Gibco Laboratories, Grand Island, NY) with sodium bicarbonate and 10% FCS (HyClone Laboratories, Logan, UT). Saline G is a 1. Abbreviation used in this paper: HE DME with sodium bicarbonate and 10% FCS. balanced salt solution containing 125 mM NaCI, 5 mM KCI, 0.7 mM MgSO4, 0.1 mM CaCI2, 1 mM KH2PO4, and 1 mM Na2HPO4. Forskolin (Calbiochem-Behring Corp., La J...

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Section: Discussionsupporting

confidence: 93%

“…Primary cultures of Schwann cells were prepared as described by Brockes et al (5) and modified by Meador-Woodruff et al (9). Briefly, the sciatic nerves of 2-d-old rat pups were excised, treated with collagenase and trypsin, and plated in 10-cm glass petri dishes in HF media.…”

Section: Preparation Of Cultured Schwann Cellsmentioning

confidence: 99%

Developmental changes in myelin-induced proliferation of cultured Schwann cells.

Yoshino¹,

Mason²,

DeVries³

1987

The Journal of Cell Biology

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“…Cultured peritoneal macrophages that had been treated with MEF for 24 or 48 hr were fixed and processed for electron microscopy as described (17). RESULTS…”

Section: Methodsmentioning

confidence: 99%

Macrophage-mediated myelin-related mitogenic factor for cultured Schwann cells.

Baichwal

Bigbee

DeVries

1988

Proc. Natl. Acad. Sci. U.S.A.

131

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Conditioned medium from cultured peritoneal macrophages that have phagocytosed a myelin membrane fraction is mitogenic for cultured Schwann cells. Production of the mitogenic supernatant was time-and dose-dependent with a maximal Schwann cell-proliferative response from supernatants after 48-hr incubation of cultured macrophages with myelin-enriched fraction (200 ,ug of protein per ml). The response was specific for myelin membrane: supernatants derived from macrophages incubated with axolemma, liver microsomes, polystyrene beads, or lipopolysaccharide were not mitogenic. Lysosomal processing of the myelin membrane was necessary for the production of the mitogenic factor, which was shown to be heat labile and trypsin sensitive. There was no species specificity because myelin membranes isolated from the central and peripheral nervous systems of rat, bovine, and human were equally potent in eliciting mitogenic supernatant. However, supernatants derived from central nervous system myelin membranes were two to three times more mitogenic than those obtained from peripheral nervous system fractions of the same species. Previous observations that myelin is mitogenic for cultured Schwann cells may, in part, involve the intermediate processing of myelin by macrophages that are present in Schwann cell cultures. These results suggest that macrophages play a crucial role in Schwann cell proliferation during Wallerian degeneration.The source of the mitogenic signal for Schwann cell division during Wallerian degeneration is not clear. Removal of myelin sheaths accompanying Wallerian degeneration has been ascribed to Schwann cells (1, 2) as well as macrophages (3-5). Beuche and Friede (5) observed that Wallerian degeneration proceeding without nonresident phagocytic cells (macrophages) showed no Schwann cell proliferation and no active intracellular digestion of myelin-implying that myelin membranes were removed solely by macrophages after nerve degeneration. This observation also suggests that Schwann cell proliferation is related to myelin removal by macrophages. Salzer and Bunge (6) using dorsal root ganglion explant cultures showed that only myelin-related Schwann cells proliferate after axotomy. In contrast, however, in vivo studies by Pellegrino et al. (7) (9). The presence of macrophages in our Schwann cell cultures and the possible involvement of macrophages in removal of myelin debris during Wallerian degeneration (10) prompted us to study the role of macrophages in mediating mitogenicity of myelin for cultured Schwann cells. Using rat peritoneal macrophages, we have shown that macrophages stimulated with MEF produce a soluble factor(s) mitogenic for cultured Schwann cells. Production of the soluble mitogenic factor shows a time-and dose-dependent response. Other membrane fractions or nonspecific agents do not stimulate macrophages to produce a mitogenic-conditioned medium. The myelin membrane undergoes lysosomal processing in the macrophage before mitogenic factor is produced. Sensitivity of the mitogenic sup...

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“…Much evidence has shown that the digestive process of myelin is intimately related to Schwann cell proliferation (1,2,5,8,11,20,21). The removal of the myelin sheath elicited proliferative response of Schwann cells (5,12,16).…”

mentioning

confidence: 99%

The role of Schwann cells and macrophages in the removal of myelin during Wallerian degeneration.

Han

Piao

Guo

et al. 1989

Acta Histochem. Cytochem.

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Axonal changes, in particular the breakdown and removal of the myelin sheath, were studied using morphological method and cytochemical technique in the sciatic nerves of rats following transection. The details of axonal loss were examined during the first few days after transection. Axonal degradation was immediately accompanied by the fragmentation of the myelin sheath. It was found that: (a) a part of the myelin sheath separated from Schwann cells and smashed into debris, then the myelin debris was phagocytosed and digested by macrophages at endoneurial space; the others, most of the myelin sheath, remained within Schwann cells until being digested; (b) both small debris of myelin sheath (SDMS) and large membrane-bound myelin debris (LMBMD) were found in Schwann cells; acid phosphatase (AcPase) activity was detected in SDMS earlier than in LMBMD; (c) macrophages were found in myelin sheath tubes; they participated in removing a part of degenerating axons. Observation confirmed that Schwann cells had no ability to actively phagocytose myelin, that the majority of myelin debris were removed by Schwann cells, and that the minority of them were dealt with by macrophages. The ability of Schwann cells to digest myelin debris suggested that Schwann cells play a crucial role in vivo in removing myelin debris and that the process of myelin debris in Schwann cells might be significant for their mitotic activity.

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Differential proliferative responses of cultured Schwann cells to axolemma and myelin-enriched fractions. II. Morphological studies

Cited by 38 publications

References 38 publications

Developmental changes in myelin-induced proliferation of cultured Schwann cells.

Developmental changes in myelin-induced proliferation of cultured Schwann cells.

Macrophage-mediated myelin-related mitogenic factor for cultured Schwann cells.

The role of Schwann cells and macrophages in the removal of myelin during Wallerian degeneration.

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