By David N. Leff

Editor's note: Science Scan is a roundup of recently published biotechnology-relevant research.

A visitor from outer space who looked at TV commercials and pharmacy over-the-counter shelves might conclude that every human being on earth had arthritis. This alien observer might not be that far off.

In fact, the joint degradation and bone growths that mark rheumatoid and osteoarthritis afflict not only every member of Homo sapiens during his or her aging process (often without symptoms), but all vertebrates. Paleorheumatologists suggest these effects are not really diseases per se, but evolution at work rebuilding, repairing and remodeling bones and joints to keep up with humankind's transition from an arboreal lifestyle to standing on its own two feet.

Consider the sloth, which spends its life hanging upside down from a branch. Sloths, almost alone among animals, never get arthritis. People who lead a slothful lifestyle tend to suffer most.

Suffering and swelling are the hallmarks of arthritic joints. A physician treating the ailment can choose from some five dozen arthritis medications, all essentially painkillers. None purports to treat, cure, reverse or halt the cartilage-degradation that causes the disease. The only outright cure, such as it is, replaces the destroyed joint with a prosthesis.

Now a report in the current issue of Science, dated June 4, 1999, hints at a therapeutic step up from merely alleviating pain. It bears the title: "Purification and cloning of aggrecanase-1: A member of the ADAMTS family of proteins."

Its first author, biochemist M. D. Tortorella, is a senior research scientist in the inflammatory laboratory at DuPont Pharmaceuticals Co. in Wilmington, Del.

I think what we report in this paper," Tortorella told BioWorld Today, "is a major breakthrough, because basically aggrecanase is one of two enzymes we believe to be responsible for the aggrecan degradation that occurs in rheumatoid and osteoarthritis. Aggrecan degradation is the first event that takes place in these two diseases.

"Aggrecan," he explained, "gives cartilage its flexibility and resilience. When it's depleted, the cartilage becomes dysfunctional, and that leads to mechanical dysfunction of the joint, which eventually requires a joint replacement. The fact that we identified the two enzymes responsible for the aggrecan degradation, we think, gives us a protocol therapeutic target in terms of trying to deter, or actually stop, the disease as a whole."

The DuPont co-authors are now testing in vivo small-molecule inhibitors of those proteases, which are "potently selective for aggrecanase models." Tortorella made the point that "osteoarthritis and rheumatoid arthritis are very complex diseases, and the consensus is that there's really no true, standard animal model of them. So we are testing our candidate inhibitors in various animal models that closely mimic cartilage degradation, not arthritis. Our goal is to develop an orally available drug. So far, the results look very positive."

He concluded: "This would be the first arthritis drug, if successful, that actually stopped the process of cartilage degradation, as opposed to pain relief."

Making DNA Expression Hereditary By Using Sperm Heads As Transgene Delivery Vehicles

There are more ways than one of transferring DNA into a mammal's genome so that the engineered genes show up in the animal's offspring. Current methods include:

¿ Pronuclear microinjection, now widely used, which involves injecting transgene DNA into the pronucleus of a one-cell mouse embryo. The outcome can't yet be controlled or predicted.

¿ Murine embryonic stem cell lines transfected with vectors capable of genomic homologous recombination, which affords better control, but is limited to mice.

A paper in the May 14, 1999, issue of Science observes, "Limitations in the available strategies for modifying mammalian germ lines have fueled a search for alternative methods, including:

¿ Recombinant retroviruses to infect oocytes or preimplantation embryos.

¿ Replication-deficient adenovirus-mediated delivery systems.

¿ Spermatozoa as vehicles for DNA delivery during in vitro fertilization.

"This last approach," the Science paper pointed out, "is of limited use because of its unreliability." That paper's title, "Mammalian transgenesis by intracytoplasmic sperm injection," discloses an alternative to all of the above methods, which seeks to circumvent their respective shortcomings.

Rather than using intact spermatozoa, the co-authors, at the University of Hawaii School of Medicine in Honolulu, employ just the heads of the sperm cells, obtained by membrane disruption, freeze-drying or freeze-thawing. To test the ability of this truncated DNA delivery vehicle, they coinjected into mouse embryos the sperm heads plus a transgene fragment encoding green fluorescent protein (GFP) as a visible reporter.

The embryonic first-division cells displayed fluorescence in 64 percent to 87 percent of their number (depending on disruption technique). But in those that had received full-length sperm rather than heads alone, the expression rate was 26 percent.

"These data," the paper noted, "indicate that coinjection of membrane-disrupted sperm heads and exogenous DNA into unfertilized oocytes can efficiently produce transgenic embryos."

High proportions (17 percent to 21 percent) of embryos transferred from culture to surrogate mothers were transgenic, as evidenced by fluorescence of their skin. Of 11 GFP-expressing founder mice - seven female, four male - eight produced progeny expressing GFP.

The paper concluded, "The technique described here will have widespread applicability." An accompanying journal summary spelled this out as applicable "to a variety of animals, including cattle and pigs."