Calcium hydroxylapatite microspheres activate fibroblasts through direct contact to stimulate neocollagenesis

Abstract

Background Calcium hydroxylapatite (CaHA; Radiesse, Merz North America) restores volume and stimulates collagen production. The aim of this research was to explore the role of dilution and diffusion in microsphere distribution and the effect of CaHA concentration on activation of fibroblasts to produce collagen. Methods Ex vivo: Tissue dispersion of CaHA was assessed in abdominal tissue segments obtained from patients which were subsequently injected with CaHA diluted to 1:1 and hyperdiluted to 1:2. In vitro: Collagen type III (COLIII) and type I (COLI) expression of fibroblasts was evaluated after 24 and 72 h of incubation with CaHA concentrations of 1.5 (high dilution), 3.0, and 4.5 mg/ml (low dilution). Results Ex vivo: The 1:2 CaHA hyperdilution increased dispersion and decreased concentration of CaHA microspheres compared with the 1:1 dilution. In vitro: CaHA incubation resulted in an increased mean COLIII expression of 123% at 24 h. COLI synthesis did not change after 24 h but increased up to 124% at 72 h. Only fibroblasts in direct contact with CaHA increased COLIII expression. COLIII high‐expressing cells were fully activated by CaHA and resulted in the same level of COLIII expression per cell independent of the CaHA dilution. Conclusions A 1:2 hyperdilution of CaHA increased tissue dispersion of CaHA microspheres. Direct contact of CaHA with fibroblasts was a key factor for inducing neocollagenesis. COLIII high‐expressing cells were fully activated by CaHA and resulted in the same expression level of COLIII per cell independent of the CaHA amount in each dilution. This indicates that increased collagen expression was due to the activation of more fibroblasts.

Biostimulating fillers and induction of inflammatory pathways: A preclinical investigation of macrophage response to calcium hydroxylapatite and poly‐L lactic acid

“…Among these hypotheses are published models of CaHA acting as a calcium sink utilizing chemoattraction to upregulate fibroblasts, 45,46 and neocollagenesis via direct interactions between fibroblasts and CaHA microspheres. 47,48 Our knowledge today indicates that there are complex immunological pathways and interactions at play in all biostimulating formulations that are unique to each, as supported by this in vitro study. The various pathways are likely to result in differing outcomes changing, for example, the ratios of collagen types and other elements of the extracellular matrix, such as elastin and glucosaminoglycans, which will ultimately influence skin and soft tissue structure and function.…”

“…There are various working hypotheses to explain the apparent unique mode of action of CaHA that diverge from the foreign body response of PLLA and other biostimulatory formulations. Among these hypotheses are published models of CaHA acting as a calcium sink utilizing chemoattraction to upregulate fibroblasts, 45,46 and neocollagenesis via direct interactions between fibroblasts and CaHA microspheres 47,48 . Our knowledge today indicates that there are complex immunological pathways and interactions at play in all biostimulating formulations that are unique to each, as supported by this in vitro study.…”

A systematic review of Radiesse/calcium hydroxylapatite and carboxymethylcellulose: evidence and recommendations for treatment of the face

“…Histologic data further prove a significant increase of collagen I, angiogenesis, and elastin with CaHA/CMC, as compared to HA, supporting the biostimulatory activity of the filler 39 . Direct contact of CaHA with fibroblasts is a key factor for inducing neocollagenesis 40 . Importantly, current knowledge and scientific observations concerning the effects of CaHA/CMC on the restoration of mechanical properties of the skin, have led to the concept that this filler has “regenerative” properties and can be included among other regenerative treatments 41 …”

“…39 Direct contact of CaHA with fibroblasts is a key factor for inducing neocollagenesis. 40 Importantly, current knowledge and scientific observations concerning the effects of CaHA/CMC on the restoration of mechanical properties of the skin, have led to the Recommendations for the use of CaHA/CMC encompass injection of the product through a cannula with a preferred size of 22G, or 25G, to avoid vascular injections. Beer et al 23 compared, the efficacy of CaHA/CMC injected with a cannula or needle in an RCT split-face study.…”

Letter to the Editor: Post hoc analysis of “Clinical and histological comparative outcomes after injections of poly‐L‐lactic acid and calcium hydroxyapatite in arms: A split side study”

“…The empirical quantification is thus in agreement with previous reports indicating that PLLA generates collagen via a subclinical inflammatory response, while CaHA regenerates collagen and elastin via a mechanical interaction with minimal inflammatory cell infiltration. 9,10 Overall, Mazzuco…”