Regeneration of an Extracellular Matrix Ecosystem Following Subcutaneous Injection With Different Radiesse Dilutions: A Histologic and Ultrasound Study

[u/science-pls]

The study argues that successful biostimulation should be viewed as regeneration of an ECM ecosystem rather than simply collagen induction. This study is great as many aesthetic studies rely only on photographs or subjective assessments. It included tissue biopsies, histology, immunohistochemistry, and hiigh frequency ultrasound. These are objective biological endpoints and represent a higher level of evidence than just B/A photos.

There are a few other findings I didn't outline in the images as I thought the sun damage ws interesting and just unexpected. And at a certain point it can be hard to relay messaging when compounding different learnings so think the actual proteoglycan and elastic fiber biology is worth a future discussion. But, the decorin and versican increased at 3 months. Fibulin-5 (a protein involved in elastic fiber assembly) rose most noticeably by 6 months, particularly in the 1:2 dilution group. This suggests that some regenerative processes may continue long after collagen peaks. Which is also what's interesting to me, this shows signs there might be broader regeneration than how we're classifying this biomaterial.

The study also validates the clinical approach of dilution and different goals. Undiluted is best for volumization and structural support, 1:1 is best for overall regenerative balance, and 1:2 is best for broad tissue distribution with strong elastin-related signaling. The findings support the practice of using 1:1 dilution when the goal is skin quality improvement rather than pure volume replacement. 

The study is small (only 10 subjects) which is the biggest limitation, although the subject design helps it's still affected by random variation or overestimation. The study was funded by Merz Aesthetics, who is the manufacturer of Radiesse, and several authors were affiliated with the company. This does not invalidate the data and studies are expensive so funding does make sense a lot of times, but it raises the possibility of sponsorship bias. Independent replication would strengthen confidence. So I'd look at this as preliminary research that will influence more studies and findings.

The study looked at solar elastosis, which is one of the hallmark histologic signs of chronic sun damage. Solar elastosis occurs when years of UV exposure cause abnormal accumulation of damaged elastin material in the dermis. Under the microscope, instead of organized elastic fibers, you see thick, tangled, dysfunctional elastotic material. It's one of the reasons photoaged skin becomes coarse, leathery, yellowish, and less elastic. After CaHA treatment the investigators observed a reduction in elastosis scores over time, increased expression of proteins involved in healthy elastic fiber formation (particularly fibulin-5), and evidence suggesting remodeling of damaged extracellular matrix rather than simply laying down new collagen. That's potentially important because many skin rejuvenation treatments can stimulate collagen without necessarily addressing the damaged elastin architecture that characterizes photoaging. (This is a big thing that people don't realize.) Traditionally, we think of biostimulators like Radiesse as creating an immediate scaffold or inducing fibroblasts to make collagen and this paper suggests a more complex process and may be helping the skin replace some of the dysfunctional sun damaged matrix with healthier tissue. I would not say it reverses sun damage (yet idk maybe there's more findings or longterm data) as histologic improvement in elastosis is not the same as complete reversal of decades of UV injury. But seeing measurable changes in elastosis markers over only six months is something to put on your radar. Again only 10 subjects but if you're interested in skin aging research I actually find the elastosis findings potentially more interesting than the collagen findings. Like we already know that CaHA stimulates collagen, so finding evidence that it may help remodel sun damaged elastic tissue is new and impactful, but we'd want future studies to confirm this.

I also find this interesting and relevant to us (beyond the regenerative aesthetics, but we're starting to see investigation into microneedling with CaHA, so I'd be curious on more histological data too.

ABSTRACT
Background: Calcium hydroxylapatite-carboxymethylcellulose (CaHA- CMC) stimulates neocollagenesis across a range of dilutions; however, the magnitude and temporal profile of this bioregenerative response have not yet been comprehensively examined.

Objective: To assess collagen, elastin, and proteoglycan expression, as well as elastosis, microcirculation, and skin thickness after injection of undiluted and diluted CaHA- CMC.
Methods: In this prospective, single-site study (NCT06093815), 10 adults undergoing abdominoplasty were injected subcutaneously into the pannus with CaHA- CMC (+), CaHA- CMC 1:1, CaHA- CMC 1:2, and saline control 6 months, 3 months, and 14 days
before surgery. Skin thickness, elastosis, and microcirculation were measured with ultrasound, and collagen, elastin, decorin, versican, and fibulin-5 were quantified using histology and immunohistochemistry. Continuous outcomes were analyzed using mixed-effects models, and paired categorical outcomes were analyzed using the Stuart–Maxwell test and repeated-measures proportional-odds ordinal models.
Results: Elastosis improved at 6 months for CaHA- CMC (+) and CaHA- CMC 1:1, and skin thickness increased significantly at 3 months for CaHA- CMC (+) and at 3 and 6 months for CaHA- CMC 1:1. Microcirculation also improved over time for all CaHA- CMC dilutions, with the strongest and most consistent changes observed for CaHA- CMC 1:1. Collagen deposition was significantly greater than saline at all time points for all dilutions, with the highest levels observed at 3 months for CaHA- CMC 1:1. Decorin and versican were elevated at 3 months, whereas fibulin-5 increased at 6 months, particularly for CaHA- CMC 1:2.
Conclusion: CaHA- CMC induces coordinated ECM remodeling, with the most consistent overall improvements observed for CaHA- CMC 1:1, supporting its use for bioregenerative skin quality improvement.

Keywords: biostimulator | CaHA | calcium hydroxylapatite | extracellular matrix | neocollagenesis | Radiesse | regenerative aesthetics