Choosing Between PLLA and CaHA for Your Anti-Ageing Treatment: An In-Depth Comparison

Introduction to Collagen Biostimulators in Anti-ageing

As individuals seek effective solutions to combat the visible signs of ageing, the landscape of anti-ageing treatments continues to evolve. Among the prominent choices available, Poly-L-lactic Acid (PLLA) and Calcium Hydroxyapatite (CAHA) have gained significant attention.

Understanding the Molecules: PLLA vs. CAHA

Calcium hydroxylapatite is a biocompatible, biodegradable, and resorbable biostimulatory filler consisting of calcium hydroxylapatite (CaHA) microspheres (25–45 μm diameter) suspended in a 70% aqueous carboxymethylcellulose gel carrier. It is indicationed for moderate-to-severe facial wrinkles, such as nasolabial folds and marionette lines; enhancing fullness of the cheeks and other facial contours; improving volume in hands; and improvement of jawline contour. CaHA is often used for re-volumisation of other areas of the face and body and is also used in a diluted form for skin tightening.

CaHA filler provides immediate volume replacement via carrier carboxymethylcellulose gel, which is subsequently replaced over time by native collagen induced by the CaHA microspheres. This neocollagenesis maintains the volume provided initially by the carrier gel, and also improves skin quality and thickness.

While physiochemically distinct, in the clinic CaHA is often considered alongside poly-L-lactic acid as an option for biostimulation-based revolumization.

PLLA creates volume through promotion of a subclinical foreign body inflammatory response, which promotes collagen synthesis that becomes apparent as volume over the course of several months. For PLLA, volume increases seen immediately after injection are related to swelling and the suspension of microparticles, and wane within hours to days.

This method leads to the formation of more disorganized type III collagen, which may not yield the most desirable aesthetic results. In contrast, CAHA is derived from natural minerals and provides substantial regenerative benefits with a favorable safety profile.

Mechanisms of Action: Cellular Pathways

As CaHA and PLLA are biostimulators, their main mechanism of action of anti-ageing changes are through the production of new collagen (neocollagenesis). CaHA and PLLA are chemically distinct and lead to neocollagenesis through different pathways.

Immune pathways are determined early following injection and involve differential recruitment of immune cells. Immediately after injection, material is surrounded by blood from injured vessels, lipids, sugars, ions, and proteins (e.g., albumin, fibrinogen, fibronectin, and gammaglobulins), which are adsorbed on the particle surface within minutes. The different surface properties of CaHA and PLLA lead to attachment of distinctive collections of extracellular proteins and a divergence of pathways leading to neocollagenesis.

CaHA particles function as a scaffold to support resident fibroblast function and induce pathways for multiple aspects of extracellular matrix (ECM) regeneration such as Hyaluronic Acid synthesis, angiogenesis, and organization of type I, type III collagen, elastin, and proteoglycans. Microscopic (Histologic) studies suggest minimal infiltration of inflammatory cells, potentially leading to restoration of normal skin structure and function.

The PLLA tissue response appears to be more inflammatory in nature, and protein adsorption is followed by the recruitment of immune cells, namely neutrophils and macrophages, from Day 2 to Day 10 after injection. By 1 month, other immune-mediating white blood cells such as mast cells, mononuclear macrophages, foreign body cells, and lymphocytes surround PLLA microparticles. As a result of this foreign body reaction, PLLA particles are encapsulated by more immature, less organized type III collagen, while more organized, and mature collagen type I is not found in close proximity to the PLLA particles or surrounding cellular infiltrate and is observed only at the periphery of the granulomatous reactions. These differential immune cell responses and distinct patterns of neocollagenesis suggest distinct modes of action that likely occur through early divergence of tissue response pathways.

Additionally, an advantage of using CaHA lies in its dual action; it not only acts as a filler but can also stimulate the biological processes essential for skin repair when used hyperdiluted in the dermis (skin) layer. This regenerative capability also means that CaHA improves skin texture over time, making it a more holistic solution for those seeking sustainable anti-ageing treatments, through improving volume, skin laxity and skin quality.

One upside of using PLLA versus CaHA may be the significance of response after a single treatment, as patients report more significant 'skin tightening' after a single session.

While both options hold their merits, the increasingly favorable safety and regenerative profile of CaHA is compelling for aesthetic practitioners and patients alike.