Scaffolds in Tissue Engineering
This article was originally published in Start Up
Executive Summary
Stem-cell-related strategies may predominate these days in tissue engineering, but cell therapy companies know that providing the right microenvironment for nurturing tissue growth remains a difficult and essential challenge. Thus, start-ups remain committed to the developent of cellular matrices that provide the appropriate structure, environment, and bioactivity to encourage tissue growth. The four start-ups profiled in this issue represent a cross-section of strategies.
Stem-cell-related strategies may predominate, but start-ups remain committed to the development of cellular carrier matrices to encourage tissue growth.
Outside of stem cells, it’s fair to say that the related areas of cell therapy and tissue engineering have not been particularly trendy areas for early-stage start-up investment in recent years—especially when it comes to the engineering of novel scaffolds that encourage the growth of tissue and organs. Of the companies highlighted in START-UP’s analysis of 2007’s trends in Series A financings, only the aesthetics company Follica Inc., which raised $5.5 million in December 2007, [See Deal] made the cut, and its strategy, rather than applying a bioactive cellular matrix of some sort, is to use a known drug to reprogram stem cells in the scalp to treat male- or female-pattern baldness. (See "The A-List: 2007’s Trend Shaping Series A Financings," START-UP, January 2008 (Also see "The A-List: 2007's Trend Shaping Series A Financings" - Scrip, 1 Jan, 2008.).) Nor did any tissue engineering start-ups make the prior year’s trends list, but one of 2005’s top movers, Tengion Inc., a developer of autologous organs, was recognized there for its $50 million Series B financing in June 2006. It was also the beneficiary of a $33 million Series C round in October 2007. [See Deal] [See Deal] (See "Tengion Inc.," START-UP, September 2005 (Also see "Tengion Inc." - Scrip, 1 Sep, 2005.).)
Apart from Tengion, most of the tissue-engineering-related money flow in 2007 went to stem-cell-oriented companies. Fate Therapeutics Inc. launched last November with $12 million in hand to develop its platform for stimulating adult stem cells or to reprogram them to mimic the properties of embryonic stem cells, which can then be directed to differentiate into designated cell types. [See Deal] Pluristem Therapeutics Inc. raised just under $7 million in May 2007 for its program to purify mesenchymal stem cells from umbilical cord blood, for use in the treatment of severe degenerative, malignant, and autoimmune diseases [See Deal] (a strategy similar to that of Osiris Therapeutics Inc., which has a purified mesenchymal stem cell product in Phase III for treating severe refractory graft versus host disease). And allogeneic stem cell developer Mesoblast Ltd. raised $11.8 million in December 2007 for its orthopedic regeneration programs. [See Deal]
But cell therapy companies know that providing the right microenvironment for nurturing tissue growth remains a difficult and essential challenge—one impetus for companies like Fate and Follica to attempt to use drugs to reprogram existing cells in their microenvironments. It’s a lesson cardiac cell therapy researchers learned the hard way, when they moved into large-scale studies before understanding enough about the mechanisms by which certain cell types, dosing regimens, and modes of administration might lead to cell regeneration or repair. (See "Cardiac Cell Therapy: Are There Easier Ways to Restore Function? Probably." IN VIVO, November 2006 (Also see "Cardiac Cell Therapy: Are There Easier Ways to Restore Function? Probably" - In Vivo, 1 Nov, 2006.).) Thus, even as strategies aimed at purifying, recruiting, or reprogramming stem cells gain momentum, start-ups are still focused on the development of cellular matrices. Some of these devices are purely structural, while others can incorporate growth factors--even stem cells. These matrices may comprise engineered materials that provide the appropriate structure, environment, and bioactivity to encourage tissue growth, using advances in nanotechnology and robotics to fine-tune their electric charge, concentration, particle size, and particle organization. (See "Multiple Paths of Convergence in Tissue Engineering," START-UP, January 2007 (Also see "Multiple Paths of Convergence in Tissue Engineering" - Medtech Insight, 1 Jan, 2007.).) Others are tissue-based, biocompatible biomaterials.
The start-ups profiled in this issue represent a cross-section of these strategies. Buoyed by observations that proteins secreted by fibroblasts cause hair follicles to grow, and that some of those same proteins encourage stem cells to induce hair follicle growth, Histogen Inc. (Also see "Histogen Inc." - Scrip, 1 Feb, 2008.) is developing a fibroblast-derived extracellular matrix aimed at the aesthetics market as well as wound healing and research applications. Tissue Regenix Group PLC (Also see "Tissue Regenix Ltd." - Scrip, 1 Feb, 2008.) is building scaffolds from "de-cellularized" animal tissue using a process that maintains the activity of proteins such as collagen and elastin so that once embedded into a patient, they can encourage cell recruitment and tissue formation. Humacyte Inc. (Also see "Humacyte Inc." - Scrip, 1 Feb, 2008.) is hoping its collagen matrix derived from smooth muscle cells, for use in arterial grafting, will capture the imagination of investors in the same way as has Tengion. And to enhance bone growth, BioCeramic Therapeutics Ltd. (Also see "BioCeramic Therapeutics Ltd." - Scrip, 1 Feb, 2008.) is developing strontium-containing glass-based material as a bone filler and coating—a strategy similar to that pursued by Orthovita Inc., for example, which machines glass-resin composites for use in orthopedics. (See "Orthovita: The Most Natural Thing," IN VIVO, June 2001 (Also see "Orthovita: The Most Natural Thing" - In Vivo, 1 Jun, 2001.).)--Mark L. Ratner