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Pío del Río Hortega and the discovery of the oligodendrocytes.

Pérez-Cerdá F, Sánchez-Gómez MV, Matute C - Front Neuroanat (2015)

Bottom Line: Del Río Hortega became internationally recognized and established an important neurohistological school with outstanding pupils from Spain and abroad, which nearly disappeared after his exile due to the Spanish civil war.Yet, the difficulty of metal impregnation methods and their variability in results, delayed for some decades the confirmation of his great insights into oligodendrocyte biology until the development of electron microscopy and immunohistochemistry.This review aims at summarizing the pioneer and essential contributions of del Río Hortega to the current knowledge of oligodendrocyte structure and function, and to provide a hint of the scientific personality of this extraordinary and insufficiently recognized man.

View Article: PubMed Central - PubMed

Affiliation: Achucarro Basque Center for Neuroscience, Departamento de Neurociencias and CIBERNED, Universidad del País Vasco (UPV/EHU) Leioa, Spain.

ABSTRACT
Pío del Río Hortega (1882-1945) discovered microglia and oligodendrocytes (OLGs), and after Ramón y Cajal, was the most prominent figure of the Spanish school of neurology. He began his scientific career with Nicolás Achúcarro from whom he learned the use of metallic impregnation techniques suitable to study non-neuronal cells. Later on, he joined Cajal's laboratory. and Subsequently, he created his own group, where he continued to develop other innovative modifications of silver staining methods that revolutionized the study of glial cells a century ago. He was also interested in neuropathology and became a leading authority on Central Nervous System (CNS) tumors. In parallel to this clinical activity, del Río Hortega rendered the first systematic description of a major polymorphism present in a subtype of macroglial cells that he named as oligodendroglia and later OLGs. He established their ectodermal origin and suggested that they built the myelin sheath of CNS axons, just as Schwann cells did in the periphery. Notably, he also suggested the trophic role of OLGs for neuronal functionality, an idea that has been substantiated in the last few years. Del Río Hortega became internationally recognized and established an important neurohistological school with outstanding pupils from Spain and abroad, which nearly disappeared after his exile due to the Spanish civil war. Yet, the difficulty of metal impregnation methods and their variability in results, delayed for some decades the confirmation of his great insights into oligodendrocyte biology until the development of electron microscopy and immunohistochemistry. This review aims at summarizing the pioneer and essential contributions of del Río Hortega to the current knowledge of oligodendrocyte structure and function, and to provide a hint of the scientific personality of this extraordinary and insufficiently recognized man.

No MeSH data available.


Related in: MedlinePlus

Drawings of the cerebral cortex (A) and white matter (B,C) after staining with the Golgi-Hortega method or the silver carbonate procedure by Hortega (inset in A). (A) Notice pyramidal neurons (PN), protoplasmic astrocytes (PA), vessels (V), and type I oligodendrocytes (OLGs; O-I) with variable number of processes, many of them divided in “Y” or “T”. Some OLGs have processes mainly oriented in the direction of projecting axons (O-I1), while others have a perivascular (O-I2) or perineuronal (O-I3; see inset) localization. (B) Note a fibrous astrocyte (FA), some OLGs of the first type (O-I) and one of the second type (O-II), as well as microglia cells (M). (C) See type I OLGs similar to those in (A, B) (O-I) or with long processes that follow axons (O-I4), and two dwarf astrocytes (DA). Vessels (V) are also drawn in (B,C). Magnification in Figures (A–C) is similar. Modified from Del Río Hortega (1928).
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Figure 1: Drawings of the cerebral cortex (A) and white matter (B,C) after staining with the Golgi-Hortega method or the silver carbonate procedure by Hortega (inset in A). (A) Notice pyramidal neurons (PN), protoplasmic astrocytes (PA), vessels (V), and type I oligodendrocytes (OLGs; O-I) with variable number of processes, many of them divided in “Y” or “T”. Some OLGs have processes mainly oriented in the direction of projecting axons (O-I1), while others have a perivascular (O-I2) or perineuronal (O-I3; see inset) localization. (B) Note a fibrous astrocyte (FA), some OLGs of the first type (O-I) and one of the second type (O-II), as well as microglia cells (M). (C) See type I OLGs similar to those in (A, B) (O-I) or with long processes that follow axons (O-I4), and two dwarf astrocytes (DA). Vessels (V) are also drawn in (B,C). Magnification in Figures (A–C) is similar. Modified from Del Río Hortega (1928).

