If shark cartilage is extracted for I day (the usual practice
for calf cartilage) rather than 41 days, only a small amount of activity
is detected. This may be be. cause shark cartilage possesses a more tightly
calf cartilage, as judged by (i) the resistance
of shark, but not calf, cartilage to dissolution by 4M guanidine and (ii)
histological examination by safranin 0 post-extraction, which showed disruption
of the collagen. proteoglycan structure in calf, but not shark, cartilage.
The concentration of guanidine is also important in extracting the inhibitor
from shark cartilage. Guanidine concentrations of 2M and above extract
more material, but some of the chemicals in this material cause severe
inflammation in the rabbit cornea.
While the mechanism by which angio- genesis inhibitors function is unknown,
a critical step in capillary advancement is the degradation of surrounding
connective tissue (14). It has been speculated that angiogenesis
inhibitors block proteolytic enzymes, such as trypsin or collagenase,
responsible for this degradation (1, 15). We found that shark cartilage
contains about one-fiftieth of the specific trypsin inhibitory activity
of calf cartilage extracts. However, the shark extract had much more potent
angiogenesis inhibitory activity than the calf ex- tract. The result is
significant because trypsin inhibition had been correlated with angiogenesis
inhibition in calf cartilage (1, 15).
We also found, using a film plate assay (16), that shark cartilage contains
inhibitory activity against type I collagenase from rabbit cornea. For
example, 3.75 mg of extract per milliliter caused 44 percent inhibition
of 0.05 U of collagenase. However, when the specific activity of the shark
extract was increased 20 times by fractionation on a Biogel A 1.5- m column
(maximum collagenase inhibi- tion was observed at 35,000 daltons) and this
material was tested for angiogenesis inhibitory activity in the rabbit
corneal assay, no significant inhibition was observed.
SCIENCE. VOL. 221
Inhibition of capillary growth induced by V2 carcinoma by polymer pellets
containing shark fin extract. The left corneas of three rabbits were implanted
with tumors and empty polymer pellets and served as controls. The
right corneas were implanted with tumors and polymer pellets containing
the shark cartilage extract. The rabbits were killed on day 19 because
the tumors in all the left eyes be- came three-dimensional and necrotic.
2. Lower halves of rabbit corneas 19 days after the implantation of V2
tumor (T) and a polymer pellet (P) containing the inhibitor (a) or V2 tumor
and a pellet with- out the inhibitor (b). The tip of the tumor was initially
placed 2.0 mm from the edge of the cornea, and the pellet (surface area,
I mm2) was placed directly below it with its tip 1.0 mm from the corneal
edge. The blood vessels appear as a black sheet sweeping over the polymer
pellet and the tumor in the control (b). However, they do not grow nearly
as rapidly in the experimental cornea (a) and form a zone of inhibition
However, a more purified type I collagenase inhibitor
against other types of collagenases, particularly
type IV, which can degrade casement membrane collagen (17), should be tested.
The high angiogenesis inhibitory activity present in shark cartilage should
not only be helpful in exploring the enzyme inhibition profile of angiogenesis
inhibitors also in cartilage, but also in conducting antitumor studies.
Department of Nutrition and Food Science and Whitaker
Health Sciences, Technology, and
Management, Massachusetts Institute
of Technology, Cambridge 02139, and Department
Children's Hospital Medical Center
Boston, Massachusetts 02115
References and Notes
1. R. Langer, H. Brem, K. Falterman, M. Klein,
Science 193, 70 (1976).
2. R. Langer, H. Conn, J. Vacanti, C. Haudenschild,
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Biotechnol. 8, 9 (1983).
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C. Lillehei, Exp. Cell Res. 105, 99 (1977).
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Experientia 30, 595 (1974).
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14. D. Ausprunk and J. Folkman, Microvasc.
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Soble, R. Eisenstein, Lab. Invest. 32, 217 (1975).
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18. Supported by the MIT Sea Grant and NIH grant
We thank J. Glowacki, J. Schuck, 0. Bronster,
M. van Beuzekom, J. Murray, J. Sudhalter, and B. J. Wint for assistance.
To whom correspondence should be addressed at Massachusetts Institute of
Technology. 19 April 1983; revised I July 1983
to Shark Cartilage index
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