Biodegradable llers are de ned as having a limited life span usually ranging from a couple to several months, or even to a couple of years. ey usually consist of puri ed dermal compo- nents from human, animal, or bacterial sources and can be divided into the following categories: xenogra s (donor and recipient are from di er- ent species), autogra s (donor and recipient are from the same individual), homogra s (donor and recipient are from the same species), and synthetic materials.
Collagens from various sources and with speci c characteristics exist. erefore, it is important to discuss the di erent products separately.
Collagen of Bovine Origin
Prior to the introduction of the hyaluronic acids, collagen was the most widely used ller and was considered the gold standard with which other dermal llers were compared. e classical bo- vine enzyme-digested collagen (95 % type I, 5 % type III) is available in several preparations, which can be distinguished by the collagen con- tent and the addition of glutaraldehyde for sta- bilization (Homicz and Watson 2004). Glutar- aldehyde crosslinks lysine residues within the collagen structure, thereby increasing the stabil- ity of the product and its ability to resist in vivo enzymatic degradation.
Depending on the collagen content and the degree of crosslinking, di erent products should be used for di erent levels of the dermis. For ex-
ample, Zyderm 1 and Zyderm 2, which are llers with noncrosslinked collagen, should be injected super cially into the papillary level of the der- mis. Zyplast, a crosslinked form, should be in- jected more deeply into the reticular layer. All of these products are easy to inject. Furthermore, overcorrection is recommended for Zyderm 1 and Zyderm 2, as these collagen preparations will loose volume over time.
Zyderm Collagen was cleared for market- ing in 1981 by the Food and Drug Administra- tion (FDA) a er reviewing clinical data based on a large case series of 9,427 tested and 5,109 treated patients (Cooperman et al. 1985; Matti and Nicolle 1990). In addition to this case series, which focused mainly on safety issues, a recent clinical trial showed that it was e ective for at least several months (Cooperman et al. 1985; Matti and Nicolle 1990)
As collagen may elicit hypersensitivity reac- tions, pretesting is so far mandatory. Pretesting consists of an intradermal injection of Zyderm 1 collagen into the volar aspect of the forearm. A minimum of one skin test should be admin- istered and evaluated a er 28 days.
Collagen of Porcine Origin
A few porcine collagen-based llers have been described in the literature (Saray 2003). How- ever, they have not been widely used. A novel porcine collagen ller, Evolence, was introduced into the European market in 2004. In contrast to other collagens, this product is crosslinked by mimicking the process of collagen glycation using d-ribose as the crosslinking agent. A ran- domized clinical trial is currently under way with the objective of presenting the superior ef- cacy of Evolence to bacterial hyaluronic acid for the treatment of nasolabial folds. Data on the e cacy of the implant have not yet been pub- lished. e company that produces this collagen ller states a product durability of at least 1 year. In the recent Conformité Européenne (CE) cer- ti cation of Evolence, pretesting was not consid- ered a prerequisite.
Collagen of Human Origin
Collagen of human origin can be of allogenous or autologous nature.
Collagen of Allogenous Nature (from Cadaver)
In addition to bovine or porcine sources, colla- gen can be derived from human cadavers. Data is available for two products: Dermalogon and Cymetra. Both products derive from pooled hu- man cadaverous tissue from accredited tissue banks. Overcorrection is recommended by the manufacturer. Here again the available data on the e cacy and safety of the product are limited. Cymetra was tested against Zyplast in a random- ized controlled trial. A total of 47 patients were treated: 20 received Cymetra and 27 received Zyplast. Various photometric outcome measures
Collagen of Allogenous Nature (from Culture)
Later-generation noncadaverous collagen prod- ucts are CosmoDerm and CosmoPlast. ey are made from natural human collagen grown un- der controlled laboratory conditions. ere is no need for a pretreatment skin test for these ster- ile devices, which are composed of highly puri- ed human-based collagen that is dispersed in phosphate-bu ered physiological saline contain- ing 0.3% lidocaine. CosmoDerm is a noncross- linked formulation that is used in the treatment of super cial lines, whereas CosmoPlast is cross- linked and is used primarily in the treatment of more pronounced wrinkles. ese products are not available in countries outside of the United States; regulations surrounding products of hu- man origin vary on a country-by-country basis (Bauman 2004). No clinical trials are available because the FDA concluded that since Cos- moDerm and CosmoPlast represent a material source change to Zyderm and Zyplast (from bo- vine- to human-based collagen), they did not re- quire new clinical e cacy studies to be carried out.
Collagen of Autologous Nature
e commercial preparation Autologon consists of dermal extracellular matrix, primarily col- lagen (types I, III, and VI), that has been har- vested from the patient‘s own skin. It requires the excision of the patient‘s skin and is therefore mostly suitable for those undergoing surgical procedures. Here again, overcorrection is rec- ommended by the manufacturer. e available data on the e cacy and safety of the product are limited (Sclafani et al. 2000).