Mentions: Del Río Hortega rendered the first systematic description of oligodendrocytes (OLGs) in an article published in 1928 (Del Río Hortega, 1928; Figures 1, 2). Nevertheless, the complete story of his discovery had already begun when he described microglia (Del Río Hortega, 1920; Castellano-López and González-de Mingo, 1995; Pasik and Pasik, 2004) as the third element, mentioning the existence of a new cell type of neuroglia, the interfascicular glia, made up by cells showing very fine processes and arranged in groups among axonal tracts. Surely this distinction was only made possible using the new silver carbonate impregnation method developed by him (Del Río Hortega, 1918). In 1921, he named these cells as oligodendroglia or glia with very few processes (Del Río-Hortega, 1921), because they were present not only in white matter but diffusely distributed in all regions of the CNS and commonly grouped next to neurons in gray matter. He was aware that as many other histochemical techniques involving metallic silver impregnations, his silver carbonate method had very specific requirements, which did not, however, guarantee reproducible results in every preparation. Despite the results were very variable in terms of staining, he predicted the relationship of oligodendroglia with myelination, its implication in neuronal trophism, and its ectodermal origin. In fact, one year later (Del Río Hortega, 1922) proposed that these cells were functionally similar to Schwann cells in the CNS and responsible for myelination. However, the demonstration of oligodendroglia as cells that produce and maintain the myelin sheaths that insulate CNS axons had to wait for the introduction of electron microscopy in the 1960s (reviewed in Verkhratsky and Butt, 2007; Butt, 2013). This temporal gap, together with difficulties in oligodendroglia staining until the introduction of immunohistochemical techniques, and that the seminal articles by Del Río Hortega were published in Spanish, made his discovery of oligodendroglia not recognized internationally, as his discovery of microglia was, and restricted to scientists, who were histologists (Castellano-López and González-de Mingo, 1995; Pasik and Pasik, 2004).


Pío del Río Hortega and the discovery of the oligodendrocytes.

Pérez-Cerdá F, Sánchez-Gómez MV, Matute C - Front Neuroanat (2015)

Drawings of the cerebral cortex (A) and white matter (B,C) after staining with the Golgi-Hortega method or the silver carbonate procedure by Hortega (inset in A). (A) Notice pyramidal neurons (PN), protoplasmic astrocytes (PA), vessels (V), and type I oligodendrocytes (OLGs; O-I) with variable number of processes, many of them divided in “Y” or “T”. Some OLGs have processes mainly oriented in the direction of projecting axons (O-I1), while others have a perivascular (O-I2) or perineuronal (O-I3; see inset) localization. (B) Note a fibrous astrocyte (FA), some OLGs of the first type (O-I) and one of the second type (O-II), as well as microglia cells (M). (C) See type I OLGs similar to those in (A, B) (O-I) or with long processes that follow axons (O-I4), and two dwarf astrocytes (DA). Vessels (V) are also drawn in (B,C). Magnification in Figures (A–C) is similar. Modified from Del Río Hortega (1928).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4493393&req=5

