Opinion ID: 1038335
Heading Depth: 4
Heading Rank: 3

Heading: combining the conditioned medium

Text: with a pharmaceutically acceptable carrier to form the composition. Id. at claim 1 (emphases added). According to the patentees, a novel and important aspect of their invention is the difference between the conditioned medium produced by cells cultured in twodimensions and in three-dimensions. “While growth of cells in two dimensions is a convenient method for preparing, observing and studying cells in culture,” twodimensional cultures lack “characteristic[s] of whole tissue in vivo.” Id. at col. 2 ll. 15–18. In a section titled SKINMEDICA INC v. HISTOGEN INC 5 “Background of the Invention,” the inventors detail the relevance of that deficiency. Cell lines grown as a monolayer or on beads, as opposed to cells grown in three-dimensions, lack the cell-cell and cell-matrix interactions characteristic of whole tissue in vivo. Consequently, such cells secrete a variety of cellular metabolites although they do not necessarily secrete these metabolites and secreted proteins at levels that approach physiological levels. Conventional conditioned cell culture medium, medium cultured by cell-lines grown as a monolayer or on beads, is usually discarded or occasionally used in culture manipulations such as reducing cell densities. Id. at col. 1 ll. 37–47. The inventors explain in the written description that some researchers have attempted to create cell cultures that replicate the valuable characteristics of whole tissue in vivo. As they say, a “few investigators have explored the use of three-dimensional substrates” to grow cells with such characteristics. Id. at col. 2 ll. 19–20. In such systems, “three-dimensional substrates are inoculated with the cells to be cultured,” and those cells “penetrate the matrix and establish a ‘tissue-like’ histology.” Id. at col. 2 ll. 30–33. “Additionally,” according to the inventors, “various attempts have been made to regenerate tissuelike architecture from dispersed monolayer cultures,” which “could grow to more than ten cells deep” and could develop “organoid structures.” Id. at col. 2 ll. 37–41. The inventors also detail how certain skin cell lines could form “friction ridges if kept for several weeks without transfer,” and other cell lines could form “capillary tubules” in the presence of certain growth factors. Id. at col. 2 ll. 45–51. “However,” the inventors state, “the long term culture and proliferation of cells in such systems has not been achieved.” Id. at col. 2 ll. 55–57. 6 SKINMEDICA INC v. HISTOGEN INC As part of the written description, the inventors discuss a system that is closer to achieving the goal of long term culture and proliferation of cells and that more closely replicates the valuable characteristics of whole tissue in vivo. They indicate that a three-dimensional cell culture system “will sustain active proliferation of . . . cells in culture for much longer time periods than will monolayer systems” and “supports the maturation, differentiation, and segregation of cells in culture in vitro to form components . . . analogous to counterparts found in vivo and . . . proteins [in] the condition[ed] medium more closely resembling physiological ratios.” ’ Id. at col. 11 ll. 11–19. As the inventors describe them in the specification, three-dimensional cell cultures are created by inoculating a “three-dimensional framework” with cells. That framework is expressly defined as “a three-dimensional scaffold” that is “inoculated with stromal cells” and is “composed of any material and/or shape that (a) allows cells to attach to it . . . and (b) allows cells to grow in more than one layer.” ’ Id. at col. 6 ll. 42–47. The inventors explain that a number of non-exhaustive factors may contribute to the success of such a three-dimensional culture system, including, for example, that the “threedimensional framework provides a greater surface area for protein attachment”; the three-dimensionality of the framework permits “stromal cells [to] continue to grow actively, in contrast to cells in monolayer cultures, which grow to confluence, exhibit contact inhibition, and cease to grow and divide”; “[t]he three-dimensional framework allows for a spatial distribution of cellular elements which is more analogous to that found in the counterpart tissue in vivo”; “[t]he elaboration of growth and regulatory factors by replicating stromal cells” in a three- dimensional culture may stimulate “proliferation” and the “regulat[ion] [of] differentiation of cells in culture”; “[t]he increase in potential volume for cell growth in the threeSKINMEDICA INC v. HISTOGEN INC 7 dimensional system may allow the establishment of localized microenvironments conducive to cellular maturation”; and “[t]he three-dimensional framework maximizes cell-cell interactions by allowing greater potential for movement of migratory cells . . . in the adherent layer.” Id. at patent col. 11 ll. 20–53. In addition, the patentees highlight the importance of maintaining and maximizing “proliferative activity” during three-dimensional culturing and describe ways to do so. For example, they teach that “proliferating cells may be released from the matrix” used in a three- dimensional culture and “stick to the walls of the culture vessel where they may continue to proliferate and form a confluent monolayer.” Id. at col. 14 ll. 20–24. That “should be prevented or minimized” by “[r]emoval of the confluent monolayer or transfer of the culture to fresh media in a new vessel” because the presence of confluent monolayers in the culturing vessel will “shut down” continued proliferation in a three-dimensional culture system. Id. at col. 14 ll. 24–31. During prosecution of the ’494 patent, the patentees also discussed the importance of sustained proliferation of cells in three-dimensional cultures and the importance of the components in the culture medium for achieving such growth. At one point, the examiner of the ’494 patent rejected a set of proposed claims, which included the three-dimensional culturing limitation, over Shipley combined with U.S. Patent No. 5,032,508 (’508 patent) (issued to Naughton, et al.). 3 That patent discloses a “three-dimensional skin culture system” that uses a “three-dimensional matrix” to culture a variety of cells and that “allow[s] for normal cell-cell interactions and the 3 Gail Naughton, a defendant in this case and an inventor of the ’494 and ’796 patents, was also an inventor of the ’508 patent. 8 SKINMEDICA INC v. HISTOGEN INC secretion of natural growth factors, and the establishment of a connective tissue network virtually identical to that found in vivo.” ’508 patent col. 27 ll. 10–35. The written description of the ’508 patent additionally explained that “three-dimensional skin cultures have applicability to many fields of industry including use . . . as a source of naturally secreted pharmacologic agents.” Id. at col. 27 l. 68–col. 28 l. 4. To overcome the obviousness rejection, the inventors of the ’494 patent argued that “the conditioned medium from cells cultured in three-dimensions has desirable properties not exhibited by medium conditioned by cells cultured [in] two dimensions” and that “nowhere in Naughton et al., is there a teaching or suggestion that sustained proliferation of the cells in culture is a result of factors or components of the conditioned medium.” 4 Response to Office Action, Exhibit to Response to Claim Construction Brief, SkinMedica v. Histogen, No. 3:09-cv122, (S.D. Cal. July 21, 2009), ECF No. 47-1 at 30 (second emphasis added).