Humoral and Tissue Factors in Tissue
Differentiation
by
P.
J.
GAILLARD1
From the Laboratory for Experimental Histology, State University of Leyden
I T was shown by Gaillard (1931,1935,1942) that pure strains of fibroblastic cells
are very sensitive to those differences in the culture media which go hand in hand
with the process of ageing of the donors used for preparing the media, the dimensional growth of the explants being used as a criterion. Moreover, strains of
different origin reacted in a different way, thus demonstrating that cells which
are morphologically alike can behave quite differently in vitro. When cultivating
such a pure strain derived from the anlage of the frontal bone of a 15-day-old
chicken embryo successively in a range of culture media prepared from 10-, 15-,
and 18-day-old embryos, serum from a newly hatched chicken, and serum from
an adult hen, histological bone formation occurred after 12 days of cultivation.
This means that the realization of this obviously existing potentiality depended
on the composition of the successive media.
The same principle emerged from experiments with the cartilaginous primordium of long bones from rat embryos (Gaillard, 1942; Verdam, 1946) and from
human and chick fetuses (Zaaijer, 1953). During the cultivation of thyroid
gland tissue derived from 8-day-old chicken embryos (Gaillard, 1949a, 1952) the
'age' of the medium also appeared to be decisive for the development of organotypical structure.
These and other observations led to a chemical analysis of the culture media
used, but so far no conclusive results have been obtained.
Another factor came under consideration through cultivating human parathyroid tissue (Kooreman & Gaillard, 1950c), human ovarian cortex (Gaillard,
19496, 1950a, 19506, 1951), and rabbit anterior hypophysis tissue (Gaillard,
1942). In these cases only those cultures tended to show an organotypical character which became completely encapsulated by a layer of epithelial cells some
days after explantation. Thus in cultures of ovarian cortical tissue a complete
degeneration of the parenchyma even occurred when no capsule of germinal
epithelium was present. Likewise in the above-mentioned experiments of Miss
Zaaijer with human bone primordia the encapsulation by a sheath of epidermal
1
Author's address: Laboratory for Experimental Histology, Faculty of Medicine, State University of Leyden, Wassenaarseweg, Boerhaavekwartier, Leiden, Holland.
[J. Embryol. exp. Morph. Vol. 1, Part 3, pp. 289-290, September 1953]
290
P. J. GAILLARD—FACTORS IN D I F F E R E N T I A T I O N
cells appeared necessary for a balanced development of the epiphysial versus
diaphysial zones.
The role of the epithelial encapsulation, however, has not yet been fully analysed, although it seems highly improbable that mechanical factors are of great
importance. In the case of the ovarian cortex it became evident that the epithelial
cell layer gave rise to cord-like proliferations with numerous oocytes and that this
layer was thus responsible for regenerating ovarian cortical tissue, while the interior parenchyma completely degenerated. In the other cases, however, nothing
of this kind could be found, but it became clear that some kind of mutual influence existed between epithelium and subcutaneous connective tissue and cartilage in Miss Zaaijer's experiments.
The importance of these tissue interactions as determining factors in histological differentiation processes was most clearly demonstrated in experiments with
confronted explants of the anterior and posterior lobes of the rabbit hypophysis
(Gaillard, 1937,1942). In contrast with a series of other tissues, the posterior lobe
tissue caused a typical change of structure in the adjacent parts of the anterior
lobe fragments. By the 'disappearance' of acidophil cells and by the development
of cyst-like structures some structural features characteristic of intermediate lobe
tissue occurred, and indeed it was suggested that perhaps in vivo the continuous interaction of posterior and anterior lobe tissue is responsible for the
development and existence of the intermediate lobe of the hypophysis.
REFERENCES
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(1949a). Ned. Tijdschr. Geneesk. 93, No. 5.
(19496). Journees Cyto-Embr. Belgo-Need., Gand.
(1950a). Proc. Akad. Sci. Amst. 53, 8.
(19506). Proc. Akad. Sci. Amst. 53, 9.
(1951). Methods in Medical Research, 4. Chicago: The Yearbook Publishers.
(1952). Versl. gewone Vergad. Akad. Amst. 61, No. 2.
KOOREMAN, P. J., & GAILLARD, P. J. (1950). Arch. Chir. need. 2, fasc. 4.
VERDAM, H. D. (1946). Thesis, State University of Leyden.
ZAAIJER, J. J. P. (1953). Thesis, State University of Leyden.