Figure 1: Drawings of the cerebral cortex (A) and white matter (B,C) after staining with the Golgi-Hortega method or the silver carbonate procedure by Hortega (inset in A). (A) Notice pyramidal neurons (PN), protoplasmic astrocytes (PA), vessels (V), and type I oligodendrocytes (OLGs; O-I) with variable number of processes, many of them divided in “Y” or “T”. Some OLGs have processes mainly oriented in the direction of projecting axons (O-I1), while others have a perivascular (O-I2) or perineuronal (O-I3; see inset) localization. (B) Note a fibrous astrocyte (FA), some OLGs of the first type (O-I) and one of the second type (O-II), as well as microglia cells (M). (C) See type I OLGs similar to those in (A, B) (O-I) or with long processes that follow axons (O-I4), and two dwarf astrocytes (DA). Vessels (V) are also drawn in (B,C). Magnification in Figures (A–C) is similar. Modified from Del Río Hortega (1928).
Mentions: Del Río Hortega rendered the first systematic description of oligodendrocytes (OLGs) in an article published in 1928 (Del Río Hortega, 1928; Figures 1, 2). Nevertheless, the complete story of his discovery had already begun when he described microglia (Del Río Hortega, 1920; Castellano-López and González-de Mingo, 1995; Pasik and Pasik, 2004) as the third element, mentioning the existence of a new cell type of neuroglia, the interfascicular glia, made up by cells showing very fine processes and arranged in groups among axonal tracts. Surely this distinction was only made possible using the new silver carbonate impregnation method developed by him (Del Río Hortega, 1918). In 1921, he named these cells as oligodendroglia or glia with very few processes (Del Río-Hortega, 1921), because they were present not only in white matter but diffusely distributed in all regions of the CNS and commonly grouped next to neurons in gray matter. He was aware that as many other histochemical techniques involving metallic silver impregnations, his silver carbonate method had very specific requirements, which did not, however, guarantee reproducible results in every preparation. Despite the results were very variable in terms of staining, he predicted the relationship of oligodendroglia with myelination, its implication in neuronal trophism, and its ectodermal origin. In fact, one year later (Del Río Hortega, 1922) proposed that these cells were functionally similar to Schwann cells in the CNS and responsible for myelination. However, the demonstration of oligodendroglia as cells that produce and maintain the myelin sheaths that insulate CNS axons had to wait for the introduction of electron microscopy in the 1960s (reviewed in Verkhratsky and Butt, 2007; Butt, 2013). This temporal gap, together with difficulties in oligodendroglia staining until the introduction of immunohistochemical techniques, and that the seminal articles by Del Río Hortega were published in Spanish, made his discovery of oligodendroglia not recognized internationally, as his discovery of microglia was, and restricted to scientists, who were histologists (Castellano-López and González-de Mingo, 1995; Pasik and Pasik, 2004).

Bottom Line: Del Río Hortega became internationally recognized and established an important neurohistological school with outstanding pupils from Spain and abroad, which nearly disappeared after his exile due to the Spanish civil war.Yet, the difficulty of metal impregnation methods and their variability in results, delayed for some decades the confirmation of his great insights into oligodendrocyte biology until the development of electron microscopy and immunohistochemistry.This review aims at summarizing the pioneer and essential contributions of del Río Hortega to the current knowledge of oligodendrocyte structure and function, and to provide a hint of the scientific personality of this extraordinary and insufficiently recognized man.

View Article: PubMed Central - PubMed

Affiliation: Achucarro Basque Center for Neuroscience, Departamento de Neurociencias and CIBERNED, Universidad del País Vasco (UPV/EHU) Leioa, Spain.

ABSTRACT
Pío del Río Hortega (1882-1945) discovered microglia and oligodendrocytes (OLGs), and after Ramón y Cajal, was the most prominent figure of the Spanish school of neurology. He began his scientific career with Nicolás Achúcarro from whom he learned the use of metallic impregnation techniques suitable to study non-neuronal cells. Later on, he joined Cajal's laboratory. and Subsequently, he created his own group, where he continued to develop other innovative modifications of silver staining methods that revolutionized the study of glial cells a century ago. He was also interested in neuropathology and became a leading authority on Central Nervous System (CNS) tumors. In parallel to this clinical activity, del Río Hortega rendered the first systematic description of a major polymorphism present in a subtype of macroglial cells that he named as oligodendroglia and later OLGs. He established their ectodermal origin and suggested that they built the myelin sheath of CNS axons, just as Schwann cells did in the periphery. Notably, he also suggested the trophic role of OLGs for neuronal functionality, an idea that has been substantiated in the last few years. Del Río Hortega became internationally recognized and established an important neurohistological school with outstanding pupils from Spain and abroad, which nearly disappeared after his exile due to the Spanish civil war. Yet, the difficulty of metal impregnation methods and their variability in results, delayed for some decades the confirmation of his great insights into oligodendrocyte biology until the development of electron microscopy and immunohistochemistry. This review aims at summarizing the pioneer and essential contributions of del Río Hortega to the current knowledge of oligodendrocyte structure and function, and to provide a hint of the scientific personality of this extraordinary and insufficiently recognized man.

No MeSH data available.


Related in: MedlinePlus